Acanthobothrium usengozinius, Spuy & Smit & Schaeffner, 2022

Spuy, Linda Van Der, Smit, Nico J. & Schaeffner, Bjoern C., 2022, Threatened, host-specific affiliates of a red-listed host: Three new species of Acanthobothrium van Beneden, 1849 (Cestoda: Onchoproteocephalidea) from the endangered white skate, Rostroraja alba (Lac´ep`ede), International Journal for Parasitology: Parasites and Wildlife 17, pp. 114-126 : 118-120

3.2. Acanthobothrium usengozinius n. sp. ( Figs. 3 and 4)

Description (based on whole mounts of five mature and two immature worms; two mature worms examined with SEM): Worms 6.3–8.8 mm long, greatest width at level of scolex, 32–45 proglottids per worm, euapolytic. Scolex consisting of scolex proper and cephalic peduncle. Scolex proper with four bothridia, 540–631 long by 372–508 wide. Bothridia free posteriorly, 215–245 wide; each bothridium with three loculi and specialised anterior region in form of muscular pad. Muscular pad 78–109 long by 139–163 wide, falciform in shape, with

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pronounced posterior margin, bearing accessory sucker and one pair of hooks at posterior margin; accessory sucker 23–26 long by 43–54 wide. Anterior loculus (A) 235–257 long; middle loculus (M) 126–143 long; posterior loculus (P) 94–106 long; loculus length ratio (A: M: P) 1.00: 0.54: 0.41; maximum width of scolex at level of middle loculus. Velum absent.

Hooks bi-pronged, hollow, with tubercle on proximal surface of axial prongs; internal channels of axial and abaxial prongs continuous, smooth; axial prongs slightly longer than abaxial prongs; lateral and medial hooks approximately equal in size. Lateral hook measurements: A 62–73, B 135–151, C 129–141, D 190–216. Medial hook measurements: A ′ 64–74, B ′ 139–162, C ′ 125–142, D ’ 193–228. Bases of lateral and medial hooks approximately equal in length; base of lateral hook slightly overlapping base of medial hook along medial axis of bothridium ( Fig. 3D); medial hook base slightly wider than lateral hook base. Tissue covering almost entire length of each prong of hooks. Short cephalic peduncle 572–1080 long by 119–124 wide.

Cephalic peduncle densely covered with gladiate spinitriches, filitriches not observed ( Fig. 4D). Apical pad and distal bothridial surface covered with acicular filitriches and very sparsely interspersed gladiate spinitriches ( Fig. 4E). Proximal bothridial surface and bothridial rims covered with gladiate spinitriches, interspersed with acicular filitriches ( Fig. 4F). Anterior region of strobila covered in acicular filitriches ( Fig. 4G). Anterior region of terminal proglottid covered in capilliform filitriches ( Fig. 4H).

Proglottids acraspedote. Immature proglottids 29–44 in number; 1–3 mature proglottids; gravid proglottids absent; terminal proglottid 795–1538 long by 275–394 wide; terminal proglottid length to width ratio 2.5–4.6: 1.0. Proglottids protandrous; genital pores marginal, irregularly alternating ( Fig. 3A), 42–58% of proglottid length from posterior margin.

Testes conspicuous in mature proglottids, oval in dorsoventral view, 42–63 long by 42–51 wide, arranged in one to two layers in intervascular field ( Fig. 3C), 42–61 in total number, 0 in post-poral field of mature proglottids, 4–5 in post-poral field of immature proglottids. Cirrus-sac obpyriform ( Fig. 3C), 151–234 long by 43–57 wide, containing armed cirrus; cirrus greatly expanded at base.

Vagina narrow, relatively thin-walled and straight proximally, extending from ootype along medial line of proglottid to anterior margin of cirrus-sac, then laterally to common genital atrium. Vaginal sphincter

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prominent ( Fig. 3C). Ovary occupying about half of proglottid length, almost reaching posterior margin of proglottid, H-shaped in dorsoventral view, lobulated ( Fig. 3C), asymmetrical, 143–180 wide at level of ovarian isthmus; poral lobe 548–679 in length; aporal lobe 616–757 in length; ovarian lobes not reaching cirrus-sac anteriorly; ovarian isthmus located posterior to mid-level of ovary. Mehlis’ gland posterior to ovarian isthmus.

Vitellarium follicular to lobulated; follicles in two lateral bands, 27–35 long by 17–20 wide, length relative to testis length 0.4–0.6: 1.0; each band consisting of two columns, extending from posterior margin of anterior-most testes to near posterior margin of ovary ( Fig. 3C). Uterus thin-walled, extending from ovarian isthmus to near anterior margin of proglottid. Eggs not observed.

Type host: White skate, Rostroraja alba (Lac´ep`ede) ( Rajiformes : Rajidae ).

Type locality: Danger Point , Gansbaai, South Africa [34 ◦ 28 ′ 50’’S, 19 ◦ 19 ′ 55’’E] .

Site of infection: Spiral intestine.

Prevalence of infection: 50% (one of two skates examined).

Type material: Holotype deposited at NMB (Accession number: XXX), paratypes in NMB (Accession numbers: XXX-XXX), IPCAS (Accession numbers: XXX-XXX) and MHNG (Accession numbers: XXX-XXX).

ZooBank number for species: XXXXXX.

Etymology: The species name “ usengozinius ” is derived from “usengozini” [Xhosa; an indigenous language to the Eastern and Western Cape of South Africa] meaning “endangered”, referring to the threatened status of both the definitive host Rostroraja alba , as well as its host-specific parasite.

Remarks