Olive Sea Snake, a Serpent with a 'Second Eye' on its Tail, Found in Indonesian Waters

A unique ability to detect light through its tail tip has been discovered in the olive sea snake (Aipysurus laevis), a species inhabiting the coral reefs of the Indo-Pacific, including waters around Indonesia. This trait, known as dermal phototaxis, allows the snake to sense light directly through its skin, bypassing its visual organs entirely. The groundbreaking research, led by a team from the University of Adelaide and published in the journal Molecular Ecology, marks the first systematic study of this phenomenon in reptiles. While similar light-sensing capabilities have been noted in aquatic animals like fish and amphibians, their investigation into sea snakes is unprecedented. Researchers tested 17 sea snakes from eight different species. The study confirmed that dermal phototaxis is not exclusive to the olive sea snake; it was also observed in two other species, A. duboisii and A. tenuis. However, five other species, including some from the Hydrophis genus, showed no such response. Based on these findings, the researchers hypothesize that this light-sensing ability evolved in a common ancestor shared by six species within the Aipysurus genus. This represents approximately 10 percent of all known sea snake species. Biologically, the skin cells in the snake's tail are light-sensitive, but they function very differently from the eyes. This remarkable adaptation, akin to a 'second eye,' could play a crucial role in the sea snake's survival strategies, potentially aiding in predator avoidance, prey detection, or even reproductive behaviors. The discovery highlights the intricate and often surprising adaptations found within Indonesia's rich marine biodiversity.