Cryopreservation of sperm in farmed Australian greenlip abalone Haliotis laevigata

Physiological evaluation of seasonal sperm quality in a biannual spawner, Pacific abalone: Effects on in-vitro fertilization and cryotolerance

Pacific abalone, Haliotis discus hannai, is a highly valuable gastropod mollusk commonly found in Southeast Asia. The present study aims to analyze the seminal plasma quality, sperm quality, and cryotolerance of the Pacific abalone sperm during its reproductive season. The seminal plasma quality was evaluated by analyzing biochemical and metabolite composition, enzymatic activity (superoxide dismutase, catalase, and glutathione), and lipid peroxidation (LPO) activity. The sperm quality was evaluated by analyzing motility, concentration, volume, ATP content, acrosome integrity (AI), plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), DNA integrity, and fertilization potential. The cryotolerance capacity was evaluated by analyzing post-thaw motility, AI, PMI, MMP, and DNA integrity. Seminal plasma osmolarity was significantly higher (1123.3 ± 1.5 mOsmL-1) in May compared to other reproductive periods, with Cl- (516.8 ± 0.5 mM) and Na+ (460.2 ± 0.4 mM) as the dominant ions. The seminal plasma pH remained constant at 6.8 throughout the reproductive season. Improved enzymatic activity and lower LPO were detected in May or June. Sperm quality indicators were similar in May and June, except for sperm production. The fertilization potential (May: 93.0 ± 4.4%, June: 86.0 ± 7.2%) and hatching rate (May: 86.6 ± 5.78%, June: 82.3 ± 3.2%) of Pacific abalone were significantly higher in May or June than they were in other reproductive seasons. The motility (May: 50.19 ± 2.35%, June: 49.96 ± 1.60%), AI (May: 44.02 ± 3.46%, June: 42.16 ± 3.61%), PMI (May: 54.12 ± 3.29%, June: 52.82 ± 2.58%), and MMP (May: 44.02 ± 3.46%, June: 42.16 ± 3.61%) of the cryopreserved sperm were similar in May and June compared with those preserved in other reproductive seasons. The DNA integrity of the cryopreserved sperm was similar in May (80.3 ± 6.7%) or June (78.9 ± 7.4%) and had a higher cryotolerance than in other reproductive seasons. Hence, it can be suggested that May and/or June are suitable periods for sperm physiology experiments, artificial reproduction, and sperm cryopreservation of Pacific abalone.

Saccharides Influence Sperm Quality and Expressions of Motility and Fertilization-Associated Genes in Cryopreserved Sperm of Pacific Abalone, Haliotis discus hannai

Pacific abalone, Haliotis discus hannai, is a highly commercial seafood in Southeast Asia. The present study aimed to determine the influence of saccharides and vitamins on post-thaw sperm quality, ATP content, fertilization capacity, hatching capacity, and mRNA content of motility and fertilization-associated genes of Pacific abalone. Sperm cryopreserved using saccharides improved the post-thaw sperm quality including motility, acrosome integrity (AI), plasma membrane integrity (PMI), and mitochondrial membrane potential (MMP). However, vitamins (l-ascorbic acid) did not result in any significant improvement in sperm quality. Sperm cryopreserved using saccharides also improved ATP content, DNA integrity, and mRNA content of motility and fertilization-associated genes of post-thaw sperm than sperm cryopreserved without saccharides. Among sperm cryopreserved using different saccharides, post-thaw sperm quality indicators (except PMI) and mRNA content of motility and fertilization-associated genes did not show significant differences between sperm cryopreserved using 3% sucrose (S) combined with 8% dimethyl sulfoxide (DMSO) and sperm cryopreserved using 1% glucose (G) combined with 8% ethylene glycol (EG). However, sperm cryopreserved using 3% S + 8% DMSO showed higher post-thaw sperm quality (motility: 58.4 ± 2.9%, AI: 57.1 ± 3.2%, PMI: 65.3 ± 3.3%, and MMP: 59.1 ± 3.2%), ATP content (48.4 ± 1.8 nmol/ml), and % DNA in tail (2.09 ± 0.20%) than sperm cryopreserved using other saccharides. When sperms were cryopreserved using 3% S + 8% DMSO, the mRNA content of motility (heat shock protein 70, HSP70; heat shock protein 90, HSP90; protein kinase A, PKA-C; axonemal protein 66.0, Axpp66.0; and tektin-4) and fertilization-associated (sperm protein 18 kDa, SP18 kDa) genes were higher than in sperm cryopreserved using other saccharides. However, changes in the mRNA contents of these genes were insignificant between sperm cryopreserved using 3% S + 8% DMSO and 1% G + 8% EG. Taken together, these results indicate that cryopreservation using 3% S + 8% DMSO can improve post-thaw sperm quality and mRNA contents better than other examined cryoprotectants. The present study suggests that 3% S + 8% DMSO is a suitable cryoprotectant for sperm cryopreservation and molecular conservation of this valuable species.

Antioxidant Activity and Oxidative Stress-Oriented Apoptosis Pathway in Saccharides Supplemented Cryopreserved Sperm of Pacific Abalone, Haliotis discus hannai

The Pacific abalone Haliotis discus hannai is a highly commercialized seafood in Southeast Asia. The aim of the present study was to determine the antioxidant activity and oxidative stress-oriented apoptosis pathway in saccharides supplemented cryopreserved sperm of Pacific abalone. Cryopreserved sperm showed impaired antioxidant defenses due to the reduced mRNA abundance of antioxidant genes (CAT, Cu/Zn-SOD, Mn-SOD, GPx, GR, and BCL-2), apoptosis inhibitor (HSP70, and HSP90) gene, and enzymatic antioxidant activity compared to fresh sperm. Such impaired antioxidant defenses caused an increase in the mRNA expression of apoptosis genes (Bax, and Caspase-3), finally leading to apoptosis. The impaired antioxidant defense also increased O₂^•− production and lipid peroxidation (MDA) levels, which further accelerated apoptosis. Considering all the experimental findings, an apoptosis pathway of cryopreserved sperm has been adopted for the first time. Specifically, sperm cryopreserved using 3% sucrose combined with 8% dimethyl sulfoxide (DMSO) showed improved mRNA stability, enzymatic activity, and DNA integrity with reduced O₂^•− production and MDA levels compared to sperm cryopreserved with the other types of examined cryoprotectants (8% ethylene glycol + 1% glucose, 6% propylene glycol + 2% glucose, 2% glycerol + 3% glucose, and 2% methanol + 4% trehalose). The present study suggests that 3% sucrose combined with 8% DMSO is suitable to cryopreserve the sperm of this valuable species for molecular conservation.

Effects of Antifreeze Protein III on Sperm Cryopreservation of Pacific Abalone, Haliotis discus hannai

Pacific abalone (Haliotis discus hannai) is a highly commercial seafood in Southeast Asia. The aim of the present study was to improve the sperm cryopreservation technique for this valuable species using an antifreeze protein III (AFPIII). Post-thaw sperm quality parameters including motility, acrosome integrity (AI), plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), DNA integrity, fertility, hatchability, and mRNA abundance level of heat shock protein 90 (HSP90) were determined to ensure improvement of the cryopreservation technique. Post-thaw motility of sperm cryopreserved with AFPIII at 10 µg/mL combined with 8% dimethyl sulfoxide (DMSO) (61.3 ± 2.7%), 8% ethylene glycol (EG) (54.3 ± 3.3%), 6% propylene glycol (PG) (36.6 ± 2.6%), or 2% glycerol (GLY) (51.7 ± 3.0%) was significantly improved than that of sperm cryopreserved without AFPIII. Post-thaw motility of sperm cryopreserved with 2% MeOH and 1 µg/mL of AFPIII was also improved than that of sperm cryopreserved without AFPIII. A combination of 10 µg/mL AFPIII with 8% DMSO resulted in the highest post-thaw motility, showing AI of 60.1 ± 3.9%, PMI of 67.2 ± 4.0%, and MMP of 59.1 ± 4.3%. DNA integrity of sperm cryopreserved using 10 µg/mL AFPIII combined with 8% DMSO was not significantly (p > 0.05) different from that of fresh sperm. Cryopreservation using a combination of AFPIII with 8% DMSO improved fertilization and hatching rates of sperm compared to that of cryopreservation without supplementation of 10 µg/mL AFPIII. Sperm cryopreserved using AFPIII showed higher mRNA abundance levels of HSP90 than those cryopreserved without AFPIII. Results of the present study suggest that 10 µg/mL AFPIII combined with 8% DMSO can be used for large scale cryopreservation of Pacific abalone sperm and for hatchery production.

Cryopreservation of sperm from farmed Pacific abalone, Haliotis discus hannai

This study aimed to improve a sperm cryopreservation protocol for farmed Pacific abalone, Haliotis discus hannai. Dimethyl sulfoxide (Me₂SO), glycerol, ethylene glycol (EG), propylene glycol (PG), and methanol were chosen as cryoprotectants (CPAs). Four different equilibration time (5, 10, 30, and 60 min), and two types of equilibration temperature (4 °C and 20 °C) were selected at the present experiment. Most equilibration temperatures with each CPA showed significant differences among different equilibration time. Post-thaw sperm motility of five CPAs showed no significant difference at two equilibration temperature. Based on these results, 8% Me₂SO, 8% EG, 6% PG, 2% glycerol, and 2% methanol were chosen to determine optimal conditions for sperm cryopreservation of H. discus hannai. The highest post-thaw sperm motility (8% Me₂SO: 50.6%, 8% EG: 45.6%, 2% glycerol: 44.5%, 6% PG: 28.7%, 2% methanol: 25.4%) was achieved after exposing sperm to liquid nitrogen (LN₂) vapor for 10 min at 5 cm above the LN₂ surface and then submerging them in LN₂ for at least 2 h followed by thawing at 60 °C with seawater and recovering them at 20 °C with seawater. In this study, 8% Me₂SO and 2% glycerol were chosen to check post-thaw sperm quality to estimate percentages of plasma membrane integrity (PMI), mitochondrial potential analysis (MP), and acrosome integrity (AI) using fluorescent techniques. No significant difference in PMI, MP, and AI was found between sperm cryopreserved with 8% Me₂SO and those cryopreserved with 2% glycerol. The current study has demonstrated that 8% Me₂SO was optimal for sperm cryopreservation for H. discus hannai with 5 min of equilibration time, 5 cm of rack height and 60 °C of thawing temperature. The present research provides more effective cryopreservation methods for H. discus hannai sperm than previous studies.

Improvement of post-thaw sperm survivals using liquid nitrogen vapor in a spermcasting oyster Ostrea angasi

Low survival of cryopreserved sperm impedes the application of cryopreservation technique in spermcasting oyster species. This study developed a simple method of liquid nitrogen vapor freezing to improve post-thaw sperm survival in the spermcasting oyster Ostrea angasi. The results indicate that the permeable cryoprotectants, dimethyl sulfoxide (DMSO), ethylene glycol (EG) and propylene glycol (PG) were non-toxic to sperm up to 20% concentration and 90 min exposure whereas methanol at 10% or higher was toxic to sperm for any exposure over 30 min. Among the treatments with permeable cryoprotectants, 15% EG produced the highest post-thaw sperm motility. Sperm motility was further improved by the addition of non-permeable cryoprotectants (trehalose and glucose), with 15% EG + 0.2 M trehalose resulting in the highest post-thaw sperm motility among all the combinations evaluated. The durations of 20, 30 and 60 min equilibrations produced a higher post-thaw sperm motility and plasma membrane integrity (PMI) than 10 min. Higher post-thaw motility and PMI were achieved by freezing sperm at the 8 cm height from the liquid nitrogen surface than at the 2, 4, 6, 10 or 12 cm height. Holding sperm for 10 min in liquid nitrogen vapor produced higher post-thaw motility and PMI than for 2, 5 or 20 min. The cryopreservation protocol developed in this study improved both post-thaw motility and PMI of O. angasi sperm at least 15% higher than those cryopreserved using programmable freezing method. Liquid nitrogen vapor freezing might have greater applicability in improving post-thaw sperm quality of spermcasting oyster species.

Cryobanking of aquatic species

This review is focused on the applications of genome cryobanking of aquatic species including freshwater and marine fish, as well as invertebrates. It also reviews the latest advances in cryobanking of model species, widely used by the scientific community worldwide, because of their applications in several fields. The state of the art of cryopreservation of different cellular types (sperm, oocytes, embryos, somatic cells and primordial germ cells or early spermatogonia) is discussed focusing on the advantages and disadvantages of each procedure according to different applications. A special review on the need of standardization of protocols has also been carried out. In summary, this comprehensive review provides information on the practical details of applications of genome cryobanking in a range of aquatic species worldwide, including the cryobanks established in Europe, USA, Brazil, Australia and New Zealand, the species and type of cells that constitute these banks and the utilization of the samples preserved.

STATEMENT OF RELEVANCE

This review compiles the last advances on germplasm cryobanking of freshwater and marine fish species and invertebrates, with high value for commercial aquaculture or conservation. It is reviewed the most promising cryopreservation protocols for different cell types, embryos and larvae that could be applied in programs for genetic improvement, broodstock management or conservation of stocks to guarantee culture production.

Dynamic changes in the sperm quality of Mytilus galloprovincialis under continuous thermal stress

Global warming is an increasingly serious problem underlying ecological change in marine flora and fauna. Mytilus galloprovincialis is an intertidal species that colonizes coasts in moderate and warm climates, and can thus withstand extreme climatic conditions; however, it successfully reproduces only within a certain temperature range. The effects of prolonged exposure to 28 °C, a temperature unsuitable for breeding activity, on sperm quality were evaluated in this study. Such heat stress induced the following: a significant reduction in concentration; a biphasic pattern of motility and mitochondrial membrane potential that first increased, and then collapsed; a decrease in the intracellular calcium concentration; a rapid increase in lipid peroxidation that was normalized after the third week of heat stress; an increase in DNA fragmentation after the third week of heat stress; and atypical morphology (i.e., sperm with a globular head, asymmetrical tail, and acrosome loss). Currently, these elevated-temperature conditions are achieved along the Mediterranean coast during the late summer, when the reproductive activity of M. galloprovincialis is suspended after massive spawning in the spring. The increasing global temperature, however, may shift their breeding season, thus significantly impacting marine ecosystems and mussel production.

Investigating membrane and mitochondrial cryobiological responses of HUVEC using interrupted cooling protocols

The success of cryopreservation protocols is largely based on membrane integrity assessments after thawing, since membrane integrity can be considered to give an upper limit in assessment of cell viability and the plasma membrane is considered to be a primary site of cryoinjury. However, the exposure of cells to conditions associated with low temperatures can induce injury to cellular structure and function that may not be readily identified by membrane integrity alone. Interrupted cooling protocols (including interrupted slow cooling without a hold time (graded freezing), and interrupted rapid cooling with a hold time (two-step freezing)), can yield important information about cryoinjury by separating the damage that occurs upon cooling to (and possibly holding at) a critical intermediate temperature range from the damage that occurs upon plunging to the storage temperature (liquid nitrogen). In this study, we used interrupted cooling protocols in the absence of cryoprotectant to investigate the progression of damage to human umbilical vein endothelial cells (HUVEC), comparing an assessment of membrane integrity with a mitochondrial polarization assay. Additionally, the membrane integrity response of HUVEC to interrupted cooling was investigated as a function of cooling rate (for interrupted slow cooling) and hold time (for interrupted rapid cooling). A key finding of this work was that under slow cooling conditions which resulted in a large number of membrane intact cells immediately post thaw, mitochondria are predominantly in a non-functional depolarized state. This study, the first to look directly at mitochondrial polarization throughout interrupted cooling profiles and a detailed study of HUVEC response, highlights the complexity of the progression of cell damage, as the pattern and extent of cell injury throughout the preservation process differs by injury site.

Cryopreservation of Greenshell™ mussel (Perna canaliculus) sperm

Cryopreservation is a valuable technique for aquaculture as it enables a library or bank of genetically valuable animals to be maintained in a cost-effective manner. Here, we describe a method to cryopreserve the sperm of the Greenshell™ mussel (Perna canaliculus) and how to use the sperm post-thawing to maximize larval production from thawed sperm in selective breeding.

Survival of tissue balls from the coral Pocillopora damicornis L. exposed to cryoprotectant solutions

In this study, the tolerance of tissue balls (TBs, 100-300 μm in diameter) from the coral Pocillopora damicornis produced using mechanical excision to exposure to cryoprotectant (CPA) solutions was tested. TBs were treated for 20 min at room temperature with solutions of ethylene glycol (EG), methanol (Met), glycerol (Gly) or dimethyl sulfoxide (Me2SO) at concentrations between 1.0 and 4.5M. Two parameters were used to evaluate the survival of TBs following CPA treatment. The Undamaged Duration of Tissue Balls (expressed in h) corresponded to the time period during which the membrane surface of TBs remained smooth and their motility was preserved. Tissue Ball Regression (expressed in μm/h) corresponded to the size reduction of TBs over time. TBs tolerated exposure to all CPAs tested at the three lower concentrations employed (1.0 M, 1.5 M and 2.0 M). No survival was achieved following exposure to a 4.5 M CPA solution. At concentrations of 3.0 and 4.0 M, higher Undamaged Duration of Tissue Balls and lower Tissue Ball Regression were obtained following treatment with EG compared to the other three CPAs. Our experiments show that TBs constitute a good experimental material to evaluate CPA toxicity on corals using large numbers of samples. Performing preliminary experiments with TBs may allow reducing the number of tests carried out with less easily available coral forms such as planulae, thereby preserving larval stocks.