Otobothrium carcharidis (Shipley & Hornell, 1906) Pinter, 1913

Beveridge, Ian & Justine, Jean-Lou, 2007, Redescriptions of four species of Otobothrium Linton, 1890 (Cestoda: Trypanorhyncha), including new records from Australia, New Caledonia and Malaysia, with the description of O. parvum n. sp., Zootaxa 1587, pp. 1-25 : 14-17

Otobothrium carcharidis (Shipley & Hornell, 1906) Pinter, 1913

( Figs. 30–40 )

Syn. Tentacularia carcharidis Shipley & Hornell, 1906 .

Types: NHMV 2089, V3317.

Type host: Carcharhinus melanopterus (Quoy & Gaimard, 1824) .

Type locality: Dutch Bay, Sri Lanka ( Ceylon), 5. i. 1905, coll. J. Hornell.

Site in host: spiral valve.

Material examined: From Carcharhinus melanopterus (Quoy & Gaimard, 1824) : types; 1 specimen, Darwin Harbour, NT, Australia ( SAM 29089); from Carcharhinus amblyrhynchoides (Whitley, 1934) : 17 specimens, Snapper Island, Qld, Australia ( SAM 29092); from Carcharhinus limbatus (Valenciennes, 1839) : 1 specimen, Nickol Bay, WA, Australia ( SAM 29095); from Carcharhinus sorrah (Valenciennes, 1839) : 1 specimen, Nickol Bay, WA, Australia ( SAM 29090); 1 specimen, Balgal, Qld, Australia ( SAM 29091); 6 specimens off Mukah, Sarawak, Malaysia ( USNPC 99237); 15 specimens, off New Caledonia, from 3 sharks ( MNHN JNC 2105A1–A5; JNC 2106A1–A7; JNC 2107A1); from Lamiopsis temmincki (Müller & Henle, 1839) : 8 specimens off Mukah, Sarawak, Malaysia ( USNPC 99271, MZUM 575); from Rhizoprionodon acutus (Rüppell, 1837) , 1 specimen, Nickol Bay, WA, Australia ( SAM 29094); 40 specimens, off Sarawak, Malaysia ( USNPC 99274-5, MZUM 576-7); from Scoliodon laticaudus Müller & Henle, 1838: 2 specimens (BO-41) off Mukah, Sarawak, Malaysia ( USNPC 99272, MZUM 574); from Sphyrna lewini (Griffith & Smith, 1834): 1 specimen, Nickol Bay, WA, Australia ( SAM 29093); 2 specimens, off New Caledonia ( MNHN JNC 2108A1–A2).

Re-description: Longest cestode 12.8 mm, maximum width 200, with 25 segments; terminal segment mature. Scolex craspedote, 440–620 (522, n=10) long; widening posteriorly, maximum width in mid-region of pars bulbosa 60–90 (73, n=10), in region of pars bulbosa 190–270 (220, n=10). Two bothria, not extending to anterior extremity of bulbs; pars bothrialis 190–230 (210, n=10) long, width of bothria 160; paired bothrial pits present on posterior margin of bothria, 10–15 (13, n=10) in diameter. Pars vaginalis longer than pars bothrialis, 300–510 (393, n=10) long; tentacle sheaths straight in anterior part, sinuous or almost straight anterior to bulbs. Bulbs ovoid, 100–130 (109, n=10) long, 50–70 (63, n=10) wide; prebulbar organ absent; retractor muscle originates in anterior part of bulb; pars post-bulbosa absent; bulbs splayed around pars proliferans scolecis, velum formed by bulbs variable, 0–90 (30, n=10).

Everted tentacles up to 50 long; slight basal swelling evident in some tentacles only; diameter at base 18– 25 (21, n=10), diameter in distal region 10–20 (15, n=10). Metabasal armature heteroacanthous, atypical, heteromorphous; hooks hollow. Hook files begin on bothrial surface of tentacle, terminate on antibothrial surface; 7 hooks per row; space present between hook files 1 and 1’ on bothrial surface of tentacle. Hooks 1(1’) large, uncinate, with broad base, 6.5–8.3 (7.2, n=5) long, base 5.3–7.7 (6.5, n=5) long; hooks 2(2’), erect, with broad blade and relatively long base, 6.5–8.3 (7.2, n=5) long, base 4.7–5.9 (5.4, n=5) long; hooks 3(3’) shorter, falcate, with shorter base, 4.7–6.5 (5.7, n=5) long, base 3.0–4.7 (3.8, n=5); hooks 4(4’) shorter, with smaller bases, 4.1–5.3(4.5, n=5) long, base 1.8–2.4 (2.2, n=5) long; hooks 5(5’) short, spiniform, 4.1–5.3 (4.6, n=5) long, base 0.9–1.5 (1.2, n=5) long; hooks 6(6’), 7(7') short, spiniform, 2.4–3.5 (3.0, n=5) long, base 0.6– 1.2 (0.8, n=5) long; single intercalary hook between each principal row (a), spiniform, 3.0–4.1 (3.8, n=5) long, base 1.2–1.5 (1.3, n=5) long. Distinctive basal armature present; initial files of hooks spiniform, concentrated on bothrial surface, hooks 2.1–4.1 (3.4, n=5) long, base 0.6–1.2 (0.8. n=5) long; bothrial surface with 6 pairs of plate-like hooks, slender and bill-hooked in lateral views, linguiform in dorso-ventral views, 6.5–10.6 (8.9, n=5) long, base 3.5–5.3 (4.1, n=5) in width. Antibothrial surface with file of large uncinate hooks 5.9–7.1 (5.5,

Mature segments elongate, acraspedote, 1.05–2.28 (1.60, n=5) mm long, maximum width 120–180 (156, n=5); segment length: width ratio 8.9–17.5 (12.4, n=5); genital pores alternate irregularly, 450–660 (530, n=5) from posterior end of segment. Deeply staining areas anterior and posterior to genital atrium. Hermaphroditic sac thin-walled, 100–110 (106, n=4) long, 65–110 (80, n=4) wide. Cirrus joins vagina in distal part of hermaphroditic sac; cirrus corrugated, muscular, unarmed, leads to small internal seminal vesicle at proximal pole of hermaphroditic sac; external seminal vesicle absent. Vas deferens coils posteriorly to ovarian isthmus. Testes intervascular, arranged in two columns, in single layer throughout medulla, not reaching anterior part of segment; testes 30–38 (35, n=5) long, 15-20 (17, n=5) wide; total number of testes per segment 57-66 (62, n=5), with 19–23 (21, n=5) post-ovarian and 38–44 (41, n=5) prevaginal; no testes between ovary and genital atrium. Vagina penetrates proximal pole of hermaphroditic sac, then runs posteriorly to ovarian isthmus; seminal receptacle absent. Ovary bilobed in dorso-ventral view, lobes in best developed segment 200 long, 70 wide; Mehlis’ gland posterior to ovarian isthmus, c. 50 in diameter. Vitelline follicles circum-medullary, 23– 33 (28, n=10) in diameter. Uterine duct coils anteriorly from Mehlis’ gland to level of hermaphroditic sac; uterus extends from this point to anterior quarter of segment, not reaching anterior extent of testes; uterine pore absent. Ventral osmoregulatory canal c. 15 in diameter.

Remarks. Beveridge & Campbell (1998) redescribed the single mounted type specimen of this species, confirming Pintner's (1913) decision to allocate the species to the genus Otobothrium . Their redescription established that the species was valid based on a distinctive basal armature with elongate slender bill-hooks on the tentacle. However the redescription was limited by the fact that only limited views of the metabasal armature were available, with none of the external surface and that the only mature segments which could be illustrated appeared to have very few testes. The present redescription, based on an extensive series of specimens, allows a more precise description of the species to be given.

The features of the basal armature described by Beveridge & Campbell (1998) are confirmed, but the slender "bill-hooks" described by them proved to be, in dorso-ventral views, plate-like hooks ( Fig. 39 ) observed in no other species of the genus. On the opposing surface of the tentacle, there are very broad, obliquely oriented hooks which appear in some views to be directed anteriorly, unlike the remaining hooks. The precise features of these hooks could not be determined. The basal armature of this species is complex and difficult to interpret using light microscopy. Unfortunately, very few of the numerous specimens available had tentacles sufficiently well everted to be able to examine the armature using scanning electron microscopy. In the metabasal region, Beveridge & Campbell (1998) described seven hooks in each principal row with two intercalary hooks (a and b). However, they were not able to examine the antibothrial surface of the tentacles. In the new material, there are seven hooks in each principal row but with a single intercalary hook (a) per row. This arrangement was only determined when views of the antibothrial surface of the tentacle were available. Hook b of Beveridge & Campbell (1998) is in fact hook 7 of the opposing row, but without clear views of the antibothrial surface, this feature is not apparent.

The single specimen redescribed by Beveridge & Campbell (1998) had few testes. This may be an abnormality as the new specimens had approximately 20 post-ovarian and 40 pre-ovarian testes, but none between the ovary and the genital atrium, a distinguishing feature of this species. In addition, an hermaphroditic sac was present, as found in congeners, but not noted Beveridge & Campbell (1998). Although an extensive series of specimens was available, few were mature and none was gravid. It is assumed therefore that this species is hyperapolytic.

The new collections extend the host range of the species extend its geographical to Malaysia, New Caledonia and Australia. The hosts are all members of the families Carcharhinidae and Sphyrnidae .

Figures

FIGURES 30 – 34. Otobothrium carcharidis (Shipley & Hornell, 1906). 30, Entire worm. 31, Scolex, dorso-ventral view. 32, Scolex, lateral view. 33, Mature segment. 34, Terminal genitalia. Scale-bars: Fig. 30, 0.5 mm; Figs. 31 - 34, 0.1 mm.

FIGURES 35 – 40. Otobothrium carcharidis (Shipley & Hornell, 1906). Tentacular armature. 35, Metabasal armature, bothrial surface. 36, Metabasal armature, external surface. 37, Metabasal armature, antibothrial surface. 38, Transition from basal to metabasal armature, external surface, bothrial surface on right hand side. 39, Oblique view of basal region of tentacle (slightly twisted), showing blade-like structure of hooks on bothrial surface. 40, Basal region, external surface, bothrial surface on right hand side. Scale-bar: 0.01 mm.