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 electron microscopy were used to describe a new genus of unicellular red algae, Erythrolobus coxiae (Porphyridiales, Porphyrideophyceae, 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 thylakoids and four or more chloroplast lobes extend from the pyrenoid along the cell periphery. A peripheral encircling 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 Porphyrideophyceae, also lack a peripheral encircling thylakoid and have an ER-mitochondria-Golgi association. The low molecular weight carbohydrates digeneaside and floridoside are present, unlike both Porphyridium and Flintiella, which have only floridoside. The phycobilin 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 Porphyrideophyceae and recent molecular analyses clearly establish the validity of this new red algal class and the genus Erythrolobus.

Rhodachlya madagascarensis gen. et sp. nov.: a distinct acrochaetioid represents a new order and family (Rhodachlyales ord. Nov., Rhodachlyaceae fam. Nov.) of the Florideophyceae (Rhodophyta)

“…Currently, the Compsopogonophyceae is the only class in which a peripheral encircling thylakoid is present in all taxa examined with TEM (West et al 2007b). The three genera in the Porphyridiophyceae (Porphyridium, Flintiella and Erythrolobus), the gametophyte stages of genera in the Bangiophyceae and several genera in the Rhodellophyceae all lack the peripheral encircling thylakoid (Scott et al 2006). This highly anomalous anatomical feature in R. madagascarensis is in agreement with our molecular analyses in positioning this entity as distinct among ordinal-level taxa in the Florideophyceae.…”

“…The juxtaposition of a mitochondrion with the Golgi bodies in Rhodachlya is no surprise. As discussed in Scott et al (2006), the three types of Golgi associations found in red algal cells [(1) endoplasmic reticulum (ER)-Golgi; (2) ERmitochondrion-Golgi; and (3) nuclear envelope (NE)-Golgi)] can now be regarded as the most predictable of all ultrastructural features that can be utilized to categorize each of the six red algal classes recognized by Yoon et al (2006). All genera in the Florideophyceae, Bangiophyceae and Porphyridiophyceae that have been examined by TEM possess an ER-mitochondrion-Golgi association, whereas examined genera in the Compsopogonophyceae and Stylonematophyceae have an ER-Golgi association.…”

Microscopic observation of pyrenoids in Order Ulvales (Chlorophyta) collected from Qingdao coast

“…Then the cells formed zoosporangia or gametangia, or perished directly. Pyrenoids became multiple in old cells in previous observations (Scott et al, 2006). So applying the pyrenoid number per cell as identification feature for different species needs further study.…”

Biogenesis of thylakoid membranes

“…For instance, some unicellular species, like the model organism Cyanidiioschyzon merolae, lack a pyrenoid [137], while others, like Erythrolobus coxiae and thallus-forming species like Porphyra sp., harbor such a structure [138,139]. Indeed, E. coxiae has a plastid containing a central pyrenoid surrounded by at least four plastid lobes ( Fig.…”