Somatic meiosis in the life history of Bonnemaisonia asparagoides and Bonnemaisonia clavata (Bonnemaisoniales, Rhodophyta) from the Iberian peninsula

Abstract

Carpospores isolated from Bonnemaisonia asparagoides and Bonnemaisonia clavata (Bonnemaisoniaceae, Rhodophyta) and grown in culture developed into their respective ‘Hymenoclonium’ prostrate phases. In both species, young gametophytes were initiated directly on the prostrate phase from tetrasporangia-like protuberances. Comparison of the relative fluorescence area (rfa) of nuclear DNA over the sequence of life-history stages indicated that the lowest ploidy levels (1–2C) occurred in the gametophytes, whereas the lowest ploidy levels in the prostrate phases were 2–4C. Rfa data demonstrated that meiosis occurred in the tetrasporangia-like protuberances where 1C values were recorded. The present observations establish that B. asparagoides and B. clavata have a heteromorphic diplohaplontic life history, which involves a haploid gametophyte produced directly on a diploid prostate phase after somatic meiosis. We conclude that the life history of these taxa corresponds to the Lemanea-type. This indicates that the life history of several Bonnemaisoniales with a ‘Hymenoclonium’ phase but lacking tetrasporangia requires re-investigation.