Diet-dependent UVAR and UVBR resistance in the high shore harpacticoid copepod Tigriopus brevicornis

Abstract

This study tested the hypotheses (1) that the upper shore rock pool harpacticoid copepod Tigriopus brevicornis is protected against ultra-violet radiation (UVR) by the orange pigment astaxanthin, and (2) that astaxanthin levels would be greater in summer than winter. Wild orange copepods lost their pigment and became white if fed on yeast in the dark; their colour was restored when they were fed microalgae. White T. brevicornis were significantly more susceptible to UVR than wild or restored orange T. brevicornis. At similar intensities of radiation, copepods showed duration of survival in the order UVAR > UVBR. Astaxanthin protected T. brevicornis against UVAR and UVBR, with the degree of effectiveness of protection being in the order UVAR > UVBR. There was no significant increase in astaxanthin levels during summer in T. brevicornis collected from 3 different shores. It is suggested that UVAR protection by astaxanthin largely follows from its effectiveness as an antioxidant, and that there are adequate plant resources available to maintain astaxanthin levels in T. brevicornis throughout the year.