Rhodomonas | Rhinomonas | Storeatula

Introduction

• Rhodomonas described by Karsten; type species Rhodomonas baltica (marine; Karsten 1898)
• Rhinomonas described by Hill and Wetherbee; type species Rhinomonas pauca (marine; Hill and Wetherbee 1988)
• Storeatula described by Hill; type species Storeatula major (marine; Hill 1991)

Characteristics

• Nucleomorph embedded in pyrenoid matrix, separated from pyrenoid by two inner plastid membranes
• Type of biliprotein: PE545
• Probably dimorphic
• Light microscopy: red to bright brown cryptophytes, predominantly marine, one bi-lobed plastid with a pyrenoid on the connecting bridge between the plastid lobes
• Ultrastructure of Rhodomonas: approx. rectangular periplast plates (IPC) and fibrils (SPC), combination of gullet and furrow, keeled rhizostyle (revised by Hill and Wetherbee 1989)
• Ultrastructure of Rhinomonas: hexagonal periplast plates, gullet.
• Ultrastructure of Storeatula: sheet-like IPC, SPC made of coarse fibrils, gullet, keeled rhizostyle
• Predominantly marine, only few freshwater species
  

Discussion of Phylogenetic Relationships

A mixture of genera with different periplast types across the tree provides evidence for dimorphism in this cryptophyte group (Figure 1; Marin et al. 1998; Deane et al. 2002; Hoef-Emden et al. 2002). This is most obvious from existence of two Rhinomonas strains and Storeatula major that have almost identical DNA sequences. Therefore, this genus complex requires revision to eliminate inconsistencies.

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Figure 1. Molecular phylogeny of the Rhodomonas/Rhinomonas/Storeatula genus complex. Maximum likelihood tree inferred from nuclear SSU rDNA sequences. Scale bar = substitutions per site. © 2008 Kerstin Hoef-Emden

References

Deane JA, Hill DRA, Brett SJ, McFadden GI (2002) Cryptomonad evolution: Nuclear 18S rDNA phylogeny versus cell morphology and pigmentation. J. Phycol. 38: 1236-1244

Hill DRA (1991a) A revised circumscription of Cryptomonas (Cryptophyceae) based on examination of Australian strains. Phycologia 30: 170-188

Hill DRA, Wetherbee R (1988) The structure and taxonomy of Rhinomonas pauca gen. et sp. nov. (Cryptophyceae). Phycologia 27: 355-365

Hill DRA, Wetherbee R (1989) A reappraisal of the genus Rhodomonas (Cryptophyceae). Phycologia 28: 143-158

Hoef-Emden K, Marin B, Melkonian M (2002) Nuclear and nucleomorph SSU rDNA phylogeny in the Cryptophyta and the evolution of cryptophyte diversity. J. Mol. Evol. 55: 161-179

Karsten G (1898) Rhodomonas baltica N. g. et sp. Wiss. Meeresunters. Abt. Kiel 3: 15

Marin B, Klingberg M, Melkonian M (1998) Phylogenetic relationships among the Cryptophyta: analyses of nuclear-encoded SSU rRNA sequences support the monophyly of extant plastid-containing lineages. Protist 149: 265-276