Phylogeny & Evolution of edible sea urchins

Sea urchins (Echinodermata: Echinoidea) of the order Camarodonta evolved roughly 100 mya in the mid-Cretaceous period, but at that time were small and rare. Only in the Late Eocene, approximately 40 mya – following the Paleocene/Eocene Thermal Maximum Event – camarodont echinoids experienced massive radiation.

Within a comparatively short time span of about ten million years, all of the modern camarodont families evolved, as did many of the modern camarodont genera. Camarodont echinoids are important components of diverse marine environments, largely due to their extensive ecological impact. Some researchers consider echinoids to be the single most important group of consumers to live in shallow marine habitats, ultimately controlling the structure and function of a wide range of marine communities including kelp forests, seagrass beds and coral reef ecosystems. They are intensively used in reproduction and development research and serve as model organisms for classroom education.

Human interest, however, is not limited to scientific aspects of camarodonts – their reproductive organs are considered a delicacy and camarodont sea urchins are heavily exploited by a multimillion-dollar fisheries industry. A new research project (P 29508-B25), sponsored by the Austrian Science Fund (FWF) now aims to decipher the origin and evolutionary history of camarodont sea urchins. In order to achieve this goal, genetic information at the genome level will be combined with morphological analyses.

Phylogenomic methods will provide significantly more genetic data than currently available, allowing for more robust results. In addition, the first occurrences of camarodont sea urchins in the geological record will be used to infer minimum ages of individual groups within Camarodonta. Cladistic morphological analyses will be used to create a joint phylogenetic tree for extant and extinct camarodonts.

The present talk focuses on presenting first results from this project, primarily involving sea urchins of the genus Tripneustes, one of the most wide-spread shallow-water echinoderms known to date. The novel morphological and genetic data generated by the project team challenge the current view of Tripneustes phylogeography and have already resulted in the discovery of a new species.