Brain and gonadal aromatase activity and steroid hormone levels in female and polymorphic males of the peacock blenny Salaria pavo

Abstract

In the peacock blenny Salaria pavo large males with well-developed secondary sexual characters establish nests and attract females while small "sneaker" males mimic female sexual displays in order to approach the nests of larger males and parasitically fertilize eggs. These alternative reproductive tactics are sequential, as sneakers irreversibly switch into nesting males. This transition involves major morphologic and behavioral changes and is likely to be mediated by hormones. This study focuses on the role of aromatase, an enzyme that catalyses the conversion of androgens into estrogens, in the regulation of male sexual polymorphism in S. pavo. For this, sex steroid plasma levels and aromatase activity (AA) in gonads, whole brain and brain macroareas were determined in sneakers, transitional males (i.e. sneakers undergoing the transition into nesting males), nesting males and females collected in the field. AA was much higher in ovarian tissue than in testicular tissue and accordingly circulating estradiol levels were highest in females. This supports the view that elevated AA and estradiol levels are associated with the development of a functional ovary. Transitional males are in a non-reproductive phase and had underdeveloped testes when compared with sneakers and nesting males. Testicular AA was approximately 10 times higher in transitional males when compared with sneakers and nesting males, suggesting high AA has a suppressive effect on testicular development. Nesting males had significantly higher plasma levels of both testosterone (T) and 11-ketotestosterone when compared with the other male morphs and previous studies demonstrated that these androgens suppress female-like displays in sneakers. In the brain, AA was highest in macroareas presumably containing hypothalamic nuclei traditionally associated with the regulation of reproductive behaviors. Overall, females presented the highest levels of brain AA. In male morphs AA increased from sneakers, to transitional males, to nesting males in all brain macroareas. These results suggest that the transition into the nesting male tactic is accompanied both by an increase in testicular androgen production and by a higher conversion of androgens into estrogens in the brain. The increase in androgen production is likely to mediate the development of male secondary sexual characters while the increase in brain AA may be related to the behavioral changes associated with tactic transition.

Oestradiol and prostaglandin F2α regulate sexual displays in females of a sex-role reversed fish

“…, with a range of 1.9-26.4 ng ml 21 , values that are similar to those previously described for females captured in the field during the reproductive period [42]. In addition, the mean E2 level of ovariectomized females fell within the normal range of values for females of other fish species in reproductive conditions (e.g.…”

Brain Transcriptional Profiles of Male Alternative Reproductive Tactics and Females in Bluegill Sunfish

“…Key enzyme in estrogen biosynthesis é in territorial cichlid males [16]; é territorial blenny males [23]; é territorial black-faced blenny males [18]; ê in the sonic motor nucleus and ventromedial nucleus of nesting type I (territorial) male plainfin midshipman compared to type II (sneaker) males [24, é in territorial cichlid males [16] Somatostatin (sst) Neuropeptide that regulates endocrine pathways. Also affects neurotransmitters é in territorial blenny males [18]; éin territorial cichlid males [16] Early growth response 1 (egr1)…”

Brain aromatase mRNA expression in two populations of the peacock blenny Salaria pavo with divergent mating systems

“…These males have never been observed guarding eggs or courting nesting males with female-like displays and most likely they do not reproduce. Their testes are usually very small when compared with both parasitic and nesting males and this was confirmed during dissection (see Gonçalves et al, 2008). In Ria Formosa, fish were collected during low-tide with a hand-net from bricks used as nests.…”

“…This is in agreement with the results reported for fish where aromatase levels have been reported to be higher in forebrain regions known to regulate reproductive behaviors, particularly the preoptic and hypothalamic periventricular nuclei, central telencephalon and optic tectum (e.g., Forlano et al, 2001;Gelinas and Callard, 1993;Gelinas and Callard, 1997;Melo and Ramsdell, 2001). In the Gonçalves et al (2008) study, the pattern of aromatase activity across brain macroareas differed between morphotypes, with females presenting higher levels in posterior brain regions when compared to males, a pattern also described for the medaka Oryzias latipes (Melo and Ramsdell, 2001). In this study the interaction between the macroarea and morphotype factor was marginally non-significant (P = 0.07), but females also presented somewhat higher values of aromatase mRNA expression in posterior brain regions, in particular in the cerebellum and brainstem, when compared with the other morphotypes (Fig.…”