A re-evaluation of the ichthyodeterrent role of prostaglandins in the Caribbean gorgonian coral Plexaura homomalla

Abstract

Previous investigations have indicated that the Caribbean gorgonian coral Plexaura homomalla derives a chemical defense from prostaglandins present at high concentrations w~t h i n the coral's soft tissues. These conclusions were based on laboratory and field experiments with the hydroxy acids of prostaglandin A2 (PGA2), and not the acetoxy methyl esters of PGA2 that are present in the living gorgonian. In the present study, the consumption of food strips containing the acetoxy methyl ester of 15(R) PGA, from P. homomalla by a natural assemblage of Caribbean coral reef fishes did not differ from consumption of control stnps. In support of previous findings, treatment with the acetoxy acid, hydroxy methyl ester and hydroxy acid of 15(R) PGA2 inhibited consumption of food strips by reef fishes. Although the acetoxy methyl esters of PGA2 undergo hydrolysis when the soft tissues of P. homomalla are damaged, the process appears to be too slow to provide the gorgonian with an effective inducible defense mechanism.

Defensive properties of secondary metabolites from the Caribbean gorgonian coral Erythropodium caribaeorum

“…Although our preliminary survey indicated that chemical defense may play a n important role in the ecology of Caribbean gorgonians (Pawlik et al 1987), a direct link between specific secondary metabolites and feeding deterrence has been demonstrated in only one species besides Erythropodium caribaeorum: Harvell et al (1988) found that curcuhydroquinone and curcuquinone from Pseudopterogorgia rigida inhibited feeding in field assays. The high concentrations of prostaglandins present in some gorgonians of the genus Plexaura, particularly Plexaura homomalla, had previously been thought to play an ichthyodeterrent role (Gerhart 1984), but subsequent assays of the derivatives of these compounds a s they occur naturally in the gorgonian tissues indicated that most were inactive (Pawlik & Fenical 1989). Among octocorals in general, a purified cembranoid diterpene from the Indo-Pacific alcyonacean Sinularia maxima inhibited the feeding of fishes when assayed at natural concentrations on reefs in Guam (Wylie & Paul 1989).…”

“…Extracts and fractions isolated from extracts of Erythropodium caribaeorum were volumetrically reconstituted in a matrix of carrageenan at the same concentrations as they occurred in the gorgonian; strips of this matrix were then used in field experiments (see methods in Hawell , Pawlik & Fenical 1989). The matrix was made by combining 3 to 4 g carrageenan (Gelcarin, FF961L; FMC Corp, PA, USA) and ca 20 m1 of tuna fish puree (tuna packed in oil, pureed in a minimal volume of deionized water in a blender) with deionized water to a total volume of 60 ml.…”

“…Field assay methods were based on those of Hay (1984) as modified by Pawlik & Fenical (1989). One treatment and one control strip each were tied to a 50 cm length of 3-strand nylon rope at a distance of ca 4 and 12 cm from one end of the rope (the order was haphazard).…”

Size structure and geographic variation in chemical resistance of sea fan corals Gorgonia ventalina to a fungal pathogen

“…Kim 1994, Slattery et al 1995, Jensen et al 1996, anti-fouling (Targett et al 1983, Standing et al 1984, Wilsanand et al 1999 anti-fungal (Kim et al 2000a,b), and/or predator (e.g. Pawlik et al 1987, Sammarco et al 1987, Harvell et al 1988, Harvell & Fenical 1989, Pawlik & Fenical 1989, Fenical & Pawlik 1991, Van Alstyne & Paul 1992, Cronin et al 1995, Slattery 1999) -and competitor (e.g. Sammarco et al 1983, Rittschoff et al 1985, La Barre et al 1986) -deterrent secondary compounds.…”

Proteomic identification, cDNA cloning and enzymatic activity of glutathione S-transferases from the generalist marine gastropod, Cyphoma gibbosum

“…The endogenous function of pi-class GSTs in molluscs has yet to be defined; however, studies in mammalian systems indicate that pi GSTs are more involved than other GST classes in the detoxification of prostaglandins and other electrophilic α, β-unsaturated carbonyl compounds [21,22]. The highest concentrations of prostaglandins in nature have been found in Caribbean gorgonians [23], where the acetoxy acids, hydroxyl methyl esters and hydroxyl acids of 15(R)-prostaglandin A 2 function as feeding deterrents against generalist reef fish [24,25]. Prostaglandins in the A series can significantly induce GST activity in mammalian cells [26].…”