Meeting Abstract

P2.42  Jan. 5  Early development through gastrulation in the scleractinian corals Pocillopora meandrina and Fungia scutaria MARLOW, H.**; MARTINDALE, M.Q.; Kewalo Marine Laboratory, University of Hawaii; Kewalo Marine Laboratory, University of Hawaii marlow@hawaii.edu

Nearly all scleractinian (stony) corals engage in symbiotic associations with zooxanthellae dinoflagellates. These dinoflagellate symbionts may be acquired through vertical uptake (seeding of the oocyte by the maternal colony) or horizontal uptake (acquisition by the larval stage from the environment) and are exclusively localized to the endodermally derived gastrodermis cells of the coral. In the vertically seeded species Pocillopora meandrina, the localization of zooxanthellae has been reported to occur prior to gastrtulation (endoderm formation) through the segregation of zooxanthellae to future endoderm cells. We have conducted a detailed study of gastrulation of two species in the �robust” clade of scleractinian corals, P. meandrina (a vertically seeded species) and Fungia scutaria (a horizontally acquiring unseeded species), to compare the mechanism of gastrulation in both species and to determine how zooxanthellae are segregated exclusively to endoderm. Through cell injection, antibody labeling and in situ hybridization experiments we have show that gastrulation in both species occurs by invagination, in contrast to the prawn chip gastrulation of “complex” corals. We also found that zooxanthellae are not transferred to endoderm at the time of gastrulation in P. meandrina, but are passed there acellularly in the nutritive stage prior to gastrulation. Surprisingly, we also report intracellular microbial symbionts in P. meandrina embryos embryos. These findings underlie the import of detailed cell biological and comparative studies of early coral development.