THE HEMOGLOBIN OF THE BIVALVED MOLLUSC, PHACOIDES PECTINATUS GMELIN KENNETH R. H. READ 77/r Biological Laboratories, Harvard University, Cambridge, Mass. Hemoglobin has been reported from only a few species of bivalved molluscs ; it occurs in cells in the blood of Porouiya granitlata, Solcn Icyuincn. Tcllina planata, Capsa fragilis, Cardita acnlcata. Area tctragona, Area noac, Pcctitnculns glyciuieris, Astarte jusca (?) Griesbach, 1891), Cardita snlcata (Paladino, 1909), Anadara inflata (Kawamoto, 1928), Area pc.vata (Svedberg and Hedenius, 1934) and Area subcrenata (Kobayashi, 1935). In Tivcla stnltonun hemoglobin occurs in the brain (sic'), mantle, gills, foot and adductor muscle (Fox, 1953). Studies of absorption spectra have been carried out on the hemoglobin of Area subcrenata by Kobayashi (1935). and Svedberg and Hedenius (1934) have run ultracentrifuge sedimentation studies on the pigment of Area pc.rata; biochemically, however, the most extensively studied lamellibranch hemoglobin is that of Anadara inflata. The study of Anadara inflata hemoglobin began with the work of Kawamoto (1928), who reported the oxygen dissociation curve of the pigment. Sato (1931) and Kobayashi (1935) established the absorption spectra of the pigment and its derivatives. Work on the hemoglobin of Anadara inflata culminated with the efforts of Yagi ct al. (1955a, 1955b), who purified the hemoglobin, determined its molecular weight from sedimentation and diffusion studies, its electrophoretic mobility, iron content, nitrogen content and N-and C-terminal amino acids ; in addition, molar extinction coefficients were also reported. The present communication deals with the hemoglobin of the lucinid pelecypod, Phaeoidcs pcctinatiis Gmelin, which the author chanced on in Puerto Rico. This animal lives deep (down to 18 inches) in the mud of mangrove swamps, and when it is opened exhibits dark purplish ctenidia with an appearance reminiscent of ripe muscatel grapes. The bloom on the surfaces of the ctenidia is due to a superficial layer of pigment-free cells ; however, when the ctenidium is torn, it exhibits a bright red interior suggestive of hemoglobin. For illustration of the appearance of the gills see Figure 1. Although the clam is commonly eaten, at least in the neighborhood of La Parguera, P. R., and must therefore be some-what well known, the author can find no mention of its hemoglobin in the literature. A four-sided study of the red pigment of the ctenidia of Phaeoidcs pcctinatiis has been undertaken. First, evidence for the identity of the pigment with hemo-globin has been obtained from studies of absorption spectra ; second, the oxygen-combining properties of the pigment have been studied ; third, the behavior of the pigment in the ultracentrifuge has been examined with a view to gaining some idea of the size of the molecule ; and fourth, the histology of the pigment has been studied. 605
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