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- The swimbladder of the Lusitanian toadfish: sexual dimorphism and hormonal controlPublication . Modesto, Teresa; Canario, Adelino V. M.; Castanõ, J. P.; Malagon, M. M.; Garcia Navarro, S.The members of the family Batrachoididae produce sounds associated with courtship and agonistic interactions. While long mating calls are only produced by nesting males, agonistic short duration grunts have been recorded from toadfishes and midshipmen in both males (nesting or not) and females. Sound production results from the contraction of paired sonic muscles attached to the walls of the swimbladder, which cause a rapid variation in swimbladder volume and internal pressure. Both sonic muscle growth and sonic fibre morphology have been shown to be androgen sensitive in batrachoidids.
- 17a,20ß,21-trihydroxy-4-pregnen-3-one: the probable maturation-inducing steroid of the lusitanian toadfishPublication . Modesto, Teresa; Canario, Adelino V. M.17,20 ,21-Trihydroxy-4-pregnen-3-one (17,20 ,21-P) was identified as the major metabolite of incubations of Lusitanian toadfish Halobatrachus didactylus ovarian follicles with [3H]-17hydroxyprogesterone. The potency of several steroids in inducing germinal vesicle breakdown of follicle-enclosed oocytes of Lusitanian toadfish was systematically examined by using an in vitro germinal vesicle breakdown (GVBD) bioassay. 17,20 -Dihydroxy-4-pregnen-3-one (17,20 -P) and 17,20 ,21-P, two confirmed maturation-inducing steroids (MIS) in teleosts, were the most potent in inducing GVBD with ED50s ranging between 9 and 271 nM. Structure-activity relationships followed similar patterns to what has been observed in similar bioassays, i.e. a vital requirement for 17- and 20 -hydroxyl groups in C21 steroids and a reduction in activity of 14 and 5–6%, respectively, for 5-pregnene and 5 -pregnanes compared to 4-pregnenes. Corticosteroids, testosterone and 17 -oestradiol were ineffective. Folliculated oocytes stimulated by pituitary homogenate produced 17,20 ,21-P from endogenous substrates in amounts one order of magnitude higher than 17,20 -P. These results strongly support the hypothesis that 17,20 ,21-P is the likely MIS in this species.