TESTING EVOLUTIONARY DEVELOPMENTAL HYPOTHESES WITH SEA URCHINS: A STUDY OF PLASTICITY AND HOMOLOGY

Abstract

<p>Sea urchins traditionally have been considered as model organisms for developmental studies, as they transform from bilaterally symmetric larvae to pentaradially symmetric adults. They are classified universally as members in the phylum Echinodermata, but skeletal homologies between the class in which sea urchins are contained and other echinoderm classes remain contested. And, culturally, the high demand for sea urchin sushi, a delicacy known as uni, has spiked interest in sea urchin farming and how to capitalize on making a commercially more-desirable food product for human consumption.<br />In this thesis, experiments were conducted to test evolutionary developmental hypotheses about sea urchin life history plasticity, skeleton homologies, and reproductive energetics. I found that sea urchin rudiments can be resorbed, exhibiting extreme plasticity and, thereby, functioning as capacitors for ensuring metamorphose in favourable conditions; sea urchin primary podia may be considered as nonhomologous with sea cucumber ambulacral podia, in accordance with the extra-axial theory; and gravid sea urchins fed a carrot-only diet produced gonads that were more desirable commercially than were gonads produced by sea urchins fed a seaweed and carrot diet.</p>