Comparing metamorphosis in evolutionary diverged sea urchin species

Cross-species comparisons of animal development have revealed how animal body plans evolved through modifications in developmental mechanisms. However, most animals develop indirectly, first forming a larva that later transforms through metamorphosis into a morphologically distinct adult. Despite its prevalence, the cellular basis of metamorphosis remains poorly understood. The prevailing model, based largely on morphological studies of sea urchins, proposes that larval cells are discarded and replaced by a small population of stem-like “set-aside” cells that build the adult body. However, my recent work in sea cucumbers challenges this view, showing that larval cells can be reprogrammed to form adult tissues, raising the possibility that cellular reprogramming is an overlooked mechanism of metamorphosis.

To test this hypothesis, I will revisit the set-aside cell theory mechanistically in the classic sea urchin model L. pictus and the early-branching cidaroid sea urchins using imaging, gene expression analyses, and cell-tracking approaches. Because cidaroids are not readily available in North America, I will collaborate with the Formery group at the Oceanological Observatory of Banyuls-sur-Mer. By revisiting a classic model with modern tools, this project will reassess our understanding of metamorphosis and provide new insight into the evolution of developmental strategies across animals.