Tikusnema intersedis, Smales, Lesley R., 2006

Smales, Lesley R., 2006, A new acuariid species (Spirurida, Acuariidae) and other nematodes from Hydromys (Muridae, Hydromyinae) from Papua, Indonesia and Papua New Guinea, Zootaxa 1110, pp. 27-37 : 31-35

Tikusnema intersedis sp. nov. ( Figs. 1–12 )

Type host: Hydromys chrysogaster Geoffroy, 1804

Type locality: Bunala River, Imalele Valley, Ferguson Island, Milne Bay Province (9o30’S, 150o33’E) Papua New Guinea

Site in host: stomach

Date of collection: between 9 September 1992 and 3 February 1993.

Type material: Holotype male SAM AHC 32352, allotype female AHC 32352 paratypes SAM AHC 32354; AMM28576

Etymology: The species name refers to its geographic location (New Guinea) lying between Java ( Indonesia) and Australia.

Description: Long slender worms with tapered extremities, cuticle thin, with fine annulations. Lateral alae absent. Cephalic cuticular leaves each divided into 4–7 teeth, lateral tooth largest. Cordons and dorsal and ventral rim of pseudolabia faintly striated. Muscular pharynx narrower and shorter than glandular region of pharynx.

Cephalic end, en face view, optical section through pharynx showing cuticular leaves. 9. Tail tip male. 10. Tail tip female. 11. Vulva, vagina and uteri dissected from body cavity. 12. Right spicule. Scale bars: 1 & 4 = 100 m; 2, 3, & 10 = 50 m; 5, 6, 8, 9, & 12 = 25 m; 7 = 200 m.

Male: Length 32 (28–40) mm, width at mid body 375 (255–400). Cephalic end 158 (135–188) long, 195 (160–248) wide. Buccal capsule 245 (208–265) long. Muscular pharynx 450 (335–525), glandular oesophagus 3640 (2950–4760). Deirids anterior to nerve ring 240 (210–280), nerve ring 375 (315–435), excretory pore 525 (470–635) from anterior end. Posterior end curved ventrally in 1–2 loose coils. Caudal papillae arranged in 12 pairs, 4 pairs preanal 8 pairs postanal; preanal pairs large pedunculate 1st and 2nd pairs grouped together, 1st and 3rd lateral to 2nd and 4th; 5th–9th postanal pairs large pedunculate; 10th–12th pairs sessile clustered at tail tip. Longitudinal cuticular ridges present anterior to cloaca. Spicules dissimilar; right spicule shorter, robust 305 (215–370); left spicule with bifid tip enclosed in cup shaped membrane, 950 (870–1040) long, about 1/34 body length. Tail 585 (435–765) long.

Female: Length 41.5 (28–50) mm, width at midbody 460 (355–510). Cephalic end 165 (120–195) long, 220 (155–266) wide. Buccal capule 240 (198–275) long. Muscular pharynx 510 (422–603) long; glandular oesophagus 4495 (3705–5440) long. Deirids 240 (125–305), nerve ring 385 (300–410), excretory pore 555 (390–700) from anterior end. Ovejector amphidelphic, vagina vera directed transversely (1 measurement) 200 long, vagina uterina parallel to body wall (1 measurement) 250 long. Vulva circular, without lips, 15 (13.5–17) mm from anterior end. Tail conical, with terminal knob, 480 (340–570) long. Eggs thick shelled 43 (40–46) by 27.5 (26.5–30).

Larva: (measurements of 1 specimen). Length 8mm, width at midbody 535. Buccal capsule 150 long. Oesophagus 1750 long; nerve ring 220, excretory pore 400 from anterior end. Cephalic leaves and cordons not developed. Tail 185 long.

Remarks

Tikusnema intersedis sp. nov. is one of 3 species in the genus, each occurring in a murid rodent with a semi­aquatic life style. Tikusnema javaense Hasegawa, Shiraishi & Rochman, 1992 occurs in Rattus argentiventer (Robinson & Kloss, 1916) from Java, Indonesia and Tikusnema vandycki Smales, 1995 in Xeromys myoides Thomas, 1889 from Queensland, Australia. All 3 species have the cephalic end characterized by large triangular pseudolabia, at the posterior end of which are cuticular leaves divided into teeth, separated dorsally and ventrally by cordons that do not extend posteriorly. Tikusnema intersedis differs from its congenors in being an overall larger worm and having up to 7 teeth on the cuticular leaves of the pseudolabia, as compared with 3 teeth in T. javaenese and 4–5 teeth in T. vandycki . Tikiusnema intersedis has a longer left spicule, a shorter female tail, and a shorter buccal capsule, than the other 2 species. It can be further distinguished from T. vandycki in having the deirids anterior to the nerve ring, The eggs of T. intersedis are smaller than those of T. vandycki . Tikusnema intersedis has 12 pairs of caudal papillae including 3 pairs on the tail tip, T. javaense and T. vandycki have 10 pairs with 1 pair on the tail tip. The detailed morphology of the left spicule tip differs in each of the 3 species ( Fig. 6 , this study; Fig. 7 p.177 Gibbons et al 1992; Fig. 14, p.92, Smales 1995). There are prominent paired cuticular ornamentations on the region of the glandular oesophagus of T. javaense and tiny, difficult to find ornamentations on T. vandycki but none were found on T. intersedis . Comparative measurements of the 3 species are given in Table 2.

The single juvenile studied had not yet developed the characteristic cephalic features of the cordons although the structures of oesophagus and buccal capsule were consistent for the genus.

Figures

FIGURES 1 – 12. Tikusnema intersedis sp. nov. 1. Anterior end, lateral view. 2. Cephalic region, dorsal view. 3. Cephalic region, lateral view. 4. Posterior end male, ventral view. 5. Cephalic end, en face view. 6. Left spicule tip. 7. Posterior end female, lateral view. 8.