Summary
Armandia brevis responds negatively to light during the benthic phase and positively to light during the epitokous phase of its life history. In addition to the prostomial photoreceptors this slender translucent marine worm possesses eleven pairs of ocelli arranged serially from the 7th to the 17th segments.
Each ocellus is located at the inner edge of the epidermis slightly in front of the parapodium and contains a single photoreceptor cell which gives off approximately 15 sensory processes. These processes are composed of a central core of neurofibrils surrounded by a mitochondrial layer and a compact array of microvilli. The sensory processes project into and nearly fill the ocellar cavity which is lined by squamous glial cells.
The pigment cup enclosing the photoreceptor is composed of about 30 cuboidal cells packed with brown granules. The pigment cells form a mesothelium, being in direct continuity with the coelom. The cup is separated from the glial cells by a basal lamina which separates the epidermal tissues from the mesodermal derivatives of the body wall. Slender muscle fibers traverse the coelom and pass between the cells of the pigment cup.
The prostomial photoreceptors were re-examined and found in this material to be composed of microvilli rather than of folds containing labyrinthine tubular infoldings of the cell surface as previously reported.
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The author thanks Dr. Richard M. Eakin for support and criticism. This investigation was financed by a postdoctoral fellowship, number 1-F2-GM-20, and grant number GM 10292 from the National Institute of General Medical Science.
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Hermans, C.O. Fine structure of the segmental ocelli of Armandia brevis (Polychaeta: Opheliidae). Z. Zellforsch. 96, 361–371 (1969). https://doi.org/10.1007/BF00335214
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DOI: https://doi.org/10.1007/BF00335214