Cryptomonas Ehrenberg 1831

Introduction

• Described by Ehrenberg (genus: 1831; species: 1832; figures of species: 1838); no type designated
• Lectotype: Cryptomonas curvata (Hoef-Emden and Melkonian 2003)

Characteristics

• Type of biliprotein: PE566 or colorless (leucoplast present; formerly genus Chilomonas; Ehrenberg 1831; Joyon 1963; Sepsenwol 1973)
• Dimorphic
• Light microscopy: olive-green to brownish or colorless freshwater cryptophytes, one deeply bi-lobed plastid or two separate plastids, a cell invagination with a slit-like opening extending into a gullet, with or without pyrenoids, cryptomorphs with straight furrow, campylomorphs with curved furrow and refractive granulum closely appressed to left furrow margin, antapices of campylomorph cells may be bent to the dorsal side
• Ultrastructure of cryptomorphs: inner periplast component made of polygonal plates, surface periplast component consisting of fine fibrils, non-keeled rhizostyle (references summarized in Hill 1991a)
• Ultrastructure of campylomorphs (formerly genus Campylomonas; Hill 1991a): inner periplast component continuous (sheet-like), keeled rhizostyle
• Freshwater only
  

Discussion of Phylogenetic Relationships

Phylogenetic trees demonstrate that the separation into three genera based only on ultrastructure or pigment content (polygonal periplast plates [Cryptomonas] vs. sheet-like periplast [“Campylomonas”], and phycoerythrin 566 vs. leucoplast [“Chilomonas”]) result in an unnatural system. Instead of forming three clearly separated groups corresponding to morphologically defined genera, strains displaying different morphotypes intermingle in most sub-clades and some strains are even dimorphic with both cell types in a culture (Figure 1; Hoef-Emden and Melkonian 2003; Hoef-Emden 2007). “Chilomonas” not only evolved from photosynthetic species, loss of photosynthesis occurred three times independently (Hoef-Emden 2005). Therefore, the former genera Campylomonas and Chilomonas have been included in Cryptomonas (Hoef-Emden and Melkonian 2003). Until 2003 no valid type, neotype or lectotype of Cryptomonas had been designated. Since the figures by Ehrenberg of Cryptomonas curvata were the only ones that could be clearly assigned by morphology to extant strains, this species has been chosen to be the lectotype species (Hoef-Emden and Melkonian 2003). These examinations also show that Pringsheim's scepticism towards the application of a morphospecies concept in Cryptomonas was justified (Hoef-Emden 2007). Several Cryptomonas species can be identified only by molecular signatures.

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Figure 1. Molecular phylogeny of the genus Cryptomonas. Maximum likelihood tree inferred from nucleomorph SSU rDNA sequences. Scale bar = substitutions per site. © 2008 Kerstin Hoef-Emden

Other Names for Cryptomonas Ehrenberg 1831

• Chilomonas
• Campylomonas
• Cryptochrysis
• Pseudocryptomonas

References

Ehrenberg CG (1831) Symbolae physicae seu Icones et Descriptiones Animalium Evertebratorum sepositis Insectis que ex itinere per Africanum borealem et Asiam occidentalem Friderici Guilelmi Hemprich et Christiani Godofredi Ehrenberg medicinae et chirurgiae doctorum studio novae aut illustratae redierunt. Mittler, Berlin

Ehrenberg CG (1832) Über die Entwickelung und Lebensdauer der Infusionsthiere; nebst ferneren Beiträgen zu einer Vergleichung ihrer organischen Systeme. Abh. Königl. Akad. Wiss. Berlin, Physik. Klasse 1831: 1-154

Ehrenberg CG (1838) Die Infusionsthiere als vollkommene Organismen: Ein Blick in das tiefere organische Leben der Natur. Nebst einem Atlas von colorirten Kupfertafeln. Voss, Leipzig

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

Hoef-Emden K (2005) Multiple independent losses of photosynthesis and differing evolutionary rates in the genus Cryptomonas (Cryptophyceae): Combined phylogenetic analyses of DNA sequences of the nuclear and nucleomorph ribosomal operons. J. Mol. Evol. 60: 183-195

Hoef-Emden K (2007) Revision of the genus Cryptomonas (Cryptophyceae) II: Incongruences between classical morphospecies and molecular phylogeny in smaller pyrenoid-less cells. Phycologia 46: 402-428

Hoef-Emden K, Melkonian M (2003) Revision of the genus Cryptomonas (Cryptophyceae): a combination of molecular phylogeny and morphology provides insights into a long-hidden dimorphism. Protist 154: 371-409

Joyon L (1963) Sur la présence d'un leucoplaste chez la Cryptomonadine decolorée Chilomonas paramecium (Ehrenberg). C. R. Hebd. Séances Acad. Sci. 256: 3502-3503

Sepsenwol S (1973) Leucoplast of the cryptomonad Chilomonas paramecium. Exp. Cell Res. 76: 395-409

Skuja H (1948) Taxonomie des Phytoplanktons einiger Seen in Uppland, Schweden. Symb. Bot. Ups. 9: 346-367