Tylencholaimus

Ahad, Sumaya & Ahmad, Wasim, 2016, Description of two new and six known species of the genus Tylencholaimus de Man, 1876 (Nematoda: Dorylaimida) with a diagnostic compendium and key to species, Zootaxa 4107 (4), pp. 451-490 : 481-482

Key to species of the genus Tylencholaimus

(Modified after Peña-Santiago 2008)

1. Didelphic species, with two functional ovaries............................................................... 2

- Monodelphic species, only one functional ovary............................................................ 13

2. Anterior portion of pharynx weakly or not muscular and enlarging more or less abruptly............................. 3

- Anterior portion of pharynx distinctly muscular and enlarging more or less gradually................................ 6

3. Lip region offset by a depression, both parts of pharynx not separated by a distinct constriction....................... 4

- Lip region offset by a constriction, both parts of pharynx separated by a distinct constriction.................... savaryi

4. Odontostyle with narrow lumen................................................................. ladakhiensis

- Odontostyle with wider lumen........................................................................... 5

5. Smaller species, body length 0.55–0.69 mm; vaginal cells present........................................ cynodonti

- Larger species, body length 0.70–0.90 mm; vaginal cells absent............................................ cosmos

6. Smaller species, body length less than 0.7 mm ............................................................... 7

- Larger species, body length equal to or more than 0.7 mm ..................................................... 9

7. Vulva more posterior, V> 60....................................................................... innebus

- Vulva more anterior, V <60............................................................................. 8

8. Odontostyle 6.5 µm long; pharyngeal expansion occupying more than half of total neck length; tail conical and relatively lon- ger (c = 21).................................................................................. mongolicus

- Odontostyle 8.5 µm long; pharyngeal expansion occupying about one-third of total neck length; tail hemispherical and rela- tively shorter (c = 41)....................................................................... .. suryawanshii

9. Lip region 15–18 µm wide; 8–10 contiguous ventromedian supplements.................................... tahatikus

- Lip region less than 13 µm wide, male, if present, with 2–4 spaced ventromedian supplements....................... 10

10. Longer odontostyle, more than 9 µm long......................................................... paracrassus

- Shorter odontostyle, less than 9 µm long.................................................................. 11

11. Body more stout, a <25; lip region more than 10 µm wide; V <57......................................... crassus

- Body more slender, a> 25; lip region less than 10 µm wide; V> 57............................................. 12

12. Oviduct very long, 3–4 times the uterus in length; large cells present around the vagina....................... congestus

- Oviduct hardly longer than uterus; large cells absent around the vagina....................................... .. teres

13. Mono-opisthodelphic species, only the posterior ovary is functional.......................................... gertii

- Mono-prodelphic species, only the anterior ovary is functional................................................. 14

14. Perioral region disc-like............................................................................... 18

- Perioral region not disc-like............................................................................ 15

15. Anterior portion of pharynx not or weakly muscular, enlarging abruptly into the basal expansion......................26

- Anterior portion of pharynx slender but muscular, enlarging more or less gradually into the basal expansion............. 16

16. Posterior uterine sac very well developed, 2–4 times the corresponding body diameter long..........................35

- Posterior uterine sac absent or very reduced, exceptionally reaching 1.5 times the corresponding body diameter.......... 17

17. Lip region less than 3.5 µm high; odontostyle 4.5–6.0 µm long; female tail up to 16 µm long......................... 36

- Lip region more than 3.5 µm high; odontostyle 5.5–8.0 µm long; female tail 15 µm long or more.....................44

18. Anterior portion of pharynx distinctly muscular and enlarging gradually......................................... 19

- Anterior portion of pharynx weakly or not muscular and enlarging abruptly....................................... 20

19. Posterior uterine sac 1.0–1.5 times the body diameter; tail conical.................................... .. conicaudatus

- Posterior uterine sac absent; tail cylindroids, with rounded end............................................. pusillus

20. Pharyngeal expansion occupying up to one-third of total length; tail well and regularly curved ventrad........... leptodorus

- Pharyngeal expansion occupying at least one-third of total length; tail not curved ventrad........................... 21

21. Tail conical or elongate conical.......................................................................... 22

- Tail rounded-conoid to hemispherical..................................................................... 23

22. Post-vulval sac absent; tail 18–25 µm long........................................................... ... minutus

- Post-vulval sac 61–90 µm long; tail 31–41 µm long................................................ longicaudatus

23. Odontophore with asymmetrical basal knobs; post-vulval sac absent........................................ .. arakii

- Odontophore with symmetrical basal knobs; post-vulval sac present............................................ 24

24. Body 0.76–0.96 mm long; pharyngeal expansion more than 100 µm long................................. constrictus

- Body 0.46–0.61 mm long; pharyngeal expansion less than 80 µm long.......................................... 25

25. Post-vulval sac 12–18 µm or 0.6–0.9 times the corresponding body diameter long; female tail hemispheroid, 10.5 µm long................................................................................................ imperanus

- Post-vulval sac lacking; tail convex conoid, 19–22 µm long.............................................. minimus

26. Odontophore with two well developed basal flanges appearing as two posteriorly directed lobes, the ventral flange larger than the dorsal lobe.................................................................................. confusus

- Odontophore base bearing symmetrical basal knobs......................................................... 27

27. Odontophore base with three exceptionally large globe-shaped basal knobs.................................. porosus

- Basal knobs of odontophore smaller and not globe-shaped.................................................... 28

28. Tail conical elongate, more than 50 µm long, c’> 3................................................. leptonchoides

- Tail shorter, conical or rounded, less than 40 µm long, c’ <2................................................... 29

29. Posterior uterine sac well developed, more than three body diameter long........................................ 30

- Posterior uterine sac less than one body diameter long....................................................... 31

30. Body 0.8–1.0 mm long; lip region 10.5–12.5 µm wide; V =58–61......................................... formosus

- Body 0.71–0.76 mm long; lip region 7.5 µm wide; V = 63–65........................................... airolensis

31. Body more than 0.65 mm long.......................................................................... 32

- Body up to 0.65 mm long, but mostly less long............................................................. 33

32. Longer tail; 25–32 µm, c’ = 1.3–1.7; prerectum 5.3–10.0 anal body diameter long............................ mirabilis

- Shorter tail, 19–21 µm, c’ = 0.9–1.1; prerectum 1.2 anal body diameters long................................. decens

33. Body 0.30–0.46 mm long; female tail conical and longer, c’ = 1.6–2.4...................................... gallaicus

- Body 0.48–0.65 mm long; female tail rounded and shorter, c’ = 0.8–1.3.......................................... 34

34. Pharyngeal expansion occupying 56–60% of total neck length; V = 68–69..................................... vigil

- Pharyngeal expansion occupying about 40% of total neck length; V= 70–78................................ rumjhumi

35. Vulval lips symmetrical; prerectum about twice the anal body diameters long.................................. stecki

- Vulval lips asymmetrical, the anterior one swollen and more prominent than the posterior one; prerectum 6–10 anal body diameters long................................................................................. vulvulatus

36. Body more than 0.6 mm long; neck length more than 190 µm long.............................................. 37

- Body shorter than 0.6 mm long; neck length less than 190 µm long............................................. 38

37. More slender nematodes, a> 29; pharyngeal expansion more than 80 µm long............................... chathami

- More stout nematodes, a <29; pharyngeal expansion less than 80 µm long.................................... nanus

38. Tail short and hemispherical, 9–11 µm long.............................................................. loofi

- Tail rounded-conoid, 14–16 µm long..................................................................... 39

39. Posterior uterine sac present............................................................................. 41

- Posterior uterine sac absent............................................................................. 42

40. Neck length = 148–155 µm; V = 60–63; posterior uterine sac 6–9.5 µm long................................. maritus

- Neck length = 168–178 µm; V = 71–72; posterior uterine sac 25 µm long................................... australis

41. Body 0.49–0.55 mm long; tail 13 µm long or more....................................................... ibericus

- Body 0.38–0.50 mm long; tail up to 12 µm long............................................................43

42. Lip region 5.5–6.0 µm wide; odontostyle as long as lip region diam.; pharyngeal expansion 54–58 µm long..... micronanus

- Lip region 6.5–7.0 µm wide; odontostyle shorter than lip region diam.; pharyngeal expansion 68–76 µm long....... parvus

43. Odontostyle asymmetrical and with thickened wall; pharyngeal-intestinal junction with glandular organs...... asymmetricus

- Odontostyle symmetrical, its wall not thickened; no glandular organ present at pharyngo-intestinal junction............. 45

44. Odontostyle up to 7.0 µm long.......................................................................... 46

- Odontostyle 7.0 µm long or more........................................................................ 47

45. Body 0.74–0.85 mm long; more slender body, a =30–33................................................. terrestris

- Body less than 0.70 mm long; more stout body, a <29....................................................... 48

46. Post-vulval sac completely absent; vagina directed forwards; tail conical, its ventral side straight.............. americanus

- Post-vulval sac although vestigial; vagina not directed forwards; tail convex conoid.......................... proximus

47. Body 0.51–0.65 mm long; tail conical....................................................................49

- Body 0.63–0.95 mm long; tail convex conoid to rounded.....................................................50

48. Vulva pore-like and more anterior, V = 60–64; tail without indentation........................................ cedari

- Vulva a transverse slit and more posterior, V = 65–68; tail with an indentation at its subterminal portion............... pini

49. Neck 205–226 µm long............................................................................. notrus

- Neck 172–206 µm long................................................................................ 51

50. Odontophore bearing small basal knobs; female genital tract poorly differentiate male absent................ nagauriensis

- Odontophore lacking any differentiation at its base; female genital system well differentiated; male present........ obscurus