Steroidogenesis by testis and accessory glands of the Lusitanian toadfish, Halobatrachus didactylus, during reproductive season

In teleost fish sex steroids are essential for gonadal function and have marked effects in reproductive and agonistic behavior and in the expression of secondary sexual characteristics. The Lusitanian toadfish, Halobatrachus didactylus, has two male morphotypes: type I males are territorial nest-holders and have large accessory glands while type II males are smaller, have a relatively large testis and small accessory glands. In the present study, the steroidogenic activity of the testis and accessory testicular glands of the Lusitanian toadfish were examined in vitro as well as their presence in urine. The testis of type I males produced 11-ketotestosterone (11KT) and 11-beta-hydroxy-4-androstene-3,17-dione (11 beta A) from tritiated 17-hydroxyprogesterone, while those of type II males produced testosterone (T) and 11 beta,17 beta-dihydroxy-4-andosten-3-one (11 beta T), but not 11KT. Additionally, the testis and accessory glands of both morphs produced mostly 5 beta,3 alpha-reduced and 17,20 alpha-hydroxylated metabolites. Type I, but not of type II, males synthesised 5 beta-reduced androgens in their accessory glands. The presence of 11 beta A exclusively in the urine of type I males during reproductive season suggests an association with maintenance of secondary sexual characteristics and behavior in this morph. The urine of both types of males contained two 5 alpha-androstane and 5 beta-pregnane glucuronides. Among the latter steroids, those that are 17,21-dihydroxylated are potentially metabolites from cortisol and were found only in type I males during the spawning season. The diversity of metabolites produced by the testis and accessory glands and the presence of some in urine is suggestive of a potential role in chemical communication and reproductive behavior. (C) 2015 Elsevier Inc. All rights reserved.