Occurrence of polynucleate spores of the crustose coralline alga Lithophyllum yessoense (Corallinales, Rhodophyceae): growth and survival

Abstract

Nonnucleate, uninucleate, binucleate, trinucleate and tetranucleate spores were found in sporophytes of Lithophyllum yessoense. The formation of polynucleate spores was caused mainly by the irregular distribution of nuclei in tetrasporangia. Both nuclei in a binucleate spore took part in development, suggesting that polynucleate spores grow into chimaeric crusts. The relative growth rate was higher in sporelings developed from trinucleate and tetranucleate spores (c. 12% d−1) than from uninucleate and binucleate spores (c. 5% d−1). However, the survival rates of sporelings developed from trinucleate and tetranucleate spores were less than half of those developed from uninucleate and binucleate spores. Polynucleate spores frequently occurred at low water temperature, especially at less than 12.1°C, indicating that successful reproduction via spores would be limited by low water temperature in winter, although this is when spore production is highest in southwestern Hokkaido.