File:American malacological bulletin (1988) (18157487991).jpg

Title: American malacological bulletin
Identifier: americanmal6719881990amer (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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134 AMER. MALAC. BULL. 6(1) (1988)
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Fig. 5. Cross section through the girdle, ventral part. Two papillae (p) are connected by cups with their scales (ct, connective tissue; c, cuticle; e, epidermis; scu, spicule cup; vs, ventral scale (decalcified) (left is lateral, upper side is ventral). Fig. 6. Epidermis on the dorsal side of the girdle (bl, basal lamina; co, collagen; mv, microvilli; nu, nucleus; tf, tonofilaments; arrows indicate branches of the cup of a dorsal scale running down between the microvili of the epidermal cells). Fig. 7. Distal part of a ventral papilla (c, cuticle; sc, spicule cell; scu, spicule cup). A cilium protruding from the ciliary cell can be seen (arrow). This cell invaginates into the distal part of the spicule cell (double arrow). vesicular bodies are also present. Distally, the cell is elongated and protrudes up to the cuticle. Relatively large (0.5 /jm in diameter) microvilli protrude into the cuticle. One cilium (9+2 structure) runs to the base of the spine, scale, clapper or hair (in these sections we refer to all these formations as "spicules") (Fig. 7). This cilium originates from a striated rootlet that consists of several parts (Fig. 8). Branches of the ciliary cell invaginate into other cells, especially into the distal area of the spicule cell (Figs. 9, 10). Two centrioles are pre- sent in this invagination. In longer papillae, the distal part of the ciliary cell contains many microtubules. This zone then resembles a dendrite. SPICULE CELL The spicule cell connects the spicule with the papilla. Again, the nucleus is large and does not contain much con- densed chromatin. Especially in the distal half of the cell agranular ER, numerous microtubules and many mitochon- dria are present. This zone is also characterized by the in- vagination of the ciliary cell mentioned above. The mem- branes of both cells are parallel to each other, and the spicule cell forms a dense network of microfilaments around this part of the ciliary cell (Fig. 9). Distally, the spicule cell bears numerous microvilli that are connected with the organic cup or shaft of the spicule (Fig. 11). The calcareous element is placed in or on top of this organic structure. It does not con- tain any cellular elements. In all parts of the girdle, the cilium of the ciliary cell at the base of the spicule is oriented towards the girdle margin, i.e. the papillae are polarized. Structures resembling small neurons (fibers containing numerous microtubles) can be found from the basal lamina far up into the papilla. However, no synapse or direct connection to a cell could be seen so far. VENTRAL PAPILLAE The ventral papillae are oriented at an angle of 10-20°

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