Influence de la salinité sur la structure des branchies et l’ultrastructure des ionocytes Chez le tilapia <i>Sarotherodon melanotheron heudelotii</i> provenant d'un estuaire hypersalé (Saloum, Sénégal).

Abstract

Ouattara et al. J. Appl. Biosci. 2014. Influence de la salinité sur la structure des branchies et l'ultrastructure des ionocytes chez le tilapia provenant d'un estuaire hypersalé (Sénégal). 6808Influence de la salinité sur la structure des branchies et l'ultrastructure des ionocytes Chez le tilapia Sarotherodon melanotheron heudelotii provenant d'un estuaire hypersalé (Saloum, Sénégal). 6809ABSTRACT Objective: This study describes the structure of gills and the ultrastructural changes in gill ionocytes of the tilapia S. m. heudelotii from a hypersaline estuary (Saloum, Senegal), subject to variations in salinity of 0,3; 35; 70 and 90‰ in laboratory for 72 h. Methodology and Results: Juvenile S. m. heudelotii were subjected to concentrations of salinity ranging from freshwater (0,3‰) to hypersaline water (90‰). The gills structure and the location of ionocytes were studied by photonic histology and ionocytes ultratrastructure described by transmission electronic microscopy. Four gill arches were identified. At 0,3‰ of salinity, ionocytes were observed at the base of filaments, while at 35‰ and more, they have been examined on the filaments and lamellae. Three types of ionocytes were identified according to the composition of the cytoplasm and two types according to the opening of the apical crypt. Conclusion and Application: This study shows for the first time that tilapia s. m. Heudelotii adapts to changes in concentration of salinity by modification of the location and ultrastructure of its gill ionocytes. These results suggested that this species can also fit perfectly into the high salinity, that other tilapia do not support, for example Oreochromis niloticus. It might therefore serve as a biological model in the perspective of a fish farming in brackish water or seawater. Indeed, tilapia culture is carried out mainly in fresh water that is keenly competed for direct consumption by human people and for industrial uses. However, marine and lagoon ecosystems have enormous fish farming potential, but very less exploited. Furthermore, these results may help to understand the phenomena of speciation in some species associated with the environmental disruption caused by climate change.