Large subunit rDNA gene sequences and reproductive morphology reveal Stenopeltis to be a member of the Liagoraceae (Nemaliales, Rhodophyta), with a description of Akalaphycus gen. nov.

A morphological and gene sequence study has shown the red algal genus Stenopeltis to be a member of the Liagoraceae (Nemaliales), not the Polyidaceae (Gigartinales) where it was placed after being segregated from Rhodopeltis. Post-fertilization events in Stenopeltis gracilis (the type of the genus) include a spreading, diffuse gonimoblast arising directly from the zygote ( = post-fertilization carpogonium), and no auxiliary cells, features characteristic of the Liagoraceae. Moreover, phylogenetic analyses based on LSU (large subunit) rDNA sequences clearly place Stenopeltis in a clade with members of the Liagoraceae. These observations are at odds with the existing taxonomic placement of the genus and a re-interpretation of earlier observations purporting to show the presence of auxiliary cells is presented. The morphology and reproduction of the three species currently attributed to the genus, S. gracilis (the type), S. setchelliae, and S. liagoroides, are described. LSU sequences as well as carpogonial branch and cystocarp morphology of S. setchelliae are distinct from those of S. gracilis (the type), and the segregate genus Akalaphycus is proposed to accommodate S. setchelliae and S. liagoroides.