ISSN:
1432-0878
Keywords:
Mollusca
;
Chitons
;
Photoreceptor
;
Fine Structure
;
Cilia
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Onithochiton neglectus a common littoral chiton possesses large numbers of small eyes embedded in the outer layer of the shell, the tegmentum. These are arranged in a definite pattern on each shell valve. Each eye lies in a pocket, and is surrounded by pigment laid down in the shell. There is a lens, cup of retina cells and an optic nerve running in an optic canal through the shell. Glial elements are present. The retina cells give rise centrally to a packed array of microvilli, a rhabdom. Cilia are present at the edge of the rhabdom; they have a 9 + 2 arrangement of ciliary filaments and do not appear to be involved in the formation of microvilli. Cells at the periphery of the eye cup give rise to large whorls of membranes, lamellate bodies. These bodies are derived from the membranes of cilia having a 9 + 2 pattern, and form into an extra-cellular space. Nerve processes from the retina cells pass into the optic canal. On the basis of previous work it is thought that the lamellate bodies are also sensory. These structures are discussed in relation to other microvillar and lamellate structures described from photoreceptors.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00335443
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