Life histories of Predaea ollivieri and P. pusilla (Nemastomatales, Rhodophyta)

Abstract

The life histories of Predaea ollivieri J. Feldmann and P. pusilla (Berthold) J. Feldmann were studied in vitro. In P. ollivieri, carpospore germination was unipolar, and sporophytes were formed of sparsely branched uniseriate filaments. In P. pusilla, carpospore germination was bipolar, and sporophytes were formed of uniseriate filaments consolidated in a pseudoparenchymatous crust. Carpospore development was observed in both species when irradiances ranged between 5–40 μmol m−2 s−1 combined with seawater temperature of 16, 18 or 21°C; no development was observed at 80 μmol m−2 s−1 or 14°C. Tetrasporophytes of P. ollivieri developed tetrasporangia in summer, autumn, winter and spring conditions. When the irradiance and temperature were high (40 μmol m−2 s−1, 21°C; hot-summer), bisporangia were produced instead of tetrasporangia. In summer and autumn conditions, some tetraspores gave rise to dioecious gametophytes, with male and female structures identical to those of the mother plant. In P. pusilla, tetrasporangia were not observed, but monosporangia were present in summer, autumn, winter and spring conditions, and bispores in hot-summer conditions. In late spring and summer, some monospores gave rise to dioecious gametophytes, with male and female structures identical to those of the mother plant. In both species, all types of spores were capable of producing new sporophytes that repeat this process for several successive generations. This capacity of sporophyte self-generation appears to promote survival by increasing the number of individual plants of the population.