Nugininema titokis, Smales, L. R., 2016

Smales, L. R., 2016, The gastrointestinal helminths of Rattus niobe (Rodentia: Muridae) with descriptions of two new genera and three new species (Nematoda) from Papua New Guinea and Papua Indonesia, Zootaxa 4117 (2), pp. 183-197 : 189-191

Nugininema titokis sp. nov.

( Figs 15–26 )

Type host. Rattus niobe (Thomas)

Site in host. Small intestine.

Material examined. Holotype male, allotype female from Rattus niobe Mount Banarip (9° 53´S 149° 23´E), near Munimun, Milne Bay Province, Papua New Guinea, coll. P. German 15. iv. 1992, AM W.48479, AM W.48489, paratypes 3 females, same data AM W48499 . Transverse sections were prepared from 2 males and 2 females, same collection data.

Other material examined. 1 female from R. niobe Ofekaman (5° 5´S 141° 33´E), Telefomin area, Sanduan Province AM W.48500.

Etymology. The species name is derived from the native language name for the host in Sanduan Province.

Description. General: Small nematodes usually coiled at the anterior and/ or posterior ends, males slightly smaller than females. Cephalic vesicle prominent with small number of annulations, 4–6 in female, buccal capsule vestigial. Mouth opening triangular with rudimentary lips; cephalic and labial papillae not seen. Deirids dome shaped, at about same level as excretory pore.

Synlophe: (sections of 2 males, 2 females examined) Longitudinal ridges continuous, arise between posterior margin of cephalic vesicle and anterior region of mid body, extend to just anterior to bursa or vulva; 10–16 ridges in anterior body male, 9–13 anterior body female, 17 mid body male, 15–17 mid body female, 9–13 posterior body female. Axis of orientation from right ventral to left dorsal, about 50° to sagittal plane in anterior, pre frontal in mid body, losing orientation posteriorly; 4–8 ridges dorsal side, 4–9 ventral side; anterior ridges 1´–6´increasing in size, ridges 5´, 6´large, ridge 6´largest; anterior ridges 1–3 decreasing in size, ridge 4 slightly larger in male, anterior ridges 1–6 decreasing in size in female; ridges in mid body all similar size, ridges reduced in size posteriorly.

Male: (Measurements of 3 specimens) Body length 2.90–3.25 (3.01) mm, maximum width 60.0–69.0 (63.3). Cephalic vesicle 27.0–30.5 (28.6). Oesophagus 300, 350 (2 measurements) long; deirids 184.0, excretory pore 184.5 (1 measurement) from anterior end. Bursa slightly dissymmetrical, right lobe larger, dorsal lobe with cleft; pattern of rays 1-3-1; dorsal lobe shorter than lateral lobes. Dorsal ray symmetrical, divided at about 1/3 its length, terminal divisions rays 9, 10 symmetrical, rays 8 arising from dorsal trunk at same level; lateral rays 6 curve dorsally, 4, 5 ventrally ray 4 largest; rays 3 large, lie parallel with lateral rays before diverging ventrally, rays 2 more slender diverge distally, recurve ventrally, reaching margin of bursa. Genital cone not prominent. Spicules equal, filiform 440–470 (455) long, tips simple, pointed. Gubernaculum 53 (1 measurement) long.

Female: (Measurements of 5 specimens) Body length 3.00–4.20 (3.58) mm, maximum width 67.0–87.1 (75.9). Cephalic vesicle 23.8–28.9 (26.1) long. Oesophagus 360 (1 measurement) long; deirid 195.5, excretory pore 178.5 (1 measurement) from anterior end. Vulva opens 71.4–102.0 (93.0) from tail tip; posterior end flexed ventrally just behind vulva. Monodelphic ovejector with vestibule 50–65 (58), longer than sphincter 25–30 (28), shorter than infundibulum 70, vagina 20–30 (25) long. Eggs thin shelled, ellipsoidal, about 10 in utero, 56.1–66.0 (61.1) long 28.9–34.0 (32.0) wide.

Remarks. This heligmonellid parasite of an endemic species of Rattus , from the island of New Guinea Nugininema n. gen. has all the characteristics of the subfamily Nippostrongylinae ( Beveridge et al. 2014). Within this large clade comprising some 31 genera ( Beveridge et al. 2014; Digiani & Durette-Desset, 2014), the features of the synlophe: lacking a carene, with an oblique axis of orientation of the synlophe ridges on the anterior body which has 2 enlarged ridges ventrally and 15–17 ridges small ridges with sub frontal orientation along the mid and posterior body, distinguish this genus from all others in the subfamily. The new genus comes closest to the genera Hasanuddinia Hasegawa & Syafruddin and Melomystrongylus Smales both of which have hypertrophied ventral ridges. Nugininema differs from Hasanuddinia in having the ventral right ridges hypertrophied only in the anterior body and 15–17 ridges with sub frontal orientation at the mid body as compared with ventral ridges large, maintaining an oblique axis of orientation along the body and 10–12 ridges at the mid body ( Hasegawa & Syafruddin, 1994). Nugininema differs from the genus Melomystrongylus which has a single hypertrophied ventral ridge in having 2 large ridges on the right ventral quadrant, dorsal ridges decreasing in size rather than increasing in size from left to right and a subfrontal rather than oblique axis of orientation at the mid body ( Smales 2009; Smales & Heinrich 2010). The genus Nugininema also resembles the genus Montistrongylus Smales in having ventral ridges largest but differs from it having 2 right ventral ridges much larger, rather than the left ventral ridges largest, the axis of orientation not maintained along the body and rays 8 symmetrical not asymmetrical ( Smales & Heinrich 2010).

Figures

FIGURES 15 – 26. Nugininema titokis n. gen., n. sp. In all illustrations of the synlophe in transverse section the dorsal aspect of the body is oriented towards the top of the page and the left side of the nematode is on the left side of the page. Long arrow shows axis of orientation of synlophe; dorsal and ventral ridges (numbers with superscripts) numbered. 15. Male anterior end, right lateral view; 16. Male transverse section, anterior end; 17. Female transverse section, anterior end; 18. Female cephalic end; 19. Male transverse section, mid body; 20. Female transverse section, mid body; 21. Female posterior end, right lateral view; 22. Gubernaculum, ventral view; 23. Spicule tip. 24. Spicule anterior end, lateral view. 25. Female posterior end, lateral view. 26. Bursa, partially unrolled, right lateral view, rays numbered. Scale bars in µm: 15, 50; 16 – 21, 25, 26, 25; 22 – 24, 12.5.