Improving motility and fertilization capacity of low-quality sperm of sterlet Acipenser ruthenus during storage

Transferrin maintains the motility rate, ATP content, and DNA integrity of common carp spermatozoa during short-term storage

Short-term sperm storage is a straightforward and cost-effective method of managing logistics in large scale fish hatchery operations but may result in decline in sperm quality. For effective artificial reproduction of fish, use of an appropriate additive to optimize sperm storage conditions is essential. In this study, it was investigated the effect of purified seminal plasma transferrin (Tf) at 10 μg/ml on relevant parameters in common carp Cyprinus carpio sperm during short-term storage. We compared sperm motility and curvilinear velocity, adenosine triphosphate (ATP) content and DNA fragmentation of fresh spermatozoa to that stored for 24, 48, 72, and 144 h with or without Tf. The percentage of motile cells and the curvilinear velocity of spermatozoa in stored samples for 72 h with transferrin supplementation were greater compared to samples with no added protein. The ATP content in samples without added transferrin was reduced (P < 0.05) after 72 h of storage, in contrast to the levels observed in transferrin-supplemented sperm. A time-dependent increase in DNA fragmentation was observed. Significantly lower DNA damage, expressed as percent tail DNA (10.99 ± 1.28) and olive tail moment (0.54 ± 0.12), was recorded in Tf-supplemented samples stored for 48 h compared to that with no Tf. Hence, it is concluded that the beneficial effects of transferrin on common carp sperm could serve as an additional tool for developing and enhancing short-term sperm preservation procedures commonly used in aquaculture.

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.

Common carp (Cyprinus carpio) sperm reduction during short-term in vitro storage at 4 °C

This study was designed to optimize a short-term storage protocol for common carp sperm at 4 °C under aerobic condition. Sperm from individual males were collected directly with or without extenders. The results demonstrated that in general, it was similar effect to collect sperm directly in extenders and keeping sperm for 0.5 h after collection without extenders. Sperm was diluted with eight selected extenders (sperm: extender = 2:1, 1:1 and 1:9) and undiluted sperm was used as a control. Sperm and seminal plasma parameters (sperm motility, velocity, membrane integrity, sperm concentration, osmolality and pH in seminal plasma) were evaluated in sperm stored on ice under aerobic conditions at 0, 2, 4, 6 and 8 days post stripping (DPS) using the computer- assisted sperm analysis system. Results showed that 1:1 and 2:1 dilution maintained higher sperm function and more sperm for a longer period. After 8 DPS, the best sperm quality and quantity was recorded in the common carp seminal plasma supplemented with 50 mM NaCl, Cejko extender (2 mM CaCl₂, 1 mM MgSO₄, 20 mM Tris, 110 mM NaCl, 40 mM KCl, pH 7.5 and 310 mOsm/kg) supplemented with/without 25 mM KCl/NaCl. The reduction of spermatozoa number with time during short-term storage but varied according to different dilution ratios and extenders. At 8 DPS, sperm count has dropped by 22.9 % in a dilution of 1:1 compared to 50.3 % in sperm without dilution. Extenders with diluted 1:1, especially Cejko solution, largely postponed sperm reduction, 21.3 % compared to 55.5 % for sperm stored without extenders.

Seasonal changes in the milt quality of spotted scat, Scatophagus argus: Implications for artificial propagation

The current study investigated the correlation among sperm production (milt volume, spermatocrit and sperm count), sperm motility characters and biochemical composition of seminal plasma during different seasons to estimate the quality of semen in the Spotted scat (Scatophagus argus). The sperm of 120 males were collected over a period of 2 years seasonally viz., summer, pre-monsoon, monsoon and post-monsoon. During the collection period, it was observed that there were significant (p < 0.05) seasonal variations in the semen quality including sperm motility and production more in the summer season than other seasons. The osmolality of seminal plasma varied from 343.33 to 370.33 mOsm/kg. The pH of seminal plasma elevated from 7.37 to 7.63 during monsoon and summer seasons. The motility of S. argus sperms correlated with the concentration of biochemical compounds viz., Ca²⁺, Mg⁺ and Cl^- during the summer season. Based on the present observation it could be highlighted that sodium and potassium were negatively correlated (p < 0.01 and p < 0.05) effect on total protein (r = -0.826; -0.956), glucose (r = -0.819; -0.717), cholesterol (r = -0.978; -0.849), AST (r = -0.853; -0.897), ALT (r = -0.970; -0.967), calcium (r = -0.850; -0.697), magnesium (r = -0.852; -0.843) and chloride (r = -0.906; -0.926). In conclusion, many physical and biochemical compositions of S. argus semen improved during that the summer and pre-monsoon season as compared to that of monsoon and post-monsoon. Fertility tests were performed to determine the ability of spermatozoa to fertilize an egg. Highest fertilization (79.92 ± 4.60%) and hatching (80.75 ± 3.89%) rates were observed during summer, while the rates were lowest during monsoon (40.50 ± 4.52%; 53.92 ± 7.38%). This work forms a compiled data for standard semen quality, which in turn will help to select good milters for hatchery production, cryopreservation and assisted breeding programs of this fish.

Changes in Phenotypes and DNA Methylation of In Vitro Aging Sperm in Common Carp Cyprinus carpio

The purpose of the current study was to analyze phenotypic and functional characteristics of common carp (Cyprinus carpio) spermatozoa during in vitro aging and to investigate whether global DNA methylation is affected by sperm aging. Milt was collected from five individual males, stored in vitro on ice in a refrigerator for up to 96 h post stripping (HPS) and used to fertilize eggs with intervals of 1, 24 and 96 h. Computer-assisted sperm analysis and a S3e Cell Sorter was employed to determine the spermatozoa phenotypic characteristics (motility, velocity, concentration and viability). In addition, pH and osmolality of the seminal fluid and the capacity of the spermatozoa to fertilize, hatching rate and health of the resulting embryos were examined at different aging times. Whole-genome bisulfite sequencing was used to compare the global and gene-specific DNA methylation in fresh and aged spermatozoa. The results demonstrated that spermatozoa aging in common carp significantly affects their performance and thus the success of artificial fertilization. The methylation level at the cytosine-phosphate-guanine (CpG) sites increased significantly with 24 HPS spermatozoa compared to the fresh group at 1 HPS and then decreased significantly at 96 HPS. A more detailed investigation of gene specific differences in the DNA methylation was hindered by incomplete annotation of the C. carpio genome in the public databases.

Optimization of Sperm Management and Fertilization in Zebrafish (Danio rerio (Hamilton))

The aim of the present study was to investigate the spontaneous motility of spermatozoa and to optimize sperm collection, short-term sperm storage, and fertilization in zebrafish Danio rerio. The movement of spermatozoon in water was propagated along the flagellum at 16 s after sperm activation then damped from the end of the flagellum for 35 s and fully disappeared at 61 s after activation. For artificial fertilization, milt must be added to an immobilizing solution, which stops the movement of sperm and keeps the sperm motionless until fertilization. E400 and Kurokura as isotonic solutions were shown to be suitable extenders to store sperm for fertilization for 6 h. E400 stored sperm for 12 h at 0-2 °C. Sperm motility decreased only to 36% at 12 h post stripping for the E400 extender and to 19% for the Kurokura extender. To achieve an optimal level of fertilization and swim-up larvae rates, a test tube with a well-defined amount of 6,000,000 spermatozoa in E400 extender per 100 eggs and 100 µL of activation solution has proven to be more successful than using a Petri dish. The highest fertilization and swim-up larvae rates reached 80% and 40-60%, respectively, with milt stored for 1.5 h in the E400 extender at 0-2 °C.