File:American malacological bulletin (1986) (18156225785).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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68 AMER. MALAC. BULL. 4(1) (1986)
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Fig. 6 a-e. Cleavage, blastula and gastrula stages of Corbicula fluminea. (a) photomicrograph of cleavage, showing blastomeres, BL Horizon- tal field width = 260 ^m. (b) SEM of blastula. Horizontal field width = 160 //m. (c) Photomicrograph of gastrulae in marsupial gill. Horizontal field width = 700 pm. (d) Photomicrograph of gastrula, phase contrast. Horizontal field width = 285 ^im. (e) Photomicrograph of gastrula. Horizontal field width = 285 ^m. BP, blastopore. GASTRULA FORMATION Following blastulation, cell proliferation and cell migra- tion produce a gastrula which is bluntly cone-shaped. A large blastopore provides the vegetal pole of the gastrula with an almost flared appearance (Fig. 6c,d,e). Gastrulae appear about 30 hours after fertilization and measure 175-180 /*m in diameter. DEVELOPMENT OF THE TROCHOPHORE In dissections of fresh tissue of C. fluminea, trochophore larvae were frequently seen in the inner, mar- supial gills. They could be visualized with SEM, packed into the gill chambers and measuring about 180 long. With light microscopy we observed the living trochophores at length as they made their way out of the gill chambers (when artificially freed from gill membranes) and either drifted passively or swam actively there (Fig. 7). Invariably the apical cilia (Scheitelorgan) were "anterior" as the trochophore swam vertically, horizontally or occasionally in a circular path along with other trochophores. When thus observed, the apical cilia of the trochophore are quite mobile and will bend or momen- tarily retract as the trochophore comes in contact with other larvae or with predators.

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