TARRANT, A.M.; Woods Hole Oceanographic Institution: Effects of Estrogens on Reef-building Corals: Comparisons with Vertebrates

The vertebrate endocrine system is well-characterized, with many reports of disruption by environmental chemicals. In contrast, reef-building corals are less compartmentalized, physiological regulation is poorly understood, and the potential for disruption is unknown. While endocrine-like activity has not been systematically studied in corals, several classical vertebrate hormones (e.g., steroids, iodinated organic compounds, neuropeptides, and indoleamines) occur in cnidarians. A cascade of signals comparable to the vertebrate hypothalamic-pituitary-gonadal axis has not been identified in cnidarians, but compounds similar to several components of this pathway have been identified including putative GnRHs and vertebrate-like sex steroids. Specifically, estrogens are present in coral tissue, released during spawning and can affect coral growth and reproduction. The role of estrogens in cnidarians has not been demonstrated, but estrogens are hypothesized to act as hormones or pheromones to regulate coral gametogenesis and/or spawning. If estrogens do play a role in coral reproduction, then natural or synthetic estrogens may accumulate in tissues and affect reproductive processes. More research is needed to explain the mechanism of estrogen action in corals. Several nuclear receptor genes have been identified in corals, but cnidarians contain no known orthologs of vertebrate estrogen receptors; thus other potential signaling pathways need to be investigated. Elucidation of coral regulatory pathways will provide insight into evolution of hormonal signaling. These studies will also improve understanding of how cnidarians respond to environmental cues and will provide a basis to investigate disruption of physiological processes by physical and chemical stressors.