Light and Electron Microscopic Observations on Erythrolobus coxiae gen.et sp.nov. (Porphyridiophyceae, Rhodophyta) from Texas U.S.A.

Abstract

Low molecular weight carbohydrates, phycobilin pigments and cell structure using light and transmission elec- tron microscopy were used to describe a new genus of unicellular red algae, Erythrolobus coxiae (Porphyridiales, Porphyridiophyceae, Rhodophyta). The nucleus of Erythrolobus is located at the cell periphery and the pyrenoid, enclosed by a cytoplasmic starch sheath, is in the cell center. The pyrenoid matrix contains branched tubular thy- lakoids and four or more chloroplast lobes extend from the pyrenoid along the cell periphery. A peripheral encir- cling thylakoid is absent. The Golgi apparatus faces outward at the cell periphery and is always associated with a mitochondrion. Porphyridium and Flintiella, the other members of the Porphyridiophyceae, also lack a peripheral encircling thylakoid and have an ER-mitochondria-Golgi association. The low molecular weight carbohydrates dige- neaside and floridoside are present, unlike both Porphyridium and Flintiella, which have only floridoside. The phyco- bilin pigments B-phycoerythrin, R-phycocyanin and allophycocyanin are present, similar to Porphyridium purpureum. The cells have a slow gliding motility without changing shape and do not require substrate contact. The ultrastructural features are unique to members of the Porphyridiophyceae and recent molecular analyses clearly establish the validity of this new red algal class and the genus Erythrolobus.