Meeting Abstract
Morphology and nervous systems are tightly linked in animal evolution, yet the development of nerves involves similar gene networks. Nerve nets are adaptive in marine environments, while nerve cords tend to predominate in land animals. Deuterostome animals show nerve nets and nerve cords in different configurations, depending on their environment and life history. For example, ascidians have a dorsal central nervous system, but this is found only in swimming tadpoles. After metamorphosis, the adult develops a nerve net, and in some species the central nervous system can be extirpated entirely after the nerve net is established. Tailless ascidians have lost their notochord and muscle, yet develop a nerve cord as larvae. Vertebrates have a central nervous system but have reduced or lost their nerve nets and have evolved neural crest that contribute to the nervous system. Hemichordates have an extensive nerve net and also a central nervous system as adults. We will discuss the results of our studies on neural development and regeneration in hemichordates. By studying the process of regeneration in hemichordates, we have identified several new cell types that appear to facilitate regeneration and may contribute to the nervous system. We are actively working to define this unique cell population. We will present our results in a robust phylogenetic framework and discuss hypotheses of loss vs. gain in the evolution of deuterostome nervous systems.
