Prey species and abundance affect growth and photosynthetic performance of the polyphagous sea slugElysia crispata

Abstract

Some sacoglossan sea slugs steal functional macroalgal chloroplasts (kleptoplasts). In this study, we investigated the effects of algal prey species and abundance on the growth and photosynthetic capacity of the tropical polyphagous sea slugElysia crispata. Recently hatched sea slugs fed and acquired chloroplasts from the macroalgaBryopsis plumosa,but not fromAcetabularia acetabulum. However, adult sea slugs were able to switch diet toA. acetabulum, rapidly replacing the great majority of the original kleptoplasts. When fed withB. plumosa, higher feeding frequency resulted in significantly higher growth and kleptoplast photosynthetic yield, as well as a slower relative decrease in these parameters upon starvation. Longevity ofA. acetabulum-derived chloroplasts inE. crispatawas over twofold that ofB. plumosa. Furthermore, significantly lower relative weight loss under starvation was observed in sea slugs previously fed onA. acetabulumthan onB. plumosa. This study shows that functionality and longevity of kleptoplasts in photosynthetic sea slugs depend on the origin of the plastids. Furthermore, we have identifiedA. acetabulumas a donor of photosynthetically efficient chloroplasts common to highly specialized monophagous and polyphagous sea slugs capable of long-term retention, which opens new experimental routes to unravel the unsolved mysteries of kleptoplasty.