Branchial chloride cells in sea bass (Dicentrarchus labrax) adapted to fresh water, seawater, and doubly concentrated seawater

Abstract

Branchial chloride cells (CC) were studied in sea bass (Dicentrarchus labrax) maintained in seawater (SW: 35 per thousand) or gradually adapted to and subsequently maintained in fresh water (0.2 per thousand) or doubly concentrated seawater (DSW: 70 per thousand). Changes were observed in the location, number, and structure of CCs, that were discriminated by light, scanning, and transmission electron microscopy, as well as by immunofluorescence on the basis of their high Na(+)/K(+)-ATPase antigen content. The number of CCs increased in both fresh water and doubly concentrated seawater compared to control fish maintained in SW. In both experimental conditions, these cells were found on the gill filament (as in control fish) and even on the lamellae, especially in hypersaline conditions. Structural changes concerned the shapes and sizes of CCs and their apical outcrops and particularly the structures of their functional complexes (mitochondria, tubular system, and endoplasmic reticulum), which developed significantly in DSW adapted fish. The changes in the expression of the Na(+)/K(+)-ATPase were evaluated by assessing the enzyme's density at the ultrastructural level following immunogold labeling. This parameter was significantly higher in doubly concentrated seawater. The adaptative significance of the quantitative and morphofunctional changes in branchial chloride cells is discussed in relation to the original osmoregulatory strategy of this marine euryhaline teleost.

Morphological Studies on the Gills of Puffer Fish (Lagocephalus sceleratus, Gmelin, 1789)

“…As in all other teleosts, in L. sceleratus gills, the chloride cells must play an important role in osmoregulation. According to results of (Varsamos et al, 2002), there is no strict separation in function between filament and lamellar epithelium, as chloride cells were also observed in the lamellar region of sea bass gills. In contrast to freshwater specimens, seawater-acclimated fish showed a marked increase in the number and size of chloride cells (Carmona et al).…”

Laser scanning cytometry and tissue microarray analysis of salinity effects on killifish chloride cells

“…An elegant recent study on O. mossambicus larvae indicates that FW CC are transformed into SW CC during salinity acclimation while accessory cells represent a newly differentiated cell type unique to SW fish (Hiroi et al, 1999). Interestingly, in some euryhaline teleosts such as Dicentrarchus labrax the number of CC is lowest in 1× SW and increases upon salinity transfer to FW and 2× SW (Varsamos et al, 2002). In this context, it is important to note that the energy requirements for osmoregulation increase in very dilute environments, and are accompanied by increases in CC number (Laurent and Hebibi, 1989;Perry and Laurent, 1989;Greco et al, 1996;Moron et al, 2003).…”

Multiplicity of expression of Na+,K+–ATPaseα-subunit isoforms in the gill of Atlantic salmon (Salmo salar): cellular localisation and absolute quantification in response to salinity change

“…There is consensus that in euryhaline teleost species, ion transporting cells may appear in both filament and lamellar positions, in some cases depending on salinity and other stressors, and also with clear species specific differences (Tipsmark et al, 2007;Uchida et al, 1996;Varsamos et al, 2002). At least in salmonids, it has been convincingly demonstrated that ionocytes appear in both locations in freshwater (FW) whereas in seawater (SW) most lamellar MRCs regress and the filament MRCs increase in number and particularly in size (Seidelin et al, 2000;Uchida et al, 1996).…”