In comparative neuro-anatomy there are evolutionary links between mollusks and vertebrates. Noting the relative position in the brain of the Mollusk Optical lobes, could they have evolved into the Optic Tectum?
Graeme,
Interesting.... Parsimony would say they are homologous. Anatomically the optic nerve for gastropods enters the cerebral ganglion and the major processing of visual information (and olfactory) is located there. I am assuming the cerebral ganglion is homologous with the Cerebrum of vertebrates - also where both visual and olfactory centers are located. However i don't think we can say that any aspect of the mollusk nervous system evolved into the vertebrate homolog as they are on divergent lineages. So i think it is safe to say that the common ancestor of the two lineages had already developed the basic central nervous system ("Bauplan") that has been elaborated in each (same for reptiles, amphibs, teleosts, etc.).
No. I say gastropoda (snails) because that is the mollusc group i am most familar with. It is a very old divergence where the protostome invertebrates split from the deuterostomes.
Ran across this paper that discusses the early origin of the nervous system in chordates and the invertebrates: Meinertzhagen and Okamura. 2001. The larval ascidian nervous system: the chordate brain from its small beginnings. Trends in Neurosciences 24:401-410.
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