Meeting Abstract
The nervous system is present in all but two animal phyla – one of them being Porifera, sponges. Sponges have no neurons and yet have organized behavior and finely tuned sensation. Furthermore, sponges have genes involved in the nervous system of other animals (informally called ‘neural’ genes). Do these genes impart a sensory capacity in sponges and does their presence suggest that the sponge sensory system is homologous to the nervous system? I carried out an RNA-seq study to determine whether candidate ‘neural’ genes might be differentially upregulated in the osculum, a demonstrated sensory structure that is the excurrent vent of the sponge filtration system. Four candidate ‘neural’ genes – mGluR, GABAR, Kir and Bsh – were significantly upregulated in sponges with oscula compared to those in which oscula were still developing or in sponge body tissues. While glutamate (L-Glu) and GABA have been shown to trigger and arrest (respectively) sponge contraction behavior, glutamate and GABA receptors themselves may have roles in normal metabolic processes and therefore their upregulation in tissues may reflect differential activity of other activities that occur in the osculum. The data presented suggest that genes involved in the nervous system of bilaterians may not be effective markers for sensory/coordinating systems in sponges. Instead, studying ‘neural’ genes without the assumption that they hold sensory or coordinating functions may provide a less biased way of investigating sensory-neural origins.
