Rotylenchus Wimbii 2021, n. sp.
Creators: name: Singh, Phougeishangbam Rolish
name: Karssen, Gerrit
name: Gitau, Kelvin
name: Wanjau, Cecilia
name: Couvreur, Marjolein
name: Pili, Njira Njira
name: Gheysen, Godelieve
name: Bert, Wim
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Nematoda
Chromadorea
Rhabditida
Hoplolaimidae
Rotylenchus

description: Rotylenchus wimbii n. sp.
Figures 1 and 2, Tables 1 and 2.
Description
Female
Body moderately large (0.6-0.8mm), habitus spiral to 6-shaped when heat relaxed. Lateral field differentiation starting as single areolated band, gradually forming two areolated bands up to level of metacorpus valve and further continuing as three areolated bands up to isthmus level, after which bands becomes smooth till tail terminus. Longitudinal cuticular striations in anterior region absent. Labial region hemispherical with 4 annuli, not offset from body but appears to have a slight depression under LM. En face showing rounded labial disc, marked from rest of labial region, not elevated, slit like oral aperture, lateral sectors with two amphidial apertures and smaller than subdorsal and subventral sectors. Basal lip annule with 2 to 3 longitudinal striations (from six face views) forming 3 to 4 irregular blocks, but in one specimen with five striations forming six irregular blocks. Stylet robust with large, rounded, and sometimes indented knobs. Dorsal pharyngeal gland opening at 4 to 6µm from stylet base. Pharynx with well-developed median bulb, valves, slender isthmus, and gland overlapping intestine by maximum 30 µm dorsally. Secretory-excretory pore often at level of pharyngo-intestinal junction. Hemizonid distinct, just above secretory-excretory pore, about two body annuli long. Reproductive tract didelphic-amphidelphic, each branch equally developed with outstretched ovaries containing rows of developing eggs, vulva at 55 to 60% of body length from anterior end, without distinct epiptygma. Spermatheca indistinct to rounded, not filled. Tail very short with commonly truncated tip or sometimes slightly hemispherical to rounded tip. Phasmid pore like, 7 to 17 annuli anterior to anus.
Male
Not found.
Diagnosis and relationships
Rotylenchus wimbii n. sp. is characterized by a moderate body size of 0.6 to 0.8 mm, a hemispherical, continuous lip region with four annuli, basal lip annule with 3 to 4 irregular blocks, absence of longitudinal cuticular striations at anterior region, lateral field with four lines forming three equal bands which are areolated around pharynx level, a robust stylet of less than 30µm of which 45 to 53% is cone and with rounded to sometimes indented knobs, didelphic-amphidelphic reproductive system, vulva without distinct epiptygma, indistinct to empty spermatheca, very short truncated tail with 5 to 9 annuli, and pore like phasmids located at 7 to 17 annuli anterior to anus. According to Castillo and Vovlas (2005), the matrix code of this species is A4, B1, C1, D4, E1, F2, G3, H (commonly truncated), I2, J2, K1.
This new species is morphologically closest to Rotylenchus abnormecaudatus Van den Berg and Heyns, 1974 and Rotylenchus brevicaudatus Colbran, 1962. The females of these three species have similar body sizes, lip region of more or less hemispherical to rounded and very slightly offset to continuous with 4 to 5 annuli, stylet length below 30µm, lateral field areolation only at pharynx level, absence of longitudinal cuticular striations, vulva position of 52 to 62% of body length from anterior end, phasmids positioned at 7 to 17 annuli anterior to anus, and short tail with only 5 to 11 tail annuli. The new species differs from R. abnormecaudatus in having 4 vs 4 to 5 lip annuli, a slightly longer cone part of stylet (45-53% vs 42-45%), and often truncated vs irregularly rounded tail terminus. Rotylenchus abnormecaudatus has also been reported with a peculiar and irregular arrangement of annuli and lateral field ending in the posterior part of tail which is not seen in other species including R. wimbii n. sp. While males of R. wimbii n. sp. and R. abnormecaudatus are not known and subsequently, no sperm is observed in the female spermathecae, males of R. brevicaudatus have been reported and the female spermatheca are often filled with sperm. Rotylenchus wimbii n. sp. further differs from R. brevicaudatus by the presence of 2 to 3 longitudinal striations on the basal lip annule vs 6 to 12 such longitudinal striations as reported by Sher (1965) from the study of six face views of the 20 female topotypes supplied by R.C. Colbran, and commonly truncated vs hemispherical tail terminus. Information on the number of longitudinal striations on basal lip annule for R. abnormecaudatus is not available.
The new species is also comparable to Rotylenchus cypriensis Antoniou, 1981, Rotylenchus mabelei
Female character
Note: All measurements, except ratios and V%, are in µm and in the format: mean ± standard deviation (range).
Van den Berg and De Waele, 1989, and Rotylenchus unisexus Sher, 1965, all of which are species without males and reported to occur in South Africa and Kenya. The new species can be separated from R. cypriensis in continuous vs well offset lip region and absence vs presence of a ventral mucron at the tail tip. It can be differentiated from R. mabelei by a slightly smaller body (0.6-0.8 vs 0.9-1.1 mm), a lesser number of tail annuli (5-7 vs 14-18), and the position of phasmids with respect to anus (7-17 anterior vs 3 anterior to 5 posterior of anus). Finally, our new species can be differentiated from R. unisexus by the longitudinal striae on basal lip annule (3-4 vs 16-18 striae), tail annuli number (5-9 vs 9-13), and phasmid position (7-17 annuli anterior vs 6-7 annuli anterior of anus). An additional comparison of the new species with female morphological characters and morphometrics of all the Rotylenchus species that have been reported from Africa till date is provided in Table 2.
Etymology
The species epithet refers to its host. Wimbi originates from Swahili and is used as a common name for finger millet in Eastern Africa.
Type host and locality
The new species was found parasitizing the host plant Eleusine coracana (L.) Gaertn. (Planta: Poaceae), commonly known as finger millet, Kipkaren Estate, Eldoret, Kenya. The host status was also confirmed by a positive greenhouse test at the National Plant Protection Organization, Wageningen, The Netherlands. The GPS coordinates of the type location are 00°30.395’ N; 035°14.825’E.
Type material
Female holotype (Slide: WT 3796) and seven female paratypes in two slides (Slides: WT 3797 and WT 3798) are deposited at the National Plant Protection Organization, Wageningen Nematode Collection (WaNeCo), the Netherlands. One slide containing 10 female paratypes is deposited at Ghent University Museum, Zoology Collections, Belgium. An additional slide containing eight female paratypes is also deposited at UGent Nematode Collection (Slide: UGnem-300) of Nematology Research Unit of Ghent University, Belgium.
Root staining
Several stained spiral-shaped nematodes were observed in the host roots which are Rotylenchus. As no other Rotylenchus species or other spiral PPN such as Scutellonema and Helicotylenchus was detected from the corresponding soil sample, the PPN observed in the roots are most likely R. wimbii n. sp. confirming that this novel species can parasitize finger millet.
description: Published as part of Singh, Phougeishangbam Rolish, Karssen, Gerrit, Gitau, Kelvin, Wanjau, Cecilia, Couvreur, Marjolein, Pili, Njira Njira, Gheysen, Godelieve & Bert, Wim, 2021, Rotylenchus wimbii n. sp. (Nematoda: Hoplolaimidae) associated with finger millet in Kenya, pp. 1-14 in Journal of Nematology 53 (1) on pages 3-6, DOI: 10.21307/jofnem-2021-016, http://zenodo.org/record/12175581