Short-term storage and management of sperm in vitro is an easy and economical process in which suitable extenders can be utilized to extend the storage period and prevent sperm function impairment. Therefore, the current study aimed to evaluate the effect of suitable extenders during the short-term storage of sterlet sperm and determine their fertilizing capacity and hatching success. Three extenders containing a composition of 16, 20, and 24 mM NaCl, 1 mM KCl, 0.1 mM CaCl2, 10 mM Tris, pH 8.0 with osmolarity of 46, 55, and 62 mOsm/kg, were used to dilute the sperm of four sexually mature sterlet males (n = 4). Using a CASA system, the motility and velocity of undiluted and diluted sperm with extenders (E1 - E3) were assessed over 6 days at 0-2 °C. The short-term stored diluted sperm was then used in the fertilization and hatching assay, and undiluted fresh and stored sperm was used as a control. A two-way factorial analysis of variance (ANOVA) model confirmed significant effects on sperm motility, curvilinear velocity (VCL), and straight-line velocity (VSL) (P < 0.001), as well as their interaction with the extender. The model was decomposed into a one-way ANOVA to examine the impacts of extenders and storage time. With increasing storage periods, the sperm motility and velocity gradually decreased for diluted sperm with three extenders (E1-E3) but sharply decreased for undiluted sperm (Control). The motility of undiluted sperm was found 3.77 ± 4.09% at 4 days, whereas sperm diluted with extenders showed 57.57 ± 12.33% (E1), 64.34 ± 11.86% (E2), and 61.40 ± 12.41% (E3) motility at 6 days. This study explored extenders optimized with higher osmolarity (39-62 mOsm/kg) and lower K+ (1 mmol/L) as the most suitable medium for storing sterlet sperm for 6 days. After 6 days post storage, sperm diluted with extenders E1-E3 achieved a fertilization rate of 31.29 ± 14.2%, 31.66 ± 8.84%, and 30.67 ± 10.02%, respectively, and hatching success of 29.58 ± 13.4%, 30.50 ± 7.89%, and 27.95 ± 9.62%, respectively with freshly ovulated eggs.

• Keywords
• CASA, Fertilization rate, Hatching rate, Sperm motility, Sperm short-term storage, Sperm velocity,
• MeSH
• Fertilization * drug effects   MeSH
• Sperm Motility * drug effects   MeSH
• Fishes * physiology   MeSH
• Spermatozoa * physiology   drug effects   MeSH
• Semen Preservation * veterinary   methods   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

Increasing global rates of diminished fertility in males has been suggested to be associated with exposure to environmental contaminants (ECs). The aquatic environments are the final repository of ECs. As the reproductive system is conserved in vertebrates, studies on the effects of ECs on fertility endpoints in fishes provide us with valuable information to establish biomarkers in risk assessment of ECs, and to understand the ECs-related fertility threat. The aim of the present review was to evaluate associations between ECs and fertility determinants to better understand ECs-related male fertility threat in male fishes. Wildlife studies show that the reproductive system has been affected in fishes sampled from the polluted aquatic environment. The laboratory studies show the potency of ECs including natural and synthetic hormones, alkylphenols, bisphenols, plasticizers, pesticides, pharmaceutical, alkylating, and organotin agents to affect fertility determinants, resulting in diminished fertility at environmentally relevant concentrations. Both wildlife and laboratory studies reveal that ECs adverse effects on male fertility are associated with a decrease in sperm production, damage to sperm morphology, alternations in sperm genome, and decrease in sperm motility kinetics. The efficiency of ECs to affect sperm quality and male fertility highly depends on the concentration of the contaminants and the duration of exposure. Our review highlights that the number of contaminants examined over fertility tests are much lower than the number of contaminants detected in our environment. The ECs effects on fertility are largely unknown when fishes are exposed to the contaminants at early developmental stages. The review suggests the urgent need to examine ECs effects on male fertility when a fish is exposed at different developmental stages in a single or combination protocol. The ECs effects on the sperm genome are largely unknown to understand ECs-related inheritance of reproductive disorders transmitted to the progeny. To elucidate modes of action of ECs on sperm motility, it is needed to study functional morphology of the motility apparatus and to investigate ECs-disrupted motility signaling.

• Keywords
• fertility endpoints, industrial pollutants, pesticides, pharmaceuticals, sperm quality,
• Publication type
• Journal Article MeSH
• Review MeSH

Sturgeon sperm maturation occurs outside the testes during the transit of testicular spermatozoa (TS) through the kidneys and the Wolffian ducts. A method of in vitro TS maturation in sterlet Acipenser ruthenus was used to investigate the effects of temperature and hormonal stimulation of spermiation on the ability of TS to complete this process. Spermatozoa motility parameters after in vitro maturation of testicular sperm, concentrations of sex steroid hormones and testis morphology were studied in three groups of sterlet: (1) after overwintering in ponds (OW), (2) adapted to spawning temperature (ST), and (3) adapted to spawning temperature with hormonal induction of spermiation (ST-HI). Blood plasma concentrations of testosterone, 11-ketotestosterone and 17,20β-dihydroxy-pregnenolone increased significantly after hormonal induction of spermiation (group ST-HI). In all groups, TS were not motile. After in vitro sperm maturation, motility was up to 60% only in group ST-HI. The data suggest that the ability of TS to be matured in vitro was not related to the environmental temperature, while hormonal stimulation of spermiation during the spawning season was an absolute requirement for optimal in vitro maturation.

• Keywords
• Wolffian duct, hormonal stimulation of spermiation, kidney, seminal fluid, sex steroid hormones, sperm maturation, spermatozoan motility, sturgeon,
• Publication type
• Journal Article MeSH