Cryobanking of aquatic species

Assessment of male reproductive traits in endangered leuciscids from the Iberian Peninsula: first attempts to store gametes both at short- and long-term

During the spring of 2022, several endangered leuciscid species (Anaecypris hispanica, Squalius aradensis, Anachondrostoma Occidentale, and Iberochondrostoma lusitanicum) were sampled both at the Vasco da Gama aquarium facilities and in some rivers of the Algarve region, Portugal. Sperm samples were extracted by gentle abdominal pressure and sperm motion parameters were assessed for the first time in four species, using a computerized analysis system. The results obtained showed that spermatozoa kinetic patterns were similar for all 4 species, with high motility and velocity values after the sperm activation time and with a marked decrease after 20. On the other hand, sperm longevity was highly variable between species, with short longevities (around 40 s) for A. hispanica and S. aradensis, and longer longevities (100-120 s) for A. occidentale and I. lusitanicum, which could indicate a latitudinal pattern in terms of sperm longevity. At the same time, morphometric analysis was carried out for the four target species, revealing that spermatozoa showed similar sizes and shapes to other external fertilizers belonging to Leuscididae, with small spherical heads, uniflagellate, and without acrosomes. In addition, a short-term gamete storage trail was performed by diluting sperm in 1:9 (sperm:extender) and storing them at 4ºC. Although the results obtained were uneven among the species studied, the dilution and extender used generated motilities above 40% up to day 4 of storage in S. aradensis and I. lusitanicum, and up to days 1-2 in A. hispanica and A. occidentale, respectively. Finally, gamete cryopreservation trials were also carried out on these threatened species. Although cryopreserved samples showed significantly lower motility than fresh samples, some protocols generate acceptable percentages of viability, DNA integrity, and sperm motility in some species such as I. lusitanicum and A. occidentale. The data revealed that the protocol based on 10% DMSO plus 7.5% egg yolk generated the best results.This study is the first to assess the reproductive traits of wild and captive populations of endangered leuciscids endemic from the Iberian Peninsula, describing the spermatozoa kinetics and developing protocols for managing male gametes both in short- and long-term storage. Outcomes will provide new and useful tools to complement the management and conservation of ex situ breeding programs that are being developed for these four endangered species.

The growth performance of pond-reared common carp (Cyprinus carpio) larvae propagated using cryopreserved sperm

The aim of our study was to determine the efficacy of utilizing cryopreserved common carp sperm (in comparison to fresh sperm) for propagation at a Hungarian aquaculture facility. The sperm was frozen in 5 mL straws using an extender method that was previously tested in common carp. Sperm motility was monitored using a computer-assisted sperm analysis system. The hatching and malformation rates among the specimens were recorded before the stocking of larvae in both groups. The growth (body weight, total length) and survival rates of the fish were measured during the pre-nursing (from May to June: between 1 and 26 days post hatching) and grow-out periods (from June to October: between 26 and 105 days post hatching) of the same year. The fresh sperm, which was collected and pooled prior to fertilization, showed high MOT (97%), pMOT (92%), VCL (106 µm s-1), LIN (75%), and ALH (1.84 µm). Prior to the fertilization trial of the cryopreserved sperm, low MOT (34%), pMOT (14%), and VCL (61 µm s-1) values were observed in frozen-thawed sperm. A significantly higher hatching rate was measured in the fresh sperm group (87%) when compared to the cryopreserved sperm group (42%). No significant difference in the overall malformation rate was observed in larvae originating from either the fresh or frozen sperm. A significant difference between the two test groups was observed in the incidence of deformed tails (fresh: 20%, cryopreserved: 55%). Except for one sampling period, no significant difference in the body weight and total length of the fish larvae was found between the two groups throughout the pre-nursing and grow-out periods. A significantly higher larvae survival rate was noted in the fresh sperm (72%) as compared to the cryopreserved group (43%) by the end of the pre-nursing stage. However, no significant difference in survival rate was observed for the cryopreserved sperm (96%) in comparison to the fresh sperm (95%) by the end of the grow-out stage. The results of this study showed, for the first time in large-scale pond culturing, an equal growth and viability in larvae propagated from cryopreserved sperm when compared to fresh sperm (despite the limited available rearing ponds provided by the commercial company).

Cryopreservation-Induced Morphological Changes in Freshwater Fish Sperm: A Systematic Review

A systematic review was performed to summarize the scientific evidence and critically evaluate the effects of cryopreservation on sperm morphology in freshwater fish, and to assess the methodologies for sperm morphology classification. The search strategy was applied to four electronic databases (CAB Direct, Pub Med, Scopus, and ISI Web of Science). The main inclusion criteria involved studies on semen from freshwater fish subjected to the cryopreservation process and evaluation of sperm quality through morphology. The risk of bias was assessed with respect to randomization, allocation concealment, blinding, incomplete outcome data, and selective reporting. A total of 6 publications reporting sperm cryopreservation from 4 species with a total 74 fish individuals were included in this review. A high methodological variability among the results of the studies was observed due to the species-specific protocols and diversity of freshwater fish species studied. All included studies reported negative effects of cryopreservation on sperm quality, especially morphology, highlighting the increase in incidence of sperm abnormalities. However, only five studies statistically compared abnormalities between groups (fresh and cryopreserved sperm). Our results suggest the need to elaborate on a new morphological classification of fish spermatozoa, by considering the structure and physiology of fish sperm. This classification should be developed based on the sperm characterization and observing damage caused by different cryopreservation protocols.

Addition of Cryoprotectant DMSO Reduces Damage to Spermatozoa of Yellow Catfish (Pelteobagrus fulvidraco) during Cryopreservation: Ultrastructural Damage, Oxidative Damage and DNA Damage

Spermatozoa cryopreservation protocols have been established for yellow catfish (Pelteobagrus fulvidraco), but cryopreservation can still cause cellular damage and affect spermatozoa viability and fertility. Therefore, the aim of this paper was to evaluate the effects of adding or not adding cryoprotectants during low-temperature storage on the ultrastructural damage, oxidative damage, and DNA damage of thawed yellow catfish spermatozoa. The mixed semen of three male yellow catfish was divided into a fresh spermatozoa group, a frozen spermatozoa group (DMSO+) with a cryoprotectant (10% DMSO), and a frozen spermatozoa group without a cryoprotectant (DMSO-). Ultrastructural of the spermatozoa after thawing were observed under an electron microscope and the spermatozoa were assayed for SOD, MDA, and T-AOC enzyme activities, as well as for DNA integrity. In terms of movement parameters, compared with DMSO-, the addition of DMSO has significantly improved sperm motility, curve line velocity (VCL), and straight line velocity (VSL). The ultrastructural results showed that although thawed spermatozoa exhibited increased damage than fresh spermatozoa, 10% DMSO effectively reduced the damage to the plasma membrane, mitochondria, and flagellum of spermatozoa by cryopreservation, and most of the spermatozoa were preserved with intact structure. The results of oxidative damage showed that compared with frozen spermatozoa, 10% DMSO significantly increased the activities of SOD and T-AOC enzymes and clearly reduced the activity of the MDA enzyme. The antioxidant capacity of spermatozoa was improved, lipid peroxidation was reduced, and the oxidative damage caused by cryopreservation was mitigated. The DNA integrity of spermatozoa showed that 10% DMSO clearly reduced the DNA fragmentation rate. In conclusion, 10% DMSO can effectively reduce the ultrastructural damage, oxidative damage, and DNA damage of yellow catfish spermatozoa during cryopreservation; it can also further optimize the cryopreservation protocol for yellow catfish spermatozoa. Meanwhile, it also provides a theoretical basis for the future optimization of the cryopreservation protocols.

Tissue Culture Innovations for Propagation and Conservation of Myrteae-A Globally Important Myrtaceae Tribe

Myrteae is the most species-rich tribe in the Myrtaceae family, represented by a range of socioeconomically and ecologically significant species. Many of these species, including commercially relevant ones, have become increasingly threatened in the wild, and now require conservation actions. Tissue culture presents an appropriate in vitro tool to facilitate medium-term and long-term wild germplasm conservation, as well as for commercial propagation to maintain desirable traits of commercial cultivars. So far, tissue culture has not been extensively achieved for Myrteae. Here, tissue culture for Eugenia, one of the most species-rich genera in Myrteae, is reviewed, giving directions for other related Myrteae. This review also focuses on ex situ conservation of Australian Myrteae, including using seed banking and field banking. Despite some progress, challenges to conserve these species remain, mostly due to the increasing threats in the wild and limited research. Research into in vitro methods (tissue culture and cryopreservation) is paramount given that at least some of the species are 'non-orthodox'. There is an urgent need to develop long-term in vitro conservation for capturing the remaining germplasm of threatened Myrteae.

Comparative transcriptome analysis reveals molecular damage associated with cryopreservation in Crassostrea angulata D-larvae rather than to cryoprotectant exposure

BACKGROUND

The Portuguese oyster Crassostrea angulata, a bivalve of significant economic and ecological importance, has faced a decline in both production and natural populations due to pathologies, climate change, and anthropogenic factors. To safeguard its genetic diversity and improve reproductive management, cryopreservation emerges as a valuable strategy. However, the cryopreservation methodologies lead to some damage in structures and functions of the cells and tissues that can affect post-thaw quality. Transcriptomics may help to understand the molecular consequences related to cryopreservation steps and therefore to identify different freezability biomarkers. This study investigates the molecular damage induced by cryopreservation in C. angulata D-larvae, focusing on two critical steps: exposure to cryoprotectant solution and the freezing/thawing process.

RESULTS

Expression analysis revealed 3 differentially expressed genes between larvae exposed to cryoprotectant solution and fresh larvae and 611 differentially expressed genes in cryopreserved larvae against fresh larvae. The most significantly enriched gene ontology terms were "carbohydrate metabolic process", "integral component of membrane" and "chitin binding" for biological processes, cellular components and molecular functions, respectively. Kyoto Encyclopedia of Genes and Genomes enrichment analysis identified the "neuroactive ligand receptor interaction", "endocytosis" and "spliceosome" as the most enriched pathways. RNA sequencing results were validate by quantitative RT-PCR, once both techniques presented the same gene expression tendency and a group of 11 genes were considered important molecular biomarkers to be used in further studies for the evaluation of cryodamage.

CONCLUSIONS

The current work provided valuable insights into the molecular repercussions of cryopreservation on D-larvae of Crassostrea angulata, revealing that the freezing process had a more pronounced impact on larval quality compared to any potential cryoprotectant-induced toxicity. Additionally, was identify 11 genes serving as biomarkers of freezability for D-larvae quality assessment. This research contributes to the development of more effective cryopreservation protocols and detection methods for cryodamage in this species.

Ultrastructural examination of cryodamage in Paracentrotus lividus eggs during cryopreservation

This study examinates the challenges of cryopreserving sea urchin (Paracentrotus lividus) eggs, a task hindered by factors like low membrane permeability and high sensitivity to cryoprotective agents (CPAs). While successful cryopreservation has been achieved for some marine invertebrates, eggs remain problematic due to their unique characteristics. The study explores the impact of various CPAs and cryopreservation techniques on sea urchin eggs, employing scanning and transmission electron microscopy to analyze cellular damage. The findings reveal that exposure to low CPA concentrations (0.5 M) did not induce significant damage to eggs. However, high concentrations (3 M) proved highly detrimental. Every cryopreservation approach investigated in this study resulted in irreversible damage to the sea urchin eggs, rendering them nonviable for future use. The research sheds light on the importance of understanding the structural alterations induced by CPAs and cryopreservation methods. This knowledge is essential for refining cryopreservation methods, potentially paving the way for successful preservation of these challenging cells.

The Effects of Larval Cryopreservation on the Epigenetics of the Pacific Oyster Crassostrea gigas

High mortalities and highly variable results during the subsequent development of post-thaw larvae have been widely considered as key issues restricting the application of cryopreservation techniques to support genetic improvement programs and hatchery production in farmed marine bivalve species. To date, few studies have been undertaken to investigate the effects of cryodamage at the molecular level in bivalves. This study is the first to evaluate the effect of larval cryopreservation on the epigenetics of the resultant progenies of the Pacific oyster Crassostrea gigas. The results show that the level of DNA methylation was significantly (p < 0.05) higher and lower than that of the control when the trochophore larvae were revived and when they developed to D-stage larvae (day 1 post-fertilization), respectively, but the level returned to the control level from day 8 post-fertilization onwards. The expression of the epigenetic regulator genes DNMT3b, MeCP2, JmjCA, KDM2 and OSA changed significantly (p < 0.05) when the trochophore larvae were thawed, and then they reverted to the control levels at the D- and later larval developmental stages. However, the expression of other epigenetic regulator genes, namely, MBD2, DNMT1, CXXC1 and JmjD6, did not change at any post-thaw larval developmental stage. For the newly thawed trochophore larvae, the amount of methylated H3K4Me1 and H3K27Me1 significantly changed, and the expression of all Jumonji orthologs, except that of Jumonji5, significantly (p < 0.05) decreased. These epigenetic results agree with the data collected on larval performances (e.g., survival rate), suggesting that the effect period of the published cryopreservation technique on post-thaw larvae is short in C. gigas.

Alterations in Gene Expression and the Fatty Acid Profile Impact but Do Not Compromise the In Vitro Maturation of Zebrafish (Danio rerio) Stage III Ovarian Follicles after Cryopreservation

The vitrification of ovarian follicles is a strategic tool that may contribute to advances in aquaculture and the conservation of many important species. Despite the difficulties inherent to the cryopreservation of oocytes, some successful protocols have been developed for different species, but little is known about the capacity of oocytes to develop after thawing. Therefore, the profiles of the reproductive pathway genes and fatty acid membrane composition during the initial stages of development were analyzed in fresh ovarian follicles and follicles after the vitrification process. There were differences in the expression of the hypothalamic-pituitary-gonad axis genes during the follicular development in the control group as well as in the vitrified group. Similarly, alterations in the composition of fatty acids were observed after vitrification. Despite this, many alterations were observed in the vitrified group; more than half of the stage III ovarian follicles were able to grow and mature in vitro. Therefore, the vitrification of ovarian follicles may impact them at molecular and membrane levels, but it does not compromise their capability for in vitro maturation, which indicates that the technique can be a strategic tool for aquaculture.

Cryopreservation effect on DNA methylation profile in rainbow trout spermatozoa

Spermatozoa are the cells that are most commonly used for cryopreservation of valuable genetic resources in aquaculture. It is known that fish spermatozoa transmit to the embryo not only their genetic but also their epigenetic profile, especially DNA methylation. Therefore, any alteration of the DNA methylation profile in spermatozoa induces the risk of transmitting epigenetic alterations to the offspring. The aim of this study was to assess the effect of cryopreservation on DNA methylation in rainbow trout spermatozoa. To trigger variable cellular response after freezing-thawing, spermatozoa from mature males were cryopreserved with dimethyl sulfoxide, methanol or glycerol as cryoprotectant. We observed that dimethyl sulfoxide was the best to preserve thawed spermatozoa functions. Methanol only slightly preserved all the cellular parameters, while glycerol failed to protect motility and fertilization ability. The consequences on DNA methylation were assessed using Reduced Representation Bisulfite Sequencing (RRBS). Sperm cryopreservation did not thoroughly impact DNA methylation, although 335-564 differentially methylated cytosines were characterized depending on the cryoprotectant. Very few of them were shared between cryoprotectants, and no correlation with the extent of cellular damage was found. Our study showed that DNA methylation was only slightly altered after sperm cryopreservation, and this may render further analysis of the risk for the progeny very challenging.

The initial steps toward the formation of somatic tissue banks and cell cultures derived from captive Antillean manatee (Trichechus manatus manatus) skin biopsies

The declining population of the Antillean manatee caused by ecosystem degradation and rising pollution has prompted interest in developing conservation strategies for this species. Given this scenario, somatic tissue banks are important tools for acquiring knowledge about the species, as well as for obtaining somatic cells for biotechnological and ecotoxicological applications. Therefore, we aimed to assess the effects of slow freezing (SF) and solid-surface vitrification (SSV) of the dermis of captive Antillean manatees on the histology and ultrastructure of the tissue and cell viability in culture. While the SSV did not change the dermis thickness, the SF maintained the tissue proliferative potential, assessed by the nucleolar organizer region area, similar to noncryopreserved tissues. Moreover, both techniques reduced the number of fibroblasts and increased the percentage of collagen fibers. Nevertheless, only tissues cryopreserved with SF and noncryopreserved tissues were able to produce cells after in vitro culture. Although SF did not alter cell viability and proliferative activity, cells derived from cryopreserved tissues showed decreased metabolism, altered apoptosis, increased levels of reactive oxygen species, and mitochondrial membrane potential compared to cells from noncryopreserved tissues. In summary, we demonstrated for the first time that Antillean manatee somatic tissues can be cryopreserved by SF, and cells can be obtained after in vitro culture. Improvements in cryopreservation conditions, especially vitrification, of somatic samples are needed to increase the quality of somatic tissue banks in this species.

Effects of supplementation of cryopreservation media with cysteine on the post-thaw quality and fertility of brown-marbled grouper (Epinephelus fuscoguttatus) spermatozoa

The cryopreservation process is associated with the generation of excessive reactive oxygen species, which causes a series of cellular damage to spermatozoa. The objective of the current study was to investigate the effect of different concentrations of cysteine on post-thaw sperm quality of brown-marbled grouper sperm. Semen samples were frozen with cysteine supplemented at 0.5, 1, 2, 5, 10 mM and the control group (no additive). After thawing, sperm quality parameters were analyzed. In comparison to the control, cysteine treatment groups yielded relatively higher sperm total motility, progressive motility, and curvilinear velocity. Different concentrations of cysteine had no effect on average path velocity, straight linear velocity and viability (P > 0.05), while an increase in the concentration of cysteine resulted in a significant improvement in the mitochondrial membrane potential, SOD activity, and ATP content (P < 0.05). As for lipid peroxidation, the extent of which in cysteine treated spermatozoa was less than the control, although the differences were not statistically significant (P > 0.05). In terms of fertilizing capacity, a greater hatching rate (91.7 ± 1.2%) was obtained in thawed sperm treated with 2 mM cysteine, compared to the control (84.3 ± 4.2%; P < 0.05). Overall, it is concluded that the addition of cysteine is helpful in maintaining the function of frozen-thawed brown-marbled grouper sperm, which can be recommended as an effective antioxidant to improve the semen cryopreservation efficiency.

Effect of non-permeable cryoprotectant sucrose on the development of spotted knifejaw (Oplegnathus punctatus) embryos

In this study, the toxicity of sucrose to Oplegnathus punctatus embryos was evaluated. Embryos at the 4-6 somite, tail-bud, heart formation, and heart-beating stages were exposed to 0, 0.5, 1,1.5, 2, 2.5, or 3 M sucrose for 1 h. Survival rates of embryos at the tail-bud, heart formation, and heart-beating stages after rehydration for 1 h were not affected by treatment with 2 M sucrose (the maximum concentration). Embryos at the tail-bud, heart formation, and heart-beating stages were exposed to 2 M sucrose for 0, 30, 60, 90, 120, 150, or 180 min. Long-term developmental indicators, including rates of survival, hatching, swimming, and malformation, were evaluated for 4 days after rehydration. Based on the survival rates 10 min after rehydration, the longest tolerance time for embryos at the three stages was 120 min. Based on long-term developmental indicators, the longest tolerance times were 60 min at the tail-bud, 60 min at the heart formation stage and 30 min at the heart beating stage. The malformation rates increased as the treatment time increased. The malformation rates were 100% when embryos were exposed to sucrose for ≥120 min. Malformation was divided into larval and embryonic abnormality. As the exposure time increased for tail-bud stage embryos, the rate of larval malformation increased. Treatment at heart formation and heart-beating stages resulted in higher rates of failure to hatch at exposure time. Based on these results, toxicity tests of non-permeable cryoprotectant in embryos requires the observation of development for at least 2 days after rehydration. Based on long-term observation, it was concluded that dehydration before freezing was not the direct cause of larvae deformity that hatched from frozen-thawing embryo. These results provide a reference for the singly use of representative non-permeable cryoprotectant sucrose.

The Increasing Role of Short-Term Sperm Storage and Cryopreservation in Conserving Threatened Amphibian Species

Multidisciplinary approaches to conserve threatened species are required to curb biodiversity loss. Globally, amphibians are facing the most severe declines of any vertebrate class. In response, conservation breeding programs have been established in a growing number of amphibian species as a safeguard against further extinction. One of the main challenges to the long-term success of conservation breeding programs is the maintenance of genetic diversity, which, if lost, poses threats to the viability and adaptive potential of at-risk populations. Integrating reproductive technologies into conservation breeding programs can greatly assist genetic management and facilitate genetic exchange between captive and wild populations, as well as reinvigorate genetic diversity from expired genotypes. The generation of offspring produced via assisted fertilisation using frozen-thawed sperm has been achieved in a small but growing number of amphibian species and is poised to be a valuable tool for the genetic management of many more threatened species globally. This review discusses the role of sperm storage in amphibian conservation, presents the state of current technologies for the short-term cold storage and cryopreservation of amphibian sperm, and discusses the generation of cryo-derived offspring.

The Use of Ovarian Fluid as Natural Fertilization Medium for Cryopreserved Semen in Mediterranean Brown Trout: The Effects on Sperm Swimming Performance

D-532 fertilization solution is generally used to replace the water or ovarian fluid during artificial reproductive practices in salmonids due to its ability to boost sperm motility and increase fertilization rates compared with natural activation media. However, the maintenance of ovarian fluid in a reproductive microenvironment gives it the advantage of protecting the eggs from potential harmful factors from the external environment and simplifying the field operations related to its removal when D-532 is used alone. In light of this, the aim of the present study was to investigate in vitro, for the first time, the effect of ovarian fluid (OF 100%) on post-thaw sperm swimming performance of Mediterranean trout, comparing it with D-532 and a mixed solution of 50% D-532 and 50% ovarian fluid (OF 50%). The percentage of motile spermatozoa and movement duration was significantly increased in OF 100% and OF 50% compared with D-532. Sperm velocity was higher in D-532, but significant differences were recorded only with OF 100%. In conclusion, these results suggest that the presence of ovarian fluid alone or in combination with D-532 in an artificial microenvironment of reproduction represents a key factor in potentially increasing fertilization success when the frozen semen of Mediterranean brown trout is used.

Use of cryoprotectors and antioxidants in sturgeon semen cryopreservation

In recent years, the possibility of increasing the low cryoresistance of sturgeon sperm by using antioxidants in basic cryoprotective media has been studied. The goal of this work was to review the current literature on impact of the cryoprotectors, well-known antioxidants and new multifunctional compounds on the activity indicators and fertilizing capability of sperm, as well as on biomarkers of cryostress. A special attention is given to the radical scavenging activity of studied compounds in relation to the highly reactive oxygen species, to prevent and negate oxidative stress damage of sturgeon sperm. Also, new trends for future research through the application of novel polyfunctional antioxidants to sturgeon sperm cryopreservation were indicated.

The Effects of Cryopreservation on the Cell Ultrastructure in Aquatic Organisms

This review provides an update on the current state of cryopreservation studies coupled with ultrastructural observation. Research in these fields has evolved and advanced since its inception in the 1950s. Different techniques have different advantages, but the researcher's technical proficiency is also necessary to derive a sound conclusion. Sperm samples are the most widely studied specimen because they are less sensitive to freezing and have high fluidity in the membrane and low water content. Some studies have also investigated oocytes, embryos, larvae, and algae from aquatic species. Cryopreservation studies have formulated a method applicable to every species of interest to preserve their biodiversity and prevent extinction. However, the avoidance of cryoinjury because of intracellular ice formation is a species-specific challenge. More comprehensive studies on ultrastructural observation can assist in understanding the underlying mechanisms of failed cellular responses to cryopreservation. Thus, optimizing protocols and increasing the survival rates of thawed samples can improve current cryopreservation techniques. Nevertheless, investigations into the effects of freezing on organisms' ultrastructure remain limited, especially regarding aquatic organisms.

An automated modular open-technology device to measure and adjust concentration of aquatic sperm samples for cryopreservation

Repositories for aquatic germplasm are essential for safeguarding valuable genetic diversity for species relevant to aquaculture, biomedical research, and conservation. Development of aquatic germplasm repositories is impeded by a lack of standardization within laboratories and across the research community. Protocols for cryopreservation are often developed ad hoc and without close attention to variables, such as cell concentration, that strongly affect the success and reproducibility of cryopreservation. The wide dissemination and use of specialized tools and devices as open hardware can improve processing reliability and save costs. The goal of the present work was to develop and prototype a modular and open-technology approach to help to standardize the cell concentration of germplasm samples prior to cryopreservation. The specific objectives were to: 1) design and fabricate prototypes of the automated concentration measurement and adjustment system (CMAS), incorporating custom peristaltic pumps and optical evaluation modules, and 2) evaluate the performance of the CMAS with biological samples. Linear regression models were obtained for estimation of aquatic sperm concentration >108 cells/mL and for algae concentration > (3 × 105) cells/mL. Algae were diluted with extender medium by an automated process, resulting in a dilution precision of ±12.6% and ±6.7% in two trials, attaining means of 89% and 71% of the target cell concentration. The development of the CMAS as open technology can provide opportunities for community-level standardization in cryopreservation of aquatic germplasm and can invite new users, makers, and developers into the open-technology community. This will increase the reach and capabilities of much-needed aquatic germplasm repositories.

L-carnitine solution used on Rhamdia quelen thawed sperm activation boosts sperm movement, maintains larval quality, and permits to optimize the sperm use

The activation of cryopreserved sperm with solutions containing L-carnitine can improve sperm quality after thawing, owing to its involvement in several metabolic pathways. Sperm movement and viability for fertilization, hatching, and larval normality were assessed in Rhamdia quelen thawed sperm activated with L-carnitine solutions. Sperm from 24 males were cryopreserved in 0.25 mL straws. After thawing, the sperm movement was assessed by CASA (Computer-Assisted Sperm Analysis) in samples activated with distilled water containing 0.0 (control), 47.8, 96.2, 144.5, 192.3, and 240.7 mM L-carnitine, and another one with 79.9 mM D-fructose (control). Sperms from another 24 males were cryopreserved in an identical manner and used in the fertilization assays. Considering the sperm movement, fertilization assays were carried out using 0.0, 96.2, and 144.5 mM L-carnitine, and 79.9 mM D-fructose solutions. Greater motility and velocity were achieved with 144.5 mM L-carnitine at 28 and 18 s after activation, respectively. Linearity was not affected by time. The greater mean motility was provided by 144.5 mM as well as the greater mean velocity and linearity by 192.3 mM L-carnitine. Fertilization and hatching were not influenced; however, 144.5 mM L-carnitine and 79.9 mM D-fructose solutions produced more normal larvae. In summary, the L-carnitine solution increased sperm movement and maintained larval quality and production, similar to a conventional fructose activation solution.

Establishment of a Coilia nasus Gonadal Somatic Cell Line Capable of Sperm Induction In Vitro

Coilia nasus is an important economic anadromous migratory fish of the Yangtze River in China. In recent years, overfishing and the deterioration of the ecological environment almost led to the extinction of the wild resources of C.nasus. Thus, there is an urgent need to protect this endangered fish. Recently, cell lines derived from fish have proven a promising tool for studying important aspects of aquaculture. In this study, a stable C. nasus gonadal somatic cell line (CnCSC) was established and characterized. After over one year of cell culture (>80 passages), this cell line kept stable growth. RT-PCR results revealed that the CnGSC expressed some somatic cell markers such as clu, fshr, hsd3β, and sox9b instead of germ cell markers like dazl, piwi, and vasa. The strong phagocytic activity of CnGSC suggested that it contained a large number of Sertoli cells. Interestingly, CnGSC could induce medaka spermatogonial cells (SG3) to differentiate into elongated spermatids while co-cultured together. In conclusion, we established a C. nasus gonadal somatic cell line capable of sperm induction in vitro. This research provides scientific evidence for the long-term culture of a gonadal cell line from farmed fish, which would lay the foundation for exploring the regulatory mechanisms between germ cells and somatic cells in fish.

Post-thaw dilution of Rhamdia quelen sperm improves the reproductive success

The aim was to evaluate the effect of a post-thaw dilution of Rhamdia quelen sperm in 1.1% NaCl (325 mOsm kg^-1; pH 7.6; 24 °C) solution on the quality and reproductive capacity. Sperm from eight males were cryopreservation in nitrogen vapor at - 170 °C for 18 h in 0.25 mL straws in a freezing medium containing 5% fructose, 5% Powdered milk, and 10% methanol. The samples were thawed and post-thaw diluted (1:20) in NaCl solution or not (control). The higher spermatozoa velocities were observed in the post-thaw diluted samples (curvilinear (VCL) - 69 ± 11 µm s^-1; average path (VAP) - 45 ± 8 µm s^-1; straight-line (VSL) - 43 ± 8 µm s^-1) compared to the control (VCL - 47 ± 10 µm s^-1; VAP - 31 ± 6 µm s^-1; VSL - 30 ± 6 µm s^-1). Greater straightness (STR), progression (PROG), and beat cross frequency (BCF) were observed in the post-thaw diluted samples (STR - 96 ± 7%; PROG - 666 ± 128 µm; BCF - 42 ± 2 Hz) than in control (STR - 95 ± 5%; PROG - 463 ± 92 µm; BCF - 40 ± 2 Hz). The strongly curled tail was the only morphology change that differ between the post-thaw diluted (5 ± 2%) and control (2 ± 1%). Membrane integrity, mitochondrial activity, and normal larvae rate were not different between treatments. Fertilization and hatching were higher in the post-thaw diluted sperm (93 ± 3%; 82 ± 9%) when compared to control samples (65 ± 13%; 55 ± 17%). Were used oocytes from one female, limiting these results. The post-thaw dilution improved the sperm kinetics and reproductive parameters. Thus, this methodology can be included in the sperm cryopreservation protocol for R. quelen.

Restoring Genetic Resource through In Vitro Culturing Testicular Cells from the Cryo-Preserved Tissue of the American Shad (Alosa sapidissima)

Simple Summary

Cryopreservation and in vitro culture of germ cells are key techniques for the genetic resource preservation of the declining population of American shad. Two types of cryopreserved samples, namely testis pieces and testicular cells of American shad, were comparatively analyzed for cell viability. The results showed that the cell viability of the cryopreserved testis pieces was much higher than that of the cryopreserved testicular cells. The viability of the cells from the cryopreserved testis pieces ranged from 65.2 ± 2.2 (%) to 93.8 ± 0.6 (%), whereas the viability of the dissociated cells after cryopreservation was 38.5 ± 0.8 (%) to 87.1 ± 2.6 (%). Moreover, the testicular cells isolated from the post-thaw testicular tissue could be cultured and propagated in vitro. Our findings would benefit further investigations on genetic resource preservation and other manipulations of germ cells in a commercially and ecologically important fish species.

Abstract

Germ cells, as opposed to somatic cells, can transmit heredity information between generations. Cryopreservation and in vitro culture of germ cells are key techniques for genetic resource preservation and cellular engineering breeding. In this study, two types of cryopreserved samples, namely testis pieces and testicular cells of American shad, were comparatively analyzed for cell viability. The results showed that the cell viability of the cryopreserved testis pieces was much higher than that of the cryopreserved testicular cells. The viability of cells from the cryopreserved testis pieces ranged from 65.2 ± 2.2 (%) to 93.8 ± 0.6 (%), whereas the viability of the dissociated cells after cryopreservation was 38.5 ± 0.8 (%) to 87.1 ± 2.6 (%). Intriguingly, the testicular cells from the post-thaw testicular tissue could be cultured in vitro. Likewise, most of the cultured cells exhibited germ cell properties and highly expressed Vasa and PCNA protein. This study is the first attempt to effectively preserve and culture the male germ cells through freezing tissues in the American shad. The findings of this study would benefit further investigations on genetic resource preservation and other manipulations of germ cells in a commercially and ecologically important fish species.

Assessment of larval quality of two bivalve species, Crassostrea angulata and Chamelea gallina, exposed and cryopreserved with different cryoprotectant solutions

Marine bivalves are valuable resources, however, some shellfish populations are endangered due to factors such as anthropogenic pressure, pathologies or lack of reproduction synchrony. Portuguese oyster (Crassostrea angulata) and striped venus clam (Chamelea gallina) have high socio-economic value and their endangered natural populations require rehabilitation. Cryopreservation is a valuable method for the preservation and management of genetic resources for aquaculture and restocking. Larvae cryopreservation is particularly valuable since diploid organisms are obtained upon thawing. The objective of this work was the establishment of C. angulata and C. gallina D-larvae cryopreservation through the selection of permeant cryoprotectant in the freezing solution, namely ethylene glycol (EG) and dimethyl sulfoxide (Me₂SO). Cryoprotectants exposure showed that, in C. angulata, Me₂SO promoted significantly higher incidence of abnormalities and enhanced glutathione reductase activity when compared to control (larvae without cryoprotectant exposure) or even to EG treatment. However, for both species, EG significantly reduced D-larvae average path velocity (VAP). In C. angulata post-thaw D-larvae, EG treatment promoted significantly lower motility and velocity when compared to control and Me₂SO treatment. Superoxide dismutase (SOD) activity showed a reduction in C. angulata post-thaw D-larvae when compared to control, which was compensated by the enhancement of glutathione peroxidase (GPX) activity. In C. gallina post-thaw D-larvae, only motility, velocity and SOD activity were significantly lower than control. Therefore, the best treatment to cryopreserve C. angulata D-larvae was EG while for C. gallina Me₂SO produced better results. This work established for the first time D-larvae cryopreservation protocols for C. angulata and C. gallina.

Effects of Cryopreservation on Sperm with Cryodiluent in Viviparous Black Rockfish (Sebastes schlegelii)

Black rockfish is an economically important fish in East Asia. Little mention has been paid to the sperm cryopreservation in black rockfish. In this study, the optimal cryodiluent was selected from 48 combinations by detecting various sperm parameters. Transcriptome and methylome analysis were further performed to explore the molecular mechanism of inevitable cryoinjuries. The results showed that cryopreservation had negative effects on the viability, DNA integrity, mitochondrial activity, total ATPase and LDH of sperm even with optimal cryodiluent (FBS + 15% Gly). Transcriptome and methylome analysis revealed that the expression of 179 genes and methylation of 1266 genes were affected by cryopreservation. These genes were enriched in GO terms of death, G-protein coupled receptor signaling pathway, response to external stimulus and KEGG pathways of phospholipase D signaling pathway and xenobiotic and carbohydrate metabolism pathways. The role of PIK3CA and CCNA2 were highlighted in the protein-protein interaction network, and the sperm quality-related imprinted gene mest was identified among the 7 overlapping genes between transcriptome and methylome. Overall, the cryodiluent for black rockfish sperm was optimized, providing a feasible method for cryopreservation. The transcriptome and methylome data further demonstrated the underlying molecular mechanisms of cryoinjuries, proving clues for improvement of cryopreservation method of black rockfish.

The Protective Role of Melatonin in Sperm Cryopreservation of Farm Animals and Human: Lessons for Male Fish Cryopreservation

Simple Summary

In recent years, cryopreservation of fish sperm has been a rapidly evolving technique that contributes both to the improvement of genetic reproduction programs and the proper management of broodstock as well as to ensuring the viability of endangered species. However, this technique can cause significant damage to sperm, making the use of cryoprotectants and antioxidants in cryopreservation solutions imperative. The hormone melatonin has demonstrated positive effects on the cryopreservation of sperm in both farm animals and humans. Therefore, the plethora of research that has been conducted on animals and humans could be expanded to fish cryopreservation, making melatonin potentially a very promising alternative cryoprotectant.

Abstract

Cryopreservation is a technique that offers various advantages, especially in fish, among others, that makes the reproduction of species easier through a constant supply of sperm, synchronization of the gamete availability of both sexes, storage of semen for genetic improvement programs, reduction in the cost by eliminating the need to maintain male broodstock, and conserving the gametes of endangered species. However, freezing and warming procedures for cryopreservation lead to a reduction in the quality and viability of cryopreserved sperm because of oxidative stress. For this reason, the enrichment of extender media with antioxidants is a common method of cryopreservation of the semen of several fish species. Recently, many studies have been published for the protective role of antioxidants and especially of melatonin on male fertility preservation both in farm animals and humans, demonstrating the beneficial effects of melatonin as a sperm cryoprotectant. On the other hand, very few studies were conducted using melatonin as an antioxidant in different male fish species for semen cryopreservation. We conclude that the use of moderate concentrations of melatonin are beneficial to semen preservation, and the mechanisms through which melatonin acts positively on spermatozoa need to be further investigated to establish improvement protocols for cryopreservation in fish species.

Is catalase an effective additive to alleviate oxidative stress during cryopreservation of zebrafish sperm at the repository level?

The goal of this study was to investigate whether supplementation of cryoprotective medium with catalase (CAT), an antioxidation enzyme, is efficient for zebrafish sperm cryopreservation from the viewpoint of high-throughput genetic repository operations. Three cryoprotectants (10%, v/v), dimethylacetamide (DMA), dimethylformamide (DMF), and methanol were used. The objectives were to evaluate the effects of CAT on sperm motility, plasma membrane integrity, and concentration for: 1) fresh sperm at equilibration up to 60 min; 2) post-thaw sperm after cooling at 10, 20, and 40 °C/min), and 3) post-thaw fertilization and embryo survival rates. Catalase addition did not improve sperm motility, regardless of the cryoprotectants added. After 10-min exposure to DMA or methanol, membrane integrity was significantly decreased (70-75%) compared to controls. With catalase, sperm cells maintained membrane integrity and after 50 min equilibration, cell concentrations were maintained with CAT compared to cryoprotectant-only test groups. However, after cryopreservation and thawing, CAT did not affect the outcome of motility, membrane integrity, cell concentration, fertilization, or embryo survival assays. Analysis of cooling rates also indicated that CAT did not affect 3-hpf fertilization or 24-hpf survival rates. Overall, addition of CAT could provide some protection of sperm from oxidative stress before freezing, but not after thawing. We propose that decisions concerning routine use of CAT for repositories, especially those handling tens of thousands of frozen samples per year, would depend on whether efficient high-throughput operation, or specific research questions are programmatic goals.

Development of a Sperm Cryopreservation Protocol for Critically Endangered Mohashol, Tor tor (Hamilton)

This study dealt with the development of a sperm cryopreservation protocol of Tor tor. Sperm was collected from hormone-induced males and the concentration and pH of sperm were estimated as 4.3 ± 0.1 × 10¹⁰ cells/mL and 8.6 ± 0.2, respectively. Activation of sperm motility was evaluated in different osmolalities of NaCl solution where motility of sperm decreased with increasing osmolality of extenders, and was completely inhibited at 319 mOsmol/kg. Similarly, the swimming duration of activated sperm was affected as the osmolality of the extender increased. The duration of initial motility of sperm was recorded as 8.4 ± 0.4 minutes at 48 mOsmol/kg, while the highest motility was recorded as 68.0 ± 7.2 minutes at 128 mOsmol/kg. To evaluate the toxicity of cryoprotectants, sperm was incubated with dimethyl sulfoxide (DMSO) and methanol at 5%, 10%, and 15% concentrations, respectively, for 5-45 minutes. Alsever's solution with 5% and 10% DMSO produced better motility during 5-10 minutes of incubation and 15% DMSO seemed toxic to sperm. For the cryopreservation of sperm, Alsever's solution, egg yolk citrate, and urea egg yolk were used as extenders with DMSO and methanol. Alsever's solution with 10% DMSO provided the highest equilibration (90.0% ± 3.5%) and post-thaw (80.0% ± 3.5%) motility followed by that of 87.0% ± 2.0% and 79.0% ± 1.9% with egg yolk citrate plus DMSO, and 82.0% ± 2.6% and 78.0% ± 2.0% with urea egg yolk plus DMSO, respectively. The sperm cryopreservation protocol developed through this study can be applied for long-term preservation of genetic materials of the critically endangered T. tor, and eventually, it will be an effective tool for protecting them from extinction.

Efecto de etilenglicol y leche en polvo en la criopreservación de semen de bocachico Prochilodus magdalenae

Bocachico Prochilodus magdalenae es una especie endémica y la más importante de la pesquería continental colombiana. No obstante, sus capturas han disminuido aproximadamente el 67% en los últimos cuarenta años, por tanto ha sido categorizada como vulnerable a la extinción. La criopreservación de semen, es una herramienta biotecnológica de conservación por tanto el objetivo del presente estudio fue evaluar la criopreservación de semen de bocachico con etilenglicol (EG) y leche en polvo descremada (LP). La solución crioprotectora estuvo compuesta por EG (6, 8 o 10%), LP (3, 5 o 7%) y glucosa 6%. La calidad del semen descongelado se evaluó con un software tipo CASA (computer assisted semen analysis). El porcentaje de inclusión de EG, no afectó significativamente ninguno de los parámetros de calidad seminal evaluados (p>0,05), a excepción de la tasa de eclosión (p<0,05); mientras que, la LP afectó significativamente el porcentaje de espermatozoides estáticos (p<0,05) y las tasas de fertilización y eclosión (p<0,01). La mayor movilidad total se obtuvo cuando EG se incluyó a 10% y la LP a 7% (38,4±18,4%) (p<0,05); pero las mayores tasas de fertilización (54,3-64,2%) y eclosión (47,7-57,5%) se obtuvieron cuando EG se incluyó a 6 u 8% y la LP se incluyó a la menor concentración evaluada (3%), sin observarse diferencia significativa entre estos tratamientos (p>0,05). Los resultados permiten concluir que la combinación EG 6% con LP 3% permiten la criopreservación de semen de Prochilodus magdalenae de buena calidad y capacidad fecundante.  

Effect of Trehalose and Sucrose in Post-thaw Quality of Crassostrea angulata Sperm

Sperm cryopreservation can be a helpful tool in reproductive management and preservation of biodiversity. However, the freezing methodologies lead to some damage in structure and function of cells that may compromise post-thaw sperm activity. Cryoprotectant supplementation with sugars proved to be a successful strategy to reduce cryodamage in sperm of several species, once allowing to stabilize the plasma membrane constituents. Therefore, this study intends to understand the effects of sugars in the plasma membrane, DNA integrity, and oxidative response during Portuguese oyster sperm cryopreservation. Three cryoprotectants solutions with an initial concentration of 20% dimethyl sulfoxide (DMSO) and 20% DMSO complemented with 0.9 M trehalose or sucrose in artificial seawater were employed. Sperm samples of mature males were individually collected and diluted 1:10 (v/v) in artificial seawater followed by addition of cryoprotectants [1:1 (v/v)]. Thereafter, sperm was loaded into 0.5 ml straws, maintained at 4°C for 10 min, frozen in a programmable biofreezer at -6°C/min from 0 to -70°C, and stored in liquid nitrogen. Samples were thawed in a 37°C bath for 10 s. Several techniques were performed to evaluate post-thaw quality. Sperm motility and DNA integrity were analyzed by using computer-assisted sperm analysis (CASA) software and comet assay. Flow cytometry was employed to determine membrane and acrosome integrity and to detect intracellular reactive oxygen species (ROS) and apoptosis activity. Lipid peroxidation was determined by malondialdehyde (MDA) detection by using spectrophotometry. Sperm antioxidant capacity was evaluated through glutathione peroxidase, glutathione reductase, and superoxide dismutase. Motility was not affected by the extenders containing sugars; these compounds did not reduce the DNA damage. However, both the trehalose and sucrose protected plasma membrane of cells by increasing cell viability and significantly reducing MDA content. The same finding was observed for the ROS, where live cells registered significantly lower levels of ROS in samples cryopreserved with sugars. The activity of antioxidant enzymes was higher in treatments supplemented with sugars, although not significant. In conclusion, the addition of sugars seems to play an important role in protecting the Crassostrea angulata sperm membrane during cryopreservation, showing potential to improve the post-thaw sperm quality and protect the cells from cryoinjuries.

Effect of egg yolk of free-range chicken and methanol as a cryoprotective agent for the sperm preservation of cyprinid fish, Neolissochilus soroides (Valenciennes, 1842)

The objective of this study was to determine the optimum concentration of egg yolk of free-range chicken as a cryoprotective agent on cyprinid fish, Neolissochilus soroides sperm after 48 h frozen. One level of methanol (10%) combined with six levels of egg yolk solution (0%, 5%, 10%, 15%, 20% and 25%) were tested. Fish Ringer's solution was used as an extender. The diluted sperm was equilibrated for 10 min at 5 °C, then kept at -10 °C temperature for 48 h. Sperm was thawed for 1 min at 40 °C. Spermatozoa viability, abnormality, and fertilization rates were analysed afterwards. The one-way ANOVA showed that the combination methanol with several concentrations of egg yolk solution had a significant effect on spermatozoa viability, abnormality, and fertilization rates (P < 0.05) by improving semen character. The study revealed that the 5% egg yolk solution combined with 10% methanol resulted in the highest rates of viability (82.13 ± 1.75%) and fertility rates (92.96 ± 1.94%), with the lowest abnormality (25.25 ± 2.22%). A 5% egg yolk solution was identified as the best cryoprotective agent for N. soroides spermatozoa preservation at -10 °C for 48 h.

Effects of Inositol Supplementation in Sperm Extender on the Quality of Cryopreserved Mesopotamian Catfish (Silurus triostegus, H. 1843) Sperm

In this study, the effects of supplemented inositol on sperm extenders were examined on the spermatozoa motility rate and duration, total antioxidant and oxidant status, apoptotic spermatozoa and DNA damage, during the sperm post-thaw process of Mesopotamian Catfish (Silurus triostegus, H. 1843). The semen was frozen in diluents containing different inositol concentrations (5, 10, 20 and 40 mg). Increasing levels of inositol linearly improved the spermatozoa motility rate and duration significantly (p < 0.05). MDA and TOS were linearly decreased, however, TAS and GSH linearly increased (p < 0.05). The increasing inositol levels resulted in a linear and quadratic decrease in DNA damage in the comet assay, 8-hydroxydeoxyguanosine and the determined percentage of apoptotic spermatozoa (p < 0.05). These results suggest that there are many positive effects of the use of supplemental inositol on enhancing sperm cryopreservation efficiency in Silurus triostegus.

Supplementation of the freezing medium with Coenzyme Q10 attenuates oxidative stress and improves function of frozen-thawed giant grouper (Epinephelus lanceolatus) spermatozoa

Incorporation of Coenzyme Q10 (CoQ10) to the freezing medium provides advantageous effect for sperm cryopreservation in a variety of animal species, yet which has not been tested in giant grouper (Epinephelus lanceolatus). This research was designed to elucidate if CoQ10 could be used as a potential additive to improve giant grouper sperm quality after cryopreservation. After the process of freezing and thawing, various sperm quality parameters including motility, viability, apoptosis, mitochondrial membrane potential (MMP), intracellular reactive oxygen species (ROS) generation, DNA fragmentation as well as fertilization rate were evaluated with CoQ10 added at concentrations of 0, 25, 50 and 100 μM. Compared to the control group (0 μm), addition of CoQ10 in the medium yielded significantly higher total motility and curvilinear velocity, whereas the progressive motility, straight-line velocity and average path velocity were not differ from each other. An obvious improvement in viability was observed in spermatozoa cryopreserved with 25 and 50 μM CoQ10, while the apoptosis rate in CoQ10 treated groups (25, 50 and 100 μM) exhibited significantly lower values than that of the control. Besides, the production of ROS was significantly decreased with CoQ10 addition groups when compared with the control. In consistent with the improvement in antioxidant defense, CoQ10 supplementation in the medium also enhanced mitochondrial activity and reduced DNA fragmentation. In addition, freezing medium supplemented with CoQ10 also improved the fertilization success, a significantly higher fertilization rate was recorded at the concentration of 50 μM, but this value was not differ from that of 25 μM. Overall, the antioxidant CoQ10 provided an obvious beneficial effect on post-thaw quality of giant grouper spermatozoa. It was concluded that the optimal concentration of CoQ10 is 50 μM in the freezing medium.

Development of alternative and sustainable methodologies in laboratory research on sea urchin gametes

The aim of the present work is to develop a laboratory-scaled methodology for an on-demand supply of semen from the sea urchin Paracentrotus lividus. Firstly, sea urchin specimens were acclimatized to the long-term rearing in a recirculating aquaculture system and gonad maturation was obtained under controlled conditions. Semen samples were then collected from mature sea urchins and cryopreserved. Finally, post-thawing motility was evaluated, to verify whether the cryopreserved semen had maintained enough viability to be used in laboratory activities. The post-thawing motility parameters remained quite unchanged for up to 60 min after activation; moreover, the semen even retained the ability of motility activation for 60 min after thawing. This motility pattern makes the use of cryopreserved semen a feasible option in spermiotoxicity bioassays. The preliminary ecotoxicity test, carried out using motility parameters as endpoints, showed sensitivity levels to cadmium falling in the same order of magnitude as those recorded for fresh sea urchin semen and for cryopreserved sea bream semen. . Therefore, semen samples produced and stored according to the developed methodology described in this paper, can be considered a promising and sustainable alternative to those collected from mature sea urchins harvested in the field.

Production of functional sperm from cryopreserved testicular germ cells following intraperitoneal transplantation into allogeneic surrogate in yellowtail (Seriola quinqueradiata)

The aim of this study was to establish a method for the cryopreservation of spermatogonia of the yellowtail (Seriola quinqueradiata), which is the most commonly farmed fish in Japan. Testicular cells were prepared by enzymatic dissociation of testicular fragments containing an abundance of type A spermatogonia and were added to cryomedium containing dimethyl sulfoxide (DMSO), ethylene glycol, glycerol, or propylene glycol at concentrations of 0.5-2.5 M. The cells were then frozen and stored in liquid nitrogen for 3 days. After thawing, their survival and transplantability were evaluated. Testicular cells were most successfully cryopreserved in 1.0 M DMSO as indicated by survival of 34% of cells. Furthermore, in situ hybridization using the yellowtail vasa probe showed that these recovered cells contained a similar proportion of germ cells to fresh testicular cells before freezing. Transplantation of the recovered cells into the peritoneal cavities of allogeneic larvae resulted in 94% of surviving recipients having donor-derived germ cells in their gonads after 28 days. Sperm were then collected from seven randomly selected recipients once they reached 2 years of age and used to fertilize wild-type eggs, which led to an average of 26% of the first filial (F1) offspring being derived from donor fish, as confirmed through the use of microsatellite markers. Thus, we successfully cryopreserved yellowtail spermatogonia and produced functional sperm via intraperitoneal transplantation into allogeneic recipients.

Embryonic fate after somatic cell nuclear transfer in non-enucleated goldfish oocytes is determined by first cleavages and DNA methylation patterns

Reducing the variability in nuclear transfer outcome requires a better understanding of its cellular and epigenetic determinants, in order to ensure safer fish regeneration from cryobanked somatic material. In this work, clones from goldfish were obtained using cryopreserved fin cells as donor and non-enucleated oocytes as recipients. We showed that the high variability of clones survival was not correlated to spawn quality. Clones were then characterized for their first cleavages pattern in relation to their developmental fate up to hatching. The first cell cycle duration was increased in clones with abnormal first cleavage, and symmetric first two cleavages increased clone probability to reach later on 24 h- and hatching-stages. At 24 h-stage, 24% of the clones were diploids and from donor genetic origin only. However, ploidy and genetic origin did not determine clones morphological quality. DNA methylation reprogramming in the promoter region of pou2, nanog, and notail marker genes was highly variable, but clones with the nicest morphologies displayed the best DNA methylation reprogramming. To conclude, non-enucleated oocytes did allow authentic clones production. The first two cell cycles were a critical determinant of the clone ability to reach hatching-stage, and DNA methylation reprogramming significantly influenced clones morphological quality.

Characteristics and Cryopreservation of Semen of Sex-Reversed Females of Salmonid Fish

Sex reversal has been used as a breeding strategy by salmonid fish to produce genetically and phenotypically single sex populations. Production of all-female fish has great importance for the creation of monosex female triploids of salmonid fish, which are valued for their sterility, lack of female maturation, and larger commercial size. Among salmonids, the majority of rainbow trout (Oncorhynchus mykiss) production is based on all-female production with a high proportion of all-female triploid production in Europe. The main aim of this review is to present the recent knowledge regarding sex-reversed females (SRFs) of salmonid fish. We discuss the methods of sex reversal as well as their effects on the morphology and histology of the reproductive tract. We focus on the characteristics of SRF semen as well as the factors determining semen quality. The lower quality of SRF sperm compared to that of normal males has resulted in the need for the artificial maturation of semen. Most importantly, methods of semen storage-both short-term and long-term (cryopreservation)-that can improve hatchery operations are presented with the special emphasis on recent progress in development of efficient cryopreservation procedures and use of cryopreserved semen in hatchery practice. Moreover, we also address the emerging knowledge concerning the proteomic investigations of salmonid sperm, focusing primarily on the proteomic comparison of normal male and SRF testicular semen and presenting changes in SRF rainbow trout sperm proteome after in vitro incubation in artificial seminal plasma.

Strengthening the global network for sharing of marine biological collections: recommendations for a new agreement for biodiversity beyond national jurisdiction

Biological collections are fundamental to marine scientific research and understanding of biodiversity at various scales. Despite their key importance, sample collections and the institutes that house them are often underfunded and receive comparatively little attention in the discussions associated with global biodiversity agreements. Furthermore, access to collections can be limited by inadequate systems, infrastructure, and networks. With negotiations underway for a new implementing agreement on biodiversity beyond national jurisdiction, marine genetic resources (MGR), including questions on the sharing of benefits, remains the most debated and contentious element. Disparities remain between States regarding access to and utilization of marine biological samples (including MGR) from areas beyond national jurisdiction. Addressing capacity gaps related to collections could provide a point of agreement during negotiations and enhance global inclusivity in access to and utilization of MGR. Here, we examine both existing capacity and regional gaps in marine collections. We propose the strengthening of a distributed network of marine biological collections, building on existing initiatives and emphasizing best practices to bridge regional gaps. Our recommendations include: promoting scientific best practice for the curation of collections; alignment with ocean observing, and sampling initiatives; a potential pairing scheme for collections in developing and developed States; raising awareness of collections and benefits to marine science including through a global registry/directory; and promoting sustainable funding mechanisms to support collections and sustain global generation of contributors and users.

Cryopreservation of Marine Invertebrates: From Sperm to Complex Larval Stages

Marine invertebrates represent the vast majority of marine biodiversity; they are extremely diverse playing a key role in marine ecosystems, thus playing an important role at the socioeconomic level. Some invertebrates such as sea urchins, ascidians, and horse-shoe crabs are very well-known model organisms for research and biocompound discovery. In this chapter we revisit the importance of cryopreservation for the conservation and rational use in research, fisheries management, or aquaculture and provide comprehensive protocols for the cryopreservation of sperm, embryos, and larvae.

Major challenges in cryopreservation of sea urchin eggs

Cryopreservation of gametes, embryos and larvae of marine invertebrates has been investigated in many studies throughout the years. There are many favorable studies on sperm cryopreservation but oocytes are still under research as no successful results have been sustainably obtained for this type of cells. The preservation of both maternal and paternal gametes separately would provide a reliable source of genetic material for their application to conservation, aquaculture and fundamental research. Unfortunately to date, it has not been possible to cryopreserve eggs from marine organisms. The aim of this review is to go over the factors that have been historically considered as obstacles for oocyte cryopreservation in aquatic organisms and discern those that may specifically apply to eggs of the sea urchin Paracentrotus lividus.

Effect of melatonin supplementation to a cytoprotective medium on post-thawed Brycon orbignyanus sperm quality preserved during different freezing times

The aim of the present study is to verify the viability of frozen B. orbignyanus sperm cells after freezing with dilution media containing different concentrations of the melatonin and after different freezing times. Semen from 15 males was collected and pooled as five pools from three random animals. Oocytes (100) from three females were separately used for fertilization. There were three treatments: (C) Control Medium: 90% of extender Beltsville thawing solution (5% concentration) + 10% methylglycol (MG); (M1) Control Medium + 1 mM melatonin; and (M2) Control Medium + 2 mM melatonin. Sperm samples were diluted in media at a final proportion of 1:4 [125 μl sperm (25% V/V) + 337.5 μl BTS (65% V/V) + 37.5 μl MG (10% V/V)]. Melatonin was added at final solution. Three Dry shipper freezing times were used: T1 (15 min), T2 (12 h) and T3 (24 h). The samples were transferred, stored in a cryobank and thawed in a water bath at 60 °C for 5 s and evaluated concerning viability, morphology and fertilization rate. B. orbignyanus semen frozen in M2 presented the highest fertilization rate (8.40 ± 2.54%). The highest vitality (85.2 ± 2.8%), motility (64.63 ± 8.3%), motility duration (84.22 ± 11.4 s) and progressive motility (17.01 ± 1.2%) rates were maintained for M2. The highest number of altered cells was observed in C (57.4 ± 5.9%). Melatonin at 2 mmol L^-1 associated with the cryoprotectant methylglycol in cryopreservation could be used to improve a cryobank for endangered Brycon orbignyanus populations.

The systematic development and optimization of large-scale sperm cryopreservation in northern pike (Esox lucius)

In our study, a systematic development of a new large-scale sperm cryopreservation protocol was carried out in northern pike (Esox lucius). The effect of 2 sugar based (glucose and trehalose) extenders, 3 dilution ratios (1:3, 1:9 and 1:19) 2 vol straws (0.5 and 5 mL) and a 10 mL cryotube, 2 different cryopreservation methods (Polystyrene box-P. box and Controlled Rate Freezer-CRF), as well as 3 different thawing periods (3, 3.5 and 4 min) were investigated on the motility of thawed sperm. The glucose based extender showed significantly higher pMOT (1:3-18 ± 16%, 1:9-20 ± 13%, 1:19-16 ± 12%) at all dilution ratios than in the trehalose based extender (1:3-0.3 ± 1%, 1:9-1±1%, 1:19-4±2%). A similar tendency was recorded in VCL and STR at a ratio 1:3 and 1:9. No significant difference was measured in sperm movement between the P. box and CRF using the 0.5 mL straw. Similarly no significant difference was observed in all motility parameters with 10 mL cryotube frozen in CRF at a ratio 1:3-1:19. An effective and short thawing period (3 min) was experimentally specified for the 10 mL cryotube cryopreserved in the CRF. In all large-scale cryopreservation methods, high pMOT (straw CRF: 57 ± 10%, straw P. box: 50 ± 9%, cryotube CRF: 41 ± 10%), and STR were measured, and no significant difference was recorded in all motility parameters. Our results demonstrate the effectiveness of our newly developed extender and the applicability of 3 different large-scale cryopreservation methods in pike sperm. Our protocols could be new prospective candidates for future exploitation in hatchery practice.

Translation of Cryobiological Techniques to Socially Economically Deprived Populations—Part 1: Cryogenic Preservation Strategies

Use of cold for preservation of biological materials, avoidance of food spoilage and to manage a variety of medical conditions has been known for centuries. The cryobiological science justified these applications in the 1960s increasing their use in expanding global activities. However, the engineering and technological aspects associated with cryobiology can be expensive and this raises questions about the abilities of resource-restricted low and middle income countries (LMICs) to benefit from the advances. This review was undertaken to understand where or how access to cryobiological advances currently exist and the constraints on their usage. The subject areas investigated were based on themes which commonly appear in the journal Cryobiology. This led in the final analysis for separating the review into two parts, with the first part dealing with cold applied for biopreservation of living cells and tissues in science, health care and agriculture, and the second part dealing with cold destruction of tissues in medicine. The limitations of the approaches used are recognized, but as a first attempt to address these topics surrounding access to cryobiology in LMICs, the review should pave the way for future more subject-specific assessments of the true global uptake of the benefits of cryobiology.

Development stage of cryopreserved mussel (Perna canaliculus) larvae influences post-thaw impact on shell formation, organogenesis, neurogenesis, feeding ability and survival

Cryopreservation of genetic material from farmed aquatic species is a valuable technique to advance selective breeding programs for stock improvement. In this study, effects of cryopreservation on development of trochophore and D-stage larvae of Greenshell™ mussel (Perna canaliculus) were evaluated through histology, light microscopy, scanning electron microscopy, and confocal microscopy. Larvae of both life stages were motile immediately post-thawing, but survival declined rapidly from 4 days post-fertilisation (dpf). At 18 dpf, ~23% of non-cryopreserved control larvae had progressed to the pediveliger stage, while <1% of cryopreserved larvae had survived. Control larvae grew faster and larger, and consumed more food than larvae cryopreserved at either life stage (trochophore or D-stage). Settlement competency was achieved in the control larvae at 21 days post-fertilization, with most remaining individuals developing eye spots. Organogenesis was delayed in all cryopreserved larvae, and eyespots did not appear at all. Neurogenesis was stunted in cryopreserved trochophore larvae but seemed to progress almost normally in their cryopreserved D-stage counterparts. Developing abnormalities in shell morphology rapidly became apparent in all mussels post-thaw, with trochophore larvae being most highly afflicted. These delays in organogenesis and overall development are indicative of cryo-injuries sustained at a cellular level. Our results show that D-stage larvae are somewhat more resilient to cryopreservation than trochophore larvae. D-larvae are good life-stage candidates for cryobanking genetic resources in this species because there is generally an excess of larvae from selective breeding family crosses and these can be banked and stored for later use. Further on-going research aims to improve the long-term viability of cryopreserved D-larvae for successful rearing.

Sperm collection and storage for the sustainable management of amphibian biodiversity

Current rates of biodiversity loss pose an unprecedented challenge to the conservation community, particularly with amphibians and freshwater fish as the most threatened vertebrates. An increasing number of environmental challenges, including habitat loss, pathogens, and global warming, demand a global response toward the sustainable management of ecosystems and their biodiversity. Conservation Breeding Programs (CBPs) are needed for the sustainable management of amphibian species threatened with extinction. CBPs support species survival while increasing public awareness and political influence. Current CBPs only cater for 10% of the almost 500 amphibian species in need. However, the use of sperm storage to increase efficiency and reliability, along with an increased number of CBPs, offer the potential to significantly reduce species loss. The establishment and refinement of techniques over the last two decades, for the collection and storage of amphibian spermatozoa, gives confidence for their use in CBPs and other biotechnical applications. Cryopreserved spermatozoa has produced breeding pairs of frogs and salamanders and the stage is set for Lifecycle Proof of Concept Programs that use cryopreserved sperm in CBPs along with repopulation, supplementation, and translocation programs. The application of cryopreserved sperm in CBPs, is complimentary to but separate from archival gene banking and general cell and tissue storage. However, where appropriate amphibian sperm banking should be integrated into other global biobanking projects, especially those for fish, and those that include the use of cryopreserved material for genomics and other research. Research over a broader range of amphibian species, and more uniformity in experimental methodology, is needed to inform both theory and application. Genomics is revolutionising our understanding of biological processes and increasingly guiding species conservation through the identification of evolutionary significant units as the conservation focus, and through revealing the intimate relationship between evolutionary history and sperm physiology that ultimately affects the amenability of sperm to refrigerated or frozen storage. In the present review we provide a nascent phylogenetic framework for integration with other research lines to further the potential of amphibian sperm banking.

Ultraestrutura e criopreservação de sêmen de jundiá amazônico (Leiarius marmoratus) em cativeiro

RESUMO Os objetivos do presente estudo foram analisar a ultraestrutura do espermatozoide do jundiá amazônico e avaliar a sua criopreservação com três agentes crioprotetores (metanol 10%, DMSO 10% e etilenoglicol 10%) e duas soluções ativadoras (NaCl 0,29% e NaHCO3 1%). Como diluente, foi utilizada uma solução de glicose a 5%, sendo o sêmen envasado em palhetas de 0,25mL e congelado em vapor de nitrogênio (botijão dry shipper). No sêmen fresco, o espermatozoide apresentou comprimento de 25,46±2,54μm, cabeça esférica (1,51±0,18μm), ausência de acrossoma, peça intermediária com formato cônico (0,93±0,17μm), ligeiramente assimétrica, com presença de vesículas, e flagelo único (21,48±2,45μm). O sêmen descongelado apresentou valores mais altos (P<0,05) para duração, vigor e taxa de motilidade espermática com os crioprotetores metanol 10% e DMSO 10%. A duração da motilidade espermática foi maior (P<0,05) com o ativador NaHCO3 1% (21-96 s). O sêmen de Leiarius marmoratus criopreservado com DMSO e metanol apresentou, respectivamente, 7,32±4,21% e 8,94±6,69% de taxa de motilidade. No entanto, os resultados não foram satisfatórios para estabelecer um protocolo para a espécie.

DNA methylation stability in fish spermatozoa upon external constraint: Impact of fish hormonal stimulation and sperm cryopreservation

Highly differentiated mature spermatozoa carry not only genetic but also epigenetic information that is to be transmitted to the embryo. DNA methylation is one epigenetic actor associated with sperm nucleus compaction, gene silencing, and prepatterning of embryonic gene expression. Therefore, the stability of this mark toward reproductive biotechnologies is a major issue in animal production. The present work explored the impact of hormonal induction of spermiation and sperm cryopreservation in two cyprinids, the goldfish (Carassius auratus) and the zebrafish (Danio rerio), using LUminometric Methylation Assay (LUMA). We showed that while goldfish hormonal treatment did increase sperm production, it did not alter global DNA methylation of spermatozoa. Different sperm samples repeatedly collected from the same males for 2 months also showed the same global DNA methylation level. Similarly, global DNA methylation was not affected after cryopreservation of goldfish spermatozoa with methanol, whereas less efficient cryoprotectants (dimethylsulfoxide and 1,2-propanediol) decreased DNA methylation. In contrast, cryopreservation of zebrafish spermatozoa with methanol induced a slight, but significant, increase in global DNA methylation. In the less compact nuclei, that is, goldfish fin somatic cells, cryopreservation did not change global DNA methylation regardless of the choice of cryoprotectant. To conclude, global DNA methylation is a robust parameter with respect to biotechnologies such as hormonal induction of spermiation and sperm cryopreservation, but it can be altered when the best sperm manipulation conditions are not met.