Melomystrongylus somoroensis, Smales & Heinrich, 2010

Smales, L. R. & Heinrich, B., 2010, Gastrointestinal nematodes of Paramelomys rubex (Rodentia: Muridae) from Papua Indonesia and Papua New Guinea with the descriptions of three new genera and four new species of Helligmonellidae and Herpetostrongylidae (Nematoda: Trichostrongylida), Zootaxa 2672 (1), pp. 1-28: 10-12

publication ID 10.11646/zootaxa.2672.1.1


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scientific name

Melomystrongylus somoroensis

sp. nov.

Melomystrongylus somoroensis   sp. nov.

( Figs 38–50 View FIGURES 38–50 )

Type host. Paramelomys rubex (Thomas)  

Site in host. Small intestine.

Material examined. Holotype male, allotype female from Paramelomys rubex Somoro Summit, Torricelli Mts   , (3° 24´S; 142° 8´E), West Sepik District, Sanduan Province , Papua New Guinea, coll. T. Flannery 16. vi. 1988, AM W.36787, W.36788; paratypes 1 male, 3 females, same data AM W.36789. GoogleMaps  

Other material examined. From Paramelomys rubex   Papua New Guinea, Sanduan Province; 2 males, 1 anterior end Somoro Summit, Torricelli Mts. , (3° 24´S; 142° 8´E): Indonesia, Papua; 1 male Mokwan area , Arfak Mts (1° 6´S; 133° 56´E), AM GoogleMaps   W.36785, W.36786.

Etymology. The specific name is derived from the type location of the species.

Description. General: Small worms, prominent cephalic vesicle present with about 3 annulations; buccal capsule vestigial. Mouth opening triangular with rudimentary lips; labial and cephalic papillae not observed. Oesophagus claviform. Nerve ring, deirids and excretory pore at about same level in mid oesophageal region. Synlophe (based on sections from 5 worms) of continuous pointed longitudinal cuticular ridges in both sexes, extends from posterior margin of cephalic vesicle to immediately anterior to bursa or vulva; 13–15 ridges in anterior, 15–17 in midbody, 17–18 in posterior. Axis of orientation of ridges passing from ventral right to dorsal left sides, inclined about 60° from sagittal axis in anterior and mid body; 5–7 ridges dorsal side, 7–8 ridges ventral side. In anterior body ridges 1– 5 increasing, ridge 6, 7 decreasing in size; ridges 1´–4´(male) 1´–5´(female) increasing in size, ridge 5´(male) 6´(female) largest, ridges 6´–8´increasing in size (male) 7´– 8´about same size (female) 7–8 decreasing in size. In mid and posterior body ridges becoming smaller losing size gradients; and orientation.

Male: (Measurements of 4 specimens) Length 1930–2400 (2090), maximum width 56–68 (61). Cephalic vesicle 25–32 (29) long. Oesophagus 235–290 (265) long; nerve ring 120, deirids, excretory pore 125, 196 from anterior end. Bursa (based on 4 worms) slightly asymmetrical, right lobe larger; pattern of rays 3–2 for both lobes; rays 2, 3 4, diverge distally, recurved ventrally; rays 5, 6 recurved dorsally. Dorsal lobe with median notch, shorter than laterals; dorsal trunk bifurcates at about 2/3 its length, each branch dividing again at distal tip; terminal divisions, rays 9, 10, symmetrical, rays 8 arising at same level from dorsal trunk proximally to division of dorsal ray, right ray slightly larger than left. Genital cone elongated, heavily sclerotised; ventral lip with unpaired papilla 0, dorsal lip with paired papillae 7. Spicules filiform tips hooked 310–330 (318) long. Gubernaculum 37–44 (40) long.

Female: Length 2300–2500 (2400), maximum width 63–73 (67). Cephalic vesicle 30–36 (33.5) long. Oesophagus 265–310 (292) long; nerve ring, deirids, excretory pore 126, 133 from anterior end. Monodelphic ovejector, vulva near posterior end, 78, 80 from tail tip; vagina 45, sphincter, 20, shortest, infundibulum 50, vestibule, 70, longest element. Tail reflected ventrally, 47.5–59.5 (52.7) long; tail tip relatively long, conical. Eggs thin shelled, ellipsoidal, about 6 in utero 52.8–59.5 (56.8) by 28.9–33 (30.4).

Remarks. Having an hypertrophied ventral ridge in the anterior region of the synlophe, an asymmetrical bursa and the dorsal ray divided distal to the level of the branching of rays 8 places the new species within the genus Melomystrongylus   . Melomystrongylus somoroensis   n. sp. differs from its congener M. sepikensis   in the number of ridges, 13–18 compared with 8–16, the length of the spicules, 310–330 compared with 450–610, and a longer female tail, 47.5–59.5 compared with 16.5 –24.0 ( Smales 2009). The generic diagnosis of Melomystrongylus   includes: “bursa asymmetrical, left lobe larger”, the determination having been made after examining bursae that had not been completely rolled flat. In M. somoroensis   the right lobe is the larger one and since this could also be the case for M. sepikensis   the diagnosis needs to be reconsidered.


Tavera, Department of Geology and Geophysics


Australian Museum