Local and geographic variation in the defensive chemistry of a West Indian gorgonian coral (Briareum asbestinum)

Abstract

We sampled the between-colony and between-habitat variation in defensive chemistry of colonies of Briareum asbestinum, one of the most ubiquitous and chemically deterrent of the West Indian gorgonians. The basis of deterrence appears to reside in a diverse complement of 5 to 15 briarane and asbestinane diterpenoids found in individual colonies. Variation in chemistry of colonies is extensive throughout the Bahamas and the Virgin Islands: the complement of compounds is slightly different a t each site in the Bahamas and colonies from all the Bahamian sites are distinct from those a t the St. Croix (US Virgin Islands) site. St. Croix colonies not only differ in their composition of compounds, but also have fewer major diterpenoids than colonies from shallow water sites in the Bahamas. The shallow St. Croix extracts also differ in being dominated by asbestinanes instead of briaranes as in the Bahamas. The qualitative chemistry of colonies also vanes locally between depths near San Salvador and Chub Cay, 2 islands in the Bahamas. At both sites, the ratio of briarane to asbestinane diterpenoids was higher in shallow (1 to 12 m) water colonles than In deeper ones (25 to 40 m). To determine whether the qualitative differences in chemistry between depths could be induced or were fixed, colonies were transplanted from shallow to deep reefs in San Salvador. After 7 mo, newly grown tlssue from transplanted colonies still retained the same shallow water diterpenes. This experiment suggests that the qualitative differences in chemistry observed with depth are fixed in adult colon~es. We also sampled quantitative variation in colonies from St. Croix and the Bahamas. Although we expected higher levels of compounds in shallow colonies because both productivity and numbers of predators are higher in shallow waters, at both sites levels of compounds were higher in deeper waters Briareum asbestinum is unusual in being heavily invested with a diversity of extremely deterrent diterpenoids. The outstanding feature of this chemical defense system is the qualitative variation In the chen~lstry of colonies from different habitats, which appears to be genetically fixed, raising the question of what selective agents maintain the variation in chemistry among different habitats

Chemical mediation of interactions among marine organisms

“…273 Moreover, the larvae of this species synthesize the asbestinane diterpenes. 279 Similarly, pukalide 72 and 11 P-acetoxypukalide 73 were found in the eggs of the Pacific soft coral Sinularia polydactyla.…”

“…300 A geographic comparison of colonies of the gorgonian Briareum asbestinum from two regions within the Caribbean, the Bahamas and St. Croix, showed that the two chemically defended populations produced different classes of diterpenes. 273 More recently, a study of the defenses of Annella mollis, A. reticulata and Rumphella sp. addressed geographic differences in the palatability of crude extracts of colonies collected from two distant tropical islands in the Pacific Ocean, Guam and Lizard Island, Australia.…”

Compounds from Deep-Sea Bubblegum Corals, Paragorgia arborea, Elicit Anti-Predation Behavior in Fish

“…Hay and Steinberg [50] suggested that species (e.g., coral and algae) subjected to high feeding pressures have larger concentrations of metabolites against herbivory than others in less pressured environments, which may be an evolutionary consequence of self preservation. Secondly, a species with a slower growth rate might generate a surplus of natural products [48]. Thirdly, similar species living in different geographical locations may be ingesting different prey items, leading to differences in the concentration and type of metabolite produced.…”

“…Maida et al [47] reported significant differences in flexibilide and sinulariolide metabolites of the soft coral Sinularia flexibilis among different sites at Lizard Island, Great Barrier Reef (Australia). Metabolite concentrations varied among the gorgonian coral Briareum asbestimum from different depths and geographical locations [48].…”

Chemical antifouling defences of sea stars: effects of the natural products hexadecanoic acid, cholesterol, lathosterol and sitosterol

“…temperature, light) and biological (e.g. life history, competition, size) variables (Harvell et al 1993, Becerro et al 1997, Maréchal et al 2004). The sterol composition of sea stars, such as Asterias rubens, can also be influenced by food availability, since most of the sterols are derived from the diet and only a few sterols are synthesized de novo (Voogt & Van Rheenen 1976).…”