The morphometric changes in the gills of the estuarine crab Chasmagnathus granulatus under hyper- and hyporegulation conditions are not caused by proliferation of specialized cells.

GENOVESE, G.; LUQUET, C. M.; PAZ, D. A.; ROSA, G. A.; PELLERANO, G. N.

Journal of Anatomy

Wiley-Blackwell

Año: 2000 vol. 197 p. 239 - 246

0021-8782

Chasmagnathus granulatus is a hyper-hyporegulating crab that inhabits changing habitats of salinity inBrazil, Uruguay and Argentina. Since the gills are the main sites for active ion transport in crabs, theadaptive changes in the gill epithelium occurring under different conditions of salinity were studied by meansof morphological and morphometric analysis, and immunohistochemical identi®cation of cell proliferation(BrdU technique). In anterior (1±3) gills the epithelium thickness from crabs acclimatised to 12, 34 and44 g}l ranged from 1±27 to 2±46 lm, with no signi®cant change during acclimatisation, thus denoting arespiratory function. Medial (4±5) gill epithelium was slightly thicker in extreme salinities, but thesedifferences were not statistically signi®cant. In contrast, epithelial thickness of the posterior (6±8) gillsincreased signi®cantly up to 8±10 lm (dorsal zone of gill 8) both in hyper- and hyposaline media comparedwith seawater. The dark areas measured in gill 8 treated with AgNO$ revealed putative ion transportingtissue, especially at 12 and 44 g}l, corresponding to the zones of higher epithelial thickness. Hence theseareas seem to participate both in hyper- and hyporegulation. Proliferating cells labelled with BrdU almostnever occurred in the gills}salinity combinations studied during the initial 48 h of transfer from seawater tohyperconcentrated or diluted media, thus suggesting an increase in cell size rather than cell proliferation.