Mycosporine-like amino acids in azooxanthellate and zooxanthellate early developmental stages of the soft coral Heteroxenia fuscescens

The ontogenetic changes of MAAs in the soft coral Heteroxenia fuscescens was studied in relation to their symbiotic state (azooxanthellate vs. zooxanthellate) under different temperature conditions in the Gulf of Eilat, northern Red Sea. The HPLC chromatograms for extracts of the planulae, azoo- and zooxanthellate primary polyps of H. fuscescens from all dates of collection yielded a single peak at 320 nm that has been identified as the compound palythine. Concentration of palythine in planulae at 23 °C was 7.57 ± 1 nmol mg^{- 1} protein and at 28 °C reached 17.29 ± 1 nmol × mg^{- 1} protein. Concentration of palythine in azooxanthellate primary polyps was 16.4 ± 3 nmol × mg^{- 1} protein and 28.37 ± 2.8 nmol × mg^{- 1} protein at 23 °C and 28 °C respectively. The palythine concentration for zooxanthellate primary polyps at 23 °C was 13 ± 3 nmol × mg^{- 1} protein and at 28 °C 32.7 ± 2 nmol mg^{- 1} protein. Palythine concentrations were significantly higher at 28 °C in the different animal groups and correlated linearly with the ambient collection temperature. This study shows for the first time that UVR and temperature act synergistically and affect the MAA levels of early life-history stages of soft corals.