. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ON THE GROWTH OF BIVALVE GILLS 77. Figure 3. Gill filaments of two filibranch bivalves demonstrating the lengthened lobules with the equidistantly arranged ciliated knobs (kn), which increase in number from the distal end. The proposed distal growth zone (gz) is indicated, (al Anadara sp. (shell size about 5 cm); (b) \f\tilnx edulis (shell size of cm), fg: food groove, gb: gill base, ilj: interlamellar junction, ils: interlamellar space. remain and stabilize the small distance between the outer margins (Fig. 3b); the fir
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ON THE GROWTH OF BIVALVE GILLS 77. Figure 3. Gill filaments of two filibranch bivalves demonstrating the lengthened lobules with the equidistantly arranged ciliated knobs (kn), which increase in number from the distal end. The proposed distal growth zone (gz) is indicated, (al Anadara sp. (shell size about 5 cm); (b) \f\tilnx edulis (shell size of cm), fg: food groove, gb: gill base, ilj: interlamellar junction, ils: interlamellar space. remain and stabilize the small distance between the outer margins (Fig. 3b); the first ones appeared at about the 30th filament (counted anteriorly from the budding zone). Again, the margins strongly resemble filamentary structures. All adjacent filaments are attached to each other by equidistant ciliated knobs (Fig. 3b). In dissections of the gills of adult Mytilus, we observed that the ciliated knobs form equidis- tant lines, which are arranged parallel to the gill base along the whole gill. The number of lines increased with the size of the demibranchs and the length of their filaments. In contrast to Anadara, Mvtilus shows new lines of knobs only near the ventral end of the filaments. No inserted lines of knobs were detected in lateral views of the lamina. Thus, unlike growth in Anadara, the main growth zone responsi- ble for elongation must be restricted to this area. Budding -ones of eulamellibranch gills The four representatives of the Palaeoheterodonta (Unio) and Heterodonta (Dreissena, Corbicula, and Pisidiinn) stud- ied possess eulamellibranch gills. Again, an undifferentiated budding zone lies at the posterior end of each species' gills (Fig. 4). In each example, the transverse folds form in a way similar to that of protobranchs and filibranchs: the folds split into inner and outer demibranchs. Apart from these com- mon differentiation events, species-specific differences ex- ist in the relative size of the budding zone and in the extension of a seg
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
