Optimization of handling and refrigerated storage of guppy Poecilia reticulata sperm

Membrane molecule bouncer regulates sperm binding activity in immature oocytes in the viviparous teleost species Poecilia reticulata (guppy)

Generally, in vertebrates, the first step toward fertilization is the ovulation of mature oocytes, followed by their binding to sperm cells outside of the ovary. Exceptionally, the oocytes of poeciliid fish are fertilized by sperm cells within the follicle, and the developmental embryo is subsequently released into the ovarian lumen before delivery. In the present study, we aimed to identify the factor(s) responsible for intrafollicular fertilization in a viviparous teleost species, Poecilia reticulata (guppy). Sperm tracking analysis in this regard indicated that in this species, sperm cells reached immature oocytes including the germinal vesicle, and the insemination assay indicated that the immature oocytes robustly adhered to the sperm cells; similar binding was not observed in Danio rerio (zebrafish) and Oryzias latipes (medaka). We also identified the Ly6/uPAR protein bouncer as the factor responsible for the observed sperm binding activity of the immature oocytes in this species. The recombinant bouncer peptide acted as an inhibitory decoy for the sperm-oocyte binding in guppy. On the other hand, ectopic expression of guppy bouncer in zebrafish oocytes resulted in interspecific sperm-oocyte binding. These results argue that bouncer is responsible for sperm-immature oocyte binding. Our findings highlight the unique reproductive strategies of guppy fish and enhance our understanding of the diverse reproductive mechanisms in vertebrates.

Chlorothalonil as a potential endocrine disruptor in male zebrafish (Danio rerio): Impact on the hypothalamus-pituitary-gonad axis and sperm quality

Chlorothalonil is a broad-spectrum organochlorine fungicide widely employed in agriculture to control fungal foliar diseases. This fungicide enters aquatic environments through the leaching process, leading to toxicity in non-target organisms. Organic contaminants can impact organism reproduction as they have the potential to interact with the neuroendocrine system. Although there are reports of toxic effects of chlorothalonil, information regarding its impact on reproduction is limited. The aim of the present study was to evaluate the influence of chlorothalonil on male reproductive physiology using the zebrafish (Danio rerio) as ecotoxicological model. Zebrafish were exposed for 7 days to two concentrations of chlorothalonil (0.1 and 10 μg/L) along with a control group (with DMSO - 0.001%). Gene expression of hypothalamus-pituitary-gonad axis components (gnrh2, gnrh3, lhr, fshr, star, hsd17b1, hsd17b3, and cyp19a1), as well as hepatic vitellogenin concentration were assessed. In sperm cells, reactive oxygen species (ROS) content, lipid peroxidation (LPO), mitochondrial functionality, and membrane integrity and fluidity were evaluated. Results indicate that exposure to the higher concentration of chlorothalonil led to a reduction in brain gnr2 expression. In gonads, mRNA levels of lhr, star, and hsd17b1 were decreased at both chlorothalonil concentrations tested. Similarly, hepatic vitellogenin concentration was reduced. Regarding sperm cells, a decreased ROS level was observed, without significant difference in LPO level. Additionally, a higher mitochondrial potential and lower membrane fluidity were observed in zebrafish exposed to chlorothalonil. These findings demonstrate that chlorothalonil acts as an endocrine disruptor, influencing reproductive control mechanisms, as evidenced by changes in expression of genes HPG axis, as well as hepatic vitellogenin concentration. Furthermore, our findings reveal that exposure to this contaminant may compromise the reproductive success of the species, as it affected sperm quality parameters.

In Vitro Storage of Functional Sperm at Room Temperature in Zebrafish and Medaka

The longevity of sperm in teleost such as zebrafish and medaka is short when isolated even in saline-balanced solution at a physiological temperature. In contrast, some internal fertilizers exhibit the long-term storage of sperm, >10 months, in the female reproductive tract. This evidence implies that sperm in teleost possesses the ability to survive for a long time under suitable conditions; however, these conditions are not well understood. In this study, we show that the sperm of zebrafish can survive and maintain fertility in L-15-based storage medium supplemented with bovine serum albumin, fetal bovine serum, glucose, and lactic acid for 28 days at room temperature. The fertilized embryos developed to normal fertile adults. This storage medium was effective in medaka sperm stored for 7 days at room temperature. These results suggest that sperm from external fertilizer zebrafish and medaka has the ability to survive for at least 4 and 1 week, respectively, in the body fluid-like medium at a physiological temperature. This sperm storage method allows researchers to ship sperm by low-cost methods and to investigate key factors for motility and fertile ability in those sperm.

Is it possible to store spotted wolffish (Anarhichas minor) sperm by refrigeration?

Spotted wolffish Anarhichas minor reproduction in captivity is dependent on in vitro fertilization. However, it is often challenging to acquire sufficient fresh sperm to fertilize the eggs that are obtained. In this study, we evaluate the possibility to store spotted wolffish sperm by refrigeration. Spotted wolffish sperm has the particularity that is already motile on stripping, and currently it is not possible to immobilize and reactivate. Thus, sperm refrigeration protocols should focus in extending this motility period that usually lasts up to 2 days. In a first experiment, we evaluated the possibility that the motility period of the sperm was limited by contamination with urine. The urea concentration in the sperm obtained both by stripping (17.10 ± 1.98 mg/dL) and directly from the testis (12.59 ± 2.37 mg/dL) was similar (p > 0.05), which indicate that the sperm collection method used avoid contamination with urine. Afterwards, we tested the possibility that the sperm motility period was limited by energy stores. The ATP concentration (initial value 5.65 ± 0.86 nmol/109 cells) remained stable (p = 0.099) during 30 h after sperm collection, and similar values (p = 0.329) were recorded at end of sperm storage in both diluted (3.88 ± 1.35 nmol/109 cells) and undiluted samples (4.76 ± 1.08 nmol/109). This indicates that the low intracellular ATP consumption, derived from the slow sperm motility, can probably be compensated rapidly enough by mitochondrial synthesis of ATP in the spotted wolffish sperm. In both experiments, diluted sperm kept higher percentage of motile cells during the storage time.

Artificial insemination and parthenogenesis in the whitespotted bamboo shark Chiloscyllium plagiosum

Non-lethal methods for semen collection from elasmobranchs to better understand species reproduction has accompanied the development of artificial insemination. Ejaculates (n = 82) collected from whitespotted bamboo sharks Chiloscyllium plagiosum (n = 19) were assessed and cold-stored raw or extended at 4 °C. Females (n = 20) were inseminated with fresh or 24–48 h cold-stored raw or extended semen and paternity of offspring determined with microsatellite markers. Insemination of females with fresh semen (n = 10) resulted in 80 hatchlings and 27.6% fertility. Insemination of females with semen cold-stored 24 h (n = 4) and 48 h (n = 1) semen resulted in 17 hatchlings and fertilization rates of 28.1% and 7.1% respectively. Two females inseminated with fresh or cold-stored semen laid eggs that hatched from fertilization and parthenogenesis within the same clutch. Parthenogenesis rate for inseminated females was 0.71%. Results demonstrate artificial insemination with cold-stored semen can provide a strategy for transport of male genetics nationally and internationally, precluding the need to transport sharks. Production of parthenotes in the same clutch as sexually fertilized eggs highlights the prevalence of parthenogenesis in whitespotted bamboo sharks and poses important considerations for population management.

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.

Impacts of the biocide chlorothalonil on biomarkers of oxidative stress, genotoxicity, and sperm quality in guppy Poecilia vivipara

Chlorothalonil is a fungicide present in antifouling paints and other formulations used in agriculture, although studies have shown this chemical to be toxic to fish species. To clarify the deleterious effects of chlorothalonil for these non-target organisms, the present study evaluated the toxic effects of this biocide for the estuarine guppy Poecilia vivipara in terms of an acute mortality test (96 h) and the analysis of biomarkers of oxidative stress, genotoxicity, and sperm quality. The LC₅₀ calculated for P. vivipara was 40.8 μg/L of chlorothalonil. For the analysis of biomarkers, fish were exposed (96 h) to 1 and 10 μg/L of chlorothalonil. It was observed that chlorothalonil alters the levels of pro- and antioxidants towards oxidative stress. In the gills, a negative effect on total antioxidant capacity (ACAP) was detected, while there was a reduction in the activity of glutathione S-transferase (GST) in the liver. However, levels of glutathione (GSH) and the activity and glutamate-cysteine-ligase (GCL) increased in both tissues, as a possible detoxification response. Following chlorothalonil exposure, oxidative damage measured by lipoperoxidation (LPO) significantly increased at the cellular level only (red blood cells (RBCs) and sperm cells). An increase in fluidity of membranes, reactive oxygen species concentration and micronuclei (MNs) incidence were also seen in RBCs. In sperm cells, LPO increased, while membrane and mitochondrial functionality as well as sperm motility decreased. Based on these results, chlorothalonil can be considered as a toxic compound for fish, causing genotoxicity and affecting the RBCs physiology and the fertility of males of P. vivipara.

Life-time exposure to waterborne copper IV: Sperm quality parameters are negatively affected in the killifish Poecilia vivipara

In previous studies, we have shown that copper (Cu) is significantly accumulated in various tissues of killifish Poecilia vivipara following chronic exposure. Also, we showed that chronic metal exposure disrupted energy production and growth in this species. In the present study, we aimed to evaluate if chronic exposure to this metal could also affect reproductive parameters of P. vivipara males (sperm quality). In order to test that, newborn (<24 h-old) fish were exposed to two concentrations of waterborne Cu (5 and 9 μg/L) for 345 days. After exposure, fish were euthanized and the testes were collected for sperm analysis. We could observe that exposed animals had reduced sperm motility and period of motility. Also, the sperm of exposed fish had reduced plasma membrane integrity, mitochondrial functionality and DNA integrity when compared to sperm of control animals. It is suggested that the well-known association of Cu with elevated oxidative damage, endocrine disruption and energetic disturbance are involved with the observed outcomes. The results obtained in the present study show that chronic exposure to environmentally relevant concentrations of waterborne Cu caused reductions in all parameters used to evaluate sperm quality. Therefore, it is concluded that life-time exposure to this metal may disrupt fish reproduction and negatively affect the maintenance of its populations.

The role of alkalinization-induced Ca2+ influx in sperm motility activation of a viviparous fish Redtail Splitfin (Xenotoca eiseni)

Mechanisms regulating sperm motility activation are generally known in oviparous fishes, but are poorly understood in viviparous species. The mechanism of osmotic-shock induced signaling for oviparous fishes is not suitable for viviparous fishes which activate sperm motility within an isotonic environment. In addition, the presence of sperm bundles in viviparous fishes further complicates study of sperm activation mechanisms. The goal of this study was to establish methodologies to detect intracellular Ca2+ signals from sperm cells within bundles, and to investigate the signaling mechanism of sperm activation of viviparous fish using Redtail Splitfin (Xenotoca eiseni) as a model. Motility was assessed by classification of bundle dissociation and computer-assisted sperm analysis, and intracellular Ca2+ was assessed using the fluorescent probe Fura-2 AM. Bundle dissociation and sperm motility increased with extracellular Ca2+ and pH levels. Intracellular Ca2+ signals were detected from sperm within bundles, and increased significantly with extracellular Ca2+ and pH levels. Major channel blockers known to inhibit Ca2+ influx (NiCl2, ruthenium red, GdCl3, SKF-96365, nimodipine, verapamil, methoxyverapamil, mibefradil, NNC 55-0396, ω-Conotoxin MVIIC, bepridil, and 2-APB) failed to inhibit Ca2+ influx, except for CdCl2, which partially inhibited the influx. We propose a novel mechanism for motility regulation of fish sperm: an alkaline environment in the female reproductive tract opens Ca2+ channels in the sperm plasma membrane without osmotic shock, and the Ca2+ influx functions as a second messenger to activate motor proteins controlling flagella movement.

Development of germplasm repositories to assist conservation of endangered fishes: Examples from small-bodied livebearing fishes

Germplasm repositories are a necessary tool for comprehensive conservation programs to fully preserve valuable genetic resources of imperiled animals. Cryopreserved germplasm can be used in the future to produce live young for integration into other conservation projects, such as habitat restoration, captive breeding, and translocations; thus compensating for genetic losses or negative changes that would otherwise be permanent. Although hundreds of cryopreservation protocols for various aquatic species have been published, there are great difficulties in moving such research forward into applied conservation projects. Successful freezing of sperm in laboratories for research does not guarantee successful management and incorporation of genetic resources into conservation programs in reality. The goal of the present review is to provide insights and practical strategies to apply germplasm repositories as a real-world tool to assist conservation of imperiled aquatic species. Live-bearing (viviparous) fishes are used as models herein to help explain concepts because they are good examples for aquatic species in general, especially small-bodied fishes. Small live-bearing fishes are among the most at-risk fish groups in the world, and need urgent conservation attention. However, development of germplasm repositories for small live-bearing fishes is challenged by their unusual reproductive characteristics, such as formation of sperm bundles, initiation of spermatozoa motility in an isotonic environment, internal fertilization and gestation, and the bearing of live young. The development of germplasm repositories for goodeids and Xiphophorus species can provide examples for addressing these challenges. Germplasm repositories must contain multiple basic components, including frozen samples, genetic assessment and information systems. Standardization and process generalization are important strategies to help develop reliable and efficient repositories. An ideal conservation or recovery program for imperiled species should include a comprehensive approach, that combines major concerns such as habitat (by restoration projects), population propagation and maintenance (by captive breeding or translocation projects), and preservation of genetic diversity (by repository projects). In this context, strong collaboration among different sectors and people with different expertise is a key to the success of such comprehensive programs.

Sperm handling in aquatic animals for artificial reproduction

Artificial reproduction involves collection and handling of gametes in a way that secures their quality and maximizes the fertilization outcome. In addition to initial sperm quality, numerous steps can affect the final result of fertilization, from the sperm collection process until gamete mixing (or co-incubation) when the spermatozoon enters or fuses with the oocyte. In this review, we summarize the whole process of sperm handling, from collection until fertilization for fish, penaeid shrimp, bivalve mollusks and marine mammals. To obtain sperm from captive animals, techniques vary widely across taxa, and include stripping by abdominal massage or testis surgical removal in fish, spermatophore collection in penaeid shrimps, gonadal scarification or temperature shock in bivalve mollusks, and voluntary collection via positive reinforcement in mammals. In most cases, special care is needed to avoid contamination by mucus, seawater, urine, or feces that can either activate sperm motility and/or decrease its quality. We also review techniques and extender solutions used for refrigerated storage of sperm across the aforementioned taxa. Finally, we give an overview of the different protocols for in vivo and in vitro fertilization including activation of sperm motility and methods for gamete co-incubation. The present study provides valuable information regarding breeder management either for animal production or species conservation.

Activation of free sperm and dissociation of sperm bundles (spermatozeugmata) of an endangered viviparous fish, Xenotoca eiseni

Knowledge of sperm motility activation for viviparous fishes has been limited to study of several species in Poeciliidae, and the dissociation of sperm bundles is even less understood. The goal of this study was to use the endangered Redtail Splitfin (Xenotoca eiseni) as a model to investigate the activation of sperm from viviparous fishes by study of free sperm and spermatozeugmata (unencapsulated sperm bundles). The specific objectives were to evaluate the effects of: (1) osmotic pressure and refrigerated storage (4 °C) on activation of free sperm, (2) osmotic pressure, ions, and pH on dissociation of spermatozeugmata, and (3) CaCl₂ concentration and pH on sperm membrane integrity. Free sperm were activated in Ca²⁺-free Hanks' balanced salt solution at 81-516 mOsmol/kg. The highest motility (19 ± 6%) was at 305 mOsmol/kg and swim remained for 84 h. Glucose (300-700 mOsmol/kg), NaCl (50-600 mOsmol/kg), and KCl, MgCl₂, and MnCl₂ at 5-160 mM activated sperm within spermatozeugmata, but did not dissociate spermatozeugmata. CaCl₂ at 5-160 mM dissociated spermatozeugmata within 10 min. Solutions of NaCl-NaOH at pH 11.6 to 12.4 dissociated spermatozeugmata within 1 min. The percentage of viable cells had no significant differences (P = 0.2033) among different concentrations of CaCl₂, but it was lower (P < 0.0001) at pH 12.5 than at pH between 7.0 and 12.0. Overall, this study provided a foundation for quality evaluation of sperm and spermatozeugmata from livebearing fishes, and for development of germplasm repositories for imperiled goodeids.

Effects of Roundup formulations on biochemical biomarkers and male sperm quality of the livebearing Jenynsia multidentata

Roundup® formulations are the most consumed glyphosate-based herbicides in the world. When applied, they may reach water bodies and exert toxicity toward non-target species. This study evaluated and compared the effects of different variations of Roundup on biochemical biomarkers as oxidative parameters and Acethylchorinesterase (AChE) activity, and sperm quality of the livebearing Jenynsia multidentata. Fish were acutely (96 h) exposed to Roundup Original® (RO), Roundup Transorb® (RT) and Roundup WG® (RWG) at 0.0, 0.5, 1 and 5 mg L-1 of nominal glyphosate. The highest mortality (60%) was observed for fish exposed to RT at the highest concentration tested and at 0.5 mg L-1 non-mortality was observed, so this concentration was chosen for the experiments. Fish exposed to RO and RT (24 and 96 h) presented a state of oxidative imbalance, which caused lipid peroxidation (LPO) in their livers. Oxidative stress was more severe in RO treatment, which may be resulted in the highest hepathosomatic index at 96 h. However, fish exposed to RT presented a marked inhibition of AChE activity from membrane cells of muscle and brain tissues. Sperm quality was investigated in livebearing exposed (24 and 96 h) to the three formulations. Spermatozoa motility and concentration were affected by all formulations. Overall, Roundup formulations are harmful to the fish J. multidentata at 0.5 mg L-1 of glyphosate; however, mechanisms and potential of toxicity are different between formulations. The J. multidentata also represents a sensitive species and a good regional bio-monitor.

The effects of osmolality on sperm quality in Jenynsia multidentata (Cyprinodontiformes: Anablepidae)

Sperm quality tests on fish are classically used for evaluating cryopreservation procedures, and they are also promising to assess aquatic toxicity and biomarkers of xenobiotic effects on reproduction. Osmotic shock from the storage medium is one of the main factors affecting sperm quality during evaluation. Thus, the objective of this study was to evaluate the effects of different osmolalities (240-460 mOsm/kg) for at least 4 days on the sperm quality parameters of the viviparous fish Jenynsia multidentata. The level of significance was (P < 0.05). The plasma osmolality of J. multidentata is 326 ± 3.9 mOsm/kg. The motility of fresh semen was higher in osmolalities of 280 and 300 mOsm/kg but did not differ between osmolalities from 240 to 320 mOsm/kg. Above 380 mOsm/kg, the motility observed was 0%. Over the time period studied motility increased with increasing osmolality, and the most constant and long-lasting rates were between 300 and 320 mOsm/kg. On the 4th day of evaluation, higher membrane integrity rates were observed between 280 and 360 mOsm/kg, higher mitochondrial membrane potential was observed between 300 and 460 mOsm/kg, and higher DNA integrity rates were observed between 260 and 380 mOsm/kg. Moreover, osmolalities ≥460 and ≤240 resulted in the lowest motility and DNA integrity levels. Over 4 days, the plasma membrane integrity was significantly lower at ≤260 and ≥400 mOsm/kg, and the mitochondrial membrane potential was significantly lower only in osmolalities ≤240 mOsm/kg. Therefore, we conclude that for sperm quality preservation in J. multidentata, an osmolality of 300-320 mOsm/kg of the most suitable diluent is necessary. Furthermore, we conclude that the storage of sperm in a hyposmotic (<260 mOsm/kg) or hyperosmotic (>400 mOsm/kg) solution affects not only motility but also other sperm quality parameters.

Effect of short-term semen storage in salmon (Oncorhynchus mykiss) on sperm functional parameters evaluated by flow cytometry

The short-term storage of salmonid semen is a viable method for in vitro fertilisation. Previous studies have found that short-term storage affects sperm motility, compromising quality and fertilising capacity. However, the functional characteristics of the spermatozoa of O. mykiss during storage time and its relation to the spawning period are little known. This study was designed to evaluate the effects of in vitro short-term storage on sperm functional parameters in O. mykiss, determined by flow cytometry. Semen samples of the first spawning - undiluted (SSD) and diluted (SD) (Storfish(®) 1 : 2v/v; IMV AI solutions, France) - were stored at 4 °C for 14 days. Motility, viability (PMI: plasma membrane integrity) and mitochondrial membrane potential (ΔΨM) were assessed. On the fifth day of storage, spermatozoa showed a motility >70% (SSD: 78.3% versus SD 85.0%), PMI (81.5% SSD/87.2% SD) and ΔΨM (72.5% SSD/SD 80.0%) (P < 0.05). However, a significant decline in the percentage of all functional parameters (P < 0.05) was observed after 5 days of storage for all samples of both undiluted (SSD) and diluted semen. In conclusion, the results here provide new data on O. mykiss sperm quality with respect to in vitro short-term storage evaluated by flow cytometry.

Toxic effects of the herbicide Roundup in the guppy Poecilia vivipara acclimated to fresh water

Although it is believed that glyphosate-based herbicides are relatively nontoxic to humans, its broad use in agriculture and consequent contamination of aquatic systems is a concern. In the present study, reproductive (sperm quality) and biochemical parameters (acetylcholinesterase and glutathione S-transferase activity, lipoperoxidation, and antioxidant capacity against peroxyl radicals) were evaluated in adult guppies (Poecilia vivipara) acclimated to fresh water and exposed (96 h) to environmentally realistic concentrations of glyphosate (130 and 700 μg L(-1)) as the commercial formulation Roundup. Male guppies exposed to Roundup showed a poorer sperm quality, measured as reduced plasmatic membrane integrity, mitochondrial functionality, DNA integrity, motility, motility period and concentration of spermatic cells, than those kept under control condition (no Roundup addition to the water). Most of the spermatic parameters analyzed showed strong association to each other, which may help to understand the mechanisms underlying the observed reduction in sperm quality. Exposure to Roundup did not alter the biochemical parameters analyzed, though differences between genders were observed and deserve further investigations. Findings from the present study suggest that exposure to environmentally relevant concentrations of Roundup may negatively affect at long-term the reproduction of P. vivipara, with consequent changes in fish populations inhabiting environments contaminated with the herbicide.