LIFE HISTORY STUDIES ON THE RED SEA SOFT CORAL XENIA MACROSPICULATA GOHAR, 1940. I. ANNUAL DYNAMICS OF GONADAL DEVELOPMENT

¹ Department of Zoology, The George S. Wise Center for Life Sciences, Tel Aviv University, Tel-Aviv 69978, Israel

Xenia macrospiculata Gohar, 1940 is a dominant xeniid species on the coral reefs of the Gulf of Eilat. The colonies are dioecious and the gonads develop along the four lateral and two sulcal mesenteries, except for the anthocodial part of the polyps. The population starts to reproduce at a markedly early age of two years and the percentage of sexually mature colonies increases with coral size. The sex ratio of the population is significantly skewed toward a higher abundance of males.

A synchronization of gonadal development occurs among the polyps within a colony. In every annual cycle the development of initial gonadal primordia starts in September or October and it lasts until April-May. In addition to these gonads, more oocytes and sperm sacs continue to appear along the mesenteries of male and female colonies during the succeeding 7-8 months. Due to the prolonged period of gonadal initiation, the population contains colonies in various stages of development. The successive maturation of gametes starts every annual cycle in May and lasts for 4-5 months. During this time polyp cavities become filled with an unusual compact arrangement of various sizes of oocytes or sperm sacs. The early age of first reproduction combined with the prolonged gametogenic season increase the reproductive potential of X. macrospiculata and contribute to its high abundance at the studied reefs.