Phylogenetic Analysis of Entomoparasitic Nematodes, Potential Control Agents of Flea Populations in Natural Foci of Plague

Abstract

Entomoparasitic nematodes are natural control agents for many insect pests, including fleas that transmit Yersinia pestis, a causative agent of plague, in the natural foci of this extremely dangerous zoonosis. We examined the flea samples from the Volga-Ural natural focus of plague for their infestation with nematodes. Among the six flea species feeding on different rodent hosts (Citellus pygmaeus, Microtus socialis, and Allactaga major), the rate of infestation varied from 0 to 21%. The propagation rate of parasitic nematodes in the haemocoel of infected fleas was very high; in some cases, we observed up to 1,000 juveniles per flea specimen. Our study of morphology, life cycle, and rDNA sequences of these parasites revealed that they belong to three distinct species differing in the host specificity. On SSU and LSU rRNA phylogenies, these species representing three genera (Rubzovinema, Psyllotylenchus, and Spilotylenchus), constitute a monophyletic group close to Allantonema and Parasitylenchus, the type genera of the families Allantonematidae and Parasitylenchidae (Nematoda: Tylenchida). We discuss the SSU-ITS1-5.8S-LSU rDNA phylogeny of the Tylenchida with a special emphasis on the suborder Hexatylina.

Galling problems – the Fergusobia nematode/Fergusonina fly mutualism on myrtaceous hosts

“…However, three recent phylogenies are available (Chizhov et al, 2012;Koshel et al, 2014;Miraeiz et al, 2015). These phylogenies confirm Siddiqi's (2000) split of Hexatylina into two major groups, the super-families Iotonchioidea and Sphaerularioidea, but both Allantonematidae and Neotylenchidae appear to be paraphyletic.…”

“…If the ancestral nematodes were parasitic on roots, it is possible that they have not been found; ii) fly-plantagain, no modern fly-plant associations without nematodes have been found; iii) fly-nematode -could have occurred in a phoretic or parasitic association before becoming plant parasites. The phylogenies of Ye et al (2007a), Chizhov et al (2012), Koshel et al (2014) and Miraeiz et al (2015) suggest that Fergusobia is related to Howardula, i.e., that it could have evolved from entomoparasitic nematodes. These trees suggest that Fergusobia, anguinids and neotylenchids did not have a common ancestor.…”

“…However, in the recent phylogenetic trees, Allantonema and Bradynema are in different clades from Fergusobia and the other genera, suggesting that this adaptation is convergent. The phylogenies of Koshel et al (2014) and Miraeiz et al (2015) suggest that Skarbilovinema (Iotonchiidae) is sister to Fergusobia (Neotylenchidae). Certainly, both have fly hosts, have modified cuticle or have lost the cuticle in the entomoparasitic stage and both have a parthenogenetic generation (although this is within the host insect in Skarbilovinema vs within the plant host in Fergusobia).…”

“…Fergusobia is monophyletic (Ye et al, 2007a;Chizhov et al, 2012;Koshel et al, 2014;Miraeiz et al, 2015). Giblin- Davis et al (2003Davis et al ( , 2004b hypothesised that it may have stemmed from an ancestral hexatylinid common to both Anguinoidea and Neotylenchoidea, but this is refuted by the phylogeny of Chizhov et al (2012), which suggests that it evolved from entomoparasitic nematodes like modern Howardula.…”

Description of a new species of the genus Anguillonema Fuchs, 1938 (Nematoda: Sphaerularioidea) with an identification key to the species

“…Also in the partial 28S tree, the polyphyletic nature of members of Neotylenchidae ( Deladenus , Neotylenchus Steiner, 1931, Rubzovinema and Anguillonema ), Allantonematidae ( Howardula , Contortylenchus Rühm, 1956, Bradynema and Allantonema Leuckart, 1884) and Parasitylenchidae Siddiqi, 1986 ( Wachekitylenchus Slobodyanyuk, 1986 and Parasitylenchus ) are clear. The polyphyletic nature of the families Neotylenchidae, Allantonematidae and Parasitylenchidae, using SSU-ITS1-5.8S-LSU rDNA sequences, has already been discussed by Koshel et al (2014).…”