Species diversity of ring nematodes of the genus Criconemoides (Nematoda: Criconematidae) based on three new species from China, using integrative taxonomy

Abstract

Ring nematodes of the genus Criconemoides are a group of polyphagous, migratory rootectoparasites of plants. In a nematological survey of Zhejiang Province, three new Criconemoides species were isolated from the rhizosphere of Citrus sp., Euonymus alatus and Pterocarya stenoptera trees. In the present study, the new species characterized using an integrative taxonomic approach and described as Criconemoides parainformis n. sp., C. geraerti n. sp. and C. rotundicaudatus n. sp. Three of the species shares truncated anteriorly flattened lip region comprised of two annuli, body annuli margin smooth with few anastomoses, (except C. rotundicaudatus n. sp. it has crenated annuli margins and numerous anastomoses), excretory pore 1-2 annuli posterior to pharyngeal bulb base, (except C. geraerti n. sp. it has excretory pore at the same level, or 1-2 annuli anterior to pharyngeal bulb base), vulva closed, anus hardly visible 1-3 annuli posterior to vulva. The new species can be distinguished based on their en face view pattern under scanning electron microscope (SEM) and the tail shapes. i.e. C. parainformis n. sp. has an ellipsoid oral disc, slightly fused pseudolips and tail ending in a bilobed terminus. C. geraerti n.sp. has a hexagonal oral disc, separated pseudolips, and a bluntly conoid tail. C. rotundicaudatus n. sp. has a rounded oral disc, well developed pseudolips, and a short broadly rounded tail. Besides detailed morphological studies using SEM, genomic and mitochondrial molecular data were obtained for the three described new species. In inferred phylogenies, these three species clustered with known Criconemoides species in 18S, 28S, ITS and coxI trees. Currently, only four known Criconemoides species occur in China and the discovery of the three new Criconemoides species in present study has increased our knowledge on the diversity of Criconemoides in China.

First Report of Mesocriconema sphaerocephalum (Taylor, 1936) Loof, 1989 Associated with Bell Pepper (Capsicum annuum) in Egypt

“…Moreover, at that time, the genus Criconemella represented one of the largest groups of plant-parasitic nematodes (Barker, 1982 andIbrahim et al, 2000). That is because prior to the revision by Luc & Raski (1981), species included in this genus had been placed in six genera: Macroposthonia, Criconemoides, Xenocriconemella, Mesocriconema, Neocriconema, and Madinema. Current status of ring nematodes: Although the family Criconematidae currently contains 18 genera and five subfamilies (Geraert, 2010), most of them were characterized based on traditional data (Maria et al, 2020). Moreover, a few researchers have obtained low to moderate numbers of criconematids by extraction methods (Baermann funnel, Christie-Perry method) that depend on nematode motility, but in-depth studies of these (Barker, 1982 andMaria et al, 2020).…”

“…Powers et al (2017) provided the 18S phylogenetic classification of Criconematoidea and discussed the taxonomic placement of several species. More recently, species diversity of ring nematodes of the genus Criconemoides was recently investigated using integrative taxonomy (Maria et al, 2020). Such investigations demonstrated that morphological studies coupled with other recent technological tools are helpful to avoid the previous confusions in generic and species levels and are useful to soundly grasp the phylogenetic relationships of criconematids.…”

“…They can not only damage plant roots (Westerdahl & Duncan 2015), but also predispose them to the other biotic stresses (Inserra et al, 2014 andMaria et al, 2018a,b). Moreover, some of them were involved in the decline of cultivated crops (Nath et al, 2008 andMaria et al, 2020). Additionally, this remarkable group has been reported associated with Citrus sp.…”

Screwed up: Spirality of segments and other iterated structures suggest an underlying principle of seriality in bilaterians

“…These are not related to other serial structures of the body. In some cases, these rings are irregularly formed and a spiral arrangement can be deduced from the figures of the publications of, for example, Decraemer (1985), Figures 1, 6, and 7), Urbancik et al (1996), Figure 1), Hoschitz, Buchholz & Ott (1999, figures 19, 20, 29), Karssen and van Aelst (2002), Figure 3), Powers et al (2016), Figure 7), and Maria et al (2020), Figure 7) (see Figure 9c).…”

“…(c) The tapeworm Moniezia expansa Rudolphi, 1810 ventral view, righthanded spiral (after Child, 1900). In all images, the beginning of the spiral is marked with an arrow, the end with an asterisk Figure 1), Hoschitz, Buchholz & Ott (1999, figures 19, 20, 29), Karssen and van Aelst (2002), Figure 3), Powers et al (2016), Figure 7), and Maria et al (2020), Figure 7) (see Figure 9c).…”