Wallaceina inconstants (Podlipaev, Frolov, Kolesnikov 1990)

Synonims: Crithidia sp. ZK, Proteomonas inconstans.

Literature:

Podlipaev S.A., Frolov A.O., Kolesnikov A.A. (1990) Proteomonas inconstans n. gen., n. sp. (Kinetoplastida, Trypanosomatidae), a parasite of the bug Calocoris sexguttatus (Hemiptera, Miridae). Parazitologiya 24:339-345 (In Russian).

Kolesnikov A.A., Maslov D.A., Podlipaev S.A. (1990) Comparative restriction enzyme cleavage analysis of kinetoplast DNA from the lower trypanosomatids isolated in the North-West region of the USSR. Arch. Protistenk. 138:239-250.

Bulat S.A., Mokrousov I. V., Podlipaev S.A. (1999) Classification of trypanosomatids from insects and plants by the UP-PCR (Universally Primed PCR) technique and cross dor blot hybridization of PCR products. Europ. J. Protistol. 35:319-326.

Merzlyak E. et al. (2001) Diversity and phylogeny of insect trypanosomatids based on small subunit rRNA genes: polyphyly of Leptomonas and Blastocrithidia. J. Eukaryot. Microbiol. 48:161-169. Medline; PDF

Georgaphic distribution and biotope: The hemiptrean hosts, Nabis brevis Scholtz 1847, Nabis (Nabicula) flavomarginatus Scholtz 1847 (both from the family Nabidae) and Grypocoris (=Calocoris) sexguttatus Fabricius 1777 (Miridae) are broadly distributed in the Palearctic region. The hosts are usually found in the grass in the open landscape, in addition both nabids can be found near bodies of water. The original isolate (type culture) was obtained in the North-West of Russia (Pskov region) from G. sexguttatus in 1986. The family Nabidae was not previously known to harbor trypanosomatids.

General morphology in host and culture: Cells in the host intestine are round or oval, most with a flagellum. Cells in culture belong to three morphotypes: 1) promastigote; 2) large endomastigote; 3) small endomastigotes with a variable position of the kinetoplast. Endomastigote morphology is a diagnostic character for the novel genus Wallaceina (originally named Proteomonas, Podlipaev et al. 1990), the first genus established during the last 30 years.

Three types of colonies are formed on an agar medium: 1) large (2 mm) spheric; 2) small (0.4 mm) spheric; 3) irregular (amoeboid).

Ultrastructure: images

Genotyping and molecular phylogenetic classification. PCR-based DNA fingerprinting (RAPD and related techniques) represents a quick approach for discrimination of trypanosomatid isolates. The method is very useful when the goal is simply to investigate whether the isolate in question is different from other isolates or not. Cluster analysis can be combined with this tool, but its usefulness for taxonomy and phylogeny is limited because it fails to correctly resolve relationships among distantly related organisms. However, the method can reveal groups of closely related isolates. The UP-PCR data (Bulat et al., 1999) show that W. inconstans is a close relative of W. brevicula, and both of them are related to the trypanosomatids which were morphologically classified as a blastocrithidia (B. gerricola) and leptomonas (L. peterhoffi) - a good example of the inconsistensy of the DNA-based and morphology-based classification approaches in trypanosomatids.

A reliable identification at a group-specific level (species, subgenus, genus) can be obtained through the sequences of Spliced Leader and 5S ribosomal RNA gene repeats but these data are not yet available for W. inconstans. Available sequences include SSU rRNA, kinetoplast minicircles and NADH subunit 8 gene and mRNA sequences.

Since SL and 5S sequences are relatively short (SL exon - 39 bp, SL intron 50-100 bp), they contain little phylogenetic information, and much longer (2 kb) 18S SSU ribosomal RNA genes have been mostly utilized for phylogenetic analysis instead. A tree of the entire Trypanosomatidae family can be derived from an alignment of the most conserved nucleotides in the SSU sequences (Merzlyak et al. 2001). It shows W. inconstans among other members of the clade which was previously called 'slowly-evolving' (with regard to the SSU RNA), but the tree does not show relationships within this clade. To some extent these could be resolved in the tree derived from the complete SSU sequences (with variable positions) which could be aligned when only the members of this clade were included (Merzlyak et al. 2001). A consistency with the UP-PCR based grouping of the W. inconstans is evident.