Distribution of mycosporine-like amino acids in the sea hare Aplysia dactylomela: effect of diet on amounts and types sequestered over time in tissues and spawn

Abstract

We investigated the interaction of diet and accumulation of UV-absorbing mycosporine-like amino acids (MAAs) in body tissues and spawn of the sea hare Aplysia dactylomela to determine if MAA accumulation reflects type and level of dietary intake. Food sources were the red algae Acanthophora spicifera, Centroceras clavulatum, and Laurencia sp., and the green alga, Ulva lactuca. Adults were maintained on these foods for 40 days, after which feces were collected and tissues separated by dissection. Field animals were similarly sampled at this time. All spawn from experimental and field animals was collected over the study period. Samples, including seaweed foods, were analysed for six MAAs. Overnight consumption experiments using a variety of common seaweeds and one seagrass from A. dactylomela’s habitat showed that the four seaweeds selected as foods were among those best-eaten by Aplysia. After 40 days levels of specific MAAs in the tissues of experimental animals showed excellent correlation with those in their diets, suggesting that the MAAs were dietarily-derived. Relative MAA contents in spawn from all diet groups correlated well with those in spawn from field animals. Commonest MAAs in spawn were porphyra-334, shinorine, and palythine, in this order. Concentrations of these MAAs were maintained at constant levels over time in spawn from all diet groups eating red algae and from field animals. Spawn from the Ulva dietary group showed an initial significant decline in MAA concentrations, but levels stabilized after the first 2 weeks. Skin was rich in porphyra-334 and shinorine, and levels of these in experimental animals correlated well with comparable levels in the skin of field animals. Digestive glands contained high levels of asterina-330, particularly those of the Centroceras dietary group, where concentrations reached a maximum of 21 mg^. dry g⁻¹.