title: The echinoderm larval skeleton as a possible model system for experimental evolutionary biology.
abstract: The evolution of various body plans results from the acquisition of novel structures as well as the loss of existing structures. Some novel structures necessitate multiple evolutionary steps, requiring organisms to overcome the intermediate steps, which might be less adaptive or neutral. To examine this issue, echinoderms might provide an ideal experimental system. A larval skeleton is acquired in some echinoderm lineages, such as sea urchins, probably via the co-option of the skeletogenic machinery that was already established to produce the adult skeleton. The acquisition of a larval skeleton was found to require multiple steps and so provides a model experimental system for reproducing intermediate evolutionary stages. The fact that echinoderm embryology has been studied with various natural populations also presents an advantage.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennodai, Tsukuba, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Koga
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Morino
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Wada
mesh_terms: D000818:Animals; D005075:Biological Evolution; D004447:Echinodermata / Q000033:anatomy & histology* / Q000196:embryology*; D007814:Larva / Q000033:anatomy & histology; D008954:Models, Biological; D009024:Morphogenesis / Q000502:physiology*; D013045:Species Specificity
keywords: co-option; echinoderm; evolution of a novel structure; larval skeleton