Early development of the feeding larva of the sea urchin Heliocidaris tuberculata: role of the small micromeres
The two modes of development in sea urchins are direct development, in which the adult develops directly from the gastrula to the adult and does not feed, and indirect development, in which the adult develops indirectly through a feeding larva. In this account of the indirect, feeding larva of Heliocidaris tuberculata, the question raised is whether an evolutionary difference of unequal cell divisions contributes to the development of feeding structures in the indirect larva. In indirect development, the cell divisions at the fourth and fifth cell cycles of the zygote are unequal, with four small micromeres formed at the vegetal pole at the fifth cell division. In direct development, these cell divisions are not unequal. From their position at the head of the archenteron, the small micromeres are strategically located to contribute to the feeding tissues of the larva and the adult of H. tuberculata.
KeywordsDevelopment Evolution Morphogenesis Small micromeres Echinoderm Echinoidea Planktotroph Lecithotroph
The authors acknowledge the facilities and the scientific and technical assistance of the Australian Microscopy and Microanalysis Research Facility at the Australian Centre for Microscopy and Microanalysis, The University of Sydney.
- Byrne M, Emlet RB, Cerra A (2001) Ciliated band structure in planktotrophic and lecithotrophic larvae of Heliocidaris species (Echinodermata: Echinoidea): conservation and change. Acta Zool 82:189–199Google Scholar
- Campanale JP, Gökirmak T, Espinoza JA, Oulhen N, Wessel GM, Hamdoun A (2014). Migration of sea urchin primordial germ cells. Dev Dynamics 243:917–927Google Scholar
- Cox, G. (2007). Optical imaging techniques in cell biology (Boca Raton, FL, CRC Press, Taylor and Francis)Google Scholar
- Israel JW, Martik ML, Byrne M, Raff EC, Raff RA, McClay DR, Wray GA (2016) Comparative developmental transcriptomics reveals rewiring of a highly conserved gene regulatory network during a major life history switch in the sea urchin genus Heliocidaris. PLoS Biol 14(3):e1002391CrossRefPubMedPubMedCentralGoogle Scholar
- Morrill, J.B., and Marcus, L. (2005). An atlas of the development of the sea urchin Lytechinus variegatus. Division of Natural Sciences, New College of Florida, Sarasota, FloridaGoogle Scholar
- Morris VB (2011) Coelomogenesis during the abbreviated development of the echinoid Heliocidaris erythrogramma and the developmental origin of the echinoderm pentameral body plan. Evol Dev 13:370–381Google Scholar
- Raz E (2000) The function and regulation of vasa-like genes in germ-cell development. Genome Biology 1(3):reviews1017.1–reviews1017.6Google Scholar
- Voronina E, Lopez M, Juliano CE, Gustafson E, Song JL, Extavour C, George S, Oliveri P, McClay D, Wessel G (2008) Vasa protein expression is restricted to the small micromeres of the sea urchin, but is inducible in other lineages early in development. Dev Biol 314:276–286Google Scholar