Effect of cortisol on some osmoregulatory parameters of the teleost, Oreochromis niloticus L., after transference from freshwater to seawater

Abstract

This trial was conducted in order to determine the effects of cortisol on salt water acclimation of tilapia Oreochromis niloticus (L.). Tilapia (n=42) were injected intraperitoneally with cortisol and then were directly transferred from freshwater (FW) to 15‰ salt water (SW). Changes in plasma osmolality, chloride ion concentration (Cl-), plasma level of cortisol and gill Na+, K+-ATPase activity were measured at 6, 12, 24, 48, 72 and 168 hours after transference to 15‰ SW. Plasma osmolality and Cl- increased immediately after transference until 12-24 h. The fish injected with cortisol (F) showed higher plasma levels of cortisol than those from control group (C) that maintained the initial levels during the experiment. Gill Na+, K+-ATPase activity of C fish began to increase at first hours after transference and peak at 48h. The differences between gill Na+, K+-ATPase activity of F and C groups were significant (P<0.05) in FW, which confirm the effect of exogenous cortisol.

Enhancement of growth and feed utilization of the European sea bass (Dicentrarchus labrax) fed supplementary dietary salt in freshwater

“…Na + , Cl − , K + , Mg + and Ca 2+ ) from the water and/or through the diet (Smith, Talbot & Eddy 1989; Karnaky 1998). It is reasonable to expect that diet is an important source of salts that could satisfy the osmoregulatory requirements of the fish in low‐salinity water or even FW and might spare energy used for osmoregulation, thereby leaving more energy available for growth (Zaugg, Roley, Prentice, Gores & Waknitz 1983; Gatlin, Macenzie, Craig & Neill 1992; Nandeesha, Gangadhar, Keshavanath & Varghese 2000; Fontainhas‐Fernandes, Russell‐Pinto, Gomes, Reis‐Henriques & Coimbra 2001). Acclimation with salt‐supplemented diets (at 4–8%) was found to be useful for non‐smolting rainbow trout and other salmonids before release to the sea (Salman & Eddy 1987; Pelletier & Besner 1992; Staurnes & Finstad 2000), as such diets increase Na + –K + –ATPase activity and salinity tolerance in fish (Zaugg et al 1983; Salman & Eddy 1988; Pelletier & Besner 1992).…”

Susceptibility of Nile tilapia (Oreochromis niloticus) fed with dietary sodium chloride to nitrite toxicity

“…Supplementation of fish diets with NaCl increases the ability of fish to maintain electrolyte balance (Staurnes and Finstad 2000;Fontaínhas-Fernandes et al 2001) and elevates plasma chloride and sodium concentrations (Salman and Eddy 1987;Staurnes and Finstad 2000). NaCl added to fish diets has shown promise in preventing toxicity to waterborne cations, such as copper in rainbow trout (Oncorhynchus mykiss) (Kamunde et al , 2005Pyle et al 2003).…”

Molecular cloning and differential expression of the glucocorticoid receptorgene in the estuarine tapertail anchovy Coilia nasus

“…So GCRs are expressed quite ubiquitously in fish, especially in liver (Vijayan et al, 2003), gills (Kuo et al, 2013), and muscle (Rotllant et al, 1997). C. nasus Gcr mRNA is highly expressed in liver and muscle (Figure 2), which is consistent with the critical functions of cortisol in these tissues (Dean et al, 2003;Fontainhas et al, 2003;Marshall, 2003;Tripathi and Verma, 2004). Cortisol is a key mediator of stress-induced hyperglycemia, and importantly, it supports the increased energy demand associated with stress (Mommsen et al, 1999;Sapolsky et al, 2000).…”