Fish speciation was accompanied by changes in the urogenital system anatomy. In evolutionarily modern Teleostei, male reproductive tracts are fully separated from the excretory system, while in evolutionarily ancient Chondrostei and Holostei, the excretory and reproductive tracts are not separated. Sturgeon post-testicular sperm maturation (PTSM) occurring as a result of sperm/urine mixing is phenomenologically well described, while, in holosteans, functional intimacy of seminal ducts with kidney ducts and the existence of PTSM still need to be addressed. In Lepisosteus platostomus (Holostei), sperm samples were collected from testes (TS), efferent ducts (EDS), and Wolffian ducts (WDS). While WDS was motile, no motility was found in TS and EDS. The existence of PTSM was checked by in vitro PTSM procedure. After TS and EDS incubation in seminal fluid from WDS, no more than 5% motile spermatozoa were observed in TS, whereas in EDS the motility percentage was up to 75%. Experimental dyeing of urogenital ducts in gars and sturgeons revealed some differences in the interconnection between sperm ducts and kidneys. It is concluded that post-testicular sperm maturation occurs in gars and suggests that infraclass Holostei occupies an intermediate evolutionary position between Teleostei and Chondrostei in the anatomical arrangement of the urogenital system.

• MeSH
• Sperm Motility MeSH
• Genitalia, Male MeSH
• Fishes anatomy & histology   MeSH
• Semen MeSH
• Spermatozoa MeSH
• Testis * MeSH
• Sperm Maturation * MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't 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