The seminal vesicle as source of sex attracting substances in the African catfish, Clarias gariepinus

Abstract

Attraction tests were performed with female African catfish placed in a U-shaped two-choice maze. A conspecific was placed in both ends of the aquarium behind a perforated partion. An unovulated female fish allowed to choose between water containing a male and water containing a female conspecific did not show an obvious preference. After hormonally induced ovulation, however, females spent more time at the side of the male fish. Such a preference was absent in ovulated anosmic females. When confronted with a male fish from which the seminal vesicle was extirpated and an inteact male fish, female fish spent more time on the side of the latter after ovulation. Removal of the testes and a subsequent enlargement of the seminal vesicle made males more attractive for ovulated females. These results indicate that shortly after ovulation, female African catfish are attracted by male conspecifics, and that the male pheromone originates from the seminal vesicle. Subjection to an ovulated female appeared to induce a rise in circulating gonadotropin in both male and female catfish.