Osmotic and chloride regulation and water relations in Clibanarius vittatus (Decapoda: Anomura) from the Texas Gulf Coast.
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Steady state studies delineate the osmotic and chloride ion regulatory patterns for Clibanarus vittatus. The hermit crab regulates its hemolymph hyperosmotic to the medium at salinites ranging from 5 to 50 o/ooS. The maintenance of a constant hemolymph osmolality at low salinities switches to the maintenance of an osmotic concentration a set difference above the medium at salinities greater than 20 o/ooS. Hemolymph cloride ion concentration is regulated hyperionic to the external medium in salinities below 15 o/ooS. Above this, the hemolymph chloride concentration is regulated hypoionically. This ion constitutes 40 to 45 % of the total hemolymph osmolality. Percent body water and the rates of water exchange are constant for shelled crabs acclimated to 10, 20, 35, and 50 o/oo S sea water. Shell-less crabs have a greater percent body water content than shelled hermit crabs in dilute media. Three water pools are accounted for in shelled hermit crabs, while shell-less individuals only exhibit two.