osmoregulatory disturbances induced by the parasitic barnacle loxothylacus texanus (rhizocephala) in the crab callinectes rathbunae (portunidae)

Abstract

The osmoregulatory response of the blue crab Callinectes rathbunae parasitized with the rhizocepbalan barnacle Loxothylacus texanus, and subjected to sudden salinity changes, was experimentally measured in the laboratory. Parasitized and control crabs were exposed to salinity changes every 3 h and their hemolymph osmolality measured. Two experiments, one with increasing salinity conditions (5 %, 12 %, 19 %, 25 %) and a second one with decreasing salinities (35 %, 25 %, 15 %, 5 %) were conducted. The results show that L. texanus significantly alters the hemolymph osmolality of C rathbunae maintaining it at lower than normal levels. In the increasing salinity trial, the hypoosmotic hemolymph condition of parasitized crabs was present at all salinities tested, whereas in the decreasing salinity trial a significant effect was found only at salinities of 5 % and 15 %. Since C rathbunae is constantly subjected to abrupt salinity changes in the tropical estuaries where it occurs, moving into high salinity areas may be the only way to cope with, the impact of L. texanus. (C) 2002 Elsevier Science B.V. All rights reserved.