Red Sea Soft Coral Research Articles

Substratum preferences and planulae settling of two red sea alcyonaceans: Xenia macrospiculata Gohar and Parerythropodium fulvum fulvum (Forskl)

The settling behaviour and substratum preferences of the planulae of the Red Sea soft corals Xenia macrospiculata Gohar and Parerythropodium fulvum fulvum (Forskl) were examined in the laboratory. The planulae of the two species have a short pelagic phase and they tend to settle immediately upon leaving the parent colonies. Mucous secretion is used by the larvae for crawling and adhering to the substratum. They exhibit an aggregated pattern of settlement. The developing polyps are found in depressions or pits of the substratum. The planulae preferentially settle on rough substrata and avoid smooth surfaces. They search for substrata covered with an organic coating, composed of turf or crustose coralline algae. Such substrata create better conditions for larval settlement and metamorphosis. The planulae of P. f. fulvum exhibit a striking preference for upside-down attachment on undersides of the substrata, while Xenia macrospiculata utilizes both substratum faces for settlement. Light intensity seems insignificant in determining attachment sites. The findings of the experiments correspond well with the distributional patterns of juveniles of the two species as found in the natural environment. The specific requirements for settling of both species increase their chances of successful development and thus enhance their survival.

Isolation and structure elucidation of lobophytosterol, depresosterol and three other closely related sterols : Five new C 28 polyoxygenated sterols from the red sea soft coral lobophytum depressum

A series of polyoxygenated sterols were isolated from the soft coral Lobophytum depressum. The structure of five of these sterols was elucidated and determined to be. 5β,6β - epoxy - 24ξ - methylchloestan -3β, 22(R),25-triol ( 2a), 22(R),28 - oxido - 24ξ - methylcholest - 5 - en - 3β,25,28 - triol ( 1c, lobophytosterol), 24ξ -methyl - cholest - 5 22(R),25,28 - tetraol ( 1b, depresosterol), and 5β,6β - epoxy derivatives of lobophytosterol and depresosterol, Tcompounds 2c and 2b respectively. The structures were determined mainly on the basis of the fully interpreted 1H and 13C NMR spectra as well as the mass spectrum and several chemical transformations which resulted in unambiguous structures. All identified compounds belong to the C 28 category and are the first examples of marine sterols possessing the C 28-atom in various oxidative states.