Controllo neuroendocrino del comportamento riproduttivo dei maschi del blennide Salaria pavo

The present study has been performed on a population (living in Algarve, Portugal) of the peacock blenny Salaria pavo, an intertidal euryhaline fish occurring along Mediterranean sea and adjacent Atlantic coasts. The aim of this thesis is to investigate the endocrine control of sexual behavior in the two male morphotypes (sneaker males and bourgeois males) of this blenny. Salaria pavo is characterized by clear morphological differences, in particular the two male morphotypes differ for the head crest and the anal gland. Previous studies suggested that female prefers for larger males because they are the ones to make parental cares and the crest could be a signal for females. This hypothesis could explain the lack of crest in sneaker males engaged in female-like mimicry (they are smaller than the bourgeois male, and have a livery similar to females) so they can penetrate into the nest of resident male quickly and release their sperm over eggs to have their reproductive event. In sneaker morphotype, at brain level, androgens should balance the androgen-induced behavioral defeminization with the estrogen-induced behavioral masculinization. The present study was performed on samples collected during the 2009 in order to show the effects of implants (Testosterone, Castor oil, Flutamide, 11Keto-Testosterone) over hormones‟ levels, the secondary sexual characters and the expression of androgen receptors. The experiment is divided in a field work (collecting and implanting fishes), and a laboratory work in which we evaluated Testosterone and 11-Keto-Testosterone levels (RIA protocol) and androgen receptor expression by means of RNA extraction, c-DNA synthesis and Real-time PCR from head crest and anal gland homogenates. 6 Testosterone implants promoted the development of the head crest, even in sneaker males, reduced the size of the anal gland in the bourgeois males and promoted its increase in sneaker males. 11Keto-testosterone implants exerted the main effects on differentiation of the secondary sex features and on the expression of male reproductive behavior. It also promoted the development of the testicular gland in sneaker males. Quantitative analysis for androgen receptors reported not significant variations when the analysis of variance was performed. However, they show a tendency to significance, indicating a decrease in androgen receptor levels both in the anal gland and crest of treated sneaker males in comparison to controls (Castor oil implanted). This could suggest that differences are a matter of androgen circulating levels and not of tissue sensitivity. Sneaker males may be more reactive to androgens than bourgeois males.