Browsing by Author "Martins, Rute Sofia Tavares"
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- Does the interrenal influence sex differentiation in sea bass, Dicentrarchus labrax?Publication . Martins, Rute Sofia Tavares; Canário, AdelinoSea bass Dicentrarchus labrax is one of the most important cultured species in Mediterranean aquaculture. This species remains sexually immature most of the first year of life, and at the time of marketing (2 years old), females are 18-40% heavier than males. However, in cultured populations, it is frequently reported skewed sex ratios in favour of males (reaching 70-99%), and thus, the acquisition of all-female stocks is an attractive option for sea bass aquaculture. The underlying hypothesis of this work is that in intensive culture, the sea bass interrenal tissue produces corticosteroids in response to stress, and together with them an excess of adrenal androgens shifting the normal androgen/ estrogen ratio and thus leading to gonadal masculinization. Thus, blocking cortisol production with an antagonist (Dexamethasone) during the androgen sensitive period would most likely decrease the androgen levels and thereby the sex ratios would be altered.
- Somatostatin signalling coordinates energy metabolism allocation to reproduction in zebrafishPublication . Chen, Jie; Zhao, Wenting; Cao, Lei; Martins, Rute Sofia Tavares; Canario, AdelinoBackgroundEnergy allocation between growth and reproduction determines puberty onset and fertility. In mammals, peripheral hormones such as leptin, insulin and ghrelin signal metabolic information to the higher centres controlling gonadotrophin-releasing hormone neurone activity. However, these observations could not be confirmed in lower vertebrates, suggesting that other factors may mediate the energetic trade-off between growth and reproduction. A bioinformatic and experimental study suggested co-regulation of the circadian clock, reproductive axis and growth-regulating genes in zebrafish. While loss-of-function of most of the identified co-regulated genes had no effect or only had mild effects on reproduction, no such information existed about the co-regulated somatostatin, well-known for its actions on growth and metabolism.ResultsWe show that somatostatin signalling is pivotal in regulating fecundity and metabolism. Knock-out of zebrafish somatostatin 1.1 (sst1.1) and somatostatin 1.2 (sst1.2) caused a 20-30% increase in embryonic primordial germ cells, and sst1.2-/- adults laid 40% more eggs than their wild-type siblings. The sst1.1-/- and sst1.2-/- mutants had divergent metabolic phenotypes: the former had 25% more pancreatic alpha-cells, were hyperglycaemic and glucose intolerant, and had increased adipocyte mass; the latter had 25% more pancreatic beta-cells, improved glucose clearance and reduced adipocyte mass.ConclusionsWe conclude that somatostatin signalling regulates energy metabolism and fecundity through anti-proliferative and modulatory actions on primordial germ cells, pancreatic insulin and glucagon cells and the hypothalamus. The ancient origin of the somatostatin system suggests it could act as a switch linking metabolism and reproduction across vertebrates. The results raise the possibility of applications in human and animal fertility.