engleski

Convergent loss of ommochrome pigmentation in cave- adapted isopod crustaceans

Albinism or pigment loss is an adaptation to a subterranean lifestyle and one of the prime examples of convergent evolution. It occurs in diverse cave-adapted animal groups regardless of the type of pigment they contain. The causes of melanin loss have been described in only a couple of cave-dwellers, while the mechanisms of albinism as a consequence of any other pigment deficiency are completely unexplored. Ommochromes are tryptophan derivates and a less studied class of pigments found in a wide range of invertebrates. Our research was focused on related crustaceans of the order Isopoda. Using a biochemical approach to extract and detect ommochromes in conjunction with liquid chromatography coupled to mass spectrometry (UPLC-MS) the type of biological pigments in urface isopods was determined. We identified for the first time and to the best of our knowledge ommochromes in three groups of surface isopods: families Sphaeromatidae (Flabellifera) and Trichoniscidae (Oniscidea) and the genus Proasellus (Asellota). Additionally, we quantified the precursors of ommochrome synthesis in closely related surface and cave species. Our results suggest that the disruption of ommochrome synthesis is preferentially at the beginning of this anabolic cascade since we observed the accumulation of tryptophan in cave dwellers. These results suggest that isopods are a good model to study the molecular mechanisms underlying albinism as a consequence of ommochrome deficiency. To resolve that issue, we will look for the expression changes and possible inactivating mutations in the candidate genes using a comparative transcriptomic approach on several pairs of surface-cave relatives.

ommochromes ; isopod, albinism ; caves ; transcriptome ; convergent evolution

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