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

Abstract

SummaryHemicycliophorapresently contains 132 valid species of sheath nematodes. Within several samples obtained from surveys in Canada, South Africa, Spain and the USA, we distinguished six valid and six putative unidentified species by integrating the results of morphological and molecular analyses. Valid species included:H. californica,H. gracilis,H. parvana,H. poranga,H. raskii, andH. signata. The putative unidentified species were indicated asHemicycliophorasp. 10, sp. 12, sp. 15, sp. 16, sp. 17, and sp. 18. Two new species of sheath nematodes from Spain and the USA were described and named asH. onubensissp. n. andH. robbinsisp. n., respectively.Hemicycliophora wyeiis proposed as a junior synonym ofH. parvanaandH. ripais proposed as a junior synonym ofH. poranga. Eighteen valid and 13 unidentified species of sheath nematodes were characterised using the partialCOImtDNA gene. A total of 94 new sequences of which 77 were for theCOImtDNA gene were obtained in this study. Phylogenetic relationships withinHemicycliophora, using the D2-D3 expansion segments of 28S rDNA, ITS rRNA andCOIgene sequences, are presented as inferred from Bayesian analysis.

Description of Hemicycliophora cardamomi sp. n. (Nematoda: Hemicycliophoridae) associated with Amomum longiligulare T.L. Wu and a web-based key for the identification of Hemicycliophora spp.

“…Hemicycliophora cardamomi sp. n. is different from all other species listed by Chitambar & Subbotin (2014) and species recently described by Van den Berg et al (2018) and Maria et al (2018). A comparison between H. cardamomi sp.…”

“…On the other hand, small variations of some morphological characteristics in the genus Hemicycliophora , such as the number of lip annuli and lateral field structures, are sometimes considered intraspecific variations. For example, Van den Berg et al (2018) considered H. wyei and H. ripa to be junior synonyms of H. parvana and H. poranga respectively. Descriptions of new species using the combination of morphological and molecular data enable users to both interpret morphological variation and to evaluate the presence of cryptic species in future discoveries.…”

“…Chitambar & Subbotin (2014) listed 132 valid species of the genus Hemicycliophora . Subsequently, Van den Berg et al (2018) described two new species, namely H. onubensis and H. robbinsi , and the authors also proposed H. wyei and H. ripa as junior synonyms of H. parvana Tarjan, 1952 and H. poranga Monteiro & Lordello, 1978, respectively. Recently, H. subbotini has been described by Maria et al (2018), bringing the total number of valid species to 133.…”

New records of plant-parasitic nematodes from Iceland

“…The species has been widely reported from European countries (Loof 1968;Brzeski 1998;Peña-Santiago et al 2004), Iran (Loof 1984), the Americas (Subbotin et al 2014), South Africa (Van den Berg 1981) and Svalbard, high Arctic tundra (Kerfahi et al 2017). As an obligate ectoparasite of plants, it inhibits growth and contorts the shape of root systems in farm crops (Winiszewska et al 2012;Chitambar and Subbotin 2014;Van Den Berg et al 2018). This species has been found to occur in Iceland in one location only in the basalt sand from the bank of the river Eystri-Rangá.…”

New sheath nematode, Hemicycliophora paraconida n. sp. (Rhabditida: Hemicycliophoridae) from Northern forest in Iran

“…These nematodes are a group of obligate ectoparasitic nematodes. Many species belonging to the superfamily have been found associated with agricultural crops, although pathogenicity has only been studied for a few species (van den Berg et al, 2018). Some species of Hemicycliophora e.g., H. arenaria Raski, 1958, H. conida Thorne, 1955, H. parvana Tarjan, 1952, H. poranga Monteiro & Lordello, 1978, H. similis Thorne 1955, H. typica de Man, 1921 have been reported as damaging agricultural crops such as carrot, celery, citrus, maple and tomato in several countries .…”