Ultrastructure and molecular phylogeny of the cryptomonad Goniomonas avonlea sp. nov.

We describe a new species of cryptomonad, Goniomonas avonlea sp. nov., using molecular phylogeny and comprehensive microscopic investigation. G. avonlea is a marine bacterivorous flagellate, measuring 8-11 μm long and 6-7 μm wide, with two subequal flagella that are directed anteriorly and posteriorly. G. avonlea is morphologically and genetically distinct from three other Goniomonas species that have been described to date. SEM and TEM show that G. avonlea shares ultrastructural features with other Goniomonas and cryptomonads, including the presence of bipartite ejectisomes, double septa in the transition region, flat mitochondrial cristae, a furrow complex, a rhizostyle, rectangular periplast plates, and the infundibulum. The discharged large ejectisome is straight and has a unique loose, reticulate layer. The flagellar apparatus includes non-tubular roots, microtubular roots, and a compound root that is reminiscent of the multilayered structure (MLS) observed in the flagellate cells of streptophytes and a few other eukaryotes. Molecular phylogenies based on 18S and 28S rRNA genes suggest a specific affiliation of G. avonlea to marine Goniomonas species, and support the monophyly of Goniomonas to the exclusion of plastid-bearing cryptomonads. Our study adds to a growing body of evidence for the high level of diversity and antiquity of the genus Goniomonas.