The Ultrastructure and Evolutionary Significance of the Cerebral Ocelli of Mytilus-edulis the Bay Mussel
Year: 1977
Type: article
Abstract: Purpose of the Study: \nThe cerebral ocelli of bivalves have not been previously \nexamined by electron microscopy; only their pallial eyes \nhave been studied at this level. This study examined \nthe ultrastructure of cerebral ocelli for the purpose \nof assessing the evolutionary significance of these and \nother cerebral ocelli of protostomous invertebrates. \nMethods: \nOcelli were excised from living mussels and immediately \nfixed in glutaraldehyde, post-fixed in osmium tetroxide, \ndehydrated in ethanol, and embedded in Epon. Next, the \nocelli were thin-sectioned and then photographed on a \nZeiss EM 9A. \nResults: \nThe ocellus consists of a cup shaped retina that is \ncomposed of interdigitating pigment and sensory cells. \nThere is no cornea or lens. The pigment cells contain \npale membrane-bound granules of shading pigment and have \nstubby microvilli at their apices. The sensory cells \nhave axons at their bases and long undulating arrays \nof rhabdomeric microvilli at their apices. \nConclusion: \nThe cerebral ocelli of Mytilus edulis have features \nthat conform to the similarities among the cerebral \nocelli of other molluscs, sipunculids, annelids, and \nonycophorans; these similarities indicate that the \ncerebral eyes of these forms are homologous.
Language: English
Subfield: Anatomy
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2132819228