Vasculature of the Gas-Exchange Organs in Air-Breathing Brachyurans

Abstract

Information on the blood systems of the gills of water-breathing crabs, and of the gills and lungs of air-breathing crabs, is summarized. Blood flow through the gill lamellae is channeled by rows ofpillar cells and the intralamellar septum, and distinct afferent and efferent areas are apparent. Potential flow-control structures occur at the junctions between afferent and efferent areas and where the efferent channels enter the efferent branchial vessel. The gills also receive a direct arterial supply of blood. The inner surfaces of the branchiostegites (lungs) of aquatic and amphibious crabs are vascularized, and in terrestrial forms this vasculature becomes extremely sophisticated. The lung systems of air-breathing crabs are highly effective in oxygenation of the blood. The partition of the respiratory system between and within the respiratory organs is discussed.