Evolutionary origins of coordination: physiological and molecular studies on sponges (Porifera)

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Sponges are members of the Porifera, the most primitive extant animals. Sponges are the only group of multicellular animals without a nervous system yet they have various types of slow behaviour that allow them to excrete wastes. The first genome of a sponge is just available, and in it are many molecules that we see in nervous systems in other animals. My students and I are interested in how the sponge pre-nervous systems is organized and functions in their behaviour in the ocean down to the membrane channels involved in sensing signals in the environment and the mechanisms involved in communication between individual cells. This helps us understand how the first nervous systems evolved. We recently found a new sensory cell in sponges which has the potential to clarify how animals sense flow rates in order to control fluid movement, for example in blood capilliaries and kidney tubules. This proposal will investigate a) the molecules involved in signaling between cells in the sponge, and the receptors available to receive signals on cells; b) the molecular mechanisms which sponges use to build the filtration system; and c) the physical parameters of fluid flow that guide the formation of the sponge body. Comparing genes found in sponges with those in animals with the first nervous systems (jellyfish - cnidarians) has highlighted remarkable similarities in the way signaling works in animals even without conventional nerves. Our own work for example has shown that sponges use glutamate and GABA to stimulate and inhibit contractions of tissues, just as in higher animals. Our proposed research program focuses on identifying the regions where signaling occurs between cells (is there a 'proto-synapse'?) and ultimately determining where new cells involved in signaling are produced in developing and in adult sponges.