Embryonic, Larval, and Juvenile Development of the Sea Biscuit Clypeaster subdepressus (Echinodermata: Clypeasteroida)

Author(s)

Vellutini, Bruno C. ^{[1, 2]} ; Migotto, Alvaro E. ^{[1, 2]}

Affiliation

^[1] Univ Sao Paulo, Inst Biociencias, Dept Zool, Sao Paulo - Brazil

^[2] Univ Sao Paulo, Ctr Biol Marinha, Sao Sebastiao, SP - Brazil

• Document type: Journal article
• Source: PLoS One; v. 5, n. 3 MAR 22 2010.
• Web of Science Citations: 12

Abstract

Sea biscuits and sand dollars diverged from other irregular echinoids approximately 55 million years ago and rapidly dispersed to oceans worldwide. A series of morphological changes were associated with the occupation of sand beds such as flattening of the body, shortening of primary spines, multiplication of podia, and retention of the lantern of Aristotle into adulthood. To investigate the developmental basis of such morphological changes we documented the ontogeny of Clypeaster subdepressus. We obtained gametes from adult specimens by KCl injection and raised the embryos at 26 degrees C. Ciliated blastulae hatched 7.5 h after sperm entry. During gastrulation the archenteron elongated continuously while ectodermal red-pigmented cells migrated synchronously to the apical plate. Pluteus larvae began to feed in 3 d and were similar to 20 d old at metamorphosis; starved larvae died 17 d after fertilization. Postlarval juveniles had neither mouth nor anus nor plates on the aboral side, except for the remnants of larval spicules, but their bilateral symmetry became evident after the resorption of larval tissues. Ossicles of the lantern were present and organized in 5 groups. Each group had 1 tooth, 2 demipyramids, and 2 epiphyses with a rotula in between. Early appendages consisted of 15 spines, 15 podia (2 types), and 5 sphaeridia. Podial types were distributed in accordance to Loven's rule and the first podium of each ambulacrum was not encircled by the skeleton. Seven days after metamorphosis juveniles began to feed by rasping sand grains with the lantern. Juveniles survived in laboratory cultures for similar to 9 months and died with <500 mu m wide, a single open sphaeridium per ambulacrum, aboral anus, and no differentiated food grooves or petaloids. Tracking the morphogenesis of early juveniles is a necessary step to elucidate the developmental mechanisms of echinoid growth and important groundwork to clarify homologies between irregular urchins. (AU)

• FAPESP's process: 06/01898-7 - Development and reproductive cycle of the sea biscuit Clypeaster subdepressus (Echinodermata: Echinoidea) from São Sebastião, SP
• Grantee: Bruno Cossermelli Vellutini
• Support Opportunities: Scholarships in Brazil - Master