Reclinomonas americana Flavin & Nerad 1993

Introduction

Reclinomonas is a genus of loricate Jakobids (Jakobida; Histionidae).  There is one described species, Reclinomonas americana Flavin and Nerad 1993.  Reclinomonas is known primarily because Reclinomonas americana was the first jakobid for which mitochondrial genome sequence data were published.

Characteristics

Figure 1. Reclinomonas americana. Diagram showing general appearance of live trophic cell under light microscopy.  Temporary food vacuoles and the contractile vacuole not shown.  © Alastair Simpson

Reclinomonas cells are small (5-12 μm—O'Kelly, 1997) with two flagella, and a conspicuous groove, which is usually considered to mark the 'ventral side' of the cell in jakobids.  The cell normally resides within a delicate wine-glass-shaped organic lorica—the stem of the glass (the pedicel) attaches to the substrate, and thus the organism is sessile.  The cell 'reclines' in the lorica with the ventral (grooved) side uppermost (as in the title illustration).  The lorica is adorned with very fine nail-shaped scales that can only be seen by electron microscopy (Flavin and Nerad, 1993).  About 1/3 of the way down the cell the left margin of the groove is drawn out into a short, fine microtubule-supported extension - the epipodium (Flavin and Nerad, 1993; O'Kelly, 1997) that can be mistaken for a short flagellum (Figure 1).

Reclinomonas reproduces by binary fission, after which one cell usually inherits the parental lorica. while the other swims away as a zoospore that is smaller than most trophic cells, but has longer flagella (O'Kelly, 1997).  The zoospore presumably settles and produces a new lorica.  The zoospore includes a vesicle containing the nail-shaped scales that will be attached to the newly-made lorica (Flavin and Nerad, 1993; O'Kelly, 1997).   Reclinomonas americana also forms cysts - these are usually found still within the lorica, and are rounded with a small button-like protusion (O'Kelly, 1997).

Reclinomonas has only been reported from freshwater.  Reported cultures of Reclinomonas americana were made from isolates from North America and New Zealand (Flavin and Nerad, 1993; O'Kelly, 1997). Cells are normally seen with a posterior contractile vacuole (not shown in Figure 1).

The mitochondrial genome of Reclinomonas americana ATCC 50394 was the first jakobid mitochondrial genome to be published (Lang et al. 1997).  This genome contained many more functional genes than any mitochondrial genome studied before, including four genes for a eubacterial-type RNA polymerase.  In the last decade mitochondrial genome sequences have been determined for several other jakobids, and most of the unusual features seen in Reclinomonas turn out to be typical for jakobids as a whole (Gray et al., 2004).  The mitochondrial genomes of jakobids are discussed in more detail on the Jakobida page.

Taxonomic note

Other Names for Reclinomonas americana Flavin & Nerad 1993

• Reclinomonas Flavin & Nerad 1993

References

Flavin, M. & Nerad, T. A. (1993) Reclinomonas americana n. g., n. sp., a new freshwater heterotrophic flagellate. J. Eukaryot. Microbiol. 40: 172-179.

Gray, M. W., Lang, B. F. & Burger, G. (2004) Mitochondria of protists. Annu. Rev. Genet. 38: 477-525.

Lang, B. F., Burger, G., O’Kelly, C. J., Cedergren, R., Golding, G. B., Lemieux, C., Sankoff, D., Turmel, M. & Gray, M. W. (1997) An ancestral mitochondrial DNA resembling a eubacterial genome in miniature. Nature 387: 493-497.

O’Kelly, C. J. (1993) The jakobid flagellates: structural features of Jakoba, Reclinomonas and Histiona and implications for the early diversification of eukaryotes. J. Eukaryot. Microbiol. 40: 627--636.

O’Kelly, C.J. (1997) Ultrastructure of trophozoites, zoospores and cysts of Reclinomonas americana Flavin & Nerad, 1993 (Protista incertae sedis: Histionidae). Europ. J. Protistol. 33: 337-348.

Patterson, D.J., Vørs, N., Simpson, A.G.B. & O'Kelly, C.J. (2002) Residual and predatory heterotrophic flagellates. In: Lee, J.J., Leedale, G.F.& Bradbury P. (ed.) An illustrated guide to the protozoa, second edition. pp 1302-1328. Society of Protozoologists, Lawrence, Kansas.

Penard, E. (1921) Studies on some flagellata. Proceedings of the Academy of Natural Sciences of Philadelphia. 73: 105-168

Petersen, J.B. and Hansen, J.B. (1962) One some neuston organisms III. Svensk. Botanisk. Tidskrift 57: 293-305.

Information on the Internet

• Reclinomonas page in Micro*scope.
• Reclinomonas page in the Protist Image Database (PID).
• Reclinomonas americana mitochondrial genome - OGMP.