Researchers at the University of São Paulo’s Institute of Biosciences (USP), with US colleagues and FAPESP support, have shown that oysters, mussels and other bivalves, even without eyes, use opsins, light-sensing proteins, in their skin to detect light and its direction.
The human retina uses 5 types of opsin. Bivalves without ocelli, primitive visual structures, can produce up to 9, and those with ocelli between 5 and 12. The study analysed 17 species from all five orders of the group, nine of them collected in São Sebastião on the São Paulo coast.
The team sequenced the genes active in the ocelli and the mantle edge, the part most exposed to light. It also found that how much the animals move is not linked to the number of opsins. The work was published in Proceedings of the Royal Society B.
According to the authors, this variety of proteins may point to still-unknown functions, such as regulating biological cycles. Next steps include studying other senses and the impact of chemical and light pollution on these ecologically and economically important animals.
