Gongylonema beveridgei Mawson, 1971

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 : 207-210

Gongylonema beveridgei Mawson, 1971

Gongylonema beveridgei Mawson, 1971 pp. 176–177 , figs. 27–30.

Type specimens. Holotype ♂ AHC 42822, allotype ♀ AHC 42823, 3 ♀♀, paratypes, AHC 7799

Type host. Rattus fuscipes greyii (J.E. Gray) (as R. f.murrayi Thomas) ( Rodentia : Muridae ) (Australian bush rat).

Type Locality. Pearson Island, SA.

Site of infection. stomach

Additional hosts. None.

Material examined. SA: from Rattus fuscipes greyii: Pearson Island, types; Vic: from Rattus fuscipes Marysville 1 ♂, posterior end damaged (AHC 10216); Qld: Mount Glorious, 3 ♀♀, unfertilised, 1 damaged anteriorly (AHC 12454).

Description ( Fig. 2 A–F .)

General: Nematodes with marked or some sexual dimorphism, cuticular bosses present on anterior end, prominent transverse cuticular striae present. Cephalic end with small peri-buccal ring, buccal capsule present. Oral opening elongated dorso-ventrally, 2 pairs of internal papillae on internal margins of peri-buccal ring, 2 pairs of cephalic papillae and 2 large lateral amphids. Deirids situated anteriorly, near origin of right lateral ala in male and alae in female. Oesophagus long, divided into anterior muscular and posterior glandular regions.

Male (holotype):Total length unknown, total body incomplete, anterior and posterior fragments totalling 9.8mm. Maximum width 187. Cuticular bosses sparse, restricted to left side of body, extending 422 from anterior end. Buccal capsule 52 long, 8 wide. Deirid 114 from anterior end. Lateral ala present on right side only, continues along entire body length, widening to form right caudal ala, extending to tail tip. Nerve ring 156, excretory pore 280 from anterior end. Muscular oesophagus 301, glandular oesophagus 2215 long. Spicules unequal, markedly different in length, right spicule 94, left spicule fragments totalling 468, finely striated; gubernaculum inconspicuous. Tail with unknown number of pre-cloacal pedunculated and 10 post-cloacal papillae, consisting of two pedunculated pairs, single pedunculated right papilla, 1 pedunculated pair with small median sessile papilla between them and small sessile subterminal pair. Tail 156. Phasmids not observed.

Female (allotype in italics; 3 paratypes: {1 intact, 1 in two fragments, 1 immature posterior end}): Total length 55 (47, 55) mm. Maximum width 318 260 (212, 318, 249) at tail end. Cuticular bosses relatively sparse, predominantly on dorsal and ventral surfaces, extending 1378 (1164, 1458) from anterior end. Buccal capsule 62 (50, 56) long, 13 (14, 13) wide. Deirid 135 (210, 208) from anterior end. Two lateral alae present extending most of body length. Nerve ring 198 (250, 260), excretory pore 322 (489, 458) from anterior end. Muscular oesophagus 842 (780,832), glandular oesophagus 5353 (5900, 5206). Vulva 6440 (4187, 6890, 3286) from posterior extremity. Tail conical, 228 (270, 230, 239) long. Phasmids 4 (4–5) from tail tip. Larvated eggs 60 (62) long, 33 (33) wide, with thick smooth shells.

Male: (AHC10216,posterior end)Right spicule 100,left spicule>6890.Portion of gubernaculum accommodating left spicule 125 long, that accommodating right spicule 31 long. Four pedunculated pre-cloacal and 3 pedunculated post-cloacal papillae. Tail 208 long.

Female: (AHC 12454, n=3; mean with range in parentheses) Total length 43 (41–45) mm. Maximum width 260 (249–265) at tail end. Cuticular bosses variable in density, distances they commence from cephalic end and distance they extend posteriorly: bosses occur on left lateral surface only, commencing 141 (62–186) from cephalic extremity, extending posteriorly 897 (385–1219). Fine transverse cuticular striae present. Structure of cephalic extremity not discernible. Buccal capsule 52 (52) long, 17 (16–17) wide. Deirids 157 (150–166) from cephalic end, just anterior to origin of two robust lateral alae. Nerve ring 297 (291–302) and excretory pore 571 (556–586) from anterior end. Muscular oesophagus 864 (774–954) glandular oesophagus 4808 (4717–4898) long. Vulva 4926 (4316–5539) from posterior extremity. Tail conical 216 (198–232) long. Eggs unfertilised.

Remarks. Useful measurements identified for species of Gongylonema are lengths of the body, the buccal capsule, the spicules, the gubernaculum and tail, the distance of the vulva from the posterior end and egg size (Desportes et al. 1949). The original description of G. beveridgei , based on a single male and four females provided measurements of only two of these, buccal capsule and eggs. The important morphological features associated with the tail of the male were summarised thus, “The left spicule is nine times the length of the right, the gubernaculum is shorter than the right spicule, spatulate, with a broadened tip.” ( Mawson, 1971).

The type material is in poor condition. The holotype is represented by an anterior and posterior fragment, the latter burst in the cloacal region, permitting recognition of only the right spicule and masking the number and distribution of pre-cloacal papillae. The left spicule is represented by two broken fragments totalling 468 µm in length. Given Mawson’s indication that the left spicule is 9x the length of the right and the current measurement of the right as 94 µm, the total length of the left spicule would be about 846 µm.

Mawson (1971, fig. 30) illustrated but did not describe the caudal end of the male showing 5 pre-cloacal papillae on the left and four on the right and with three pairs of post- cloacal papillae, a small papilla adjacent to the third pair on the right and two pairs and a single median papilla at the tail tip, differing from that described above and illustrated from the holotype ( Fig. 2D ).

I am able to confirm two apparently unique features of G. beveridgei , namely the occurrence of a single lateral ala on the right side of the body extending posteriorly to form the right caudal ala in the male, and sparse cuticular bosses only on the left lateral body in the male and extending only a short distance from the cephalic end ( Mawson, 1971; see Cordeiro et al., 2018). Regrettably however, the redescription of the species is incomplete and consequently comparison with other species of the genus remains problematic until such time as fresh specimens are acquired from R. fuscipes greyii .

Gongylonema beveridgei is further distinguished from G. alecturae by a shorter right spicule and tail in the male.

The badly damaged posterior end of the male (AHC 10216) from Rattus fuscipes , from Marysville Vic. and labelled G. beveridgei is not the same species. The exceptionally long left spicule measuring almost 7 mm distinguish it immediately from both G. beveridgei (846 calculated) and G. aguilarense sp. nov. (811–847). Left spicule length is closer to G. bettongiae sp. nov. from which it is distinguished by the smaller number of pre-cloacal pedunculated papillae (4 vs 5), a much larger gubernaculum and a slightly longer tail. Until more material from this host and locality can be examined the specimen is determined here as Gongylonema sp.

The data on the label containing the three unfertilised females (AHC 12454) from Mount Glorious is sparse but they include the initials MJM, indicating Dr. Mabel Josephine Mackerras, and presumably collected before 1961 when she moved from Brisbane to Canberra. The specimens are deeply amber in colour masking some features. They have some similarity to G. beveridgei but the cuticular bosses are variable in density, the distance they commence from cephalic end and the distance they extend posteriorly; in addition, they occur only on the left lateral surface. Mawson (1971) described bosses in female G. beveridgei as being more extensive than in the male and developed on both dorsal and ventral sides of the body as confirmed above, although sparse and restricted to the left side only in the male. The glandular oesophagus is shorter and the distance of the vulva from the tail tip also shorter in these females. Allowing for their shorter length due to immaturity, the sole morphological feature clearly separating these females from G. aguilarense sp. nov., which occurs in the same host species and geographical locality, are the cuticular bosses which in G. beveridgei are dense and occur on both dorsal and ventral surfaces, and the greater distance of the vulva from the tail tip. The absence of males associated with the three unfertilised females precludes specific identification and they are determined as Gongylonema sp.

Figures

FIGURE 2 A–F. Gongylonema beveridgei Mawson, 1971. A, Cephalic end female paratype, en face view. B, Anterior end, female paratype, lateral view. C, Vulva and vagina paratype female, ventral view. D, Posterior end holotype male, ventral view. E, Posterior end female allotype, lateral view. F, Right spicule and gubernaculum holotype male, lateral view. Scale bars: Figs. 2A, 2B, 2D= 20 µm, Figs. 2C, 2F = 50 µm. Fig. 2E = 100 µm.