Ultrastructure of the photoreceptor of Diplolaimella sp. (Nematoda).
The photoreceptor of the free-living marine nematode Diplolaimella sp. is ultrastructurally described. The most prominent feature of the photoreceptor is called the 'ocellar complex' and is composed of three dorso-laterally located parts. (1) The lens is an amorphous half sphere-shaped structure, about 1.5 mum in diameter. (2) The receptoral part is a stack of slightly undulating lamellae, localized just posterior to the lens. (3) The receptoral part is surrounded by a pigment cup containing electron-dense granules of 0.1-0.3 microm diameter. These three parts are embedded in a cell process, which has a more sizeable ventral extension containing the nucleus and cytoplasm characterized by a lot of free ribosomes and broad cisternae of the granular endoplasmic reticulum. This sheath cell is supposed to synthesize the pigment. The above described structure occurs bilaterally paired, some 50 microm from the anterior end.
Van De Velde
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MC
Rijksuniversiteit Gent, Instituut voor Dierkunde, K. L. Ledeganckstraat 35, Gent, Belgium.
Coomans
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