Freezing and desiccation tolerance in the Antarctic bangiophyte <i>Pyropia endiviifolia</i> (Rhodophyta): a chicken and egg problem?

Antarctic macroalgal communities of the upper intertidal zone are particularly poor compared with other coastal regions. Exposure to desiccation and freezing combined abrasive effect ice threatens life sessile organisms. One few species able colonize this environment is rhodophyte Pyropia endiviifolia. It belongs Bangiales, one oldest extant clades photosynthetic eukaryotes, which has occurred for more than billion years basically same morphological structure. Considering that extent glaciation a geologically recent event, we hypothesized pre-adaptations in bangiophytes may have contributed success P. endiviifolia Antarctica. To test this, its performance tolerance those from related species, temperate Atlantic Porphyra linearis. As evidenced by gas exchange chlorophyll fluorescence, adapted high irradiances The former was also desiccation-tolerant, showed higher glass transition temperature. Both did not differ content per dry weight, −20°C, even though ice-nucleation temperature much Membrane integrity depend on fatty acid composition endiviifolia, while enhanced tocopherol Overall, both show different strategies deal temperatures: supercooling linearis vs. freezing-tolerance This matches probability being subjected sub-zero temperatures their natural environments (lower case linearis). Surprisingly, risk dehydration habitat matched tolerance. observation does support initial hypothesis study but suggests opposite: acclimation cold results tolerance.HIGHLIGHTS● remarkably tolerant freezing.● Mechanisms could induce desiccation.