Hypocreadium toombo, Bray, Rodney A. & Justine, Jean-Lou, 2006

Bray, Rodney A. & Justine, Jean-Lou, 2006, Hypocreadium toombo n. sp. (Digenea: Lepocreadiidae) in the yellow­spotted triggerfish Pseudobalistes fuscus (Perciformes: Balistidae) and additional lepocreadiids parasitizing fishes from the waters off New Caledonia, Zootaxa 1326, pp. 37-44 : 38-41

Hypocreadium toombo n. sp. ( Figs 1–2 )

Type­host: Pseudobalistes fuscus (Bloch & Schneider) , Balistidae , yellow­spotted triggerfish.

Site: Intestine.

Type­locality: Récif Toombo , New Caledonia (22°26’S, 166°33’E, 13/12/2005).

Type­specimens: Holotype MNHN JNC1680–D1; paratypes, MNHN JNC1680 D2–5, BMNH 2006.8.23.1–5.

Note on the host: the specimen studied was 55 cm in total length, the maximum recorded for this species ( Randall 2005; Froese & Pauly 2006), and 4.7 kg in weight.

Prevalence: 50%, 1/2, intensity 20; a second, smaller (30 cm, 0.80 kg) fish, caught at Ilôt Signal, off Nouméa, 30/05/2006, did not harbour this digenean.

Etymology: This species is named after the reef from where the host was collected.

Description: Based on 10 specimens. Body almost circular, slightly longer than wide, flattened, distinct anterior notch present, 1,572–2,310 × 1,446–2,160 (2,026 × 1,863); width 89.3–97.4 (92.0) % of body­length ( Figure 1 ). No tegumental spines seen. Pre­oral lobe distinct, 27–54 (36) long. Oral sucker subglobular, with ventral aperture, 124–173 × 138–188 (149 × 167). Ventral sucker rounded, equatorial, 178–264 × 188–260 (230 × 228). Sucker­length ratio 1:1.32–1.78 (1.54); sucker­width ratio 1:1.14–1.49 (1.36). Forebody 651–983 (860) long, 40.7–44.5 (42.4) % of body­length. Prepharynx not seen. Pharynx broadly oval, 85–131 × 94–134 (109 × 117). Pharynx/oral sucker ratio 1:1.37–1.53 (1.43). Oesophagus distinct, 84–157 (111). Intestinal bifurcation in midforebody, 308–463 (402) from ventral sucker. Caeca narrow, irregularly arcuate around gonads, converge posteriorly, then turn anteriorly, terminating just posterior to testes; nearest approach to posterior extremity 282–556 (368).

Testes 2, irregularly oval, symmetrical, 234–362 × 211–345 (316 × 272), in anterior hindbody, separated by 165–260 (220). Post­testicular region 529–782 (663) long, 28.7–35.3 (32.7) % of body­length. External seminal vesicle bi­ or tripartite, at level of ventral sucker, 145–389 × 71–145 (230 × 112). Cirrus­sac large, 417–632 × 195–251 (541 × 222), claviform, reaching from point dextro­lateral to ventral sucker diagonally across posterior forebody, surrounded by gland­cells; length 23.9–29.6 (26.7) % of body­length. Internal seminal vesicle oval, in proximal end of cirrus­sac. Pars prostatica large, vesicular, folded, lined with large anuclear cell­like bodies ( Figure 2 ). Ejaculatory duct muscular, long, complexly folded, lined with tessellated surface of distinct protruding bosses, becoming larger distally. Genital atrium distinct. Genital pore just sinistral to intestinal bifurcation or just post­bifurcal, 247–399 (337) from ventral sucker.

Ovary more or less oval, intertesticular, 172–257 × 130–196 (214 × 162), usually contiguous with sinistral testis, but separated by up to 38, separated by uterus from dextral testis, 12–92 (36) from ventral sucker. Post­ovarian region 528–820 (675) long, 30.9–35.5 (33.3) % of body­length. Seminal receptacle large, saccular, between sinistral testis and ventral sucker. Laurer’s canal opens dorsally to ovary or between ovary and closest testis. Mehlis’ gland anterior to ovary. Uterus passes between ovary and dextral testis into postovarian region, then anteriorly, narrowing dorsally to ventral sucker, then widens to form metraterm. Metraterm passes anteriorly, with thick muscular wall and sheath of glandcells, often dilated with eggs, 442–708 (587) long. Post­uterine distance 407–613 (506), 22.9–26.5 (25.0) % of body­length. Eggs tanned, operculate, 63–79 × 33–39 (70 × 36). Vitellarium follicular; follicles numerous, surround gonads, well separated from bodymargins, contiguous or nearly so pre­bifurcally, contiguous or not immediately postbifurcally where follicles may form continuous narrow band dorsal to terminal genitalia, contiguous posteriorly, lateral, dorsal and median to caeca but not ventral; previtelline distance 194–287 (256), 8.97–14.9 (12.7) % of body­length; post­vitelline distance 157–252 (208), 7.72–11.4 (10.3) % of body­length.

Excretory pore dorsal to posterior extension of uterus, between caeca. Extent of vesicle obscured by eggs, arms of excretory system reach into forebody laterally to level of oesophagus or pharynx.

Figures

FIGURES 1 – 2. Hypocreadium toombo n. sp. 1. Ventral view of holotype, uterus in bold outline. 2. Terminal genitalia. Abbreviations: Ej, Ejaculatory duct; Ep, Excretory pore; Esv, External seminal vesicle; Isv, Internal seminal vesicle; Mt, Metraterm; Ov, Ovary; Pp, Pars prostatica; T, testis; Ut, Uterus. Scale bars: 1, 1 mm; 2, 200 μm.