Physiological Diversity in Metabolism in Marine and Terrestrial Crustacea

Two aspects of metabolic adaptation to increased terrestrialismare considered: (1) respiratory adaptations as reflected bycomparative cytochrome c oxidase activity in tissues of crabsfrom aquatic and terrestrial habitats, and (2) thermal acclimationpatterns in cytochrome c oxidase activity in tissues from thesecrabs. Enzymatic assays were done spectrophotometrically ongill, muscle, and mid-gut gland tissues from two aquatic species,Libinia emarginata and Callinectes sapidus, and the terrestrialOcypode quadrata. Cytochrome c oxidase was chosen for this studysince it is generally believed that the more aerobic the cellsor tissues become, the more fully developed the cytochrome systemwill be. This enzyme is also thought to have a role in thermalacclimation. In gill tissue the activity of cytochrome c oxidase is enhancedwith the advent of aerial respiration. Enzymatic activity ofgill tissue from Ocypode quadrata was significantly greaterthan it was in tissue from the aquatic species. No correlationwas observed with increased terrestrialism and enzymatic activityof muscle or mid-gut gland tissue. The thermal acclimation patternsof tissues of these three species of crabs indicate a clear-cuttendency for less enzymatic adaptation to temperature at thetissue level as these crabs evolve toward a land habitat.