Sex Steroid Levels in Porichthys notatus, a Fish with Alternative Reproductive Tactics, and a Review of the Hormonal Bases for Male Dimorphism among Teleost Fishes

Plasma levels of 11-ketotestosterone, 11-β-OH-testosterone, testosterone, and 17-β-estradiol were measured in reproductive Porichthys notatus , a teleost fish with two male morphs and alternative reproductive tactics. The two male types had contrasting androgen profiles, 11-Ketotestosterone was the predominant androgen in the Type I male morph which acoustically courts females, excavates nests, and guards eggs. Yet testosterone was predominant in the plasma of the Type II male morph which neither courts females nor nests, but instead parasitizes Type I males with sneak or satellite spawning tactics. The Type I-Type II male divergence in reproductive tactics and androgen levels is paralleled by dimorphisms in the vocal system, in body size, and in relative testis size. A review of endocrine data from six different species with male dimorphism shows consistent differences between morphotypes and a striking pattern: 11-ketotestosterone levels are uniformly elevated in each "courting male" morphotype relative to its "noncourting" conspecific. This cross-species pattern may reflect the behavioral, gonadal, or morphological differences which characterize the two morphotypes. At this point, the morphological interpretation is favored.