Reproductive potential and early spore settlement on different substrates in Gigartina skottsbergii (Gigartinaceae, Rhodophyta) from the South American Atlantic coast

Abstract

The aims of this study were to estimate seasonal spore availability in the carrageenophyte Gigartina skottsbergii from the Patagonian Atlantic coast, evaluate the effect of induction methods and culture conditions on spore release, and assess spore settlement on different substrates. Fertile fronds were collected in southern Argentina. The density and size of reproductive structures and spore output were registered seasonally. Spore release was evaluated using different induction methods and conditions. Finally, different natural substrates were assessed for spore settlement. Spore availability is restricted to winter and spring. Cystocarps and tetrasporangial sori reached maturity towards winter, and spores were released in large amounts during winter and spring, with higher tetraspore than carpospore release. Spontaneous discharge would appear to be a more advisable induction method than desiccation and high salinity. Temperature and photoperiod did not have a significant effect on total spore output. After 2 weeks of incubation, no differences were found among spore densities on glass, pebbles, clams, or mussels. Despite the low survival rate registered on all substrates, spores germinated and developed healthily. This is the first study to evaluate carpospore and tetraspore availability throughout the year and the viability of in vitro spore culture of G. skottsbergii from the South American Atlantic coast.