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

doi:2006.21.4.407

Algae > Volume 21(4); 2006 > Article

Algae 2006;21(4): 407-416. doi: https://doi.org/10.4490/algae.2006.21.4.407

Joseph L. Scott¹^*, Bart Baca², Franklyn D. Ott³ and John A. West⁴

¹Department of Biology, College of William and Mary, Williamsburg, VA 23187, U.S.A.
²Everglades University, 5002 T-Rex Avenue, Boca Raton, FL 33431, U.S.A. 3905 NE Hilltop Drive, Topeka, KS 66617, U.S.A.
⁴School of Botany, University of Melbourne, Parkville, Victoria 3010, Australia

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.

Key words: cell motility, Erythrolobus, Flintiella, floridoside/digeneaside, Porphyridiophyceae, Porphyridium,