Sperm proteins in teleostean and chondrostean (sturgeon) fishes

Oxidative stress and cryoresistance of sturgeon sperm: A review

Currently, the majority of sturgeons are relict fishes of high economic value yet endangered with extinction. Cryopreservation of sperm has great potential in fish farming and conservation, but the problem of low cryoresistance of sturgeon sperm has not yet been solved. The goal of this work was to review current literature data on the causes of low tolerance of sturgeon sperm to cryodamage. The influence of cryopreservation on the parameters of physiology and metabolism of sturgeon sperm (morphology and fine ultrastructure, mobility and fertilization ability, integrity of the plasma membrane, protein, lipid and metabolite profiles, antioxidant status, DNA damage), as well as on biomarkers of oxidative stress (lipids peroxidation levels and carbonyl derivatives of proteins) is discussed. Since the development of oxidative stress is an important mechanism of sperm cryodamage induction, the review presents the literature on the role of oxygen-derived species in damage of sturgeon reproductive cells caused by cryopreservation. Particular attention is paid to the system of antioxidant protection of sturgeon seminal plasma and spermatozoa, represented by antioxidant enzymes and low molecular weight antioxidants capable of utilizing various reactive forms of oxygen and nitrogen. The review discusses the results of lipidomic and proteomic studies of sturgeon sperm, which made it possible to obtain new data on the lipid composition of cell membranes, to detect proteins involved in the protection of sturgeon spermatozoa from oxidative damage during cryopreservation. This review presents the use of «omics» technology to elucidate the mechanism of cryodamage in sturgeon sperm. Additionally, the review summarizes information on the unique anatomical, morphological, biochemical, and physiological features of sturgeon sperm, which may be associated with low cryoresistance of sturgeon, in order to establish prospects for further research on improving the methods of the conservation of sperm of these threatened species.

Use of antioxidants and time of cold storage: effects over viability parameters and enzymatic levels in semen of rainbow trout (Oncorhynchus mykiss, Walbaum, 1792)

The cold storage of milt implies potentials alterations in its quality because the storage generates as main process, free radicals that produce spermatozoa membrane lipids damage with the consequent motility and fertilising capacity disruptions. To decrease the damage generated by free radicals the cells have antioxidant defences (proteins, enzymes, and low molecular weight substances). The objective of the present study evaluated the time storage effect and different antioxidants prepared in spermatic diluents on sperm viability of O. mykiss milt stored at 4°C. The two-way ANOVA denoted that the time storage and antioxidant influence have significant effects separated or combined on viability parameters (sperm motility and viability, proteins concentrations and superoxide dismutase enzymatic activity in seminal plasma). In contrast, only the storage time affected the fertilising capacity and catalase enzymatic activity in seminal plasma. The resulting analysis can conclude that the antioxidant presence improves the viability of cold stored milt, especially the transport conditions and the antioxidants allow the fecundity despite motility decrease.

Urine, feces, and blood contamination of frozen and fresh tambaqui (Colossoma macropomum Cuvier, 1818) sperm

Contamination of fish milt during collection can have an important effect on the quality of fresh and frozen samples. The aim of this study was to evaluate the effects of biological contaminants (urine, feces, and blood) on the sperm of Colossoma macropomum. After hormonal induction, contaminated and contaminant-free milt samples from thirteen males (6.48 ± 2.82 kg) were collected and frozen. The sperm motility was evaluated in fresh and frozen-thawed sperm. Membrane and DNA integrity and mitochondrial functionality were evaluated only in frozen samples. The results revealed lower motility for contaminated sperm in both fresh and frozen-thawed samples [urine (76.15 ± 19.38% and 8.08 ± 6.63%), feces (78.85 ± 26.07% and 1.67 ± 3.26%), and blood (79.62 ± 20.96% and 2.69 ± 4.39%), respectively] than for contaminant-free sperm (95.77 ± 6.07% and 40.00 ± 12.25%, respectively). Motility was different between contaminant-free (118.50 ± 52.08 s) and feces-contaminated (77.00 ± 42.54 s) fresh samples. However, in frozen samples, there was no difference in motility among the groups. The membrane integrity was lower in the contaminated (urine: 72.38 ± 15.55%, blood: 77.00 ± 11.50%, and feces: 68.00 ± 13.64%) than in the contaminant-free (91.46 ± 5.12%) sperm. DNA integrity and mitochondrial functionality were greater in the contaminant-free (82.85 ± 12.19% and 87.15 ± 9.01%, respectively) than in the feces-contaminated (93.38 ± 5.49% and 94.92 ± 6.73%, respectively) samples. C. macropomum sperm contaminated with urine, blood, or feces should not be used for cryopreservation, as these contaminants have detrimental effects on sperm quality.

Effect of chilled storage on sperm quality of basa catfish (Pangasius bocourti)

Basa catfish (Pangasius bocourti) is an indigenous species of the Lower Mekong River with increasing aquaculture value in Southeast Asia. Short-term semen storage has proven to be a valuable tool for assisted reproduction in fish, but little information is available on basa catfish. The present study was aimed at evaluating the effect of short-term semen storage on the sperm quality of basa catfish. Semen samples were kept at 4 °C for 7 days, either undiluted or diluted with Ca-F HBSS at different ratios (1:1, 1:3, and 1:6; semen:medium). Results showed that sperm quality was significantly affected by the time of chilled storage, characterized by a decline in sperm motility, viability, mitochondrial membrane potential (MMP), ATP content, and increased level of lipid peroxidation throughout the storage period. Compared with undiluted semen, diluted in Ca-F HBSS allowed better preservation of sperm quality during 7 days of chilled storage; dilution ratio at 1:1 was more effective than higher ratios (1:3 and 1:6) for prolonging sperm storability. In addition, sperm motility, viability, and ATP content decreased more rapidly than MMP, suggesting these indicators are more sensitive in detecting sperm damage of basa catfish during short-term chilled storage. These results obtained here will contribute to a better understanding of reproductive management in this species.

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

Improvement of sperm quality with low motility by storage could ensure higher success of fertilization and maintain higher genetic diversity, especially for sturgeons, which as endangered species have limited broodstock and gametes. Sperm was collected from mature male sterlet Acipenser ruthenus and motility was evaluated using the CASA system; samples were categorized as GS 'good sperm' (>80%) or BS 'bad sperm' (<20%). Samples from both groups were incubated with seminal plasma from good- (GSP) and bad-quality sperm (BSP), respectively for 15 min, 6 h, 24 h and 96 h at 4 °C. Motility of BS incubated in GSP increased after different storage times compared to BS incubated in BSP, while the motility and velocity of GS incubated in BSP decreased compared to GS incubated in GSP. Fertilization rates were evaluated with samples stored for 15 min and 6 h post-stripping; fertilization and hatching rate of BS after incubation in GSP increased significantly compared to the BS incubated in BSP. Inorganic ion (Na⁺, K⁺, Cl^-) concentrations and osmolality of BSP were significantly lower than that of GSP. These results indicated that sterlet sperm quality can be revitalized by incubation with GSP. Further, fertilization capacity of BS after incubation in GSP can reach similar levels to the good quality sperm (∼70%). Low ion concentration and osmolality in BSP may be a partial cause of low sperm quality. The current study is the first report on the capability to revitalize low quality sterlet sperm by storage in GSP.

Protective role of antifreeze proteins on sterlet (Acipenser ruthenus) sperm during cryopreservation

The loss of sperm quality in sterlet (Acipenser ruthenus) due to freeze-thaw process in cryopreservation was investigated in the present study. Two antifreeze proteins (AFPI or AFPIII) were used at different concentrations of 0.1, 1, 10, and 100 μg/mL. We compared motility, curvilinear velocity, and plasma membrane integrity of fresh, cryopreserved sperm, and sperm cryopreserved in the presence of antifreeze proteins. Fresh sperm (control) had 85 ± 4% motility and 160 ± 2 μm/s curvilinear velocity, respectively. After cryopreservation, the motility of frozen-thawed sperm without addition of antifreeze proteins significantly decreased (44 ± 9%), compared to the control. The highest motility of frozen-thawed sperm was obtained in cryopreserved sperm with addition of 1 μg/mL of AFPIII (58 ± 14%). No significant differences were observed in curvilinear velocity between fresh sperm and cryopreserved sperm with/without addition of AFPI or AFPIII. The flow cytometry analysis revealed that fresh sperm contained 94.5 ± 6% live cells, while the cryopreserved sperm only contained 26.6 ± 14% live cells. Supplementation of antifreeze proteins has significantly improved the percentage of live cells in frozen-thawed sperm, except 0.1 μg/ml of AFPI group. No significant difference in percentage of live cells was detected in the sperm cryopreserved with 10 μg/mL of AFPI or AFPIII, compared to fresh sperm. Thus, addition of antifreeze proteins to cryopreservation medium could be considered to improve the post-thawed sperm quality of sterlet.

Variability in the protein profiles in spermatozoa of two sturgeon species

Conventional sperm analysis (i.e., motility and fertility) has been used to evaluate sperm quality. Understanding the quality of sperm on the molecular level in the sturgeons, Acipenser baerii and A. schrenckii, is essential for the improvement of the conservation of genetic resources and farming performance. In this study, we used the iTRAQ proteomics approach to perform proteomic profiling of spermatozoa associated with sperm quality in sturgeons (Data are available via ProteomeXchange with identifier PXD006108). The results showed 291 and 359 differentially expressed proteins in A. baerii and A. schrenckii, respectively, of which 72 were common to both species and all were upregulated in high quality compared with low quality samples. The differentially expressed proteins were mainly categorized into the generation of precursor metabolites and energy and oxidation, and they were localized to the mitochondria. Three distinguishing pathways, Arginine and proline metabolism, Pyruvate metabolism and the Citrate cycle (TCA cycle) were found to play an important role in energy metabolism, and some substrates could be used in the sperm medium for storage and cryopreservation. The quantity levels of two proteins, CKMT1 and LDHB, were verified by western blot analysis. Moreover, other potential biomarkers involved in oxidation reduction, ubiquitin-proteasome-dependent proteolysis, chaperones and binding activity were also discussed. Our study is the first to use the iTRAQ-based proteomics approach to analyse the sturgeon spermatozoa proteome, and the results that we obtained are valuable for the prediction of sperm quality and reproduction management in these threatened species.

Effects of re-stripping on the seminal characteristics of pacu (Piaractus mesopotamicus) during the breeding season

Seminal characteristics in teleost fish with an annual reproductive period, such as pacu (Piaractus mesopotamicus), may vary during the breeding season. The sperm formed before the beginning of the spawning period may be stored for a long time, causing damage to the cells. Therefore, re-stripping may be an important way to eliminate the "old" and allow for the collection of "new" spermatozoids. In this study, we analyzed the seminal characteristics of hormonally induced pacu at the beginning, middle and end of the breeding season, and we analyzed samples from re-stripped males (stripped first at the beginning, re-stripped in the middle, and re-stripped again at the end of the season) during two breeding seasons. The sperm density, ionic composition, pH, and osmolality were similar among the groups. The semen volume, seminal plasma protein concentration and incidence of morphologically anomalous sperm increased over time. In addition, some parameters that are associated with good-quality semen decreased, such as sperm motility, viability and DNA integrity. Moreover, we observed a positive association among motility, viability and DNA integrity for sperm with elevated 11-ketotestosterone, but there was no such association for fshb or lhb mRNA levels in the pituitary. The semen that was obtained earlier (at the beginning) or from re-stripped males exhibited better characteristics than the other samples collected. In conclusion, collecting semen from pacu at the end of breeding season should be avoided; it is preferable to strip early and then re-strip later in the season, and this approach may be used for diverse aquaculture purposes.

Impact of tributyltin on antioxidant and DNA damage response in spermatozoa of freshwater prawn Macrobrachium rosenbergii

Effects of tributyltin (TBT) on antioxidant [total superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR)] and DNA damage levels in the spermatozoa were studied and reported here for the first time in the freshwater prawn Macrobrachium rosenbergii. Three groups of (n = 10 in each group) fishes were exposed to three different nominal concentrations of TBT viz., 1, 2, and 4 mg L(-1) along with control group for 90 days. Significant decrease of antioxidant and increased DNA damage levels were seen at higher doses of 2 and 4 mg L(-1). In prawn, the antioxidant level plays a vital role in sperm protection, activation, differential functions related to the physiology, and reproductive behavior. This study serves as a biomonitoring tool to assess the TBT effects on reproductive behavior of aquatic biota.

The in vitro effect of Lambda-cyhalothrin on quality and antioxidant responses of rainbow trout Oncorhynchus mykiss spermatozoa

There is little information in the scientific literature about effect of in vitro exposure of fish spermatozoa to pesticides. In vitro effect of Lambda-cyhalothrin (LCT) on sperm quality and oxidative stress has not been fully explored yet. The effects of LCT, which is a synthetic pyrethroid insecticide, on quality and oxidative stress of spermatozoa were investigated in vitro due to extensively use to control a wide range of insect pests in agriculture, public health, and homes and gardens. To explore the potential in vitro toxicity of LCT, fish spermatozoa were incubated with different concentrations of LCT (0.6, 1.2 and 2.4 μg/L) for 2h. Reduced glutathione (GSH), glutathione peroxidase (GSH-Px), catalase (CAT) and malondialdehyde (MDA) in spermatozoa were analyzed for determination of oxidant and antioxidant balance. Our results indicated that the percentage and duration of sperm motility significantly decreased with exposure to LCT. Activity of GSH-Px and MDA (P<0.05) and GSH levels (P<0.05) increased in a concentration-dependent manner while CAT activity decreased (P<0.05). In conclusion, the oxidant and antioxidant status and sperm quality were affected by increasing concentrations of LCT.

Bisphenol A reduces fertilizing ability and motility by compromising mitochondrial function of sperm

Bisphenol A (BPA) acts as an endocrine disruptor, affects animal reproductive success in vivo and affects sperm functions in vitro at environmentally relevant concentrations, leading to reduction in sperm motility and fertilizing ability in fish. The effect of in vitro BPA on avian sperm functions has not been explored. The present study examined the effect of environmentally relevant concentrations of BPA (0 mM, 0.18 mM, 0.37 mM, and 0.74 mM) on sperm functions in chicken in vitro. Sperm were exposed to concentrations of BPA for 30 min and analyzed for motility, fertilizing ability, live sperm percentage, and mitochondrial membrane potential (Δψm). Results showed that BPA at a concentration of 0.74 mM significantly decreased motility, fertilizing ability, live sperm count percentage, and sperm Δψm. Sperm motility was positively correlated with fertility (r = 0.73, p ≤ 0.01), live sperm percentage (r = 0.64, p ≤ 0.01), and high Δψm (r = 0.44, p ≤ 0.01). A dose-dependent and time-dependent effect of BPA was observed on sperm motility at all BPA concentrations. However, sperm's fertilizing ability was unaffected in low BPA concentration (0.18 mM and 0.37 mM). A significantly higher percentage of moribund sperm was observed at 0.37 mM and 0.74 mM BPA compared with at 0.18 mM BPA, in the negative control, and in the vehicle control. The present study confirms that environmentally relevant concentrations of BPA are capable of compromising sperm functions, leading to reduction in fertilizing ability of chicken sperm.

Effects of tetrabrombisphenol A on DNA integrity, oxidative stress, and sterlet (Acipenser ruthenus) spermatozoa quality variables

The sperm of sterlet (Acispenser ruthenus) was used to investigate the effect of the xenobiotic tetrabrombisphenol A (TBBPA) on sperm quality variables (ATP content, spermatozoa motility, and velocity), DNA integrity, and oxidative stress indices. Sperm was diluted to obtain a spermatozoa density of 5 × 10(8) cells/mL and exposed for 2 h to final concentrations of TBBPA (0.5, 1.75, 2.5, 5, and 10 μg/L). The oxidative stress indices, including lipid peroxidation, carbonyl derivatives of proteins, and antioxidant activity were significantly higher with increased concentrations of TBBPA. There was significantly less intracellular ATP in sperm samples at TBBPA concentrations of 2.5 μg/L and above. Spermatozoa velocity and percent motile sperm were significantly lower at each sampling time post-activation compared to controls. DNA damage expressed as percent DNA in Tail and Olive Tail moment was significantly higher with exposures ≥2.5 μg/L TBBPA. The results demonstrated that TBBPA and other xenobiotics can induce reactive oxygen species stress in fish spermatozoa, which could impair the sperm quality, DNA integrity, ATP content, and the antioxidant defense system. This study confirmed that fish spermatozoa can be used in in vitro assays for monitoring residual pollution in aquatic environments.

Morphological evidence for a permeability barrier in the testis and spermatic duct of Gymnotus carapo (Teleostei: Gymnotidae)

Cell-cell interactions play essential roles in the regulation of gametogenesis. The involvement of junctional complexes in permeability barriers, for example, provides structural and physiological support for male germ-cell development. This study describes morphological characteristics of the reproductive system of Gymnotus carapo, a neo-tropical freshwater fish widely distributed in South and Central America, focusing on the detection of permeability barriers using morphological and biochemical approaches. Ultrastructural analysis of testes treated with the lanthanum nitrate exclusion technique showed that the tracer penetrated the interstitial compartment of the testis, surrounding and appearing within cysts containing spermatogonia and spermatocytes in early stages of meiosis, but was not detected in the spermatid cysts or inside the lumen of spermatogenic tubules. These results suggest the presence of a permeability barrier that is stabilized after meiosis is completed and serves to protect the haploid cells from the vascular system. In the spermatic-duct region, the tracer was obstructed near the lumen of the duct. Junctional complexes and focal tight junctions between adjacent cells were observed in the testis and spermatic duct. Freeze-fracture methods indeed confirmed the presence of tight junctions, which were visualized as parallel rows of individual particles between adjacent cells. More evidence supporting the existence of a permeability barrier was gathered from differences observed in the electrophoretic protein profiles of testis and spermatic-duct fluids compared to blood plasma. Together, these observations demonstrate the existence of a permeability barrier formed by tight junctions in the testis and spermatic duct of G. carapo.

ATP content, oxidative stress and motility of beluga (Huso huso) semen: effect of short-term storage

An effective technique for short-term storage of semen is essential when processing multiple sperm samples and when semen must be transported from collection sites to hatcheries for the fertilization of ova or to laboratories for cryopreservation. In this experiment, beluga (Huso huso) sperm were used to evaluate the effects of short-term storage on several quality parameters (i.e. motility, adenosine triphosphate (ATP) content and oxidative stress indices). Sperm cells exhibited > 50% motility during 3 days of storage with an average total duration of sperm motility varying from 13.33 ± 5.77 to 278.33 ± 25.65 s, and no motile spermatozoa were recorded after 9 days of storage. The levels of oxidative stress indices (thiobarbituric acid reactive substances and carbonyl derivatives of proteins) and antioxidant activity (superoxide dismutase) increased significantly after 3 days of storage. The ATP content also decreased significantly after 2 days of storage. The results of this study can be used to develop effective reproduction management and cryopreservation protocols for this endangered fish.

Study of enzyme activities and protein content of beluga (Huso huso) semen before and after cryopreservation

Knowledge gained regarding the biochemical processes that occur during sperm collection, processing and freezing-thawing might improve current sperm cryopreservation techniques. In our present study, we determined the effect of cryopreservation on the total protein concentration (TP) and the activities of certain enzymes in semen samples from the beluga (Huso huso). The TP content of the seminal plasma of fresh semen was 0.47 ± 0.026 g/l, and the TP after cryopreservation was 1.86 ± 0.6 g/l. The activities of acid phosphatase (0.82 ± 0.042 U/l), lactate dehydrogenase (234.4 ± 19.4 U/l), arylsulfatase (143.1 ± 32.5 U/l) and β-N-acetylglucosaminidase (58.39 ± 4.14 U/l) in the seminal plasma of fresh semen were significantly lower than those in the supernatant of frozen-thawed semen samples (7.43 ± 0.64, 3224.6 ± 167.2, 422.6 ± 21.3 and 90.2 ± 5.37 U/l respectively). These parameters may be useful as biomarkers for estimating damage to the cell membrane of spermatozoa caused by freezing-thawing.

Effects of short-term storage on the motility, oxidative stress, and ATP content of Persian sturgeon (Acipenser persicus) sperm

The effective short-term storage of semen is essential when processing multiple sperm samples and when semen must be transported from collection sites to hatcheries for the fertilization of ova, or to laboratories for cryopreservation. In the present study, the spermatozoa of Persian sturgeon (Acipenser persicus) were used to evaluate the effects of short-term storage on quality parameters (the percentage of motile cells and the total period of sperm motility), oxidative stress indices, and the ATP content. Spermatozoa cells exhibited >50% motility during 6 days of storage where the average total duration of sperm motility varied from 376.42 ± 80.86 s initially to 19.28 ± 10.96 s after 6 days. No motile spermatozoa were recorded after 9 days of storage. The levels of oxidative stress indices (TBARS and CP) and antioxidant activity (SOD) increased significantly with the storage time. The ATP content also decreased significantly after 2 days of storage. The results of this study may facilitate successful reproduction management and cryopreservation protocols for this endangered fish.

In vitro effects of bisphenol A on the quality parameters, oxidative stress, DNA integrity and adenosine triphosphate content in sterlet (Acipenser ruthenus) spermatozoa

Among endocrine disruptors, the xenoestrogen bisphenol A (BPA) deserves particular attention due to widespread human exposure. Besides hormonal effects, BPA has been suspected to be responsible for adverse effect on reproductive ability of various species. In the present study the effect of BPA on the quality parameters, oxidative stress, the DNA integrity and intracellular ATP content of sterlet (Acipenser ruthenus) spermatozoa were investigated in vitro. Fish spermatozoa were exposed to concentrations of BPA possibly occurring in nature (0.5, 1.75, 2.5, 5 and 10μg/L) for 2h. Results revealed that BPA significantly decreased spermatozoa motility and velocity of spermatozoa at concentration of BPA 2.5-10μg/L. Significant positive correlation (r=0.713, P<0.05) was found between percent motile spermatozoa and ATP content. Oxidative stress was observed at concentrations 1.75-10μg/L, as reflected by significantly higher levels of protein and lipid oxidation and superoxide dismutase activity. Intracellular ATP content of spermatozoa decreased with increasing concentrations of BPA. A dramatic increase in DNA fragmentation expressed as percent tail DNA (2.2%±0.46) and Olive tail moment (0.37±0.09 arbitrary units) was recorded at concentrations of 1.75μg/L and above. The present study confirms that concentrations of BPA that can be encountered in nature are capable to induce oxidative stress, leading to impaired sperm quality, DNA fragmentation and intracellular ATP content.

The in vitro effect of duroquinone on functional competence, genomic integrity, and oxidative stress indices of sterlet (Acipenser ruthenus) spermatozoa

The sturgeon is a highly endangered fish species mostly due to over-fishing, habitat destruction, and water pollution. Duroquinone (derivative of 1,4-benzoquinone) is a xenobiotic compound widespread in the environment. The effect of duroquinone on motility, DNA integrity, and oxidative stress indices in sterlet, Acispenser ruthenus, spermatozoa was investigated. Sterlet sperm was exposed for 2h to duroquinone at concentrations of 25, 50, 100, and 150 μM. Spermatozoa motility, velocity, and ATP content were significantly decreased with exposure to duroquinone. The level of DNA damage significantly increased at concentrations of 50 μM and above. Oxidative stress indices (lipid peroxidation and content of carbonyl proteins) and superoxide dismutase (SOD) activity increased significantly with increasing concentrations of duroquinone. Oxidative stress in sterlet spermatozoa induced by duroquinone was shown to impair spermatozoa DNA integrity, motility parameters, and the antioxidant defense system. Spermatozoa motility, content of carbonyl proteins, and SOD activity were shown to be sensitive biomarkers, exhibiting strong responses to low concentrations of the xenobiotic. Results also suggested that fish spermatozoa in vitro assays may provide a simple and efficient means of monitoring residual pollutants in the aquatic environment.

Effect of short-term storage on quality parameters, DNA integrity, and oxidative stress in Russian (Acipenser gueldenstaedtii) and Siberian (Acipenser baerii) sturgeon sperm

The sperm of Russian sturgeon (A. gueldenstaedtii) and Siberian sturgeon (A. baerii) was used to evaluate the effects of short-term (liquid) storage on functional parameters (spermatozoa motility and velocity), DNA integrity and oxidative stress indices. Spermatozoa showed >50% motility during 6 days of storage with an average velocity of 133.12±15.4 to 87.9±11.23μm s(-1) in both species. No motile spermatozoa were recorded after nine days of storage. Analysis of Russian sturgeon sperm showed no significant differences in DNA damage expressed as percent tail DNA and Olive Tail Moment for first three days of storage. In Siberian sturgeon significant differences in DNA damage were detected after two days of storage. The level of oxidative stress indices (TBARS, CP) and antioxidant activity (SOD) increased significantly with storage time in both species. Results of this study can be utilized for successful reproduction management and cryopreservation protocols of these endangered species.

Influence of environmentally relevant concentrations of vinclozolin on quality, DNA integrity, and antioxidant responses of sterlet Acipenser ruthenus spermatozoa

The effects of vinclozolin (VIN), an anti-androgenic fungicide, on quality, oxidative stress, DNA integrity, and ATP level of sterlet (Acipenser ruthenus) spermatozoa were investigated in vitro. Fish spermatozoa were incubated with different concentrations of vinclozolin (0.5, 2, 10, 15, 20 and 50 μg/l) for 2 h. A dose-dependent reduction in spermatozoa motility and velocity was observed at concentrations of 2-50 μg/l. A dramatic increase in DNA fragmentation was recorded at concentrations 10 μg/l and above. After 2 h exposure at higher test concentrations (10-50 μg/l), oxidative stress was apparent, as reflected by significantly higher levels of protein and lipid oxidation and significantly greater superoxide dismutase activity. Intracellular ATP content of spermatozoa decreased with increasing concentrations of VIN. The results demonstrated that VIN can induce reactive oxygen species stress in fish spermatozoa, which could impair the sperm quality, DNA integrity, ATP content, and the antioxidant defense system.

Spermatozoa motility and variation in the seminal plasma proteome of Eurasian perch (Perca fluviatilis) during the reproductive season

This study evaluated physiological and functional sperm parameters and the seminal plasma proteome of Eurasian perch (Perca fluviatilis) over the course of their reproductive season. Spermatozoa velocity (169.56 ± 6.53 to 158.5 ± 7.4 µm sec(-1)), percent motility (95.89 ± 4.28% to 89.55 ± 4.5%), and osmolality of seminal plasma (290 ± 5 to 297 ± 12 mOsmol kg(-1)) remained stable throughout the reproductive season. Milt volume and protein concentration of seminal plasma gradually increased and reached the highest values late in the reproductive period. Spermatozoa concentration peaked in the mid-reproductive season (66.90 ± 13 × 10(9)  spermatozoa ml(-1)) and decreased towards the end (54 ± 10 × 10(9)  spermatozoa ml(-1)). A proteomic analysis of seminal plasma using two-dimensional polyacrylamide gel electrophoresis revealed 10 protein spots significantly altered over the course of the reproductive season. Subsequent protein characterization suggested that time in the reproductive season predominantly affected proteins involved in membrane trafficking, organization, cell motility, and oxido-reductase activity. This study provides new data on physiological properties of sperm and protein patterns of seminal plasma over the course of the reproductive season that should be considered in the development of methods for artificial reproduction of perch.

Comparative protein profiles: potential molecular markers from spermatozoa of Acipenseriformes (Chondrostei, Pisces)

Sturgeon and paddlefish (Acipenseriformes), the source of roe consumed as caviar, are a unique and commercially valuable group of ancient fishes. In this study, comparative proteomics was used to analyze protein profiles of spermatozoa from five sturgeon species and one paddlefish: Siberian sturgeon (Acipenser baerii), sterlet (A. ruthenus), Russian sturgeon (A. gueldenstaedtii), starry sturgeon (A. stellatus), beluga (Huso huso), and Mississippi paddlefish (Polyodon spathula). Protein profiles of spermatozoa were determined by isoelectric focusing and two-dimensional electrophoresis (2-DE) high-resolution gels. The peptides, previously selected by 2-DE analysis as potentially species-specific, were obtained by "in-gel" tryptic digestion, followed by matrix-associated laser desorption/ionization time-of-flight/mass spectrometry (MALDI-TOF/MS). Among the 23 protein spots selected, 14 were identified as isoforms of enolase B present in all species, but with different isoelectric points or molecular mass. Exceptions were A. ruthenus and H. huso, species with a close phylogenetic relationship. Glycerol-3-phosphate dehydrogenase was detected exclusively in P. spathula. Phosphoglycerate kinase was detected only in A. ruthenus and H. huso, and 3 additional proteins (fructose bisphosphate aldolase A-2, glycogen phosphorylase type IV and glyceraldehyde-3-phosphate dehydrogenase) were found exclusively in A. gueldenstaedtii and H. huso. This study points to the application of proteomics for differential characterization and comparative studies of acipenseriform species at the molecular level.

Percoll gradient separation of cryopreserved common carp spermatozoa to obtain a fraction with higher motility, velocity and membrane integrity

We attempted to select a fraction of common carp, Cyprinus carpio spermatozoa that best survived a conventional freeze/thaw procedure, by centrifugation of frozen/thawed sperm through a Percoll gradient (45% and 90%). The proportion of motile spermatozoa (65.81 ± 5.19%), their velocity (77.58 ± 31.07 μm/sec), and membrane integrity (83.66 ± 4.38% intact) were significantly higher in separated sperm than in whole samples (motility 23.36 ± 2.98%, velocity 55.55 ± 19.03 μm/sec, and membrane integrity 57.92 ± 4.65%). Our results demonstrated that Percoll gradient centrifugation shows promise as a technique for selecting high quality cryopreserved fish spermatozoa, which could be useful for cryobiological research. Further studies are needed to evaluate the potentially higher fertilizing ability of the separated spermatozoa.