Cloning and extression of growth hormone and insulin-like growth factor in response to different environmental salinities in thick-lipped grey mullet (Chelon labrosus)

Abstract

Trabajo presentado en el 8º Congreso de la Asociación Ibérica de Endocrinología Comparada (AIEC), celebrado en Madrid del 5 al 7 de septiembre de 2011.Thick-lipped grey mullet, Chelon labrosus (Risso, 1827), is a marine teleost from the family Mugilidae, very common in the estuaries and natural earthen ponds of the Bay of Cádiz, and of great importance for extensive aquaculture in this area. This euryhaline species is characterized by amphidromic life cycles, migrating to estuarine areas for feeding and other physiological processes. Growth hormone (GH) and insulin-like growth factor I (IGF-I) present a role in fish osmoregulation processes, being important pieces for the adaptation of specimens to changes in environmental salinity. We cloned pituitary GH and hepatic IGF-I in C. labrosus by cDNA library screening, using a species specific probe developed by PCR with degenerated primers, designed from the conserved regions of other teleost sequences from GenBank. In addition, changes in expression were measured in specimens maintained under different environmental salinities (0, 12, 40 and 55 ppt) during 21 days using real time RT-PCR. Moreover, cortisol levels were evaluated in plasma samples in order to assess the osmotic stress of specimens. Fish acclimated to lower salinities enhanced plasma cortisol levels, while specimens maintained at the highest salinity decreased this value compared to control. Previous studies have shown the existence of a positive interaction between GH and cortisol for improving osmoregulatory capacity in teleosts, but this relation is species-dependent. Pituitary GH and hepatic IGF-I expression will be presented and discussed under this hypothesis.Peer Reviewe