Facultatively internal fertilization and anomalous embryonic development of a non-copulatory sculpin Hemilepidotus gilberti Jordan and Starks (Scorpaeniformes: Cottidae).

Fertilized residual eggs were observed in the ovaries of spent females of a non-copulatory sculpin Hemilepidotus gilberti Jordan and Starks. Fertilized eggs were present in 23 of 35 females, and approximately 38% of the total residual eggs (n=227) were fertilized. These eggs were thought to be fertilized facultatively with spermatozoa that entered the ovary through ovarian fluid during spawning. The high calcium concentration (1.42+/-0.21 mM kg(-1)) in ovarian fluid, which is beyond the threshold concentration required for fertilization, may allow internal fertilization to occur. Embryos at various developmental stages were observed, but all were deformed and surrounded by unhardened chorions. Since no larvae were observed, all the fertilized residual eggs would have degenerated in the ovary in accordance with other unfertilized residual eggs. These observations suggest that the ovary of the oviparous fish H. gilberti is an unsuitable environment for embryos to develop, possibly because it may be unable to supply developing embryos with needed elements, such as oxygen.