Physiological plasticity in morphological variations of red seaweed Hypnea pseudomusciformis (Gigartinales, Rhodophyta) uncovered by molecular, antioxidant capacity and pigments content data

Hypnea pseudomusciformis Nauer, Cassano and M.C. Oliveira, a morphologically plastic species used as carrageenan source in Brazil, was recently described based on molecular markers. Two species previously described for the Brazilian coast (H. musciformis (Wulfen) J.V. Lamouroux and H. nigrescens Greville ex J. Agardh) are currently considered morphological variations of H. pseudomusciformis that are found in different intertidal regions. In this work, we investigated whether this morphologically plastic species also present physiological plasticity related to the different morphologies. The content of photosynthetic pigments (chlorophyll a, carotenoids and phycobiliproteins), total soluble proteins and antioxidant capacity (DPPH, ABTS, Folin–Ciocalteu reductive capacity, FRAP and iron chelating capacity) were analyzed for samples of the two morphological variations collected directly from the field or grown in culture. Physiological differences between the two morphological variants from field samples were observed for phycoerythrin, total soluble protein and for all the antioxidant assays, with the exception of DPPH. While between cultured samples, differences were found for phycocyanin, phycoerythrin and total soluble proteins. Overall, the two morphological variants have a similar physiological behavior when grown under the same culture conditions, corroborating its classification under one species. These results indicate that the physiological differences found between these variants are mostly due to environmental pressures and represent an example of phenotypic plasticity, which allows the occurrence of this species in different environments and may lead to different morphologies in the field.