Abstract
Deladenus brevis n. sp. is described and illustrated based upon its morphological, morphometric, and molecular characters. The new species is mainly characterized by its small body size (367-454 µm long females and 350, 391 µm long males) and has small lateral vulval flaps. It is further characterized by having six lines in the lateral fields, cephalic region slightly expanded, narrower adjacent to the body, short 6 to 7 µm long stylet with three posteriorly sloped knobs, no post-vulval uterine sac (PUS), conical tail, narrowing to a rounded tip, and rare males with slender tylenchoid spicules and bursa reaching the tail tip. By having six lines in the lateral fields, the new species was compared with five known species of the genus, namely D. apopkaetus, D. cocophilus, D. durus, D. obtusicaudatus, and D. persicus, having comparable number (six or seven) of lines in the lateral fields. It was further compared with D. pakistanensis having lateral vulval flaps. The differences with above-mentioned species are discussed. In molecular phylogenetic analyses using nearly full length small and large subunit ribosomal DNA (SSU and LSU D2-D3 rDNA) and cytochrome c oxidase subunit I (COI mtDNA) gene sequences, D. brevis n. sp. formed clade with species of the genus with different clade support values in Bayesian inference.
Highlights
The genus Deladenus was erected by Thorne (1941) with D. durus (Cobb, 1922) Thorne (1941) as its type species
Compared to other genera in the family Neotylenchidae (Thorne, 1941), the genus is characterized by its low cephalic region, small stylet, pharyngo-intestinal junction anterior to nerve ring, excretory pore at the level with, or immediately behind the nerve ring, pharynx lacking a median bulb, long overlap of the glands, no postvulval uterine sac (PUS), and males with bursa
The newly described species in this study has a small body size, small lateral vulval flaps and by these features, it is well delimited in the genus
Summary
The genus Deladenus was erected by Thorne (1941) with D. durus (Cobb, 1922) Thorne (1941) as its type species. The list of the valid species under the genus is given by several authors (Siddiqi, 2000; Miraeiz et al, 2017; Yu et al, 2017; Morris et al, 2018). Deladenus proximus (Bedding, 1974) appears to be an efficient sterilizer against Sirex nigricornis (Zieman et al, 2015). All species of Deladenus were assumed to be mycetophagous, until Bedding (1968) found the infective form for some species, showing that two phases occur in their life. Around 13 species of the genus are only known by their mycetophagous phase. The present paper aims to describe the newly recovered species and resolve its phylogenetic relationships with other relevant species and genera using three SSU, LSU rDNA, and COI mtDNA markers
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