Sea Slug Mucus Production Is Supported by Photosynthesis of Stolen Chloroplasts


Simple Summary Kleptoplasty is the capacity of a non-photosynthetic organism to acquire and maintain structurally intact chloroplasts from its algal food source(s), thereafter termed kleptoplasts. In animals, the capacity for long-term (several weeks to months) maintenance of photosynthetic active kleptoplasts is a unique characteristic in a handful of sea slugs, mostly within the genus Elysia. In this study, we investigated the role of kleptoplast photosynthesis on mucus production by the tropical sea slug Elysia crispata. Mucus secretion is paramount for mollusks, playing a role in locomotion, feeding, reproduction and protection. Limiting photosynthesis by rearing animals under reduced light led to lower mucus production and lower carbohydrate concentrations in the secreted mucus. This study indicates that production of mucus by kleptoplast-bearing sea slugs is supported by photosynthesis, confirming the biological relevance of kleptoplasty to the fitness of these peculiar mollusks. A handful of sea slugs of the order Sacoglossa are able to steal chloroplasts-kleptoplasts-from their algal food sources and maintain them functionally for periods ranging from several weeks to a few months. In this study, we investigated the role of kleptoplast photosynthesis on mucus production by the tropical sea slug Elysia crispata. Animals reared for 5 weeks in quasi dark (5 mu mol photons m(-2) s(-1)) showed similar growth to those under regular light (60-90 mu mol photons m(-2) s(-1)), showing that kleptoplast photosynthesis was not relevant for growth when sea slugs were fed ad libitum. However, when subjected to short-term desiccation stress, animals reared under regular light produced significantly more mucus. Furthermore, the carbohydrate content of secreted mucus was significantly lower in slugs limited in the photosynthetic activity of their kleptoplasts by quasi-dark conditions. This study indicates that photosynthesis supports the synthesis of protective mucus in kleptoplast-bearing sea slugs.



subject category

Life Sciences & Biomedicine - Other Topics


Lopes, D; Cruz, S; Martins, P; Ferreira, S; Nunes, C; Domingues, P; Cartaxana, P

our authors


This project received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 949880) (S.C.). We acknowledge support from Fundacao para a Ciencia e a Tecnologia (FCT/MCTES) through individual grants no. 2020.08672.BD (D.L.), 2020.03278.CEECIND (S.C.) and CEECIND/01434/2018 (P.C.), as well as financial support to CESAM through grant no. UIDP/50017/2020+UIDB/50017/2020+LA/P/0094/2020 and CICECO through grant no. UIDB/50011/2020+UIDP/50011/2020+LA/P/0006/2020. C.N. thanks national funds (OE), through FCT, I.P., in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19.

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