Hypocreadium patellare Yamaguti, 1938 Typical

Bray, Rodney A., Cribb, Thomas H. & Justine, Jean-Lou, 2009, New observations on the genus Hypocreadium Ozaki, 1936 (Digenea: Lepocreadiidae) in the Indo-West Pacific region, including the description of one new species, Zootaxa 2110, pp. 22-40 : 23-28

Hypocreadium patellare Yamaguti, 1938 Typical form

( Figures 2–4 )

Hosts: Abalistes stellatus (Anonymous) , Balistidae , starry triggerfish; Sufflamen fraenatum (Latreille) , Balistidae , masked triggerfish; Balistoides viridescens (Bloch & Schneider) , Balistidae , titan triggerfish. Site: Intestine.

Localities: A. stellatus, Swain Reefs (21°53’S, 152°21’E, Feb. 2001); S. fraenatum, Ningaloo (22°42’S. 113°40’E, Aug. 2003), inside Lagoon, facing Récif Toombo , New Caledonia (22°32'S, 166°27'E, 06/11/2007) and shallow, interior Lagoon near Récif Toombo , New Caledonia (22°33'S, 166°29'E, 20/11/2008); B. viridescens, Lizard Island (14°40’S, 145°28’E, April 2006).

Prevalences: A. stellatus 1 of 1; S. fraenatum Ningaloo 1 of 3 (33%) and New Caledonia 5 of 7 (71%); B. viridescens 1 of 1.

Voucher specimens: A. stellatus , QM G 230520 – 230526, BMNH 2009.2.12.36–41; S. fraenatum, Ningaloo , QM G 230527, New Caledonia, MNHN JNC 2372–1, JNC 2373–1–3, JNC 2374–1–3, JNC 2761–1, JNC 2762–1, BMNH 2009.2.12.27,42–46; B. viridescens , QM G 230528 – 230532, BMNH 2009.2.12.31–35.

Description: Measurements in Tables 1 and 2. Body usually slightly longer than wide, but almost circular and with a distinct anterior notch. No tegumental spines seen. Pre-oral lobe usually distinct. Oral sucker oval, aperture subterminal. Ventral sucker oval, with long axis at angle to equator of body, occasionally rounded, just pre-equatorial. Prepharynx usually not evident. Pharynx oval. Oesophagus distinct. Intestinal bifurcation in mid-forebody. Caeca narrow, irregularly arcuate around gonads, converge posteriorly, extremities usually pointed posteriorly.

Testes 2, irregularly oval, symmetrical, in anterior hindbody, well separated. External seminal vesicle saccular, at level of ventral sucker. Cirrus-sac large, claviform, reaching from point dextro-lateral to ventral sucker diagonally across posterior forebody, reaches over left caecum; surrounded by scattered gland-cells. Internal seminal vesicle oval. Pars prostatica bipartite, folded, lined with large anuclear cell-like bodies. Ejaculatory duct muscular, long, folded, lined with pavement [or carpet] of cobble-stone like small bosses. Genital atrium distinct. Genital pore sinistral at level of anterior part of oesophagus.

Ovary more or less oval, intertesticular or almost completely post-testicular, closest to and often slightly separated from sinistral testis and separated from dextral testis. Seminal receptacle large, saccular, between sinistral testis and ventral sucker. Laurer’s canal opens dorsally to ovary, sinistral testis or between. Mehlis’ gland anterior to ovary. Uterus usually passes between ovary and dextral testis into post-ovarian region, then anteriorly, narrowing dorsally to ventral sucker, then widens to form metraterm. Eggs tanned, operculate. Metraterm passes anteriorly, with thick muscular wall and distinct sheath of gland-cells, often dilated with eggs. Vitellarium follicular, follicles numerous, surround gonads, well separated from body-margins, contiguous and reaching to midway between caecal termination and posterior extremity posteriorly, separated and reaching to about pharyngeal level anteriorly, lateral and median to caeca.

Excretory pore dorsal to uterus, post-testicular. Vesicle division not seen, arms narrow, reach to level of oesophagus.

Remarks: These specimens look very similar to that described as Hypocreadium patellare by Bray & Cribb (1998) from the balistid, the halfmoon triggerfish, Sufflamen chrysopterum (Bloch & Schneider) , from Heron Island, in particular in the distinct anterior notch. Machida & Kuramochi (1999) redescribed, but did not illustrate, H. patellare from the type-host, the monacanthid the thread-sail filefish, Stephanolepis cirrhifer (Temminck & Schlegel) , and stated that the genital pore is ‘at bifurcal level’. We have found the genital pore to be almost always at the level of the anterior part of the oesophagus, similar to that in the original description and illustration of Yamaguti (1938) and in Bray & Cribb (1998). Machida & Kuramochi (1999) also described a single specimen under the same name and from the same host with the genital pore at the ‘postpharyngeal level’. This specimen, they reckon, has features intermediate between H. patellare and H. scaphosomum ( Manter, 1940) which now differ only in egg-size (63–81 × 33–43 vs. 51–56 (occasionally up to 66) × 32–24 (occasionally 26), respectively). The egg-size in our specimens fits that of H. patellare . H. scaphosum is not described with an anterior notch.

Abalistes stellatus was reported as the host of Hypocreadium patellare from the Red Sea by Parukhin (1989), but it has not previously been reported from this host in Australian waters, nor did we find it in two A. stellatus from New Caledonia. The reports from Sufflamen fraenatum from Ningaloo and New Caledonia are new host and locality records. This worm is distinct from the specimen of H. cavum reported in this host species from Heron Island ( Bray & Cribb 2002) in being more nearly circular (rather than distinctly wider than long) and having a much less well-developed glandular sheath around the terminal genitalia. We are not aware of a previous report of a lepocreadiid from B. viridescens . One specimen from B. viridescens has an almost post-testicular ovary, no post-ovarian uterus, a rounded ventral sucker and a genital pore at the bifurcal level. It may a teratological specimen or represent a different species.

Figures

FIGURES 1 – 2. 1. Hypocreadium cavum Bray & Cribb, 1996, ex Abalistes stellatus, Swain Reefs, ventral view, uterus in bold-outline. 2. Hypocreadium patellare Yamaguti, 1938, typical form, ex Abalistes stellatus, Swain Reefs, ventral view, uterus in bold-outline. Scale-bars: 1, 2, 500 μm.

FIGURES 3 – 4. Hypocreadium patellare Yamaguti, 1938, Typical form. 3. ex Sufflamen fraenatum, Ningaloo Reef, ventral view, uterus in bold-outline. 4. ex Balistoides viridescens, Lizard Island, ventral view, uterus in bold-outline. Scale-bars: 3, 4, 500 μm.

Tables

TABLE 1: Dimensions of Hypocreadium cavum and H. patellare Typical forms

Species	Hypocreadium cavum	Hypocreadium patellare	Hypocreadium patellare
Form		Typical	Typical
Host	Abalistes stellatus	Abalistes stellatus	Sufflamen fraenatum
Locality	Swain Reefs	Swain Reefs	Ningaloo
n	5	12	1
Length	1,922–2,430 (2,291)	905–1,687 (1,293)	1,379
Width	2,092–2,698 (2,453)	898–1,572 (1,265)	1,419
Forebody	846–1,081 (1,012)	355–764 (539)	544