File:American malacological bulletin (1988) (18152868582).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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FISCHER: AESTHETES IN LEPIDOPLEURUS CAJETANUS 155
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Fig. 3. Left half of an intermediate shell valve. KOH-treated (ap, apophyse; la, lateral triangle; m, median triangle). Fig. 4. Higher magnification of the lateral triangle, KOH-treated (arrows indicate several smaller micropores surrounding a megapore). Fig. 5. Surface of an apical cap. The cap is perforated by numerous small pores. Fig. 6. Longitudinal section of the basal area of an apical cap consisting of a network of larger and smaller (arrows) organic filaments. cells, some of the peripheral cells exhibit characteristics of decomposing cytoplasm; lysosomes and autophagous vacuoles surround an active nucleus. CENTRAL CELLS. The central cells ("sensory cells" ac- cording to Boyle, 1974) (as the photoreceptor cell is also sen- sory, I use the more neutral term "central cell") of Lepidopleurus cajetanus are prominent compared with the other species studied so far. The nuclei of all central cells (about five per aesthete) are situated in the distal part of the aesthete. Distally, underneath the apical cap, each central cell forms numerous microvilli and one cilium (9+2 structure) (Fig. 10). The cytoplasm of the central cells contains numerous mitochondria and microtubules running along the long axis of the cells. Distally the cytoplasm is filled with clear 0.3 wide vesicles. The central cells are connected together by zonulae adhaerens and septate junctions. PHOTORECEPTOR CELLS. Most of the aesthetes (but not all of them, irrespective of the position in different valve areas) contain one or two photoreceptor cells. They lie peripherally in the aesthete and do not exhibit a special orientation pat- tern, such as being always located on the same side of the aesthete body, as it is the case in Chiton olivaceus Spengler (Fischer and Renner, 1978). As in other species, they show two distinct areas, the cell body and the rhabdomere (Fig. 11). The microvilli (0.05-0.1 /*m in diameter) of the rhabdomere branch from the whole distal part of the cell; they have no regular orientation. Their cytoplasm contains small granules. One or two cilia (9+2 structure) can be present. The nucleus is relatively large (6.5 /*m) and has only a little condensed chromatin. In the perikaryon, numerous mitochondria, microtubules, glycogen and multivesicular bodies are present. A specialized agranular ER forms large areas of parallel membrane cisternae that are connected with the granular ER. Laterally these cisternae give off numerous clear vesicles (40-170 nm) that are found up to the rhabdome. M ICR AESTHETES. All micraesthetes branch off from the same zone of the main stem. Their nuclei lie in this area; they are large (6 /im) and have only little condensed chromatin. Here and in the "arm" (the part between the main stem of the aesthete and the tip of the micraesthete cell) we find numerous mitochondria and microtubules along the long axis (Fig. 12). In the basal part, multivesicular bodies or lysosomes are frequently found. Peripheral cells surround the

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