Sónia Cruz

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 slug Elysia crispata . Recently hatched sea slugs fed and acquired chloroplasts from the macroalga Bryopsis plumosa, but not from Acetabularia acetabulum . However, adult sea slugs were able to switch diet to A. acetabulum , rapidly replacing the great majority of the original kleptoplasts. When fed with B. 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 of A. acetabulum -derived chloroplasts in E. crispata was over twofold that of B. plumosa . Furthermore, significantly lower relative weight loss under starvation was observed in sea slugs previously fed on A. acetabulum than on B. plumosa . This study shows that functionality and longevity of kleptoplasts in photosynthetic sea slugs depend on the origin of the plastids. Furthermore, we have identified A. acetabulum as 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.

Fucus vesiculosus is a brown seaweed with applications in the food, pharmaceutic, and cosmetic industries. Among its most valuable bioactive compounds are the pigment fucoxanthin and polysaccharides (e.g., fucoidans). In this study, we profiled the photosynthetic pigments and carbohydrates of F. vesiculosus from six locations along the Ílhavo Channel in the Iberian coastal lagoon of Ria de Aveiro, Portugal. Photosynthetic performance (Fv/Fm), pigment, and carbohydrate concentrations were similar between locations, despite differences in environmental factors, such as salinity and periods of exposure to desiccation. Concentration of total carbohydrates (neutral sugars + uronic acids) averaged 418 mg g−1 dw. Fucose was the second most abundant neutral sugar, with an average concentration of 60.7 mg g−1 dw, indicating a high content of fucoidans. Photosynthetic pigments included chlorophylls a and c, β,β-carotene, and the xanthophylls fucoxanthin, violaxanthin, antheraxanthin, and zeaxanthin. Concentrations of fucoxanthin were higher than those reported for most brown macroalgae, averaging 0.58 mg g−1 dw (65% of total carotenoids). This study indicates that F. vesiculosus from Ria de Aveiro is a valuable macroalgal resource for aquaculture companies operating in the region, with considerable potential to yield high-value bioactive compounds.