Physiological Diversity in Metabolism in Marine and Terrestrial Crustacea

Abstract

Two aspects of metabolic adaptation to increased terrestrialism are considered: (1) respiratory adaptations as reflected by comparative cytochrome c oxidase activity in tissues of crabs from aquatic and terrestrial habitats, and (2) thermal acclimation patterns in cytochrome c oxidase activity in tissues from these crabs. Enzymatic assays were done spectrophotometrically on gill, muscle, and mid-gut gland tissues from two aquatic species, Libinia emarginata and Callinectes sapidus , and the terrestrial Ocypode quadrata . Cytochrome c oxidase was chosen for this study since it is generally believed that the more aerobic the cells or tissues become, the more fully developed the cytochrome system will be. This enzyme is also thought to have a role in thermal acclimation. In gill tissue the activity of cytochrome c oxidase is enhanced with the advent of aerial respiration. Enzymatic activity of gill tissue from Ocypode quadrata was significantly greater than it was in tissue from the aquatic species. No correlation was observed with increased terrestrialism and enzymatic activity of muscle or mid-gut gland tissue. The thermal acclimation patterns of tissues of these three species of crabs indicate a clear-cut tendency for less enzymatic adaptation to temperature at the tissue level as these crabs evolve toward a land habitat.