Trichuris musseri, Hasegawa, Hideo & Dewi, Kartika, 2017

Hasegawa, Hideo & Dewi, Kartika, 2017, Two new species of Trichuris (Nematoda: Trichuridae) collected from endemic murines of Indonesia, Zootaxa 4254 (1), pp. 127-135 : 128-129

Trichuris musseri sp. nov.

( Figs. 1–12 )

General. Small sized as a Trichuris in murids. Cuticle with fine transversal striation. Anterior part of body narrow, thread-like, tapering to cephalic end; gradually increasing to widest portion in posterior body and again slightly tapered to posterior end ( Figs. 1, 2 , 9 ). Minute cephalic stylet present. Stichosome with 1 row of stichocytes, and 1 pair of conspicuous cells at esophago-intestinal junction level ( Figs. 2–5 , 10 ). Nuclei of stichosome numerous, almost 1 nucleus per 1 to 2 subdivisions, in middle to posterior portions ( Figs. 3–5 ). Bacillary band commencing just after cephalic end, well developed in middle portion of anterior body ( Figs. 2–5 ), becoming narrower and invisible anterior to esophago-intestinal junction. Round cuticular inflations of various size bordering bacillary band present in anterior portion of body ( Fig. 2 ).

Male (9 specimens): Length 8.79 (7.89–9.24) mm. Anterior portion of body 5.32 (4.93–5.65) mm long, corresponding to 61 (58–63) % of body length. Width at middle of anterior body 57 (44–69), esophago-intestinal junction 129 (99–162) and thick portion of posterior body 182 (162–210). Round cuticular inflations present in area from 192–258 to 618–860 from anterior end. Stichosome with ca. 160 nuclei. Testis recurved posterior to esophago-intestinal junction, directed posteriorly forming convolutions, ending near anterior end of proximal cloacal tube ( Fig. 1 ). Proximal cloacal tube stout, 0.66 (0.45–0.91) mm long, united laterally to distal cloacal tube of 0.53 (0.35–0.71) mm long ( Fig. 1 ). Spicular pouch 0.18 (0.09–0.28) mm long ( Fig. 1 ). Spicule slender, 1.11 (0.90–1.28) mm long, corresponding to 12.7 (10.0–14.1) % of body length, sharply pointed distally ( Figs. 6-7 ). Distal portion of spicule with pit-like structures on one side ( Fig. 7 ). Spicular sheath densely spinose ( Figs. 6-7 ). Distal end of fully extended spicular sheath devoid of spines, with faint reticulate markings ( Fig. 8 ). Cloaca subterminal with 1 pair of simple papillae ( Fig. 6 ).

Female (10 specimens): Length 10.9 (9.3–12.4) mm. Anterior body 6.20 (5.55–7.22) mm long, corresponding to 57.0 (54.6–59.6) % of body length. Width at middle of anterior body 58 (51–67), esophago-intestinal junction 135 (121–158) and thick portion of posterior body 202 (184–218). Round cuticular inflations present in area from 162–300 to 684–1039 from anterior end. Stichosome with ca. 160–170 nuclei. Vulva 40 (10–71) posterior to esophago-intestinal junction, with anterior lip of varying degree of development and minute posterior lip ( Figs. 9, 10 ). Vagina muscular, winding posteriorly, 0.67 (0.56–0.78) mm long ( Figs. 11, 12 ). Ovary extending to preanal level ( Figs. 9, 11 ). Anus subterminal ( Fig. 11 ). Eggs lemon-shaped, thick shelled, brownish, with polar plugs, 73.6 ± SD 1.7 (71–77) by 33.0 ± SD 1.4 (30–35) (n=25), with exception of one egg sized 91 by 38 ( Fig. 12 ).

Taxonomic summary

Type host: Echiothrix centrosa Miller & Hollister, 1921 (large-bodied shrew rat) (Rattini: Murinae : Muridae ).

Site in host: Cecum.

Type locality: Kuala Navusu (00˚58’S, 120˚27’E; 38–155 m elevation), Malakosa , Central Sulawesi, Indonesia.

Date of collection: October 1975.

Type specimens: USNM 1422103 (hototype male and allotype female), USNM 1422104 (5 male and 6 female paratypes), MZB Na 720 (3 male and 3 female paratypes).

Coparasites: Musserakis sulawesiensis Hasegawa, Dewi & Asakawa, 2014 (Nematoda: Heterakidae ) ( Hasegawa et al., 2014).

Symbiotypes: AMNH M-225678 – M-225681.

Etymology. The species epithet is dedicated to Dr. G. G. Musser, an outstanding mammalogist, who has made invaluable contributions on the systematics of murid rodents of Indonesia.

Remarks. By having a stichosome, tubular intestine, vulva positioned near esophago-intestinal junction, monodelphic reproductive system and eggs with polar plugs but without membranous envelope or polar filaments, the present species belongs to the family Trichuridae in the superfamily Trichinelloidea ( Chabaud, 1974; Anderson & Bain, 1982). By possessing much thicker posterior portion of body, a bacillary band at esophageal portion, stichocytes similar in form and arranged in a single row and unembryonated eggs in the uterus, it belongs to the subfamily Trichurinae which includes only the genus Trichuris Roederer, 1761 ( Anderson & Bain, 1982) . By having a small body, the present species is readily distinguished from all congeners known from murids because all have average body length over 10 mm in males and 15 mm in females (cf. Skrjabin et al., 1957; Quentin, 1966; Bernard, 1969; Tenora, 1969; Johnson, 1973; Sadighian et al., 1974; Feliu et al., 2000; Robles, 2011; Ribas et al., 2013; Smales, 2013; Robles et al. 2014). The present species is characteristic by having a gradually-tapered and sharply pointed distal end of the spicule, being readily distinguished from most congeners parasitic in murids, which have dull or round distal end or suddenly narrowed near distal end of the spicule (cf. Quentin, 1966; Robles, 2011; Robles et al., 2014; Smales, 2013; Feliu et al., 2000; Ribas et al., 2013). Among the congeners parasitic in murids, only T. petrowi in Arvicola terrestris of Tatarstan, Russia, and T. spalacis in the mole rat, Spalacis microphthalmus, of Ukraine, have been known to have gradually tapered and pointed spicule ( Petrov & Potekhina, 1953; Skrjabin et al., 1957). However, the former species has a cephalic expansion in the male and much longer distance (> 1 mm) between the anus and posterior end of body in female, and the latter species has a smaller ratio (<58 %) of anterior body to worm length in males and smaller eggs (62–65 by 29 µm), differing from the present species ( Petrov & Potekhina, 1953; Skrjabin et al., 1957).

Figures

FIGURES 1 – 8. Male of Trichuris musseri sp. nov. collected from Echiothrix centrosa in Sulawesi, Indonesia. 1. Holotype. 2. Anterior end of holotype. 3. Middle portion of stichosome showing bacillary band at left side. 4. Enlarged view at posterior one-third of stichosome, showing surface of bacillary band partially; two-way arrow indicating width of bacillary band at this level. 5. Esophago-intestinal junction. 6. Caudal end. 7. Distal end of spicule; arrows showing pit-like structures. 8. Distal end of spicular sheath fully extended.

FIGURES 9 – 12 Female of Trichuris musseri sp. nov. collected from Echiothrix centrosa in Sulawesi, Indonesia. 9. Allotype. 10. Esopahgo-intestinal junction. 11. Caudal end. 12. Egg.