Seven species of Pseudopecoeloides Yamaguti, 1940 (Digenea, Opecoelidae) from temperate marine fishes of Australia, including five new species

Seven species of Pseudopecoeloides Yamaguti, 1940, including fi ve new are described from marine fi shes in the waters off the coasts of Queensland and both Western and South Australia. Th e new species are Pseudopecoeloides hickmani sp. n. from Pseudocaranx wrighti, Pseudopecoeloides lesteri sp. n. from Pseudocaranx dentex and Pseudocaranx wrighti, Pseudopecoeloides arripi sp. n. from Arripis georgianus, Pseudopecoeloides atherinomori sp. n. from Atherinonmorus ogilbyi and Pseudopecoeloides hafeezullahi sp. n. from Trachurus novaezealandiae. Pseudopecoeloides scomberi Hafeezullah, 1971, which was transferred to Opecoeloides Odhner, 1928 by Madhavi (1975), is reported from Scomberoides lysan and returned to Pseudopecoeloides. Pseudopecoeloides tenuis Yamaguti, 1940 is reported from a new host species, Priacanthus macracanthus. Th e Carangidae is the dominant host family for species of Pseudopecoeloides, followed by the Mullidae, Priacanthidae and Champsodontidae.

Pseudopecoeloides is a well established genus, containing elongate and slender worms with a pedunculate, non-papillate ventral sucker and a uroproct.All nominal species conform to this concept, except Pseudopecoeloides equesi Manter, 1947.P. equesi was described as bearing fi ve distinct papillae on its ventral sucker and, in his original discussion, Manter (1947) thought that it could well represent a new genus.Th is species was transferred to Dactylomyza by Aken'Ova (2003).Yamaguti (1971) listed ten species of Pseudopecoeloides, but later when Bartoli et al. (2003) devised a key to the species, they included 18 species.Th ese are listed below in our discussion of our division of the genus into two groups.
Th e data presented below are for seven species recovered from temperate marine fi shes in Australian waters.Fishes of four families are reported as hosts for these species, four from the Carangidae (trevallies, horse mackerel and queenfi sh) and one each from the Priacanthidae (big-eyes), Arripididae (ruff ) and Atherinidae (hardyheads).

Materials and methods
Fish hosts discussed in this study were collected, mainly by angling or seining, from various sites in Moreton Bay in southeastern Queensland, around Fremantle, Coogee and Woodman Point in Western Australia and off Kangaroo Island, South Australia.Opecoelids were collected live from fi sh as soon as they had died or been anaesthetised.Th e worms were washed in cold saline, then fi xed in hot saline and preserved in 5% formalin.Whole-mounts were prepared by staining in Mayer's acid haematoxylin, dehydrating in ethanol, clearing in methyl salicylate and then mounting in Canada balsam.Because of their pedunculate ventral sucker, the worms were mounted laterally or ventro-laterally.Measurements were taken using a computerised digitising system similar to that described by Roff and Hopcroft (1986) and recorded in micrometres as ranges followed by the means in parentheses.Th e length of the forebody was taken from the anterior extremity of the body to the lateral margin of the ventral sucker peduncle.In laterally mounted worms, the greatest dimension across the oral and ventral suckers was taken as the width and the depth as the length.Th e length of the ventral sucker peduncle was taken from the distal extremity to its point of attachment to the body.Figures were prepared with the aid of a drawing tube mounted on an Olympus BH2 microscope.Abbreviations: BMNH, the British Museum (Natural History) Collection at the Natural History Museum, London, UK; QM, Queensland Museum Collection, Brisbane, Australia.Yamaguti, 1940 Host: Priacanthus macracanthus Cuvier (Priacanthidae: Perciformes), red bigeye.Localities: Moreton Bay: Off Tangalooma 27°14'S, 153°19'E; off Shorncliff e 27°21'S, 153°07'E.Site: Pyloric caeca, intestine.Material studied: 11 adults.Moreton Bay, Queensland: 6 off Tangalooma, February 1993; 5 off Shorncliff e, March and April 1995.Voucher specimens: QM G230433-G230441; BMNH 2008.12.9.44-50.
Excretory pore terminal.Excretory vesicle tubular, I-shaped, passes anteriorly to terminate at point just anterior to posterior margin of ovary.
Comments: Except for a few slight morphological diff erences, the present material is almost identical to P. tenuis, as originally described.Th e diff erences observed between the present material and that of Yamaguti (1940) include: a longer forebody relative to the body length (6.6-10.4(8.7) versus 5.1%); smaller eggs measuring 39-54 × 25-34 (47 × 28) versus 54-60 × 33-39; and a genital pore which is more posteriorly situated, at 3.8-6.1 (5.1) % compared with 3.1% of the body length from the anterior extremity.Although the diff erence in egg size is signifi cant, it is not surprising, since Yamaguti measured the eggs from live worms.Th e other diff erences are most likely as a result of fi xation and may therefore not be taxonomically signifi cant.Moreover, the present material and Yamaguti's are both from priacanthids.
Pseudopecoeloides tenuis is similar to P. tenuoides in almost every metrical feature and in the bilateral constrictions adjacent to the gonads observed in Yamaguti's material and the present material.Th is resemblance was also noted by Martin (1960), but he separated the species on the basis of egg size (smaller in P. tenuoides), the sizes of the suckers (smaller in P. tenuoides) and on the occurrence of pads on the ventral sucker in P. tenuoides.Th e present material is very similar to P. tenuoides and does not exhibit the diff erences observed by Martin (1960) between his worm and Yamaguti's P. tenuis.Th e diff erence in egg size probably resulted from the fact that Yamaguti measured the eggs of P. tenuis from live material, whereas the egg measurements of P. tenuoides were probably taken from permanent mounts.Th e only noticeable diff erences between the present material and P. tenuoides are that the latter has a larger oral sucker relative to the pharynx, refl ected by a ratio of 1:2.8 versus 1:1.5-2.4 (1.9) [1.8], and it has pads in its ventral sucker.Yamaguti (1970) also observed the pads described by Martin (1960) in P. tenuoides in the material he examined from the glasseye Heteropriacanthus cruentatus (Lacepède) (Priacanthidae) (the type-host) and the bluelined surgeonfi sh Acanthurus nigroris Valenciennes (Acanthuridae) off Hawaii (type-locality).No similar pads were observed in the present material, although, if they occurred, it would have been diffi cult if not impossible to see them, since our worms were mostly mounted laterally.Th is feature needs to be investigated further before a decision regarding the status of P. tenuoides can be taken.
Excretory pore terminal to slightly dorsally subterminal.Excretory vesicle I-shaped, long, tubular, reaches anteriorly to overlap posterior margin of ovary, terminates at point anterior to mid-body.
Etymology: Th is species is named for V. V. Hickman in recognition of his contribution to the systematics of marine digeneans in the Australian region.
Comments: Specimens of Pseudopecoeloides hickmani sp.n. have an oral sucker greater than the ventral sucker, placing the species in Group A. It can be distinguished from members of this group as follows: it has a greater length/width ratio than P. tenuis, P. psettodi, P. capucini and P. wekeula; and it has a smaller pharynx than P. tenuis, a larger pharynx than P. psettodi, P. capucini and P. wekeula, relative to the size of the oral sucker (Table 1).Th e ventral sucker peduncle in the new species is longer than that of P. tenuis relative to the length of the forebody; its forebody is shorter and its post-testicular area longer relative to the length of the body than those of P. wekeula and P. capucini.P. hickmani sp.n. closely resembles P. opelu in most of its metrical features and by the fact that they are both from carangids, but it can be distinguished from the latter by its more elongate form with a width to length ratio of 1:17 versus 1:11, a slightly larger pharynx with a pharynx to oral sucker width ratio of 1:1.5 versus 1:1.8 and a longer post-testicular area measuring 31.4-37.1 (34.9) versus 21.3% of the body length.Other host: Pseudocaranx wrighti (Whitley) (Carangidae: Perciformes), skipjack trevally.
Excretory pore terminal.Excretory vesicle I-shaped, long; posterior extremity forms short narrow duct surrounded by gland cells; vesicle reaches to ovary.
Etymology: Th is species is named for Professor R. J. G. Lester for his contributions to marine parasitology.
Comments: Th e specimens from Pseudocaranx wrighti are almost identical to those from P. dentex in general appearance and in all metrical features (Tables 2, 3) and are considered to be conspecifi c.
Excretory pore terminal.Excretory vesicle I-shaped, long; posterior end forms narrow duct surrounded by gland cells; broader anterior portion extends anteriorly to about mid-body overlapping posterior half of ovary dorsally.
Etymology: Th is species is named after Arripis Jenyns, 1840 the host genus.
Comments: Th e material off South Australia is similar to that off Western Australia; however, a few diff erences worth noting were observed.Th e specimens from Western Australia are generally larger than those from South Australia, with a slightly longer forebody, but the ventral sucker of the latter is larger relative to the oral sucker.Th e most signifi cant of these diff erence is the diff erence in the size of the ventral sucker, which may relate to the allometric growth of the worms, although it is possible that diff erent species are involved.Pseudopecoeloides arripi sp.n. can be accommodated in Group A and distinguished from the other species in the group by being less elongate than P. tenuis and P. hickmani sp.n. but more elongate, as shown by the width to length ratio, with a longer post-testicular area than P. psettodi, P. capucini and P. wekeula (Table 1), and by having a shorter post-testicular region than P. tenuis, relative to the body length.Th e new species has a forebody shorter than P. capuccini and P. wekeula but longer than P. tenuis, P. psettodi and P. hickmani sp.n. relative to the body length, and a larger pharynx relative to the oral sucker than P. tenuis and P. psettodi.Furthermore, P. arripi sp.n. has larger eggs than P. hickmani sp.n. and its body tapers only slightly and ends abruptly in a rounded posterior end, whereas in the latter it tapers gradually to a rather pointed extremity.P. arripi sp.n. is closest to P. opelu but can be distinguished from it by its slightly larger pharynx to oral sucker width ratio of 1:1.4-1.8 (1.5) versus 1:1.8 and its longer post-testicular region relative to the body length.Th ese two species can further be separated by the more anterior position of the intestinal bifurcation in the new species, being at the level of the anterior margin of the ventral sucker peduncle rather than as it is in P. opelu.
Because the size of the pharynx of Pseudopecoeloides arripi sp.n. and P. opelu overlap, the main basis for separating these two species is the non-overlapping size of the post-testicular region, which we consider to be signifi cant in species of Pseudopecoeloides.In addition, it is noteworthy that P. opelu is known only from a carangid, the mackerel scad Decapterus macarellus, off Hawaii (Yamaguti, 1970).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.
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: Th e species name is derived from Atherinomorus Fowler, 1903 the host genus.
Comments: Th e nature of the caecal ends in this species is very diffi cult to discern.Th e 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.Th is 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.2008.12.9.31-43. Description (Figures 19-22): Description based on 11 gravid, unfl attened, laterally and dorso-ventrally mounted specimens and 1 immature specimen.Measurements are of 10 gravid, unfl attened, laterally mounted worms.
Etymology: Th is species is named for M. Hafeezullah in recognition of his contribution to the taxonomy of opecoelids.
Comments: Pseudopecoeloides hafeezullahi sp.n. fi ts the concept of Group A. It can be distinguished immediately from other species in the group by having the largest pharynx relative to the oral sucker, but it can further be diff erentiated as follows (Table 1).P. tenuis and P. hickmani sp.n. are more elongate species with shorter forebodies and longer post-testicular areas relative to the length of the body; additionally, P. hickmani sp.n. has a longer forebody relative to the body length.P. capucini and P. wekeula are less elongate with slightly shorter forebodies, P. psettodi has a shorter forebody and post-testicular area relative to the body length and P. wekeula has a cirrus-sac whereas P. hafeezullahi sp.n. does not.Th e new species is quite similar to P. opelu and P. arripi n. sp, but it can be distinguished by the longer post-testicular area compared with P. opelu, the slightly longer forebody than P. arripi sp.n. and by the longer ventral sucker peduncle, all relative to the body length (Tables 1, 4). or sections.Bray (1987) also examined two whole-mounted museum specimens of this species from the barred queenfi sh S. tala (Cuvier) off India, and two specimens from S. tol off Malaysia, but could not detect a uroproct.Madhavi (1975) stated that "the ends of the caeca establish close contact with the bladder but apparently do not open into it".We interpret Madhavi's observation to mean that she was still not quite certain as to the presence or absence of a uroproct.
Th e specimen from Scomberoides lysan is almost identical in every metrical feature and in general appearance to those described by Hafeezullah (1971) from S. tol, except as follows.Th e vitelline follicles in the present material are interrupted bilaterally in areas adjacent to the gonads, whereas they are continuous in Hafeezullah's material, although, in his fi gure of the worm, the vitelline follicles thin out around the gonads.Hafeezullah's worms are also much larger than the present material, being 6,828-7,056 × 504-583 compared with 3,088 × 288 (Table 2).Since the present report is based on a single specimen, it was not possible to assess variation in the vitelline distribution or size in this species.Th e "inconspicuous cirrus-sac" observed by Hafeezullah (1971) in P. scomberi was not seen in the present material.Although the occurrence of a vestigial cirrus-sac is not characteristic of most species of Pseudopecoeloides, it does not preclude the inclusion of P. scomberi in the genus, since it was observed by Yamaguti (1970) in some specimens of P. akule and in P. wekeula.Madhavi (1975) considered Hafeezullah's material to be a species of Pseudopecoelus but, because of the observations we have made regarding the caecal ends in the present material (Figure 24) and the fact that these worms are practically indistinguishable morphologically, we are treating the present material and Hafeezullah's as conspecifi c.Moreover, their hosts are congeners.Th e presence of a uroproct necessitates the return of this species to Pseudopecoeloides.

Discussion
Th e above descriptions of fi ve new species brings the total of species in this genus to 23 and creates the opportunity for some review of host-specifi city within the genus.Firstly, it must be stated that it is unlikely that all the existing records in the literature are correct.It is striking that there are at least eight families and about 20 species of fi shes reported as hosts for Pseudopecoeloides carangis and, although it is possible, this contrasts with the much narrower specifi city reported for most other species.Most probably identifi cation has been made several times on the basis of a broad similarity rather than a precise determination.Secondly, it is clear that the Carangidae is the dominant host family for species of Pseudopecoeloides; 11 of the species are reported from this family.Th e Mullidae (fi ve species), Priacanthidae (three species) and Champsodontidae (three species) are also relatively rich.Finally, there are now fi ve fi sh species that are reported to harbour at least two (and up to 3) species of Pseudopecoeloides: Carangidae -Pseudocaranx wrighti and Selar crumenophthalmus; Champsodontidae -Champsodon capensis; Mullidae -Parupeneus macronema; and Priacanthidae -Cookeolus boops and Heteropriacanthus cruentatus.In some cases these multiple infections may be pointers to possible synonymy but also to a possible rapid evolutionary expansion among certain host groups.
vesicle close to posterior extremity to form uroproct.Excretory pore terminal.Excretory vesicle I-shaped, overlaps ovary dorsally to point just anterior to its posterior margin.

Table 1 .
Pseudopecoeloides species (not immediately distinguishable from the other species) in Group A -Species with oral sucker larger than ventral sucker.Ex Pseudocaranx dentex: 4 off Kingscote; ex Pseudocaranx wrighti: 2 off North Mole.Pseudocaranx dentex and P. wrighti and 1 set of sagittal serial sections.Measurements are based on 3 gravid, unfl attened, laterally mounted specimens from P. dentex; measurements of worms from P. wrighti are given in Table3.
* values derived from measuring published fi gures directly or calculated from published measurements.Site: Intestine.Material studied:

Table 2 .
Pseudopecoeloides species (not immediately distinguishable from the other species) in Group B -Species with the oral sucker the same size as or smaller than the ventral sucker.

Table 3 .
Measurements of two specimens of Pseudopecoeloides lesteri sp.n. from Pseudocaranx wrighti off North Mole, Western Australia.