Maxvachonia chabaudi Mawson, 1972

Ni, Xue-Feng, Barton, Diane P., Chen, Hui-Xia & Li, Liang, 2022, Native species Maxvachonia chabaudi Mawson, 1972 (Nematoda: Cosmocercoidea) found in the invasive marine toad Rhinella marina (Linnaeus) (Anura: Bufonidae) in Australia, Folia Parasitologica (028) 69, pp. 1-7 : 4

Maxvachonia chabaudi Mawson, 1972 Figs. 1‒3

Small, whitish nematodes. Body cylindrical, maximum width at about region of mid-body. Cuticle with fine transverse striations. Somatic papillae absent. Cephalic end rounded. Oral aperture simple, somewhat triangular, surrounded by 3 small lips, each with inner flanges ( Figs. 2B , 3D ). Dorsal lip with 1 pair of large double cephalic papillae, subventral lips with single large double cephalic papilla and amphid ( Figs. 2B , 3D ). Buccal capsule short, with three small teeth-like projections at base ( Fig. 1E ). Oesophagus divided into anterior indistinct pharynx, cylindrical corpus, narrow isthmus and terminal posterior bulb with valves ( Fig. 1A–D ). Lateral alae only present in male ( Fig. 2A ). Nerve ring located at about 1/3‒1/2 of oesophageal length. Excretory pore discoid, situated at anterior to oesophageal bulb ( Figs. 1A–D , 3A,B ). Deirids not observed. Tail of both sexes conical, with pointed tip ( Figs. 1F,K,L , 2C,H , 3F,G ).

Male (based on two mature specimens): Body 2.07‒2.24 mm long; maximum width 140‒220. Entire oesophagus 261‒338 long (including posterior oesophageal bulb), representing 13‒15% of body length; pharynx + corpus + isthmus 213‒280 long, size of oesophageal bulb 48‒58 × 53‒72. Nerve ring 113‒138 and excretory pore 208‒256 respectively, from anterior extremity. Lateral alae narrow, extending from level of excretory pore to anterior of second precloacal papillae ( Figs. 1F , 2A,C,G ). Posterior end of body distinctly ventrally curved ( Figs. 1F , 2C,G ). Spicules slender, equal in length, distal end pointed, 88‒122 long, representing 4.3‒5.4% of body length ( Fig. 1F,G ). Gubernaculum robust, well-sclerotised, with remarkable lateral processes near the proximal end, slightly longer than spicules, 109‒146 long ( Figs. 1F,G , 2F ). Caudal papillae 15 pairs in total, arranged as follows: 6 pairs precloacal (first pair lateral, far from others), 3 pairs paracloacal (2 pairs ventral, close to cloaca; 1 pair ventrolateral, far from cloaca) and 6 pairs postcloacal (4 pairs ventrolateral and 2 pairs dorsolateral ( Figs. 1F , 2C–H ). Single precloacal medio-ventral papilla present ( Fig. 2F ). Tail 150‒200 long, representing 7.2–8.9% body length ( Figs. 1F , 2C,H ). One pair of small phasmids located at about posterior 1/3 of tail (near third pair of postcloacal papillae) ( Fig. 2H,I ).

Female (based on 33 mature specimens): Body 7.20‒14.6 mm long; maximum width 180‒400. Entire oesophagus 435‒676 long (including posterior oesophageal bulb), representing 3.6‒8.4% of body length; pharynx + corpus + isthmus 362‒580 long, size of bulb 72‒111 × 72‒111. Nerve ring 163‒300 and excretory pore 314‒483 respectively, from anterior extremity. Lateral alae absent. Vulva transverse slit, vulval lips not protruded, 411‒652 from anterior extremity, at 3.8‒7.3% of body length ( Figs. 1A–C , 3A,C ). Egg oval, thin-walled, with a small nipple at one side, 50‒80 × 38‒58 (n = 66) ( Figs. 1H–J , 3E ). Tail 1.50‒3.65 mm long, representing 20.3‒30.3% body length; tip of tail finger-like, covered with numerous nodular protuberances ( Figs. 1L,K , 3F,G ). Phasmids not observed.

H o s t: Marine toad Rhinella marina (Linnaeus) ( Anura : Bufonidae ).

L o c a l i t i e s: Cape Weymouth (-12.61611111, 143.43194444), Mareeba (-17.01861111, 143.47000000), northern Queensland; rural areas surrounding Townsville (-19.38472222, 146.96250000 and -19.38472222, 146.96250000), northern Queensland; Boyne Island (-23.93000000, 151.34777778), central Queensland, Australia .

R a t e o f i n f e c t i o n: prevalence 5.1% (33 out of 643 of R. marina specimens were infected), with an intensity of 1–9 (mean 2.7) nematodes.

S i t e o f i n f e c t i o n: intestine.

Vo u c h e r s p e c i m e n s d e p o s i t e d: two males (HBNU– N-2021A005NL), 33 females (HBNU–N-2021A006NL).

Figures

Fig. 1. Maxvachonia chabaudi Mawson, 1972 from the marine toad Rhinella marina (Linnaeus) (Anura: Bufonidae) in Australia. A–C – anterior part of female (showing variable position of vulva in different individuals), lateral view; D – anterior part of male, lateral view; E – magnified image of cephalic end, lateral view; F – posterior end of male, lateral view; G – gubernaculum and spicules,lateral view; H–J – different developmental stages of eggs; K – tail tip of female; L – posterior end of female, lateral view.

Fig. 2. Scanning electron micrographs of Maxvachonia chabaudi Mawson, 1972 from the marine toad Rhinella marina (Linnaeus) (Anura: Bufonidae) inAustralia, male.A – anterior part of body (lateral ala arrowed), lateral view; B – cephalic end (amphid arrowed), apical view; C, G – posterior end of different individuals (white arrows showing precloacal papillae, black arrow showing lateral ala), lateral view; D – magnified image of precloacal papilla; E – magnified image of postcloacal papilla; F – magnified image of cloacal region (white arrow showing precloacal medio-ventral papilla, black arrows showing paracloacal papillae); H – tail (white arrows showing postcloacal papillae, black arrow showing phasmid), lateral view; I – magnified image of phasmid. Abbreviations: d – dorsal lip; g – tip of gubernaculum; i – inner flange of lips; v – ventrolateral lip.

Fig. 3. Scanning electron micrographs of Maxvachonia chabaudi Mawson, 1972 from the marine toad Rhinella marina (Linnaeus) (Anura: Bufonidae) in Australia, female.A – anterior part of body (excretory pore and vulva arrowed), ventral view; B – magnified im- age of excretory pore; C – magnified image of vulva; D – cephalic end (amphids arrowed), apical view; E – egg (small nipple arrowed); F – tail, lateral view; G – magnified image of tail tip. Abbreviations: d – dorsal lip; v – ventrolateral lip.