Pseudopecoeloides atherinomori, Aken'Ova & Cribb & Bray, 2009

Aken'Ova, Thelma, Cribb, Thomas & Bray, Rodney, 2009, Seven species of Pseudopecoeloides Yamaguti, 1940 (Digenea, Opecoelidae) from temperate marine fishes of Australia, including five new species, ZooKeys 5 (5), pp. 1-32 : 22-24

Pseudopecoeloides atherinomori Aken’Ova, Cribb & Bray, sp. n.

urn:lsid:zoobank.org:act:F5CF0AD3-5D8E-4C2B-BD09-FBF75D31088B

Type-host: Atherinomorus ogilbyi (Whitley) ( Atherinidae , Atheriniformes ), Ogilby’s hardyhead.

Type-locality: Moreton Bay, South-East Queensland, 27°20′S, 153°07′E, March 1989.

Other localities: Off Dunwich, Stradbroke Island ; 27°30′S, 153°24'E, January and November 1994; Off Bribie Island, South-East Queensland 27°00′S, 153°05′E .

Site: Intestine.

Material studied: Ex Atherinomorus ogilbyi : 6 from Moreton Bay; 2 from off Dunwich, Stradbroke Island, (one of the specimens was unmounted and sectioned after measuring); 1 from off Bribie Island from a pooled gut-wash.

Type-material: Holotype: Queensland Museum, Reg. No. QM G 230489, paratypes: Queensland Museum , Reg. Nos. QM G 230490 - 230494, BMNH Reg. Nos 2008.12.9.28-29.

Description (Figures 15-18): Based on 6 gravid, 2 immature laterally mounted specimens, 1 dorso-ventrally mounted specimen and 1 set of sagittal serial sections. Measurements are of 6 gravid, unflattened, laterally mounted worms.

Body elongate, slender, subcylindrical; maximum width in region of gonads, 1,312 -2,155 (1,677) × 146-194 (176); width to length ratio 1:7.5-12.1 (9.6). Oral sucker ventrally subterminal to nearly terminal, spherical to subspherical, 84-130 (106) × 84-120 (104). Ventral sucker larger than oral sucker, spherical to subspherical, on very short peduncle; peduncle forms wrinkles around ventral sucker in dorsoventrally mounted worm, 117-175 (142) × 117-149 (134); sucker width ratio 1:1.2- 1.4 (1.3). Forebody relatively short, contains numerous large and small gland cells, 214-292 (258) long, 13.3-20.7 (15.8) % of body length. Prepharynx distinct, short.

Pharynx large, subspherical, with numerous gland cells along posterior margin, 62-84 (70) × 71-100 (85); pharynx to oral sucker width ratio 1:1.2-1.4 (1.2). Oesophagus moderately long, surrounded by gland cells. Intestinal bifurcation, dorsal to ventral sucker, 13-48 (32) posterior to anterior margin of ventral sucker. Caeca long, open into excretory vesicle close to posterior extremity to form uroproct.

Testes 2, entire, elongate-oval, usually separate, occasionally contiguous (n=1), tandem, in posterior half of body; anterior 91-188 (142) × 61-143 (101); posterior 97- 240 (162) × 71-123 (102). Post-testicular area 233-810 (431) long, 17.8-37.6 (25.0) % of body length. Cirrus-sac absent. Seminal vesicle naked, long, tubular, sinuous to convoluted at anterior end, elongate and saccular at posterior end, extends from region of intestinal bifurcation to point posterior to ventral sucker. Pars prostatica distinct, surrounded by gland cells. Ejaculatory duct moderately long, thick-walled, surrounded by gland cells. Genital atrium doliiform, thick-walled. Genital pore sinistrally submedian, anterior to intestinal bifurcation, level with or slightly anterior to anterior margin of pharynx, 96-144 (121) from anterior end, 5.9-9.9 (7.3) % of body length.

Ovary pre-testicular, entire, subspherical, 75-143 (100) × 65-113 (85). Mehlis’ gland distinct, antero-dorsal to ovary. Uterine seminal receptacle present. Laurer’s canal distinct, long, convoluted, thick-walled, opens at point dorso-sinistral to ovary. Uterus coils between anterior margin of ovary and region of posterior margin of ventral sucker, runs without coiling alongside anterior portion of seminal vesicle to unite with ejaculatory duct close to genital pore. Metraterm distinct. Eggs large, oval, operculate, 52-72 (62) × 26-46 (37). Vitelline follicles extend from 318-459 (389) from anterior extremity, 19.6-31.5 (23.7) % of body length, to 13-39 (28) from posterior extremity; fields confined to hindbody extending from about level of posterior margin of ventral sucker almost to posterior extremity, confluent dorsally and ventrally in post-testicular area, with follicles lateral, ventral, and dorsal to caeca.

Excretory pore terminal. Excretory vesicle I-shaped; narrow terminal portion surrounded by gland cells; vesicle widens and passes anteriorly to terminate at about mid-body.

Etymology: The species name is derived from Atherinomorus Fowler, 1903 the host genus.

Comments: The nature of the caecal ends in this species is very difficult to discern. The caeca appear to terminate blindly in the single dorso-ventrally mounted specimen, whereas they clearly open into the excretory vesicle in one of the eight laterally mounted specimens. Madhavi (1975) and Bray (1987) also had trouble in determining the relationship between the caeca and the excretory vesicle in a related species. This is discussed in the footnote attached to P. scomberi . Although Bray (1987) suggested that sectioning would solve the problem, it did not do so in the present material. However, we have concluded that the present species has a uroproct, based on observations on the single laterally mounted specimen (Figure 18).

Pseudopecoeloides atherinomori sp. n. can be accommodated in Group B ( Table 2 ): P. akule has a smaller ventral sucker and pharynx relative to the oral sucker. P. scomberi is slightly more elongate, with a width to length ratio of 1:12.8 versus 1:7.5-12.1 (9.6); it also has a smaller ventral sucker and pharynx relative to the oral sucker and a shorter forebody relative to the body length ( Table 2 ). P. atherinomori sp. n. resembles P. lesteri sp. n. in most metrical features but can be distinguished from the latter by its shorter forebody and slightly longer post-testicular area relative to the body length. Furthermore, the anterior limit of the vitelline follicles in P. atherinomori is about level with the posterior margin of the ventral sucker peduncle, whereas it is about half-way between the anterior margin of the ovary and the posterior margin of the ventral sucker peduncle in P. lesteri sp. n. P. atherinomori sp. n. also resembles P. carangis in its vitelline distribution and in some metrical features, but the latter has a smaller ventral sucker and a smaller pharynx relative to the oral sucker.

Figures

Figs 1-3. Pseudopecoeloides tenuis Yamaguti, 1940 ex Priacanthus macracanthus. 1. Whole-mount lateroventral view. 2. Terminal genitalia. 3. Ventral view of posterior end showing uroproct. Scale bars: 1, 500 µm; 2, 200 µm; 3, 100 µm.

Figs 4-6. Pseudopecoeloides hickmani sp. n. ex Pseudocaranx wrighti. 4. Whole-mount latero-ventral view. 5. Terminal genitalia. 6. Ventral view of posterior end showing uroproct. Scale bars: 4, 1mm; 5, 200 µm; 6, 100 µm.

Figs 7-9. Pseudopecoeloides lesteri sp. n. ex Pseudocaranx dentex. 7. Whole-mount latero-ventral view. 8. Terminal genitalia. 9, Ventral view of posterior end showing uroproct. Abbreviations: ms, muscular structure; pc, prostatic cells; gc, gland cells. Scale bars: 7, 250 µm; 8, 9, 100 µm.