Review articleComparative studies on the skeletogenic mesenchyme of echinoids

- Recent comparative developmental studies of echinoids are reviewed.
- Mechanisms underlying larval skeletogenesis in non-camarodont echinoids are outlined.
- Importance of comparisons among echinoids with different ontogenies is discussed.
- Usefulness of comparative studies among species with similar morphology is proposed.

Skeletogenic mesenchyme cells in echinoids are suitable for studying developmental mechanisms, and have been used extensively. Most of these studies have been performed on species in the order Camarodonta, which are modern echinoids (subclass Euechinoidea) and are considered “model” echinoid species. In contrast, species belonging to other orders are studied less frequently, especially investigations of their molecular developmental biology such as gene regulatory networks. Recent studies on mesenchyme development in non-camarodont species suggest that these species are potential sources of comparative information to elucidate the mechanisms underlying skeletogenic mesenchyme development. In this review, the importance of using comparative data to understand development and evolution is discussed.