Gongylonema neoplasticum Ditlevsen 1918

Gongylonema neoplasticum (Fibiger & Ditlevsen, 1914), Ditlevsen, 1918

Gongylonema neoplasticum (Fibiger & Ditlevsen, 1914) Ditlevsen, 1918, Pp. 1–28. Pl. I–IV, XXVI.

Type host. Rattus norvegicus (Berkenhout) (Rodentia: Muridae) (Norway rat).

Type locality. Dorpat (now Tartu), Estonia.

Site of infection. Squamous mucosa of cardiac stomach or oesophagus.

Additional hosts. Rattus rattus (Linnaeus) (Rodentia: Muridae) (black rat), Mus musculus Linnaeus (Rodentia: Muridae) (house mouse).

Material examined. NT: from Rattus rattus Darwin 2 ♂♂, 1 ♀, 1 ♀ anterior, 1 ♀ posterior fragment (AHC 49248); 2 ♂♂, 1 ♀, 1 ♀ anterior, 1 ♀ posterior fragment (QM G240165); 1 ♂, 1 ♂ anterior fragment, 1 ♀ anterior, 1 ♀ posterior (N5498). Qld: from Rattus sp. Townsville, 1 ♂, 2 ♀♀ (GL11601). From Mus musculus Townsville, 1 ♀ in two fragments (GL 11606).

Description

General: Nematodes with marked sexual dimorphism, cuticular bosses present on anterior end, sparse in males, not so in females, prominent transverse cuticular striae present. Cephalic end with 2 cuticular plates at margins of buccal opening; buccal capsule present. Oral opening elongated dorso-ventrally, 6 small lateral lips, 3 on each side of opening, 2 interlabia in dorso-ventral axis, ventral interlabia bifurcated. Two pairs of internal labial papillae, 2 pairs of cephalic papillae and 2 large lateral amphids with transverse slit-like openings. Deirids situated anteriorly near origin of lateral alae. Oesophagus long, divided into anterior muscular and posterior glandular regions.

Male: Total length 9.3 (8.4–9.6) mm. Maximum width 138 (114––59). Cuticular bosses sparse anteriorly, extending 322 (168–583) from anterior end. Buccal capsule 51 (47–54) long, 16 (15–18) wide. Deirids 101 (87– 114) from anterior end. Lateral alae present entire body length, widening posteriorly to form asymmetric caudal alae, right wider than left, extending to tail tip. Nerve ring 156 (125–177) and excretory pore 312 (270–333) from anterior end. Muscular oesophagus 343 (302–408) long, glandular oesophagus 2018 (1616–2650) long. Spicules dissimilar, unequal, right spicule 102 (94–125), left spicule 572 (544–603) long; gubernaculum 27 (25–28) long. Caudal end with 4 pairs of pedunculated pre-cloacal and 5 pairs of pedunculated post-cloacal papillae. Distal end of tail curved ventrally, 131(125–139) long. Phasmids not observed.

Female: Total length 23.9 (22.2–25.5) mm. Maximum width 194 (125–345) at tail end. Cuticular bosses abundant, extending 739 (530–954) from anterior end. Buccal capsule 52 (42–58) long, 17 (18–20) wide. Deirid 118 (100–125) from anterior end. Nerve ring 177 (156–218) and excretory pore 366 (333–399) from anterior end. Muscular oesophagus 556 (489–693) long, glandular oesophagus 3298 (3021–002). Vulva 2899 (1420–4424) from posterior extremity. Tail conical, 176 (146–239) long. Phasmids 10 (8–10) from posterior end. Larvated eggs 55 (52–58) long, 32(31–33) wide with thick, smooth shells.

Remarks. Gongylonema neoplasticum is cosmopolitan in its distribution due to the unintended introduction of its primary rodent hosts, Rattus norvegicus R. rattus, R. tanezumi Temminck and R. exulans (Peale), all shown to originate in southern China and Southeast and South Asia (Aplin et al., 2011; Song et al., 2014; Thomson et al. 2014; Puckett et al. 2016), spreading beyond Asia as a consequence of global trade.

The morphology and measurements of G. neoplasticum in this study are in agreement with numerous previous descriptions and illustrations of the species (Ditlevsen, 1918; Schulz, 1924; Yokogawa, 1925; Kruidenier & Peebles, 1958, da Costa et al. 2018, Setsuda et al. 2018, Dewi, 2019). Variability in the number of pedunculated pre- and postcloacal papillae in the male has been reported by previous authors. Readers are referred to the excellent scanning electron micrographs of da Costa et al. (2018) (Fig. 2, A–F) and Dewi (2019) (Fig. 1, A–H), especially the en face views of the complex cephalic end.

Johnston (1918) reported eggs with developed embryos in the liver of two Mus musculus in Sydney which he considered belonged to a species of Gongylonema.

Fielding (1928) reported Gongylonema sp. in Rattus norvegicus, R. rattus, one Mus musculus and one native water rat, Hydromys chrysogaster Geoffroy. Two lots of specimens in QM (GL11601 and GL11606) collected by G.M. Heydon in 1927 and 1926 and labelled Gongylonema cf. neoplasticum and Gongylonema neoplasticum may be the material in Fielding’s report as he acknowledges Heydon for identifying some of the worms. The specimens are badly darkened, do not clear well and morphological features diagnostic for the species are obscured. The length of the right spicule, 73 µm, agrees with that recorded for this species here and by other authors (Kruidenier & Peebles, 1958; Cordeiro et al., 2018). The left spicule could not be discerned nor the number and arrangement of pre- and post-cloacal papillae on the male tail. I am unable to confirm these determinations but if correct, they represent the only previously known records of this species in Australia. This is surprising given previous survey work on the parasites of rodents in north Queensland (Mesina et al 1974; Mesina & Campbell, 1975; Glazebrook & Campbell, 1977; Glazebrook et al., 1978; Chakma et al., 2016) and the review of helminths of rodents by Smales (1997).