Title: American malacological bulletin
Identifier: americanmal4519861987amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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16 AMER. MALAC. BULL. 4(1) (1986) SPECIES DESCRIPTIONS MARGARITIFERA MARGARITIFERA. The stomach of this species demonstrated the greatest dissimilarity with the typical unionacean stomach as described by previous in- vestigators. Whereas in other unionceans in which the ma- jor typhlosole always terminates well inside the left anterior duct opening, the major typhlosole in M. margaritifera did not consistently enter the duct system. This condition is somewhat dependent on the population studied. In individuals of one population sampled, the major typhlosole entered the duct. In contrast, in another population the organ terminated near the entrance of the duct. Furthermore, a few popula- tions sampled contained animals in which both conditions existed. The right duct system was always observed to arise from a single opening in the right wall of the stomach. The left anterior duct system usually arose from a single open- ing in the left wall, as in other unionaceans, except perhaps Lamellidens sp. (Dinamani, 1967), occasionally, two openings occurred (Fig. 3a). Posteriorly, the left posterior duct system commonly had a single opening, which branched into anterior
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T Fig. 4. Detail of the anterior and right side sorting areas of the stomach interior: a, M. margaritifera; b, M. marrianae; c, C. mono- donta. Legend in c applies to a and b. Lines in sorting areas indicate orientation of ciliated ridges. Abbreviations: ASA = anterior sorting area, OES = esophagus, RD = right duct system, RSA = right sorting area. Horizontal field width = 7 mm. and posterior trunks (see Fig. 2). Exceptions rarely occurred in which certain specimens showed multiple openings (Fig. 3a). Sorting areas were variously developed along the right side and anterior floor of the stomach interior. The right side sorting area was a low shelf (Fig. 4a), not strongly set off from the anterior stomach floor as it is in some species of the unionid genera Lampsilis (Kat, 1983b) and Anodonta (Smith, pers. obser.). Purchon (1958) and Dinamani (1967) did not provide sufficiently detailed descriptions of the right sorting area to make comparisons with margaritiferids. The sorting ridges of the right sorting area extended anteriorly and medial- ly from the right side wall. A weak sorting area, analogous (but not necessarily homologous) to "SA7" of Purchon (1958), was usually present, even if barely developed. The sorting area was occasionally absent altogether (Fig. 4a).

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