Photoprotective compounds in zooplankton of two adjacent tropical high mountain lakes with contrasting underwater light climate and fish occurrence

We compared temporal changes in the concentration of photoprotective compounds (PCs) in zooplankton of two adjacent (600 m apart) tropical high mountain lakes, El Sol and La Luna. The lakes have the same geological origin, age and drainage basin. However, they differ in underwater light and UV penetration and in the presence of Oncorhynchus mykiss, only found in El Sol. Whereas Daphnia ambigua from the clear La Luna had carotenoids and melanin, in El Sol, the same species lacked pigmentation. The copepod Leptodiaptomus cuauhtemoci was only found in El Sol and relied on accumulation of MAAs and carotenoids. The maximum concentration of PCs was found over the period with highest incident ultraviolet radiation (UVR). Our data suggest that tropical species of zooplankton respond to UVR by accumulating PCs that are too different in relation to exposure to UVR. However, we cannot discard the possibility that the presence of fish in Lake El Sol influences also their phenotypical and behavioral responses. Overall, zooplankton exhibited an ample phenotypic plasticity in the type and concentrations of PCs in response to the high and variable doses of UVR prevailing in low-latitude lakes, similar to the zooplankton of their high-latitude counterparts.