Osmoregulatory strategies in natural populations of the black-chinned tilapia Sarotherodon melanotheron exposed to extreme salinities in West African estuaries

Abstract

The effect of salinity was studied in natural populations of the black-chinned tilapia (Sarotherodon melanotheron) from West Africa. This euryhaline species colonizes nearly all coastal environments from bays to lagoons characterized by salinities ranging from fresh water to hypersaline water over 100 ‰. Individuals were sampled during the dry season at several locations characterized by different levels of salinity (3-102 ‰). Their osmotic status and their gills were analyzed. The branchial mitochondria-rich cells (MRC), localized at the basis of the filaments and along the lamellae in fish taken from the saline stations, showed a wide plasticity with significant differences in their number and size. The most striking results were a significant larger area (≈3x) and a higher number (≈55x) of MRC at high salinity (102 ‰) compared to low salinity (3 ‰). The major ion transporters and channels were localized by immunocytochemistry and different expression patterns have been recorded between stations. Despite an increased Na⁺/K⁺-ATPase (NKA) α-subunit expression and NKA activity, pointing to an increased monovalent ion excretion, a severe osmotic imbalance was recorded in animals living in hypersaline environments.

Analysis of the black‐chinned tilapia Sarotherodon melanotheron heudelotii reproducing under a wide range of salinities: from RNA‐seq to candidate genes

“…); contig_Tilapia_90_947 corresponds to a Na + /K + ‐transporting ATPase subunit alpha‐1, which is involved in the active ion excretion and uptake for maintaining the intracellular ionic balance (Lorin‐Nebel et al . ). Finally, of these 43 genes, six did not match any known protein.…”

Egg production in the euryhaline tilapia,Sarotherodon melanotheron heudelotii, experimentally maintained in fresh, sea and hypersaline waters

“…Because of its exceptional capacities, S. m. heudelotii is considered as an interesting model for studying the physiological adaptation to salinity (Akinrotimi et al 2007;Tine et al 2008Tine et al , 2010Ouattara et al 2009;Lorin-Nebel et al 2012;Riou et al 2012;Avarre et al 2014). It is also a good candidate for aquaculture in African lagoons and was the subject of several studies on an integrated fish-plankton aquaculture system in brackish water (Gilles et al 2008(Gilles et al , 2013.…”

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).

“…Ces résultats sont en accord avec ceux déjà rapportés par Franklin (1990) et Perry et al (1992) chez d'autres espèces de poissons. Chez le tilapia S. melanotheron, seules quelques études ont décrit une régulation endocrinienne (Tine et al, 2007) et des modifications quantitatives des cellules à chlorures et de l'activité de la pompe Na + /K + -ATPase (Ouattara et al, 2009;Lorin-Nebel et al, 2012) (Diouf, 1996). Cet estuaire a été particulièrement affecté ces dernières années par des sécheresses consécutives ; limitant fortement son approvisionnement en ED.…”