Gongylonema bettongiae, Spratt, 2023

Spratt, David M., 2023, Redescription of species of Gongylonema Molin, 1857 (Nematoda: Spiruroidea Gongylonematidae) parasitic in some Australian vertebrate hosts and description of three new species, Zootaxa 5239 (2), pp. 204-220 : 213-216

Gongylonema bettongiae sp. nov.

Type specimens. Holotype ♂ AHC 49241 , allotype ♀ AHC 49242, 10 ♂♂, paratypes AHC 49243, 15 ♀♀ paratypes AHC 49244, 10 ♂♂ paratypes QM G240161, 10 ♀♀ paratypes QM G240162, 9 ♂♂, 22 ♀♀ paratypes (N1337).

Type locality. Kempton, Tas .

Type host. Bettongia gaimardi (Desmarest) (Marsupialia: Potoroidae ) (eastern bettong)

Site of infection. Oesophageal mucosa.

Additional hosts. Potorous tridactylus (Kerr) (Marsupialia: Potoroidae ) (long-nosed potoroo); Aepyprymnus rufescens (J. Gray) (Marsupialia: Potoroidae ) (rufous rat kangaroo); Trichosurus vulpecula (Kerr) (Marsupialia: Phalangeridae ) (brushtail possum).

Material examined. Tas : from Bettongia gaimardi , types; oesophageal mucosa, 29 ♂♂, 32 ♀♀ (N1363) ; Bridgenorth , 3 ♂♂, 2 ♀♀ (AHC 16543) ; adjacent to Tamar estuary, 13 ♂♂ (AHC 46903); 1 ♀ (AHC 46904) ; Margate , 2 ♂♂ (N4273), 3 ♂♂ (N4293). From Potorous tridactylus, Margate 2 ♂♂, 7 contracted & coiled ♀♀, 1♀ anterior and posterior ends (AHC 49245), 3 ♂♂ (AHC 00000); locality unknown, 1 ♂ (AHC 11916). From Trichosurus vulpecula, Icena , 2 ♂♂, 7 ♀♀ (N966), 1 ♂ (N1055); Mt. Wellington , 16 ♂♂, 5 ♀♀ (AHC 49247) ; Kempton , ♂♂, 1♀ (N1327).

Victoria; from Potorous tridactylus oesophageal mucosa, Serendip Sanctuary Lara, 1 ♂ (AHC 10981).

New South Wales; from Aepyprymnus rufescens, Taronga Zoo , 1 ♂ posterior end; 1 ♀ anterior (AHC 49246); Grafton , 1 ♀ unfertilised (N3387). From Trichosurus vulpecula, Buckenboura State Forest, Quart Pot Rd. , 5 ♂♂, 3 ♀♀ (N1241) , 8 ♂♂, 8 ♀♀ (N1352).

Etymology. The specific name is derived from the generic and common name, eastern bettong, the most commonly infected of the hosts encountered in this study.

Description (based on specimens from Bettongia gaimardi ) ( Fig. 4 A–H .)

General: Nematodes with marked sexual dimorphism, cuticular bosses present on anterior end, prominent transverse cuticular striae present. Cephalic end with cuticular peri-buccal ring, buccal capsule present. Oral opening not elongated dorso-ventrally, 2 cuticular formations at outer margins of dorso-ventral axis and extending over opening, 6 small lateral lips, 3 on each side, on inside rim of buccal capsule, 2 pairs of internal papillae, 2 pairs of cephalic papillae and 2 large, lateral amphids. Deirids situated anteriorly near origin of lateral alae. Oesophagus long, divided into anterior muscular and posterior glandular regions.

Male (holotype in italics, mean 10 paratypes + range in parentheses): Total length 20.7 21.1(19.5–24.2) mm. Maximum width 156 177 (154–208). Cuticular bosses on all surfaces anteriorly, restricted to dorsal and ventral surfaces posteriorly, extending 848 964 (655–1192) from anterior end. Buccal capsule 52 51 (42–54) long, 18 16(13–20) wide. Deirids 125 136 (125–146) 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 208 227 (208–260) and excretory pore 353 374 (353–395) from anterior end. Muscular oesophagus 416 522 (416–613) long, glandular oesophagus 5565 5749 (5380–6431) long. Spicules dissimilar, unequal, right spicule 139 140 (135–145) long, left spicule finely striated 4749 5054 (4500–7179) long, proximal end highly ornate; gubernaculum bipartite, left side accommodating left spicule, boat-shaped 52 60 (52–62) long, right side accommodating right spicule striated, 21 32 (21–42) long. Caudal end generally with 5, rarely 4 pairs of pedunculated pre-cloacal papillae, 3 pairs of pedunculated post-cloacal papillae and 3 pairs of sessile papillae near tail tip, anterior pair larger than posterior pairs. Pairs of pre-cloacal papillae variable distances anterior to cloacal aperture. Most anterior one or two pairs often difficult to observe because tail twisted or cork-screwed, 4 th and 5 th pairs ranging 191 (166–270) and 250 (188–312) anterior to cloacal aperture. In one specimen manipulated to a near ventral view, 5 pairs of pre-cloacal papillae 25, 56, 106, 156 and 291 from anterior lip of cloaca, 3 pairs of post-cloacal papillae 31, 75 and 135 from the posterior lip. Distal end of tail curved ventrally, 156 166 (154–187) long. Phasmids not observed.

Female: (allotype in italics, mean 10 paratypes + range in parentheses): Total length 49 41 (32–49) mm. Maximum width 237 257 (186–318) at tail end. Cuticular bosses dense, occurring on all surfaces initially, confined to dorsal and ventral surfaces over most of length, extending 1367 1858 (1367–2491) from anterior end. Prominent transverse cuticular striae present. Buccal capsule 52 54 (52–62) long, 16 15 (11–17) wide. Deirid 144 144 (129– 156) from anterior end. Nerve ring 262 271 (258–302) and excretory pore 478 452 (426–478) from anterior end. Muscular oesophagus 593 639 (562–770) long, glandular oesophagus 11182 6926 (4112–12140) long. Exceptionally long (11182, 12140) glandular oesophagus in two females Position of vulva highly variable, 6890 4801 (2703– 6890) from posterior extremity. Tail conical, 177 211 (177–234) long. Phasmids 17 20 (17–21) from posterior end. Larvated eggs 54 58 (52–63) long, 32 32 (31–33) wide, with thick smooth shells.

Remarks. The glandular oesophagus in females of G. bettongiae sp. nov. and G. alecturae are the longest of the species described herein and those in G. bettongiae sp. nov the most variable by as much as a factor of three.

Specimens of G. bettongiae from T. vulpecula differ from those from the three species of potoroids in the slightly longer right and particularly left spicules and tail in males, slightly greater distance of the vulva from the tail tip and the shorter tail in females. Nevertheless, the basic morphological features are the same especially in en face view, the ornamentation on the proximal end of the left spicule and the morphology of the bipartite gubernaculum in males.

The left spicule of this species is more markedly flexed, bent, or curved throughout its length than in other species in this study and has the greatest variability in length ranging from almost 4.5 to 7 mm in potoroids and even more in specimens from T. vulpecula . Only the left spicule of G. alecturae with its highly characteristic barbed tip is greater in length,> 18 mm.

The number of pedunculated pre-cloacal papillae was more variable (4–6) in specimens from T.vulpecula although the lower number is most likely due to the twisted or cork-screwed form of the tail masking the most anterior one or two pairs.

Gongylonema bettongiae sp. nov. is distinguished from G. alecturae by the generally shorter right and much shorter left spicule, the smaller number of pre-and post-cloacal pedunculated papillae, the much shorter tail in the males, and the generally shorter muscular and longer glandular oesophagus, the shorter distance of the vulva from the posterior extremity and the shorter tail in females.

Gongylonema bettongiae sp. nov. is distinguished from G. aguilarense sp. nov. described herein by the shorter body lengths of males and generally longer lengths of females, the much longer extent of bosses and the lengths of the muscular and glandular oesophagus in both sexes, the longer right and much longer left spicule, the fewer number of post-cloacal papillae, arranged symmetrically, the longer tails in the males and the generally shorter tails in the females.

The intermediate hosts of species of Gongylonema are beetles and cockroaches ( Anderson, 1992).The occurrence of G. bettongiae in brushtail possums is not surprising as they may be lured to the ground by the smell of the fruiting bodies of underground fungal hyphae, a major component of the diet of bettongs and potoroos (Eldridge, 2006, in van Dyck & Strahan, 2008, p. 284).

Figures

FIGURE 4A–H. Gongylonema bettongiae sp. nov. A, Cephalic end female, en face view. B, Anterior end holotype male, ventrolateral view. C, Excretory pore, lateral view. D, Posterior end holotype male, lateral view. E, Left spicule tip with membranous terminal ending. F, Right spicule tip with membranous terminal ending. G. Gubernaculum accommodating both right and left spicules. H, Posterior end female, ventral view. Scale bars: Figs. 4A, 4E, 4F = 20 µm. Figs. 4B–4D, 4G, 4H = 50 µm.