#oxynoe

An image taken underwater shows the sea slug Oxynoe kylei here in Tulamben, Bali, Indonesia

Photograph: Oksana Maksymova/Alamy

Oxynoe olivacea - a sea slug with many skills

Oxynoe olivacea (Sacoglossa - Oxynoidae) is a species of shelled sacoglossan (sea slug) endemic to the Mediterranean Sea, which lives in close association with the invasive seaweed Caulerpa taxifolia, from which it feeds, and sequesters chloroplasts and secondary metabolites (kleptoplasty).

For the last three decades, the Mediterranean Sea has been under invasion of two exotic algae species, Caulerpa taxifolia and Caulerpa racemosa. C. taxifolia was introduced to the Mediterranean due to the accidental release of it from a public aquarium in Monaco.

Due to the specialization of its diet, Oxynoe olivacea has been studied as potential biological control agent against Caulerpa taxifolia. However, it has been found that this could be only possible through an artificial enhancement of their populations after cultivation of the veligers and release of juveniles during the winter season, because these sacoglossan have low feeding rates and their larvae are planktonic.

Furthermore, the  major secondary metabolite of the alga is caulerpenyne, a toxic substance with grazing deterrent properties towards herbivorous fish. However, Oxynoe olivacea is able to eat the Caulerpa and even to sequester the toxic component. Experiments with this sacoglossan have demonstrated that the mollusk is also able to biotransform caulerpenyne into more active derivatives, and use them in their own defense.

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