The latest research article from the Marine Photophysiology and Phycotechnology Laboratory (MP2Lab), part of the Department of Biology and CESAM, is featured on the cover of the scientific journal Biology Open, with an image of the tropical sea slug Elysia crispata. The study shows that different components of the light spectrum elicit distinct responses in these animals: red light promoted faster growth, while blue light was associated with greater longevity of the chloroplasts incorporated from the algae on which they feed.
Elysia crispata is one of the sea slugs belonging to the order Sacoglossa that is capable of sequestering chloroplasts from the algae it consumes and maintaining them functional within its own cells. This phenomenon, known as kleptoplasty, allows these chloroplasts — known as kleptoplasts — to remain photosynthetically active within the animal. Understanding the mechanisms that enable this association and the benefits it may provide to sea slugs is at the heart of the KleptoSlug project, led by Sónia Cruz, a CESAM/DBIO researcher, and funded by the European Research Council (ERC).
In the study, the researchers investigated how the spectral composition of light influences body weight and photosynthetic activity in Elysia crispata, exposing the animals to equivalent intensities of white, red or blue light. During feeding, sea slugs exposed to red light gained weight more rapidly, whereas those exposed to blue light showed higher concentrations of chlorophyll a, used as an indicator of kleptoplast abundance. During food deprivation, photosynthetic activity declined more rapidly under red light and more slowly under blue light, pointing to a trade-off between growth and kleptoplast longevity.
The behaviour of the sea slugs may help explain this pattern. Under blue light, the researchers observed a greater degree of parapodial closure. The parapodia are lateral body extensions containing cells that harbour kleptoplasts. The authors hypothesise that this behaviour may reduce the exposure of kleptoplasts to light and limit photo-oxidative damage, thereby helping to prolong their functionality.
The results therefore show that the spectral composition of light influences the growth of Elysia crispata, the activity of its sequestered chloroplasts and the animal’s behaviour, contributing to a better understanding of the mechanisms that enable these photosynthetic structures to be maintained within animal cells.
Conducted within the framework of the KleptoSlug project — Kleptoplasty: The sea slug that got away with stolen chloroplasts — the study was authored by Carlos Paya, a CESAM/DQ PhD student, Heta Mattila, Vesa Havurinne, Felisa Rey, a CESAM/DQ researcher, and Sónia Cruz and Paulo Cartaxana, CESAM/DBIO researchers. The work was published in Biology Open, an open-access scientific journal published by The Company of Biologists.
Article: https://doi.org/10.1242/bio.062714
