Cryopreservation of spermatozoa in cyprinid fishes

Hormone-Driven Temperature Optimization for Elevated Reproduction in Goldfish (Carassius auratus) under Laboratory Conditions

This study investigates the efficacy of hormone-induced artificial reproduction in goldfish (Carassius auratus) under controlled temperatures. Ovaprim injections significantly enhanced ovulation and sperm production compared to controls. Medium temperature (22 °C) produced the highest ovulation rates, fastest ovulation timing, and optimal sperm quality (motility and morphology) compared to high (28 °C) and low (16 °C) temperature groups. The low-temperature group exhibited reduced sperm motility duration and higher rates of sperm and larvae damage. The sperm volume of the high-temperature group was higher, but their post-injection survival rates were lower. Furthermore, the lowest spawning rate and low egg quality were noted in the high temperature. Cryopreservation using extender E4 (15% DMSO) exhibited superior post-thaw sperm motility and achieved higher fertilization rates. Fertilization rates, embryo development, and larval survival were all highest at the medium temperature. Larvae hatched from fresh sperm at medium temperature exhibited faster growth and fewer deformities. These findings suggest that hormone stimulation coupled with a medium temperature regimen is critical for successful artificial reproduction in goldfish. Cryopreservation with extender E4 holds promise for sperm banking; however, further optimization is necessary to improve fertilization success with thawed sperm. Future research could explore the influence of temperature on sperm physiology and refine cryopreservation protocols to enhance fertilization rates.

The investigation of post-thaw chilled storage and the applicability of large-scale cryopreservation in chub (Squalius cephalus) sperm

Chub (reophillic cyprinids) is one of the most sensitive bioindicator fish of environmental changes following anthropogenic activities. The improvement of different biotechnological procedures could help support its conservation and strengthen the natural populations. The aim of this study was to compare the effects of two different hormonal agents (carp pituitary extract and Ovopel™) on various motility parameters (pMOT-%, DAP-μm, VCL μm s-1, VSL-μm s-1, LIN-%, ALH-μm, BCF-Hz) of fresh and cryopreserved/thawed sperm (stored at 4 °C for 6 h). Additionally, we sought to develop a novel, large-scale cryopreservation method for chub sperm, assessing freezing methods (Styrofoam box and a controlled-rate freezer) and different containers (0.5, 5 mL straw and 4 mL cryotube) for sperm cryopreservation. The results of this study indicated no difference between the carp pituitary extract and Ovopel treated groups in either the fresh or frozen/thawed sperm (at 0, 3, 6, hour post thawing, P = 0.4351). In contrast, the quality of the thawed chub sperm was negatively affected after 3 h chilled storage in both hormonal treatments (P = 0.0036, P < 0.0001). When assessing the motility parameters of the sperm between the 5 mL straw and 4 mL cryotube groups cryopreserved in a Styrofoam Box, no difference was observed (P = 0.103). Additionally, sperm loaded in 4 mL cryotubes showed no difference in motility when cryopreserved with either the Styrofoam box or controlled-rate freezer methods (P = 0.109). A similar hatching rate was observed in sperm preserved using the Styrofoam box (35 ± 7 %) and controlled rate freezer (25 ± 9 %) methods (P = 0.300). In a second fertilization trial, hatching rate was similar between control (72 ± 19 %) and cryopreserved (4 mL cryotube and Styrofoam box, 61 ± 5 %) groups. (P = 0.257). Based on our findings and its standard features (less species specific, precise dose calculation), Ovopel can be a good candidate for the stimulation of spermiation in chub sperm prior to cryopreservation. Furthermore, our study presents a novel and applicable method for the large-scale cryopreservation of chub sperm.

Cryopreservation and Its Application in Aquaculture

Aquaculture is the major aquatic animal production segment. Problems like inbreeding depression, genetic drift, introgressive hybridization, etc. have been influencing the production of quality seeds negatively. Cryopreservation serves as a way-out for these problems and a possible answer to produce quality seeds and genetically improved varieties. It has been considered as a major strategy for conservation of fish genetic resources. Cryopreservation of fish gametes has been in vogue since 1953 and the technology is well studied and validated for many species. So far the milt of 200 fish species has been cryopreserved successfully. In this chapter, the importance of aquaculture in overcoming malnutrition, genetic issues affecting quality seed production, cryopreservation protocol employed for various fish species, problems faced in cryopreserving fish eggs and embryos and future of cryopreservation in aquaculture have been discussed.

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.

Inhibiting the influence of ovarian fluid on spermatozoa activation and spermatozoa kinetic characteristics in the common barbel Barbus barbus

As a result of evolution, various finfish species have developed different breeding strategies. However, there are some similarities, and one of them is the positive effect of ovarian fluid on spermatozoa. The opposite of this phenomenon was found in the common barbel (Barbus barbus). The present study analyzed the effect of ovarian fluid (OF), distilled water (DW) and Woynarovich solution (WS) on the motility, longevity and kinetics of barbel spermatozoa. These spermatozoa parameters were also evaluated with various dilutions of ovarian fluid (OF) in relation to distilled water [0:4 (Group OF 0%), 1:3 (Group OF 25%), 1:1 (Group OF 50%), 3:1 (Group OF 75%), 4:0 (Group OF 100%)] and spermatozoa reactivation after a 30 s (Group OFR_30s 100%) treatment in ovarian fluid. The motility analysis was carried out using computer-assisted semen analysis (CASA). The negative interaction of ovarian fluid with spermatozoa motility in the same fish species was recorded for the first time. In pure ovarian fluid, the average spermatozoa motility (MOT) decreased significantly (1.40 ± 0.94%). The negative effect of ovarian fluid-to-spermatozoa motility was reversible, and after a 30 s treatment in ovarian fluid and later dilution with water, spermatozoa motility was reactivated (from 2.25 ± 0.53% vs 69.78 ± 6.02%). The use of Woynarovich solution as an activator of spermatozoa movement had a positive effect (P < 0.05) on spermatozoa movement longevity (motility up to 90 s) and the percentage of motile spermatozoa compared to distilled water (up to 45 s) and ovarian fluid (P < 0.05).

Effects of cryopreservation on cAMP-dependent protein kinase and AMP-activated protein kinase in Atlantic salmon (Salmo salar) spermatozoa: Relation with post-thaw motility

Sperm motility in fish with external fertilization is critical for reproductive efficiency in aquaculture, especially in salmonids. Gamete preservation techniques, such as cryopreservation, however, reduce sperm motility and fertilizing capacity. Very few studies have addressed cryodamage from energetic and cell signalling approaches. In this study, cAMP-dependent protein kinase (PKA) and AMP-activated kinase (AMPK) activities were quantified in fresh and cryopreserved spermatozoa of Atlantic salmon (Salmo salar); and the relation with motility was analysed. Results indicate there was a decrease in membrane integrity and motility in post-thawed spermatozoa compared to fresh samples, however, there was about 30% of cells with intact plasma membrane but incapable of motility. The PKA and AMPK activities were less after cryopreservation, indicating that loss of motility may be related to alteration of these key enzymes. Furthermore, PKA and AMPK activities were positively correlated with each other and with motility; and inhibition decreased motility, indicating there is a functional relationship between PKA and AMPK. The PKA inhibition also decreased AMPK activity, but results from protein-protein docking analyses indicated AMPK activation directly by PKA is unlikely, thus an indirect mechanism may exist. There have been no previous reports of these kinase actions in fish spermatozoa, making these findings worthy of assessment when there are future studies being planned, and may serve as base knowledge for optimization of cryopreservation procedures and development of biotechnologies to improve reproduction efficiency in the aquaculture industry.

Seminal plasma transferrin effects on cryopreserved common carp Cyprinus carpio sperm and comparison with bovine serum albumin and antifreeze proteins

In the current study, there was evaluation of the cryopreservation effectiveness of common carp Cyprinus carpio sperm when cryopreservation medium was supplemented with proteins. Semen was diluted with Kurokura's extender composing 180 mM NaCl, 2.68 mM KCl, 1.36 mM CaCl₂, 2.38 mM NaHCO₃, and 10% dimethylsulfoxide (DMSO). Cryopreservation medium was supplemented with purified seminal plasma transferrin (Tf), bovine serum albumin (BSA) or antifreeze protein (AFP) Types I and III. Concentration of proteins evaluated was 0.1 μg/ml, 1 μg/ml, and 10 μg/ml. Motility and curvilinear velocity of spermatozoa was evaluated by the Computer Assisted Semen Analyzer (CASA). The percent of motile cells and spermatozoa curvilinear velocity of frozen-thawed sperm with supplementation of Tf and AFP III at all concentrations were greater compared to samples with no added proteins. The protective effect of BSA and AFP I was less and dose-dependent. Thus, it is concluded that incorporation of Tf in the extender before freezing improves crypreservation of common carp spermatozoa whereas supplementation with AFP III in greater concentrations was more effective.

Crioconservación de semen de dorada Brycon moorei con dimetilsulfóxido

El objetivo fue evaluar la calidad del semen descongelado de dorada Brycon moorei crioconservado con dimetilsulfóxido (DMSO) a tres porcentajes de inclusión. El semen se obtuvo de nueve machos mantenidos en cautiverio en la Estación Piscícola Repelón (Atlántico, Col), inducidos con extracto pituitario de carpa (4,5 mg/kg). El semen fue diluido en proporción 1:3 con un diluyente compuesto de DMSO a tres porcentajes 5%, 10% y 15%; glucosa al 6% y yema de huevo al 12%; empacado en macrotubos de 2,5 ml, congelados en vapores de nitrógeno y después de tres meses descongelados a 35°C durante 90 s. Semen fresco fue considerando como tratamiento control. En semen descongelado se evaluó movilidad total, tipos de movilidades, progresividad, velocidades y concentración espermática con el programa Sperm Class Analyzer SCA®; adicionalmente en semen fresco se determinó volumen, color y tiempo de activación. El semen fresco presentó movilidad mayor a 80% y tiempo de activación entre 28,5 y 41 s; mientras que, la concentración espermática osciló entre 10188,1 y 14590,2 millones/ml. La movilidad total del semen descongelado fue mayor cuando DMSO se incluyó a 5% (40,1±5,0%) o 10% (43,3±8,7%) (p>0,05); pero a 15% registró la menor movilidad (30,6±7,9%) y el mayor porcentaje de espermatozoides inmóviles (69.4±7.9%) (p<0,05); lo cual sugiere que inclusiones de DMSO por encima de 10% ocasionan mayores daños al espermatozoide de dorada. Los resultados permiten concluir que DMSO debe ser incluido entre 5 y 10%, junto con glucosa al 6% y yema de huevo al 12% para crioconservar semen de dorada.

Sperm quality and its freezing ability throughout the spawning season in Prochilodus lineatus and Brycon orbignyanus

The aim of this study was to determine fresh and frozen sperm quality evaluated over two spawning seasons (2013-2014; 2014-2015) in Prochilodus lineatus and Brycon orbignyanus. The spawning seasons were divided into two sampling periods: November to December and January to February. Males were hand-stripped after carp pituitary treatment. Fresh sperm motility rate, velocities (curvilinear = VCL; straight-line = VSL; average path = VAP), and the beat cross frequency (BCF) were determined using a Computer-Assisted Sperm Analyzer (CASA). Sperm of each species was frozen using methyl glycol as cryoprotectant and a glucose solution for P. lineatus or a NaCl solution for B. orbignyanus as extender. Diluted sperm was loaded into 0.25 mL straws, frozen in a nitrogen vapor vessel (dry shipper) and stored in a liquid nitrogen vessel. Six months later, straws were thawed in a water bath at 60 °C for 3 s and sperm quality was determined, as described for fresh sperm. No significant difference was observed for any of the fresh and frozen sperm features between the two spawning seasons or the two sampling periods in P. lineatus and in B. orbignyanus. Motility rate and velocities, but not BCF, was always higher in fresh sperm when compared with frozen sperm. Comparing both species, higher motility in frozen sperm and higher VCL and VAP in both fresh and frozen sperm were observed for P. lineatus, while higher VSL in fresh sperm and higher BCF in both fresh and frozen sperm were observed for B. orbignyanus. Sperm quality and its freezing ability of both species were sustained over the spawning season and thus fish farmers can reproduce these species and freeze their sperm in any time throughout the spawning season. P. lineatus sperm is more resistant to the cryopreservation process than B. orbignyanus.

Development of sperm cryopreservation protocol of endangered spiny eel, Mastacembelus armatus (Lacepede 1800) for ex-situ conservation

The study was conducted to develop sperm cryopreservation protocol for the endangered spiny eel, Mastacembelus armatus as well as to use the cryopreserved sperm in breeding. Activation of sperm was evaluated by observing motility in different osmolalities of NaCl solution (48-319 mOsmol/kg) and found that sperm motility decreased with increasing osmolality of the NaCl solution and it was totally inhibited at 319 mOsmol/kg. The highest motility and swimming duration of sperm were observed as 14.5 ± 0.5 min and 4.75 ± 0.25 min at 128 mOsmol/kg and 67 mOsmol/kg, respectively. The concentration of sperm was found to be 1.75 × 10¹⁰ to 2.25 × 10¹⁰ cells/ml. Evaluation of toxicity of cryoprotectants of dimethyl sulfoxide (Me₂SO) and methanol to sperm was performed at 5, 10 and 15% concentrations during 5-30 min incubation period and found that cryoprotectants with 5 and 10% concentrations produced better motility up to 10 min incubation. In the selection of suitable diluent for cryopreservation of sperm, Alsever's solution with 10% Me₂SO performed best producing 91.67 ± 1.67% and 65 ± 2.89% equilibration and post-thaw motility, respectively. In breeding trials, sperm preserved with Alsever's solution plus Me₂SO produced more or less similar fertilization (82.25 ± 4.46%) and hatching (12 ± 0.65%) to those preserved with 0.9% NaCl solution plus Me₂SO as 79.88 ± 4.67% and 11 ± 0.46% fertilization and hatching respectively. Fresh sperm used as control produced 87.63 ± 3.6% and 14 ± 0.5% fertilization and hatching respectively. Both cryopreserved and fresh sperm-derived fry performed well but the control fry showed a significantly better (P < 0.05) growth. Fry derived from four diluents did not show any significant (P > 0.05) growth difference but Alsever's solution plus Me₂SO produced better results.

Improvement of common carp (Cyprinus carpio) sperm cryopreservation using a programable freezer

The applicability of a programmable freezer for the increased-scale cryopreservation of common carp sperm was investigated. The effect of different equilibration times, cryopreservation methods, extenders, dilution ratios, activating solutions on the post-thaw motility of common carp sperm was investigated. The suitable post-thaw storage time-interval as well as fertilizing capacity of cryopreserved sperm was also examined. The motility, curvilinear velocity (VCL) and straightness (STR) values did not decrease significantly during 60min of equilibration neither in equilibrated nor thawed groups. Motility parameters of thawed sperm were similar using a conventional cryopreservation technique using a polystyrene box [motility (33%), VCL (47μm/s) and STR (88%)] and a programmable freezer: [motility (32%), VCL (54μm/s) and STR (89%)]. The highest motility and VCL was measured with a sugar based extender (grayling extender) at a ratio 1:9 (motility: 52%, VCL: 76μm/s) and 1:20 (motility: 49%, VCL: 76μm/s). The activating solution for cyprinids (ASC) could prolong sperm movement up for 2min. A storage time of six hours following thawing did not have a significant effect on the motility parameters of thawed carp sperm. Agglutination was observed during cryopreservation of an elevated volume of sperm whereas motility 47%, VCL 62μm/s and STR 91% were measured after thawing. Fertilization rate with thawed sperm (32%) was significantly lower compared to the control group (73%). According to our results, the developed method using a programmable freezer is suitable for the cryopreservation of elevated number of straws. However, carp sperm agglutination during freezing may have a negative effect on the fertilizing capacity.

Sperm cryopreservation affects postthaw motility, but not embryogenesis or larval growth in the Brazilian fish Brycon insignis (Characiformes)

Sperm cryopreservation is an important method for preserving genetic information and facilitating artificial reproduction. The objective was to investigate whether the cryopreservation process affects postthaw sperm motility, embryogenesis, and larval growth in the fish Brycon insignis. Sperm was diluted in methyl glycol and Beltsville Thawing solution, frozen in a nitrogen vapor vessel (dry shipper) and stored in liquid nitrogen. Half of the samples were evaluated both subjectively (% of motile sperm and motility quality score-arbitrary grading system from 0 [no movement] to 5 [rapidly swimming sperm]) and in a computer-assisted sperm analyzer (CASA; percentage of motile sperm and velocity). The other half was used for fertilization and the evaluation of embryogenesis (cleavage and gastrula stages), hatching rate, percentage of larvae with normal development and larval growth up to 112 days posthatching (dph). Fresh sperm was analyzed subjectively (percentage of motile sperm and motility quality score) and used as the control. In the subjective analysis, sperm motility significantly decreased from 100% motile sperm and quality score of 5 in fresh sperm to 54% motile sperm and quality score of 3 after thawing. Under computer-assisted sperm analyzer evaluation, postthaw sperm had 67% motile sperm, 122 μm/sec of curvilinear velocity, 87 μm/sec of straight-line velocity and 103 μm/sec of average path velocity. There were no significant differences between progenies (pooled data) for the percentage of viable embryos in cleavage (62%) or gastrula stages (24%) or in the hatching rate (24%), percentage of normal hatched larvae (93%), larval body weight (39.8 g), or standard length (12.7 cm) at 112 days posthatching. Based on these findings, cryopreserved sperm can be used as a tool to restore the population of endangered species, such as B. insignis, as well as for aquaculture purposes, without any concern regarding quality of the offspring.

Artificial reproduction of wild and cultured barbel (Barbus barbus, Cyprinidae) under controlled conditions

The aim of this work was to compare the effects of controlled reproduction of cultured and wild common barbel, Barbus barbus (L.). Preparations containing different GnRH analogues and dopamine receptor antagonists (Ovopel, Ovaprim) as well as human chorionic gonadotropin (hCG) (in the case of cultured fish) were applied and their influence on ovulation, spermiation and quality of gametes obtained was determined. No differences in the qualitative or quantitative parameters of semen were found between fish stimulated with different hormonal preparations and those not receiving hormonal stimulation. The high suitability of Ovaprim for ovulation induction in (cultured and wild) barbel was confirmed. The highest synchronisation of ovulation was obtained after the application of Ovopel (18 ± 3 h), but the best results of controlled reproduction (expressed as the percentage of ovulations and survival of embryos) were obtained by applying Ovaprim (83.2 ± 4.1). A significantly higher percentage of ovulation was obtained in cultured fish (80-90%) than in wild fish (< 25%).

Freeze-thawing as the factor of spontaneous activation of spermatozoa motility in common carp (Cyprinus carpio L.)

In the present study, we investigated the possibility of spontaneous carp spermatozoa activation by freeze-thawing. To evaluate this, the parameters of spermatozoa motility percentage, velocity, ATP content level and fertility rate of sperm were used. The motility and velocity of spermatozoa activated by freeze-thawing were characterized by motile spermatozoa with a median value of 16% and a velocity of 98 microm/s. In addition, the motility and velocity of sperm from the thawed samples were significantly lower than in the control (median value of 100% for sperm motility and 175 microm/s for sperm velocity). Furthermore, a spontaneously activated spermatozoa motility terminated within five minutes post-thaw time. After freeze-thawing the ATP level significantly decreased with post-thaw time (46 nmol ATP/10(9) and 10 nmol ATP/10(9) at 25s and 10 min after thawing, respectively). Fertility of spermatozoa was not significantly affected within 10 min post-thaw. On the other hand, the fertility of frozen-thawed sperm was significantly lower if compared to fresh sperm. We conclude that the freeze-thawing procedure spontaneously activated spermatozoa motility in common carp. However, this activation did not negatively affect the fertility of frozen-thawed sperm.

Applied reproductive technologies and genetic resource banking for amphibian conservation

As amphibian populations continue to decline, both government and non-government organisations are establishing captive assurance colonies to secure populations deemed at risk of extinction if left in the wild. For the most part, little is known about the nutritional ecology, reproductive biology or husbandry needs of the animals placed into captive breeding programs. Because of this lack of knowledge, conservation biologists are currently facing the difficult task of maintaining and reproducing these species. Academic and zoo scientists are beginning to examine different technologies for maintaining the genetic diversity of founder populations brought out of the wild before the animals become extinct from rapidly spreading epizootic diseases. One such technology is genetic resource banking and applied reproductive technologies for species that are difficult to reproduce reliably in captivity. Significant advances have been made in the last decade for amphibian assisted reproduction including the use of exogenous hormones for induction of spermiation and ovulation, in vitro fertilisation, short-term cold storage of gametes and long-term cryopreservation of spermatozoa. These scientific breakthroughs for a select few species will no doubt serve as models for future assisted breeding protocols and the increasing number of amphibians requiring conservation intervention. However, the development of specialised assisted breeding protocols that can be applied to many different families of amphibians will likely require species-specific modifications considering their wide range of reproductive modes. The purpose of this review is to summarise the current state of knowledge in the area of assisted reproduction technologies and gene banking for the conservation of amphibians.

Antagonist effect of DMSO on the cryoprotection ability of glycerol during cryopreservation of buffalo sperm

The objective of the present study was to investigate the synergistic effect of DMSO and glycerol added at various temperatures on the post-thaw quality of buffalo sperm. Pooled ejaculates from four Nili-Ravi buffalo bulls were divided into 18 aliquots and extended (1:10) in Tris-citric acid extender differing in glycerol:DMSO ratios (0:0, 0:1.5, 0:3; 3:0, 3:1.5, 3:3; and 6:0, 6:1.5, 6:3, respectively; %, v:v) either at 37 or 4 degrees C. Semen was packaged in 0.5 mL French straws and frozen in a programmable cell freezer. Thawing was performed at 37 degrees C for 50s. Post-thaw motion characteristics, plasma membrane integrity and acrosome morphology of buffalo sperm were determined using computer-assisted semen analyzer (CASA), hypoosmotic swelling (HOS) assay and phase-contrast microscopy, respectively. Glycerol (6%) in extender yielded better post-thaw sperm motility, velocities (straight-line and average path), plasma membrane integrity, and normal acrosomes (P<0.05). Post-thaw sperm motility and plasma membrane integrity declined in the presence of DMSO (P<0.01). The addition of glycerol (6%) at 37 degrees C yielded better post-thaw sperm motility, plasma membrane integrity and velocities than addition at 4 degrees C (P<0.05). In conclusion, glycerol is still an essential cryoprotectant for buffalo sperm. The addition of DMSO antagonized the cryoprotection ability of glycerol and reduced the post-thaw quality of buffalo sperm. Furthermore, 6% glycerol added at 37 degrees C, provided better cryoprotection to the motility apparatus and plasma membrane integrity of buffalo sperm.

Cryopreservation of sperm of two European percid species, the pikeperch (Sander lucioperca) and the Volga pikeperch (S. volgensis)

Experiments were carried out on sperm cryopreservation of two European percid fish species, the pikeperch (Sander lucioperca) and the Volga pikeperch (S. volgensis). Two experiments were conducted on pikeperch sperm. In the first, the effects of three extenders (Glucose, KCl, Sucrose) and two cryoprotectants (dimethyl-sulfoxide: DMSO, methanol: MeOH) were tested on motility and fertilization. In the second, the effects of two dilution ratios (1 : 1, 1: 9) and two cryoprotectants (DMSO, MeOH) on hatching were investigated. In the experiment on Volga pikeperch the suitability of using cryopreservation for fertilization was investigated. In the first experiment on pikeperch the highest post-thaw motility (28 +/- 21%) and fertilization rate (43 +/- 12%) was found with DMSO as cryoprotectant in combination with Glucose extender. In the second, the highest hatch rate (41 +/- 22%) was observed with MeOH as cryoprotectant and 1 : 1 sperm dilution ratio, however no significant difference was found among the results. In the experiment on Volga pikeperch hatch rates with cryopreserved sperm (60 +/- 2%) did not significantly differ from the control (60 +/- 6%). Contamination of sperm with urine seems to be a key problem in the success of sperm cryopreservation of these species.

Development of a simplified and standardized protocol with potential for high-throughput for sperm cryopreservation in zebrafish Danio rerio

Sperm cryopreservation offers potential for long-term storage of genetic resources. However, the current protocols for zebrafish Danio rerio are cumbersome and poorly reproducible. Our objective was to facilitate adoption of cryopreservation by streamlining methods from sperm collection through thawing and use. First, sperm activation was evaluated, and motility was completely inhibited when osmolality of the extender was >/=295-300mOsmol/kg. To evaluate cryoprotectant toxicity, sperm were incubated with dimethyl sulfoxide (DMSO), N,N-dimethyl acetamide (DMA), methanol, or glycerol at 5, 10, and 15% concentrations. Based on motility, DMSO, DMA, and methanol (</=10%) were less toxic; therefore, sperm were cryopreserved using these cryoprotectants at cooling rates of 10 and 20 degrees C/min. The highest motility (mean+/-S.D.) (35+/-23%; P</=0.0001) and fertility (13+/-8%; P</=0.001) in thawed sperm were obtained with the combination of 8% methanol and a cooling rate of 10 degrees C/min. Further evaluations of 8% methanol and 10 degrees C/min were performed with males from populations with high (2.05+/-0.24) and low (1.18+/-0.12) body condition (P=0.0001). Motility of thawed sperm from the two populations was 38+/-16% (range, 10 to 60%) and 78+/-10% (50 to 90%) (P=0.0001), and fertilization was 6+/-6% (0 to 18%) and 33+/-20% (5 to 81%) (P=0.0001). These values were positively related with body condition factor. Overall, this study simplified and standardized sperm cryopreservation, and established a protocol using French straws as a freezing container and an extender without powdered milk. This protocol can be readily adapted for high-throughput application using automated equipment, and motility and fertility comparable to previous reports were obtained. Male variability and sperm quality remain important considerations for future work, especially in mutant and inbred lines.

Flow cytometry and ultrastructure of cryopreserved red seabream (Pagrus major) sperm

The objectives were to assess motility, fertilizing capacity, structural integrity, and mitochondrial function in fresh versus frozen-thawed (15% DMSO was used as a cryoprotectant) sperm from red seabream (Pagrus major). Mean (+/-S.D.) rates of motility, fertilization and hatching of frozen-thawed sperm were 81.0+/-5.4, 92.8+/-1.9, and 91.8+/-5.2%, respectively; for fresh sperm, they were 87.5+/-7.7, 95.8+/-2.4, and 93.8+/-4.2%. Although motility was lower in frozen-thawed versus fresh sperm (P<0.05), there was no effect (P>0.05) of cryopreservation on fertilization or hatching. Based on scanning and transmission electron microscopy, 77.8+/-5.6% of fresh sperm had normal morphology, whereas for frozen-thawed sperm, 63.0+/-7.2% had normal morphology, 20.6+/-3.1% were slightly damaged (e.g. swelling or rupture of head, mid-piece and tail region as well as mitochondria), and 16.4+/-4.2% were severely damaged. Sperm were stained with propidium iodide and Rhodamine 123 to assess plasma membrane integrity and mitochondrial function, respectively, and examined with flow cytometry. For fresh sperm, 83.9% had an intact membrane and functional mitochondria, whereas for frozen-thawed sperm, 74.8% had an intact membrane and functional mitochondria, 12.7% had a damaged membrane, 9.9% had nonfunctional mitochondria, and 2.6% had both a damaged membrane and nonfunctional mitochondria. In conclusion, ultrastructure and flow cytometry were valuable for assessment of frozen-thawed sperm quality; cryopreservation damaged the sperm but fertilizing ability was not significantly decreased.

Effect of Cryopreservation on Sea Bass Sperm Proteins

In the present study we used two-dimensional polyacrylamide gel electrophoresis (2-DE) and matrix-associated laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry to verify whether the protein expression of sea bass sperm was affected by the cryopreservation procedure. The protein profiles differed between fresh and frozen-thawed semen as revealed by visual inspection and by image analysis software. We identified 163 spots in fresh sperm; among these, 13 were significantly decreased and 8 were absent in two-dimensional gel obtained with cryopreserved sperm. Five of these spots were analyzed with MALDI-TOF, but only three showed a significant match in the databases used in bio-informatics analysis (PeptIdent, Mascot, and MS-Fit). In particular, spot 5 showed homology with a novel protein of zebrafish (similar to SKB1 of human and mouse), spot 13 showed homology with amphibian G1/S-specific cyclin E2, and spot 20 showed homology with the hypothetical protein DKFZp566A1524 of Brachidanio rerio. The present work shows that the use of the cryopreservation procedure causes the degradation of sperm proteins and among these, two could be at least partially responsible for the observed decrease in sperm motility duration and the lower hatching rate of eggs fertilized with cryopreserved sperm.

Effects of dimethyl sulfoxide and glycine on cryopreservation induced damage of plasma membranes and mitochondria to striped bass (Morone saxatilis) sperm

Intact plasma membrane and functional mitochondria are important attributes for the fertilization capacity of fish sperm. In the present study, dimethyl sulfoxide (Me(2)SO) and glycine were investigated in an effort to improve plasma membrane integrity and mitochondrial function in cryopreserved striped bass (Morone saxatilis) sperm. Prior to freezing, no concentration of Me(2)SO (2.5, 5 or 10%) was found to affect (P>0.05) the integrity of plasma membranes after sperm were exposed for 10 min. However, mitochondrial function decreased (P>0.05) with increasing Me(2)SO concentration. Both fluorescent staining and microscopic examination of the ultrastructure of post-thaw plasma membranes indicated that with increasing Me(2)SO concentration, plasma membranes were better protected, and 10% Me(2)SO had the highest percentage of sperm with plasma membranes intact. However, sperm mitochondrial function decreased (P>0.05) with increasing Me(2)SO concentration. The inverse relationship between plasma membrane integrity and mitochondrial function, given the Me(2)SO concentration, suggests that care must be taken to select Me(2)SO concentration that will maximize the protection of both plasma membranes and mitochondrial function. The addition of glycine to the cryomedia increased (P<0.05) the percentage of sperm with post-thaw functional mitochondria and ATP content. However glycine did not provide (P<0.05) protection to post-thaw plasma membrane integrity. The highest percentage of sperm with both intact plasma membranes and functional mitochondria was obtained with 7.5% Me(2)SO and 75 mM glycine.

The cryopreservation of spermatozoa of the burbot, Lota lota (Gadidae, Teleostei)

The cryopreservation of spermatozoa of a teleost fish, the burbot, Lota lota (Gadidae) was investigated. Cryopreserved semen had the highest motility rate (46.6+/-8.0%, fresh semen control 86.5+/-8.2%) and fertility (78.1+/-2.7% embryo survival in hatching stage, fresh semen control 82.2+/-2.9%) when 10% methanol, 1.5% glucose and 7% hen egg yolk were used as cryoprotectants. Freezing was performed in 0.5-ml straws in the vapour of liquid nitrogen at 1cm above the level of liquid nitrogen and thawing in water at 25 degrees C for 20s. For optimal fertilization cryopreserved semen was first mixed with the eggs and then 25 or 50 mmol/L NaCl solution (pH 8.5) was added at a ratio of 1:24 (semen:saline solution). Under these conditions fertilization ratios in the range of fresh semen control were obtained at minimal sperm to egg ratios of 1.7 x 10(6):1. Fertilization with cryopreserved semen had no influence on the embryonic development, as the ratio of embryos which stopped development and the ratio of embryonic malformations were similar to fresh semen.