File:American malacological bulletin (1986) (17968475240).jpg

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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Text Appearing Before Image:
Fig. 2. Generalized interior and digestive duct systems of the margaritiferid stomach. Abbreviations: APR = anterior pedal retrac- tor muscle, ASA = anterior sorting area, DH = dorsal hood, LAD = left anterior duct system, LE = left embayment, LPD = left posterior duct system, MG = midgut and style sac, MT = minor typhlosole, OES = esophagus, PSA = posterior sorting area, RD = right duct system, RE = right embayment, RSA = right sorting area, T = major typhlosole, VE = ventral embayment. Horizontal field width = 13 mm.
Text Appearing After Image:
Fig. 3. Diagrammatic representation of the left anterior (open, heavy lines) and posterior (solid) duct systems of the stomach showing max- imum variation observed: a, composite of different specimens of M. margaritifera; b, specimen of M. marhanae. Horizontal field width = 17 mm. among the species studied. The stomach floor contains a ma- jor typhlosole (T) which arises from the midgut (MG) and shows a strong fold and a swollen "conical mound" (Purchon, 1958) characteristic of other unionaceans at the apex of the fold. The typhlosole then proceeds to the left where it variously enters or terminates at the opening of the left anterior digestive duct system (LAD). The minor typhlosole (MT) arises near the major typhlosole and curves to the right posterior to the right digestive duct (RD). The ventral embayment (VE) is rather uniform throughout the species examined and represents a ventral extension of the posterior stomach floor. No comparison can be made with other unionacean species studied as this structure was not discussed by previous in- vestigators. No consistent differences were detected between margaritiferid species and the few unionid species exam- ined in this study. Anteriorly, the termination of the esophagus (OES) is marked by a rim, as is the case in other unionaceans. The area immediately posterior to the esophageal rim, the anterior sorting area (ASA), is variously developed in examined margaritiferid species. The interior floor surface is covered with extensive sorting fields, which Purchon (1958) differen- tiated and identified. These sorting fields are associated with the typhlosoles, duct openings, and embayments. No special differences were noted between margaritiferid species and other unionacean species previously studied.

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