Response to environmental salinity of Na+-K+ATPase activity in individual gills of the euryhaline crab Cyrtograpsus angulatus

Abstract

The occurrence, localization and response to environmental salinity changes of Na+-K+ATPase activity were studied in each of the individual gills 4-8 of the euryhaline crab Cyrtograpsus angulatus from Mar Chiquita coastal lagoon (Buenos Aires Province, Argentina). Na+-K+ATPase activity appeared to be differentially sensitive to environmental salinity among gills. Upon an abrupt change to low salinity, a differential response of Na+-K+ATPase activity occurred in each individual gill which could suggest a differential role of this enzyme in ion transport process in the different gills of C. angulatus. With the exception of gill 8, a short-term increase of Na+-K+ATPase specific activity was observed in posterior gills, which is similar to adaptative variations of this activity described in other euryhaline crabs. However, and conversely to that described in other hyperregulating crabs, the highest increase of activity occurred in anterior gills 4 by 1 day after the change to dilute media which could suggest also a role for these gills in ion transport processes in C. angulatus. The fact that variations of Na+-K+ATPase activity in anterior and posterior gills were concomitant with the transition to hyperregulation indicate that this enzyme could be a component of the branchial ionoregulatory mechanisms at the biochemical level in this crab. The results suggest a differential participation of branchial Na+-K+ATPase activity in ionoregulatory mechanisms of C. angulatus. The possible existence of functional differences as well as distinct regulation mechanisms operating in individual gills is discussed.