The Scinaia assemblage (Galaxauraceae, Rhodophyta): a re-appraisal

Abstract

A re-examination of the four genera that comprise the Scinaia assemblage – Scinaia Bivona-Bernardi, Gloiophloea J. Agardh, Pseudoscinaia Setchell and Pseudogloiophloea Levring – has shown that both Pseudogloiophloea and Pseudoscinaia lack features that warrant independent generic status. Scinaia, Gloiophloea and Pseudogloiophloea have been separated from one another solely on cortical differences. Scinaia produces a cortex composed of either a mixture of inflated utricles and smaller cells (Scinaia forcellata Bivona-Bernardi) or of inflated utricles only (all other present species). In contrast, the cortex of Gloiophloea completely lacks utricles. Pseudogloiophloea supposedly differs from Scinaia in that its cortex is composed of a mixture of inflated utricles and conspicuously smaller (often pigmented) cells. This kind of cortex, however, is essentially identical to that found in S. forcellata, the type of the genus Scinaia. Pseudoscinaia was separated from Scinaia because its cystocarp supposedly has gonimoblast filaments lining the walls of the cystocarp cavity, rather than projecting centrally into the cavity. A re-examination of the type specimen, however, has shown that the cystocarp is essentially identical to that of Scinaia. It is concluded, therefore, that the Scinaia assemblage is comprised of only the two genera Scinaia (with cortical utricles to some degree) and Gloiophloea (completely lacking utricles). Recent proposals to erect the order Galaxaurales (as Chaetangiales) are rejected on the grounds that the gonimoblast initials in all genera studied arise directly from the carpogonium and not the hypogynous cell as has been previously claimed.