Effects of salinity challenge on the endocrine control of osmoregulation and calcium homeostasis in the sea bream

• Autor(a) principal: Guerreiro, P. M.
• Data de Publicação: 1999
• Outros Autores: Fuentes, J., Flik, G., Canario, Adelino V. M., Power, Deborah
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.1/5497

The gilthead sea bream (Sparus auratu) is a marine species often found in coastal lagoons, experimenting episodic exposures to both brackish and hypersaline environments. However, little is known about the underlying endocrine mechanisms controlling osmoregulation in this and in most marine species. This study aimed at characterising some of the endocrine basis of sea bream osmoregulation, with emphasis on calcium homeostasis. Juvenile fish were exposed to different salinities, either by direct transfer or continuous adaptation over a short period of time. Salinities ranged from 0 to 55 p.p.t. and sampling was carried out 4, 24, 96 and 192 h after transfer. Six fish per group and per time point were sacrificed and plasma and tissue samples were collected. Osmolarity, osmolites and cortisol were measured in plasma. Prolactin, growth hormone, stanniocalcin, and calcitonin mRNA expressions were determined by PCR and northern blot. Mortality occurred after 4 hours in FW. Sea bream fry (2 month old, 20-60 may) were exposed to hypersaline and dilute seawater loaded with Ca and calcium fluxes were determined. Exposure of fry to lowered external salinity (50 and 25% SW) resulted in no mortality within 24 h and significantly decreased whole body calcium influx. Results will be discussed in relation to gene expression.