Characterisation of a topotype and other populations of Hemicriconemoides strictathecatus Esser, 1960 (Nematoda: Criconematidae) from Florida with description of H. phoenicis sp. n. from the USA

Abstract

The results of morphological and molecular analyses of a Florida topotype and other populations of Hemicriconemoides strictathecatus showed that this sheathoid nematode consists of two morphotypes, both with an average stylet length of more than 70 μm, but having different tail termini, bluntly pointed or rounded. These findings confirmed the morphological similarity of H. strictathecatus with H. mangiferae, which was considered a junior synonym of this species as previously proposed by Decraemer & Geraert (1992, 1996). Populations of a sheathoid nematode with a stylet length ranging from 62.5 to 72.0 μm from Taiwan, China, South Africa and Venezuela and identified in previous studies as H. strictathecatus were found to be morphologically and molecularly different from this species and are now considered as representatives of H. litchi. Another sheathoid nematode population from Florida, considered to be H. mangiferae by McSorley et al. (1980), was also found to be morphologically and molecularly congruous with H. litchi. During nematological surveys in Florida, a new sheathoid nematode was detected on date palms imported from California into Florida and is described herein as H. phoenicis sp. n. This new species is related morphologically to the H. strictathecatus morphotype with pointed tail terminus. Both have a stylet longer than 70 μm. The new species is phylogenetically related to H. strictathecatus and H. litchi. It differs morphologically from other Hemicriconemoides species by the cuticular ornamentation of the annuli, which are marked by coarse longitudinal ridges, grooves and thick margins. Morphological and molecular characterisations of H. cocophillus from Mozambique and Florida, USA are also elucidated in this study. New phylogenies of the genus Hemicriconemoides as inferred from the analyses of the ITS rRNA, D2-D3 of 28S rRNA and partial coxI gene sequences are provided.

Characterisation of two Chinese native Hemicriconemoides species (Nematoda: Criconematidae) with updated descriptions of H. chitwoodi Esser, 1960 and Criconemoides myungsugae Choi & Geraert, 1975

“…The phylogenetic analyses of Hemicriconemoides spp. obtained in the present study agree with previous studies of this genus (Van den Berg et al, 2014, 2015, Maria et al, 2018a Overall, this study provides the molecular characterisation together with morphological and SEM observation of native Hemicriconemoides and one Criconemoides species from China. The addition of these species from China to a reference dataset will assist to provide insights into the phylogeny and biogeography of criconematid nematodes.…”

“…The addition of these species from China to a reference dataset will assist to provide insights into the phylogeny and biogeography of criconematid nematodes. Several studies have emphasised the need for an integrative taxonomical approach (Van den Berg et al, 2014, 2015Maria et al, 2018a, b). We also agreed that molecular diagnostics or phylogenetics should be combined with morphological and SEM observations in order to avoid errors in accurate species identification.…”

“…Newly obtained sequences of D2-D3 expansion segments of 28S, ITS, partial 18S and coxI and available sequences of other nematodes obtained from GenBank were used for phylogenetic reconstructions of Hemicriconemoides and Criconemoides species. Outgroup taxa for the dataset were chosen according to previously published data (Van den Berg et al, 2014, 2015Maria et al, 2018a). Multiple alignments of the different sequences were made using the Q-INS-i algorithm of MAFFT v. 7.205 (Katoh & Standley, 2013).…”

Morphological and molecular characterisation of two new Hemicycliophora species (Tylenchida: Hemicycliophoridae) with a revision of the taxonomic status of some known species and a phylogeny of the genus

“…For scanning electron microscope (SEM) studies, fixed specimens were dehydrated in a graded ethanol series, critical point-dried, sputter-coated with gold, observed and photographed with a Carl Zeiss Merlin Field Emission Scanning Electron Microscope (FE-SEM) at the University of Jaen, Spain (Abolafia et al, 2002), and a FEI Quanta FEG 250 in North West University, South Africa (Van den Berg et al, 2015).…”

DNA barcoding, phylogeny and phylogeography of the cyst nematode species of the Avenae group from the genus Heterodera (Tylenchida: Heteroderidae)

“…Furthermore, a high variability has been also shown in the mtDNA COI gene, a variability that can be employed as a powerful DNA barcoding marker. This gene fragment has already been used for discrimination of the majority of species of Longidoridae (Palomares-Rius et al, 2017), Criconematidae (Powers et al, 2014), Heteroderidae (Subbotin et al, 2017), Meloidogyne (Kiewnick et al, 2014), Pratylenchus Janssen et al, 2017), Hemicriconemoides (Van den Berg et al, 2015), and others. The usefulness of COI gene sequences for identification of some species from the Avenae group has been shown by Toumi et al (2013b) and Subbotin (2015), but only a limited number of samples were analysed in those studies.…”