Egtitus longicaudatus, Andrássy, 2012

Andrássy, István, 2012, On the “ Paractinolaimus ” genus group (Nematoda: Actinolaimidae), with description of five new and two rare species of Egtitus Thorne, 1967, Journal of Natural History 46 (7 - 8), pp. 453-494 : 482-488

Egtitus longicaudatus sp. nov.

( Figures 12A–C and 13A, B )

Holotype female: L = 2.70 mm; a = 52; b = 4.3; c = 7.1; ć = 13; V = 44 %. Paratype (young) female: L = 2.75 mm; a = 55; b = 4.2; c = 7.0; ć = 14; V = 45%. Paratype male: L = 2.50 mm; a = 48; b = 4.1; c = 76; ć = 1.0.

General characters

Body strongly twisted after fixation, well tapered towards anterior end, 48–54 µm wide at mid-region. Cuticle practically smooth, 2.5–3.5 µm thick on most of body. Lip region 17–18 µm wide, wider than adjacent neck region, lips completely amalgamated, rounded. Body at proximal end of pharynx 3.0–3.2 times as wide as head. Amphids caliciform with aperture about half the body width.

Labial and dental chambers separated, the former 8–10 µm, the latter 6–8 µm broad. No denticles in the dental chamber. Onchia simple. Odontostyle 22–23 µm long, 1.2–1.3 times longer than labial width, 2.0–2.3 µm thick, about as thick as cuticle at the same level. The aperture occupying about one-third stylet length. Guiding ring 7 µm wide, at 14–17 µm from labial field. Pharynx tripartite as usual, 600–622 µm long, at 50% enlarged. Medial part 118–130 µm, about three body widths long, occupying 18–22% of the length of pharynx. Of the gland nuclei, D = 52–53% (12% of entire length of body), AS 1 indistinct, AS 2 = 61%, PS 1–2 = 72–73%. Glandularium 282–294 µm long.

Female

Amphidelphic with well-developed gonads. Each branch 7.0–7.6 body widths long or occupying 13–15% of body length. Each branch of uterus consisting a proximal wider and a distal narrower section. Ovaries short, one-third of the corresponding gonad. Uterine eggs not observed. Vulva a short longitudinal slit with sclerotized inner pieces. Vagina 30 µm long, occupying half the body width. Distance between proximal end of pharynx and vulva nearly as long as pharynx. Rectum 1.4–1.7, pre-rectum 3.8–4.1 times the anal body width long. Tail 380–385 µm long, 14% of entire length of body, filiform, uniformly tapered to its very fine terminus.

Male

Testes two, long with straight distal ends. Spermatozoa fusiform. Spicula 70 µm long, dorylaimoid. Ventromedial supplements 9, distinct. Pre-rectum beginning within the range of the supplements. Tail conoid-rounded, 33 µm, 1.3% of total body length.

Diagnosis and relationships

Body well over 2 mm, fairly slender, lip region narrow, odontostyle longer than lip region width, pharynx enlarged just in its middle, vulva longitudinal, female and male genital organs strongly developed, male supplements 9, female tail very long.

Egtitus longicaudatus sp. nov. is the longest-tailed species within the genus, its female tail measures 380 µm, while the tail of the other congeners is 260 µm or shorter. In body size and general habitus it is closest to E. neocyatholaimus , but the much longer tail (380–385 µm, 13–14 anal body diameters versus 232–238 µm, eight anal body diameters) and the lower number of the male supplements (9 versus 12–13) clearly distinguish it from its relative.

When this new species is compared with the other three Papuan species, namely E. neocyatholaimus , E. biformis sp. nov. and E. remotus sp. nov., it also differs from them in the length of the female tail (380–385 µm versus 232–238 µm in E. neocyatholaimus , 178–225 µm in E. biformis and 86 µm in E. remotus ).

Type specimens

Holotype female on slide no. 13030. Paratypes: one (not quite mature) female and one male. Preserved in the Department of Systematic Zoology of the ELTE University , Budapest .

Type habitat and locality

Litter and detritus from around the roots of an epiphyte fern, 3500 m above sea level, in the granite mountain Mount Wilhelm (Enduwa Kombuglu in Papuan language) of Bismarck Range, Papua New Guinea; collected in August 1968 by J. Balogh and I. Loksa.

Etymology

Latin longicaudatus , long-tailed.

Key to species of Egtitus

This key is mainly based on females because males are unknown in seven species ( E. arcuatus , E. conicaudatus , E. elaboratus , E. kagoshimai , E. koriensis , E. naunii and E. nipponicus ) or incompletely described in another ( E. nudus ). On the other hand, the females are unknown in two species ( E. peteri and E. surinamensis ) which are therefore omitted from the present key. (Species should not be described based on one sex, especially in dorylaims.) It must be emphasized that some Egtitus species are very similar to one another, their separation is rather difficult or almost impossible.

1. Female tail 170–380 µm long, 8–14 times as long as anal body diameter.... 2 Female tail 70–190 µm long, 2.5–7 times as long as anal body diameter.... 6

2. Female tail very long, 380 µm or 13–14 times the anal body diameter.................................................. E. longicaudatus sp. nov. Female tail not so long, 170–260 µm or 8–11 times the anal body diameter............................................................................ 3

3. Vulva at around 40%........................... E. neocyatholaimus (Kreis) Vulva at around 50%.................................................... 4

4. Posterior half of tail more or less dorsally bent; lip region well offset................ E. neoelaboratus (Rahman, Jairajpuri, Ahmad and Ahmad) ......................................... E. kazirangus Khan and Jairajpuri [On the basis of the descriptions, these two Indian species cannot be separated from each other. They are probably identical.] Posterior half of tail slightly ventrally bent; lip region hardly offset......... 5

5. Larger species, 2–3 mm ......................... E. nudus (Wu and Hoeppli) Smaller species, 1.6–2 mm ............................. E. proximus (Yeates)

6. Odontostyle 24–29 µm long............................................. 7 Odontostyle 18–24 µm long............................................ 12

7. Ventromedial supplements 7–10.......................................... 8 Ventromedial supplements 11–13....................................... 11

8. Lip region 16–17 µm wide.............................. E. biformis sp. nov. Lip region wider than 20 µm............................................. 9 9. Lip region 22–24 µm wide........ E. itanagrus Khan, Ahmad and Jairajpuri Lip region 26–28 µm wide.............................................. 10

10. Tail abruptly tapered behind anal region... E. siddharthi Khan and Jairajpuri Tail uniformly tapered behind anal region......................................................................... E. prodenticulatus (Heyns and Argo)

11. Larger species, 2.4–2.7 mm; supplements 11........................................................................ E. shillongensis Khan and Jairajpuri Smaller species, 1.9–2.1 mm; supplements 12–13... E. sinensis Wu and Liang

12. Tail 70–90 µm long, 2.5–3.2 times as long as anal body diameter.......... 13 Tail 100 µm or longer, 4–6 times as long as anal body diameter........... 14

13. Body 2.2–2.5 mm; lip region 16–18 µm wide............. E. remotus sp. nov. Body 1.7–2.0 mm; lip region 22–25 µm wide................................ ................................. E. conicaudatus Khan, Tanaka and Yoshiga

14. Lip region 15–20 µm broad............................................. 15 Lip region 20–28 µm broad............................................. 20

15. Odontostyle distinctly arcuate.................. E. arcuatus Choi and Khan Odontostyle straight................................................... 16

16. Vulva at around 60%............. E. kagoshimai Khan, Tanaka and Yoshiga Vulva at around 50%................................................... 17

17. Body 2.6 mm; male supplements 13.................. E. zealandicus (Clark) Body 1.4–2.2 mm; male supplements 7–11............................... 18

18. Pharynx enlarged anterior to its middle, at 42–46%; supplements 10–11...... ......................................................... E. chilenus sp. nov. Pharynx enlarged at or posterior to its middle, at 50–56%; supplements 7–9 19

19. Lip region 15–17 µm wide; odontostyle longer than labial width................................................................... E. bryophilus Thorne Lip region 17–20 µm wide; odontostyle as long as or a little shorter than labial width................................................. E. africanus sp. nov.

20. Odontostyle sinuate.................................................... 21 Odontostyle straight................................................... 22

21. Aperture one-third of odontostyle length; tail 106–126 µm long.......................................................... E. nipponicus Khan and Araki Aperture one-half of odontostyle length; tail 126–153 µm long.............. ....................................................... E. elaboratus (Cobb)

22. Posterior half of tail dorsally bent............. E. japonicus Khan and Araki Posterior half of tail straight............................................ 23

23. Vulva elevated........................... E. koriensis Khan, Park and Choi Vulva flush with the body................. E. andhricus Khan and Jairajpuri. ............................................ E. naunii Khan and Jairajpuri

[There are very small differences between these two Indian species: E. andhricus 1.4–1.6 mm, tail 95–114 µm; E. naunii 1.6–2.1 mm, tail 108–135 µm; possibly identical species.]

Figures

Figure 12. Egtitus longicaudatus sp. nov. (A) Anterior end; (B) medial part of pharynx; (C) vulval region. Scale bars 20 µm.

Figure 13. Egtitus longicaudatus sp. nov. (A) Posterior end of female; (B) posterior end of male. Scale bars 20 µm.