GILLS OF CYLINDROLEBERIDID OSTRACODES EXEMPLIFIED BY LEUROLEBERIS SURUGAENSIS FROM JAPAN

Abstract

The gills of the ostracode Leuroleberis surugaensis Hiruta, 1982, a nektobenthic cylindroleberidid myodocopid from the Pacific Coast of central Japan are described. They consist of 7 pairs of integumental laminae attached to the thoracic wall. Each individual lamina has numerous lacunae (diameter up to 60 µm), smaller subcuticular spaces, an (efferent) epibranchial and a (afferent) hypobranchial canal, pillarlike cells, and cells bearing a large nucleus (5–10 µm in diameter), comparable to the nephrocytes of decapods. The lacunae form an extensive anastomosing network of arcuate sinuses containing hemolymph and amoeboid free-cells (hemocytes). The epibranchial canals open dorsally into the pericardial cavity suggesting that hemolymph contained in gills flows back to the heart through a dorsal route. The 7 pairs of gill laminae of Leuroleberis are interpreted as the major respiratory surfaces of the animal and may also be involved in the degradation of metabolic waste products. Ventilation over the respiratory surfaces is provided by the rhythmic movement of epipodial plates (fifth limb). The book gills of Leuroleberis and other cylindroleberidids are interpreted as possible epipodial remnants of lost limbs posterior to the seventh limb.