Meeting Abstract
Euthyneura gastropod molluscs have undergone several independent events of nervous system centralization, such as the gain/loss of the abdominal ganglia or visceral ganglion. Yet this clade also has homologous single neurons that have been conserved across million of years of evolution-the longest traced neuron homology of any system- making Euthyneura ideal for studying the genetic basis of nervous system evolution with cellular resolution. We compared transcriptomic profiles of sensory systems, CNS, ganglia, and single neurons from Pleurobranchaea californica to the genome of neuroscience model Aplysia californica and to transcriptomes of eight other related Euthyneura species. 9% of genes expressed in the eyes of three Aplysiidae species were potential orthologs to genes expressed in P.californica and Tritonia diomedea eyes-which are non-functional – and with Octopus bimaculoides eye transcriptomes. This analysis of Euthyneura eyes helps to further establish potential ancestral origins of molluscan eye diversity. For the first time, we assessed the homology of the abdominal/visceral ganglia in Euthyneura and found only 13% of genes showed conserved expression. The repeatedly identifiable abdominal cholinergic (ACh) motor neuron R2, that controls mucus release, has 500 conserved orthologs across 3 species of Aplysiidae. Although ACh biosyntheis genes have similar gene expression patterns in the abdominal ganglia across these species, the Bursatella leachii homologous R2 neuron does not express any ACh biosynthesis genes, suggesting a potential reorganization of abdominal ganglia structure and function.
