Meeting Abstract
Salinity acclimation capacities of southern three-spined sticklebacks (Gasterosteus aculeatus L.) living in different saline habitats of the Camargue area (Rhone delta, northern Mediterranean coast) were investigated. Individuals from lagoons with different salinity ranges and from freshwater canals were exposed to seawater (SW; 30 ‰), brackish water (BW; 15 ‰), or freshwater (FW; 5 ‰). Morphological measurements of sub-adult fish sampled from 1994 to 2017 were determined from fish inhabiting in these different habitats. Also, oxygen consumption rates and osmoregulatory parameters (branchial Na+ /K+ -ATPase, NKA activity and gene expression of the α1 subunit and α1a and α1b NKA isoforms, gill ionocytes morphology) were measured from fish living in three contrasted habitats and after exposure to and different salinities. At all the studied locations, only the leirus morphotype was observed with also limited morphological variations. No short term effect of salinity could be detected on oxygen consumption from fresh, brackish, and saltwater fish. In these animals, gill NKA activity was salinity-dependent with also less NKA α1b in FW- than in SW-fish. Ionocytes in FW-fish gills were located along the lamellae and at their base, whereas these cells were restricted to gill filaments in SW-fish. Finally, electron microscopy revealed three different types of apical structures for these ionocytes: a honeycomb-like structure and a dome shape in FW, and deeply encrypted in SW. Therefore, sticklebacks of the Camargue area living in contrasted saline conditions belong to a very homogenous euryhaline population and are not exposed to strong metabolic demands due to salinity changes.
