Geomonhystera dubia Siddiqi & Shahina, 2004

Prado-Vera, Ignacio Cid Del, Ferris, Howard & Subbotin, Sergei A., 2018, Six new and one known species of Geomonhystera (Nematoda, Monhysteridae) from moss, an epiphytic plant and soil in México and Ecuador, Zootaxa 4471 (1), pp. 76-110 : 97-99

Geomonhystera dubia Siddiqi & Shahina, 2004

Measurements. Appendix A.

Female (n=9). Body of fixed specimens ranging from almost straight to slightly arcuate ventrad; cuticle thin, 1 µm thick, with very fine transverse striae, whole body with few scattered setae; head 9–12 (9.9±0.9) µm wide; lips triangular, not fused at distal end; inner labial papillae very small, conical, 2 µm long; outer labial setae unsegmented, 5–8 (6.3±1.1) µm long or 56–80 (64±9.0) % of head width; cephalic setae thin, 3–5 (4.2±0.8) µm long, 33–50 (43±7.1) % of head width; amphid openings rounded, 3 µm diameter and 9–14 (12±1.5) µm from the anterior edge to head, both amphids at the same level; pharynx muscular, 91–122 (109±10.8) µm long or 15–22 (19±2.2) % of body length, 311–415 (355±41.2) µm from the vulva and 335–434 (395±43.9) µm from the anus; nerve ring at 44–60 (51±6.6) µm from the anterior end; cardia 3–6 (5.0±1.1) µm long and 5–10 (7.6±1.5) µm wide, composed of two small cells. Outer zone of intestinal walls with many granular refractive inclusions; rectum muscular 10–17 (15±2.3) µm long and 0.68–1.2 (0.96±0.24) times anal body diameter; anterior anal lip slightly protruding. Distance between vulva and anus 15–29 (22±4.9) µm or 1.1–2.2 (1.5±0.5) times anal body diameter. Vulval lips protrude slightly but sometimes flush with body contour; vagina with slightly thickened walls, postvulval uterine sac absent. Tail tapers evenly, 61–76 (70±4.4) µm long or 11–13 (12.4±0.7) % of body length, without caudal setae; three caudal glands, posterior to the anus and in line, ducted into a common ampulla, 5–7 (6.0±1.2) µm long and then through a conspicuous, terminal, spinneret, 2–3 (2.1±0.4) µm long.

Male. Unknown.

Diagnosis and relationships. This population of Geomonhystera is characterized by the small body size, sparse, scattered somatic setae, and fine cuticular striation; the outer labial setae are unsegmented; vulval lips protrude slightly but sometimes are flush with the body contour; vulva-anus distance anus 15–29 µm and 1.0–2.2 times anal body diameter; the outer labial setae are 56–80% of head width and the cephalic setae thin, unsegmented and 33–50% of the head width; the anterior border of the amphid to the anterior end is 9–14 µm.

We identify this population as G. dubia Siddiqi & Shahina, 2004 , by the fine striation of cuticle, the size of the amphid aperture, the shape of the body when relaxed, the position of the vulva, length of the tail, shape of the spinneret and the soil habitat. It differs from the original description in having sparse setae along the body, in the amphid being closer to the anterior end, 9.0–14 vs. 14–21 µm, and a greater range in the vulva-anus distance, 15– 29 (22) vs. 22–29 (27) µm. We consider that this Mexican population corresponds to the description of the species G. dubia which was described from soil around roots of ornamental plants by Siddiqi & Shahina (2004) and that this represents a new locality for the species.

New locality and habitat. Soil around a plum tree ( Prunus sp.) at the Colegio de Postgraduados , Campus Montecillo, Texcoco, México State, 19° 27' 47.9" N 98° 54' 15.1" W, elevation 2243 m asl.

Specimens. Four females on slide 10399 deposited in CNHE. One female deposited in each of the nematode collections of UCRNC on slide number 28544, WaNeCo on slide number WT3721, and the CPNC on slide number A-102.

Phylogenetic relationships. Five new sequences of the D2–D3 of 28S rRNA gene of the genus Geomonhystera were obtained in this study: two sequences for two samples of G. mexiquense sp. n., one sequence for G. longispiculata sp. n. and two sequences from clones of one sample of G. galindoi sp. n. Alignment included 18 sequences of Monhysteridae and four outgroup taxa and was 750 bp in length. Phylogenetic relationships within Monhysteridae are given in Fig. 14 . Representatives of the genus Geomonhystera formed a highly supported clade. Relationships among monhysterid genera were not well resolved.

Figures

FIGURE 14. Phylogenetic relationships within Monhysteridae as inferred from Bayesian analysis using the D2–D3 of the 28S rRNA gene sequence data set under the GTR+G+I model. Posterior probabilities of over 70% are given for appropriate clades. New sequences are indicated in bold.