Goniomonas

Introduction

Described by Stein; type species Goniomonas truncata (freshwater; formerly Monas truncata Fresenius 1858; Stein 1878)

Characteristics

• Aplastidic, therefore without periplastidial space, nucleomorph or biliprotein
• Phagotrophic (Jezbera et al. 2005)
• Dimorphism unknown
• Light microscopy: colorless flagellates, marine or freshwater, laterally flattened, rounded to elliptical cells with obliquely truncate anterior, truncate anterior with row of ejectosomes (Larsen and Pattersen 1990)
• Ultrastructure: inner periplast component made of elongate plates, two cell invaginations in anterior part of the cell, a furrow and a separate cytopharynx, non-keeled rhizostyle (Mignot 1965; Mignot et al. 1968; Schuster 1968; Larsen and Pattersen 1990)

Discussion of Phylogenetic Relationships

Cell shape and flagellar appendages of Goniomonas differ markedly from those of plastid-containing cryptophytes. Similarity in ejectosome structure was an early indicator for a relationship of this genus to the cryptophytes (Schuster 1968). Phylogenetic analysis provided definitive evidence (McFadden et al. 1994). Different from other cryptophyte genera, marine and freshwater species of Goniomonas seem to have separated early in evolution and evolved as two clearly distinct lineages (Figure 1; von der Heyden et al. 2004).

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Figure 1. Molecular phylogeny of the genus Goniomonas. Maximum likelihood tree inferred from nuclear SSU rDNA sequences. Scale bar = substitutions per site. © Kerstin Hoef-Emden

Other Names for Goniomonas

• Cyathomonas

References

Fresenius G (1858) Beiträge zur Kenntniss mikroskopischer Organismen. Abh. Senckenberg. Naturf. Ges. 2: 211-242

Jezbera J, Horňák K, Šimek K (2005) Food selection by bacterivorous protists: Insight from the analysis of the food vacuole content by means of fluorescence in situ hybridization. FEMS Microbiol. Ecol. 52: 351-363

Larsen J, Patterson DJ (1990) Some flagellates (Protista) from tropical marine sediments. J. Nat. Hist. 24: 801-937

Mignot JP (1965) Étude ultrastructurale de Cyathomonas truncata From. (flagellé cryptomonadine). J. Microscopie 4: 239-252

Mignot JP, Joyon L, Pringsheim EG (1968) Compléments a l'étude cytologique des cryptomonadines. Protistologica 4: 493-505

Schuster FL (1968) The gullet and trichocysts of Cyathomonas truncata. Exp. Cell Res. 49: 277-284

Stein F Ritter von (1878) Der Organismus der Infusionsthiere. W. Engelmann, Leipzig. Vol. 3.1

von der Heyden S, Chao E, Cavalier-Smith T (2004) Genetic diversity of goniomonads: An ancient divergence between marine and freshwater species. Eur. J. Phycol. 39: 343-350