Light and electron microscopical investigations on the adductor muscle and nervous elements in the larva of Anodonta cygnea L.

Zs.-Nagy, Imre and Lábos, Elemér (1969) Light and electron microscopical investigations on the adductor muscle and nervous elements in the larva of Anodonta cygnea L. A Magyar Tudományos Akadémia Tihanyi Biológiai Kutatóintézetének évkönyve, 36. pp. 123-133. ISSN 0365-3005

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Abstract

The larval adductor muscle of Anodonta cygnea can be classified as a molluscan muscle of the tropomyosin type. The diameter of its thick myofilaments is about 200 Á, while that of the thin ones is 40 Å. The thick myofilaments show a hexagonal arrangement of about 800-1400 Å lateral length. Some dense bodies also occur. A number of neuromuscular junctions can be observed in the adductor. The nerve endings contain a lot of generally emptycore vesicles of about 400-1200 Å. The main direction of axons is perpendicular to the longitudinal axis of the muscle cells. The axons correspond to the processes of cells situated dispersedly under the larval mantle. The processes of these cells are connected to each-other by synapse-like structures containing the same kind of vesicles as those of the neuromuscular junctions. In the ganglion anlages, localized in the wall of lateral pits and foot fold, differentiated, branching cells containing dense-core vesicles can also be found. The processes of these cells form primitive neuropile-like clusters of fibres. Processes containing dense-core vesicles can also be found dispersedly outside of the ganglion anlages but never occur in the adductor muscle. The sensory cells bear specific cilia on their surface, which are connected with striated ciliray rootlets. The sensory cell itself has no processes, however, there is a lot of other processes surrounding it. The possibility of functional interpretation of the structures observed on the basis of physiological data is discussed and several other ultrastructural characteristics of the glochidia are also pointed out.

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