Melomystrongylus sepikensis, Smales, 2009

Smales, L. R., 2009, Helminths Of Melomys Rufescens And Melomys Spp. (Muridae: Hydromyinae) From Papua New Guinea With The Descriptions Of A New Genus And Five New Species In The Heligmonellidae (Nematoda: Trichostrongyloidea), Raffles Bulletin of Zoology 57 (1), pp. 5-15 : 9-11

Melomystrongylus sepikensis , new species

( Figs. 15–28 )

Material examined. – Holotype male and allotype female: BBM- NG-104657B, from the small intestine of Melomys rufescens ( Muridae : Hydromyinae ) type host, 2 km south of Mt Samoro, West Sepik, Sanduan Province, Papua New Guinea, coll. A. B. Mirza, 10 May 1975.

Paratypes: 2 males, 5 females BBM-NG-105128B, from small intestine Melomys rufescens , 12 km northwest of Tep Tep , 5°57'S 146°05'E, Madang Province, coll. A. B. Mirza, 2 Dec.1975 .

Voucher specimens: 4 males, 1 female BBM-NG-105155B, 5 females, 1 male, BBM-NG-105156B, from the small intestine of Melomys rufescens , 12 km northwest of Tep Tep , 5°57'S 146°05'E, Madang Province, coll. A. B. Mirza, 2 Dec.1975 ; 1 female, BBM-NG-103717, Wanuma, 4°54'S 145°19'E, Madang Province, coll A. B. Mirza, 3 Feb.1974 ; 1 male, 2 females, AM W32617, from the small intestine of Melomys rufescens, Sideia Mission , 10°32'S 150°48'E, Milne Bay Province, coll. G. Hangay 31 Dec.1988 ; 3 males, 8 females, AM W32557, from the small intestine of

Melomys sp. , Munimun Village, Aguan, 9°53'S 149°23'E, coll P. German, 8 Aug.1992; 1 female, AM W32558, from the caecum of Melomys sp. , Boulder Camp, Goodenough Island , 9°21'S 150°16'E, Sanduan Province, coll. T. Ennis, 25 Aug.1987 ; 2 females, AM W32559 from the small intestine of Melomys sp. , Boulder Camp, Goodenough Island , 9°21'S 150°16'E, Sanduan Province, coll. T. Ennis, 25 Aug.1987 ; AM W32626 , 5 males, from the small intestine of Melomys sp. , Dokfuma Star Mountains 5º01'S 141°07'E, Milne Bay Province, coll. T. Flannery, 5 May 1987 .

Prevalence. – A total of 5 of 25 M. rufescens and 3 of 10 Melomys spp.

Etymology. – The species name reflects the locality in which this nematode is found.

Description. – Relatively robust worms; prominent cephalic vesicle present; buccal capsule vestigial. Mouth opening triangular with rudimentary lips; surrounded by 4 cephalic papillae and 2 amphids; labial papillae not observed. Oesophagus claviform. Nerve ring surrounds oesophagus at about a third its length, digitiform deirids and excretory pore at about same level, posterior to nerve ring. Synlophe of continuous longitudinal pointed cuticular ridges extends from the posterior margin of the cephalic vesicle to just anterior to the bursa or vulva; 8–14 ridges in anterior, 14–16 in midbody. Axis of orientation passing from ventral right to dorsal left sides, inclined about 65° to sagittal axis in anterior body; 4–8 ridges dorsal side, 4–8 ridges ventral side. Ridges 1–6 decreasing in size; ridges 1'–4' decreasing in size, ridge 5' largest, ridges 6'–8' decreasing in size. Posterior region of body with 15 (male) 10–14 (female) ridges reduced in size with no clear axis of orientation; 7–8 (male), 6–7 (female) ridges dorsal side, 8 (male), 7–9 (female) ridges ventral side.

Male (holotype, 2 paratypes and 7 vouchers): Length 3.2–4.3 (3.8) mm, maximum width 82.5–99 (90.5). Cephalic vesicle 20.5–42.5 (33) long, 34–39 (37) wide. Oesophagus 280–355 (322) long; excretory pore 169–221 (186), deirids 204 from cephalic end. Bursa slightly asymmetrical, left lobe larger; dorsal lobe with median dorsal notch. Dorsal ray symmetrical, divided at about half its length, each branch dividing again at distal tip; terminal divisions, rays 9, 10 symmetrical; rays 8 arising at same level proximal to division of dorsal ray, right ray 8 slightly longer than left. Rays 4, 5, 6 with common stem, reaching margin of bursa, rays 6, more slender, curving anteriorly, rays 4, 5 curving posteriorly. Rays 2, 3 with common stem, dividing into 2 widely divergent branches, curving posteriorly, reaching margin of bursa. Genital cone slightly extended, lightly sclerotized, ventral lobe with unpaired papilla 0 and dorsal lip with paired papillae 7. Spicules equal, filiform, tips pointed, 450–660 (610) long. Gubernaculum forming thin plate 38–56 (43) long.

Female (allotype, 4 paratypes and 5 vouchers): Length 3.9–5.5 (4.6) mm, maximum width 80–114 (100). Cephalic vesicle 29.5–39.5 (30) long, 33–46 (35.5) wide. Oesophagus 310–390 (345) long; nerve ring 150, excretory pore 145–248 (216), deirids 145–248 (216) from cephalic end. Vulva with prominent lips, opens 60–115 (95) from tail tip. Body wall extends over vulva and tail as praepuce in mature specimens. Monodelphic; ovejector with infundibulum, 90–100, longer than vestibule, 60–80, sphincter 30, 50, shortest element. Tail conical, tip rounded, reflected ventrally, 29–42.5 (35) long. Eggs thin-shelled, ellipsoidal, in utero 49–66 (57) by 30–39 (34).

Remarks. – Melomystrongylus new genus has all the characteristics of the subfamily Nippostrongylinae (see Durette-Desset, 1985). Lacking a carene and with a hypertrophied ventral ridge Melomystrongylus resembles Hasanuddinia Hasegawa & Syafruddin, 1994 . It can be readily distinguished from Hasanuddinia in that it has a single hypertrophied ventral ridge beginning from the excretory pore and ending in the anterior third of the body. Melomystrongylus has smaller similar sized ridges showing no clear axis of orientation in the mid and posterior body while the axis of orientation of the ridges is maintained along the whole length of the body in Hasanuddinia (see Hasegawa & Syafruddin, 1994a). The gradient of ridge size in the anterior body in Melomystrongylus is from right to left (excepting ridge 5), but in Hasanuddinia it is from left to right.

Figures

Figs. 15–28. Melomystrongylus sepikensis, new genus, new species, from Melomys rufescens and Melomys spp. from Papua New Guinea: 15, female anterior end, lateral view; 16, male cross section, anterior body; 17, female cross section, anterior body; 18, female cephalic end, lateral view showing synlophe; 19, male cross section, midbody; 20, female cross section, midbody; 21, female posterior end, lateral view showing ovejector; 22, dorsal ray; 23, female cross section, posterior end; 24, female posterior end, ventral view showing well developed praepuce; 25, bursa, left lobe, lateral view; 26, genital cone, lateral view; 27, gubernaculum, lateral view; 28, spicule tips. Scale bars: 15, 24 = 100 μm; 16, 18–20, 22, 23, 25–28 = 25 μm; 17 = 20 μm; 21 = 50 μm.