Title

Aspects of the steroid biochemistry of the scleractinian coral, Favia fragum

Date of Award

1992

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Marine Biology and Fisheries

First Committee Member

Alina M. Szmant, Committee Chair

Abstract

The steroid biochemistry of the scleractinian coral, Favia fragum (Esper), was studied in an attempt to elucidate the role of these compounds in the regulation of reproduction of corals. F. fragum exhibits a lunar periodicity in all phases of gametogenesis, embryogenesis and planulation. The timing of its reproductive events is similar among many Caribbean sites. However, in the south Florida population of Favia fragum, the peak in planulation is delayed by several days and fewer planulae are produced in comparison to the Puerto Rican population, possibly due to latitudinal differences in temperature or photoperiod.Since cytochrome P-450 and associated mixed function oxidase (MFO) enzymes are important in the metabolism of steroids as well as xenobiotics, coral tissue was assayed for the activity of these enzymes over the lunar cycle. The cytochrome P-450 content and the activities of one cytosolic enzyme and three microsomal enzymes are reported for the first time in cnidarians. In general, the MFO activity is low when compared to other invertebrates and vary greatly over the lunar period and among colonies with no apparent pattern. Coral animal tissue homogenates as well as whole colonies incubated with radiolabelled progesterone produced many metabolites including testosterone, presumably through the MFO enzyme system. This demonstrates the ability of corals to take up and metabolize steroids.Sterol profiles of coral tissues were examined over the lunar cycle to determine whether there were cyclic patterns in their presence that might be correlated with reproductive events. Many compounds were present only at specific times over the lunar period, but the cyclical nature of their presence could not be confirmed.Although this dissertation has demonstrated the ability of the coral, Favia fragum, to take up and process steroids possibly through cytochrome P-450 mixed function oxidases, the role of steroids in the regulation of reproduction in corals remains an open question and fertile territory for future research.

Keywords

Biology, Oceanography; Chemistry, Biochemistry

Link to Full Text

http://access.library.miami.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9227198