A Shift to an Ion Regulatory Role by Gills of a Semi-Terrestrial Crab, Ocypode stimpsoni

Jyuan-Ru Tsai and Hui-Chen Lin (2012) A shift to an ion regulatory role by gills of a semi-terrestrial crab, Ocypode stimpsoni. Zoological Studies 51(5): 606-618. Ocypode stimpsoni is a highly terrestrial species of the Ocypodidae that faces challenges of both gas exchange and hypotonic stress when on land. The aim of this study was to investigate the impacts of terrestrial modifications on the ion regulatory mechanism of the gills in this semi-terrestrial crab. Our results showed that the lungs were the air-breathing organ and may take the place of anterior gills for gas exchange. Epithelial cells in the anterior gills changed from a thin epithelium for gas exchange to an intermediate type epithelium for ion regulation. We also found significantly higher Na+, K+-ATPase activity in the anterior gills when crabs were transferred to 3 ‰ and 5 ‰ diluted seawater. The ion regulatory proteins in both the anterior and posterior gills showed similar localization, an indication of the involvement of the anterior gills in ion regulation. Cell thicknesses and Na+, K+-ATPase activity suggest that the anterior gills can assist with ion regulation in acclimation to dilute seawater. We concluded that the presence of the lungs caused the gills to be modified for ion regulation