Internal Gametic Association and External Fertilization in the Elkhorn Sculpin, Alcichthys alcicornis

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Abstract
Morphological studies have demonstrated that fertilization in the copulating cottid species, the elkhorn sculpin (Alcichthys alcicornis), in which fertilization previously has been assumed to occur within the female''s genital tract, occurs externally. In the ovarian cavity of impregnated female fish, a number of spermatozoa were found to have entered the micropyle and a fertilizing spermatozoon had reached the lower end of the micropylar canal, but penetration of the spermatozoon into the ooplasm did not occur until after exposure to seawater. Based on these results and past studies, it is concluded that other cottids now regarded as internally-fertilizing species may also exhibit external fertilization with internal insemination.