Holorchis gigas, Bray, Rodney A. & Cribb, Thomas H., 2007

Bray, Rodney A. & Cribb, Thomas H., 2007, Holorchis gigas n. sp. (Digenea: Lepocreadiidae) from the yellow-striped sweet-lips Plectorhinchus chrysotaenia (Perciformes: Haemulidae) from Lizard Island, Great Barrier Reef, with observations on Aephnidiogenes major, Zootaxa 1517, pp. 63-68 : 65

Holorchis gigas n. sp.

( Figs 1–2 )

Type-host: Plectorhinchus chrysotaenia (Bleeker, 1855) , Haemulidae , yellow-striped sweet-lips.

Type-locality: Lizard Island (14°40’S, 145°28’E; Dec., 2000).

Site: Intestine.

Prevalence: 1 of 4 (25%).

Type-specimens: holotype QM G223057, paratypes, QM G223058, BMNH 2006.11.8.148.

Etymology: The specific name refers to the unusually large size of these worms, gigas = giant (Latin).

Description: Based on 2 complete specimens and 1 with posterior extremity removed for DNA sequencing. Measurements in Table 1 . Body elongate, very large ( Figure 1 ). Tegument spinous to level of uterus, sparse in hindbody. Pre-oral lobe distinct. Oral sucker subglobular, subterminal. Ventral sucker rounded, in anterior fifth of body. Prepharynx short. Pharynx doliiform, with sphincter-like circular musculature distally. Oesophagus short. Intestinal bifurcation in mid-forebody. Caeca long, narrow, terminate blindly near posterior extremity.

Testes 2, irregularly oval, tandem, widely separated in about middle of hindbody. External seminal vesicle long, convoluted, reaches dorsal to about mid-level of ventral sucker. Cirrus-sac oval, thin-walled with distinct layer of gland-cells between outer wall and male-duct. Internal seminal vesicle long, slightly undulating, with thickened muscular wall ( Figure 2 ). Pars prostatica vesicular, subglobular, with thick wall, lined with anuclear cell-like bodies. Ejaculatory duct short, muscular, protruded as short cirrus into genital atrium. Genital atrium distinct, thick-walled. Genital pore submedian, distinctly separated from ventral sucker.

Ovary irregular oval, pre-testicular, but may overlap anterior testis slightly, separated from anterior testis by bulk of uterus, fairly close to ventral sucker. Seminal receptacle curved, broadly claviform. Laurer’s canal opens dorsally to Mehlis’ gland. Mehlis’ gland antero-medial to ovary. Uterus intercaecal reaches anteriorly from anterior testis, narrows at level of ovary. Metraterm of similar length to cirrus-sac, runs dorsally to cirrus-sac, distinct, but not thick walled. Eggs tanned, operculate, extremely numerous. Vitellarium follicular; fields reach just anteriorly to ovary and close to posterior extremity, mainly lateral, dorsal and ventral to caeca, encroaching but not confluent between testes, virtually confluent dorsally and ventrally in post-testicular region.

Excretory pore terminal. Excretory vesicle I-shaped, passes sinistrally to posterior testis and dextrally to anterior testis, presumably terminates dorsally to uterus.

Figures

FIGURES 1 – 3. 1 – 2. Holorchis gigas n. sp. 1. Ventral view of holotype, uterus in bold outline. 2. Terminal genitalia, with part of ventral sucker outlined. 3. Aephnidiogenes major Yamaguti from Diagramma labiosum, Heron Island, terminal genitalia, with ovary and part of ventral sucker outlined. Scale bars: 1, 2 mm; 2, 3, 500 μm.