Occurrence of ultraviolet radiation-absorbing mycosporine-like amino acids in coral mucus and whole corals of French Polynesia

Abstract

Specimens of six scleractinian species were gathered during the austral spring (October–November) 1994 on the external slope of the barrier reef of Arue, Tahiti, and in the lagoon of Arutua, a Tuamotu island. Mucus of each specimen was collected and the optical density and volume excreted were measured. After treatment, mucus was analysed for mycosporine-like amino acids (MAAs) by high-performance liquid chromatography (HPLC). Nine UV-absorbing compounds were present in coral mucus at concentrations between 1 and 500 ng g^-1 mucus. Palythine and mycosporine–gly were found in all mucus studied. Mycosporine–2glycine was recovered in 71% of specimens and shinorine in 28%. Porphyra-334 and palythinol were identified as minor MAAs. Three recently identified MAAs, palythine–serine, mycosporine–methylamine:serine and mycosporine–methylamine:threonine, were also found in mucus from Pocillopora. Within a genus, there was a qualitative similarity in MAAs determined by HPLC, irrespective of locality. Values for optical density of the mucus showed the ability of MAAs to protect the animal host and endosymbiotic algae from UV-solar flux and, as inferred from the recent literature, from oxidative forms of oxygen (HO₂ . , O ₂ ^- , HO^.) derived from photosynthesis.