Summary
The photoreceptor of Amaroucium constellatum consists of three parts: lens cells, pigment cup, and retinal cells. The three lens cells lie just beneath the epidermis and extend ventrally into the sensory vesicle. A large part of their volume is occupied by a lens vesicle, a region bounded by mitochondria. The function of the lens cells is unclear. The pigment cup, a hollow hemisphere formed by the pigment cell, acts as a light shield, presumably allowing the tadpole to respond directionally to light. No unusual morphological features of this cell have been noticed. Each of the seven to ten photoreceptor cells sends a process through the pigment cup towards the lens cells. A cilium at the tip of each process gives rise to membranous lamellae which are presumably photosensitive. The base of each photoreceptor cell seems to send processes to the cerebral ganglion. No synapses have been seen at the base of the photoreceptor cells. The cerebral ganglion consists of a cellular cortex surrounding a medullary region of neuropil. Two types of synapses, presumably chemical and electrical, are evident. Four classes of vesicles are found in these structures.
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This investigation was supported in part by Training Grant number GMO 1981 from the National Institutes of Health, by Health Science Achievement Award number RR06084, and Grant number EY00443 (to Dr. A. L. Bell) from the National Institutes of Health.
I wish to thank Dr. Allen L. Bell for his invaluable assistance and encouragement during this investigation.
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Barnes, S.N. Fine structure of the photoreceptor and cerebral ganglion of the tadpole larva of Amaroucium constellatum (Verrill) (Subphylum: Urochordata; Class: Ascidiacea). Z. Zellforsch. 117, 1–16 (1971). https://doi.org/10.1007/BF00331097
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DOI: https://doi.org/10.1007/BF00331097