Bucephalidae (Digenea) from epinephelines (Serranidae: Perciformes) from the waters off New Caledonia, including Neidhartia lochepintade n. sp.

Many bucephalid species, mainly of the subfamily Prosorhynchinae, have been described from epinepheline serranids (groupers) throughout the World’s Oceans. In this paper eight named prosorhynchine species are described and/or illustrated from epinepheline fishes from New Caledonia. Neidhartia lochepintade n. sp. in Epinephelus chlorostigma differs from other Neidhartia spp. in various combinations of distinct body-size, rhynchus size, previtelline and pre-mouth distance, post-testicular distance, cirrus-sac reach and egg-size. Other species are: Neidhartia haywardi Bott, Miller & Cribb, 2013 in Plectropomus leopardus; Neidhartia tyleri Bott, Miller & Cribb, 2013 in Plectropomus leopardus and Plectropomus laevis; Prosorhynchus freitasi Nagaty, 1937 in Plectropomus leopardus and Plectropomus laevis; Prosorhynchus robertsthomsoni Bott & Cribb, 2009 in Cephalopholis argus; Prosorhynchus longisaccatus Durio & Manter, 1968 in Cephalopholis urodeta, Epinephelus areolatus, Epinephelus cyanopodus and Epinephelus maculatus. Prosorhynchus luzonicus Velasquez, 1959 and Prosorhynchus sp. B. in Epinephelus coioides; Prosorhynchus serrani Durio & Manter, 1968 in Variola albimarginata and Variola louti; Prosorhynchus sp. A in Epinephelus morrhua; Prosorhynchus sp. immature in Epinephelus coeruleopunctatus. The new combination Neidhartia longivesicula (Bilqees, Khalil, Khan, Perveen & Muti-ur-Rehman, 2009) (Syn. Prosorhynchus longivesicula) is formed. Evidence from this paper and earlier molecular studies indicates that there are numerous morphologically similar prosorhynchine species in serranids, most of which show a high degree of host-specificity.


Materials and methods
Digeneans were collected live, immediately fixed in nearly boiling saline and then transferred to 80% ethanol. Whole mounts were stained with Mayer's paracarmine, cleared in beechwood creosote and mounted in Canada balsam. Measurements were made through a drawing tube on an Olympus BH-2 microscope, using a Digicad Plus digitising tablet and Carl Zeiss KS100 software adapted by Imaging Associates, and are quoted in micrometres. The following abbreviations are used: BMNH, British Museum (Natural History) Collection at the Natural History Museum, London, UK; MNHN JNC, Muséum National d'Histoire Naturelle, Paris, France.
Use has been made of the visual key to Prosorhynchus developed by Bray & Palm [6]. (http://www.nhm.ac.uk/ bray2009) and a similar key to the genus Neidhartia recently devised by us. We use the term ''cirrus-sac reach'' for the distance from the anterior-most extremity of the cirrus-sac to the posterior extremity of the body as a percentage of the bodylength.

Description
Based on 10 whole-mount preparations. Measurements and ratios in Table 1. Body fusiform, widest at about mid-body (Figures 1, 2). Tegument spinous; spines squamous, tiny, reach to posterior extremity. Rhynchus broad, relatively short and blunt. Mouth at about level of ovary, distinctly in post-equatorial half of body. Pharynx small, globular. Caecum oval, directed anteriorly.
Excretory pore terminal; anterior extent of vesicle obscured by eggs.

Discussion
The features that distinguish N. lochepintade from previously described Neidhartia species are discussed below; comparative metrical data in Table 2.
Neidhartia epinepheli Bott & Cribb, 2009, based on two specimens from the intestine of the highfin grouper Epinephelus maculatus (Bloch) (Serranidae) off Lizard Island on the Great Barrier Reef [2], has a relatively larger rhynchus and a longer previtelline distance. In N. epinepheli the uterus reaches anterior to the vitellarium. Other probably differences are the pre-mouth distance, post-testicular region and cirrus-sac reach.
Neidhartia ghardagae Nagaty, 1937, based on 16 specimens from a ''Serranus sp.'' from off Ghardaga in the Red Sea [29], has a relative larger rhynchus, longer previtelline distance and longer pre-mouth distance and probably a shorter post-testicular region and a shorter cirrus-sac reach.
Neidhartia haywardi Bott, Miller & Cribb, 2013, based on 10 specimens and ITS2 sequence from Plectropomus leopardus, P. laevis and the spotted coralgrouper P. maculatus (Bloch), from Heron and Lizard Islands on the Great Barrier Reef [3] has a bigger rhynchus, longer previtelline distance and shorter post-testicular distance.
Neidhartia mcintoshi Velasquez, 1959, based on two mature and four immature specimens from the muscle, stomach and intestine of the duskytail grouper Epinephelus bleekeri (Vaillant) (Serranidae) off Malabon, Rizal, Luzon Island, Philippines [48], has a longer pre-uterine extent, and probably a relatively larger rhynchus, shorter pre-mouth distance and shorter cirrus-sac reach. In connection with unusual sites of infection given, Velasquez [48] stated that the ''present species occurs as metacercaria and adult in the same host, showing evidence that infection of one fish is brought about possibly through the eating of the smaller fish by the larger''.
Neidhartia plectropomi Bott, Miller & Cribb, 2013 based on 10 specimens and ITS2 sequence from Plectropomus leopardus and P. laevis from Heron and Lizard Islands on the Great Barrier Reef [3] has a bigger rhynchus and longer previtelline distance.
Neidhartia tyleri Bott, Miller & Cribb, 2013 based on 10 specimens and ITS2 sequence from the Plectropomus leopardus, P. laevis and P. maculatus, from Heron and Lizard Islands on the Great Barrier Reef [3] is narrower, with longer previtelline and pre-mouth distances, shorter post-testicular distance and cirrus-sac reach, and larger eggs.
Pseudoprosorhynchus hainansis Shen, 1990, based on two specimens from the intestine of the Plectropomus leopardus off Hainan Island, southern China [41] is similar to Neidhartia lochepintade (and indeed the whole genus) in that the ovary is between the testes, but the rhynchus is disc-like, and the worm is long and narrow. It also appears to have a short cirrus-sac reach and smaller eggs.
These data, and the record from this deep-water serranid, indicate to us that the specimens described here belong to a new species. Prosorhynchus epinepheli Yamaguti, 1939 has been reported twice from this host, from off Tuticorin, India [18] and from the Arabian Gulf [40]. The illustrations in both papers show that the ovary lies partly anterior to and partly overlapping the anterior testis, and thus do not indicate that the worm in question is a Neidhartia. The Indian record [18] is from several host species and it is not stated from which the illustrated worm was collected. E. chlorostigma has also been listed as a host for unnamed Prosorhynchus spp. in the Arabian Gulf [11,39].
As discussed below, the generic status of Prosorhynchus epinepheli and P. longisaccatus is ambiguous as often the ovary does not lie distinctly anteriorly to the testes, suggesting that they may be Neidhartia spp. Comparison of data in Tables 2  and 6 indicates that the rhynchus is relatively much larger in P. epinepheli and P. longisaccatus. The pre-uterine distance tends to be larger in P. longisaccatus, but overlaps considerably.

Description
Based on five whole-mount preparations. Measurements and ratios in Table 1. Body widest at about mid-body ( Figure 3). Tegument spinous; spines squamous, tiny, reach to posterior extremity. Rhynchus broad, conical or bluntly conical. Mouth just posterior to ovary, well into post-equatorial half of body. Pharynx small, globular. Caecum oval, directed anteriorly.
Testes 2, irregularly oval, oblique, in about mid-body, usually well separated. Cirrus-sac elongate, more-or-less parallel sided, reaching to or almost to anterior testis, anteriorly to pharynx. Seminal vesicle elongate-oval, in proximal cirrus-sac. Pars prostatica long, in two distinct parts; proximal part narrow, coiled over seminal vesicle; distal part, wider, straighter, surrounded by dense layer of gland-cells, lining of filaments in chevron arrangement. Ejaculatory duct narrow, opening on large, complex genital lobe inside genital atrium. Genital atrium large. Genital pore distinctly separated from posterior extremity.
Ovary oval, intertesticular, overlapping testes. Mehlis' gland overlapping ovary and posterior testis. Details of proximal female system obscured by eggs. Uterus reaches anteriorly to vitelline fields, occasionally to level of vitellarium, fills much of available space to level of genital pore. Eggs numerous, tanned, operculate. Metraterm not detected, obscured by eggs. Vitellarium consists of two lateral fields of 12-15 follicles, more or less symmetrical, but with one field slightly longer than other, anterior extremity posterior to rhynchus and anterior extent of uterus, reaches anterior to caecum and gonads; posterior extremity at about level of ovary.
Excretory pore terminal; anterior extent of vesicle obscured by eggs.

Discussion
This form appears to be N. haywardi or N. plectropomi differing only in the previtelline distance, as calculated from the illustration [3, Figure 3], but it should be noted that in both species Bott et al. [3] found that the extent of the vitellarium was obscured by the uterus. N. haywardi and N. plectropomi are sister species according to the molecular study of Bott et al. [3]. We consider our specimens to be P. haywardi as the egg-sizes more nearly coincide (Table 2), but the cirrus-sac reach of our specimens tends to be greater than is apparent in either species. Both P. haywardi and P. plectropomi are reported from P. leopardus and P. laevis, and from Heron and Lizard Islands on the Great Barrier Reef.
The features distinguishing this species from its congeners can be seen in Table 2, and two further species are not easily distinguished, namely N. neidharti Nagaty, 1937 and N. epinepheli Bott & Cribb, 2009. N. neidharti was first reported in Serranus sp. locally known as ''Nagil'' from the Red Sea [29]. According to Froese & Pauly [15] this common name refers to the squaretail coralgrouper Plectropomus areolatus (Rüppell) or the roving coralgrouper P. pessuliferus (Fowler). It seems clear, therefore, that it is a parasite of Plectropomus. Chauhan [7] recorded, but did not describe, this species in Belone sp. (Beloniformes: Belonidae) from Mumbai (Bombay), India. As unlikely as this combination of hosts is, its putative hosts associations become even more puzzling when the record by Maurya et al. [27] in the freshwater long-whiskered catfish Sperata (= Mystus) aor (Hamilton) (Siluriformes: Bagridae) from Uttar Pradesh, India is considered. We are discounting the Indian records of this species. N. neidharti apparently grows to a much greater size than N. plectropomi, although there is room for confusion. In Nagaty's [29] description (p. 119) the length range is given as 561-908, whereas in the table of measurements (p. 166) the length is given as 842-2,112 (vs. 658-744 (715) for P. haywardi). This confusion also applies to width where, using the data from the description, the range is 24-27% and in the table it is 11-29% of body-length (vs. 20-24%). The body-width in Nagaty's Figure 56 is about 24% of the body-length. The pre-mouth distance may be greater than in N. haywardi.  Nagaty, 1937, in that its uterus extends past the posterior margin of the rhynchus. N. epinepheli differs by having a caecum that does not extend into the anterior third of the body and the eggs are smaller, 25-26 · 12-13, compared with 30 · 15 for N. neidharti (see Nagaty, 1937)''. The confusion in the egg-size as given by Nagaty [29] for N. neidharti, in that he gives the egg-size as 30 · 15 in the text, but 19-29 · 15-19 in the table may well invalidate one of Bott & Cribb's [2] distinctions. The other distinction is rather minor and it may be found that these species are synonymous. The pre-uterine distance is shorter than in N. haywardi in that the uterus overlaps the rhynchus.

Description
Based on seven whole-mount preparations from P. leopardus and six from P. laevis. Measurements and ratios in Table 1. Body fusiform, widest in posterior third (Figures 4,5). Tegument spinous; spines squamous, tiny, reach to posterior extremity. Rhynchus broad, with narrow conical posterior extension. Mouth at about level of ovary or just posterior, well into post-equatorial half of body. Pharynx small, globular. Caecum elongate-oval, directed anteriorly.
Testes 2, irregularly oval, oblique to tandem, in about mid-body, slightly separated or not. Cirrus-sac elongate, more-or-less parallel sided, reaching anterior testis, anteriorly to pharynx. Seminal vesicle elongate-oval, in proximal cirrussac. Pars prostatica long, in two distinct parts; proximal part narrow, coiled over seminal vesicle; distal part, wider, straighter, surrounded by dense layer of gland-cells, lining of filaments in chevron arrangement. Ejaculatory duct narrow, opening on large, complex genital lobe inside genital atrium. Genital atrium large. Genital pore distinctly separated from posterior extremity.

Discussion
We have identified the larger Neidhartia specimens as belonging to N. tyleri. Most morphological characters are similar (Table 2), but the eggs in our specimens from P. leopardus (the type-host of N. tyleri) are distinctly smaller than those described for this species [3] and our specimens from P. laevis. This species is readily distinguished from most described species (Table 2). N. neidharti is not distinguishable from the specimens from P. laevis in major features of the visual key and differs from the P. leopardus specimens only in rhynchus length ( Table 2). This feature probably distinguishes this form from N. neidharti as the P. laevis specimens do not overlap in this feature. Comparison with N. neidharti as described by Nagaty [29] is problematical as the measurements given in the description and table do not coincide, but our specimens are very distinct from the illustrated specimen [28, Figure 56] in shape (relatively more elongate, although the measurements in the table do not bear this out), the previtelline distance and pre-uterine distance.
N. coronata Durio & Manter, 1968, described from ''Serranidae, probably Epinephelus sp.'' from off New Caledonia [9], differs from our specimens in the visual key in the pre-uterine distance and cirrus-sac reach. It should be borne in mind, however, that Durio & Manter [9] stated that their description was ''based on six somewhat macerated, extended specimens''. The previtelline distance may also be a distinguishing feature.

Discussion
Measurements and ratios are given in Table 3. This species is known only from Cephalopholis argus, the coral hind Cephalopholis miniata (Forsskål) and the bluespotted hind C. cyanostigma (Valenciennes) from off Heron and Lizard Islands on the Great Barrier Reef [2,3]. Using the visual key our specimens align with four species, in addition to P. robertsthomsoni. Distinctions are tabulated in Table 4.
Prosorhynchus aguayoi Vigueras, 1955 from the greater soapfish Rypticus saponaceus (Bloch & Schneider) (Serranidae) from off Cuba, Curaçao and Jamaica [30,31,50] is a very similar species to P. robertsthomsoni but is probably wider and more fusiform, with a longer post-testicular region. The vitellarium reaches the testes in P. aguayoi and the cirrussac does not.
Prosorhynchus jexi (syn: P. epinepheli of Durio &Manter (1968)) from the longfin grouper Epinephelus quoyanus (Valenciennes) (Serranidae) from the Great Barrier Reef [2,9] differs from P. robertsthomsoni in the more restricted uterus. Bott & Cribb [2] considered that the reach of the uterus anterior to the vitellarium is a distinctive feature of P. robertsthomsoni but our observations indicate that this does not always occur ( Figure 6). The cirrus-sac does not reach the testes in P. jexi.
Prosorhynchus serrani Durio & Manter, 1968 (syn: Prosorhynchus crucibulus of Nagaty (1937)) from the yellow-edged lyretail Variola louti (Forsskål) (Serranidae) from the Red Sea and off New Caledonia [9,29] is very similar to P. robertsthomsoni but apparently has a distinctly different shaped rhynchus, in that it has a distinct narrow elongate posterior extension in contrast to the blunt rounded posterior of the P. robertsthomsoni rhynchus. It may be that the vitellarium reaches slightly more posteriorly in P. serrani in that the follicles extend just posterior to the pharynx, rather than just to the pharynx (see below).
Prosorhynchus tsengi Tsin, 1933 is a parasite of the bartail flathead Platycephalus indicus (Linnaeus) (Platycephalidae) off China [42,47]. Bray & Palm [6] pointed out that the ''original illustration of P. tsengi by Tsin [47, Figure 8] shows a lobed rhynchus, apparently with an aperture, and a straight pars prostatica, indicating that the species may in fact belong to the genus See Tables 3 and 5 for measurements and ratios based on 52 specimens. Ovary in variable position relative to testes: preovarian distance is greater than the pre-testicular distance in the specimen from C. urodeta, in 13 of 16 from E. areolatus, 8 of 13 from E. cyanopodus and 10 of 22 from E. maculatus.

Discussion
Our study of this species is based on 52 measured specimens. In our visual key only four species showed no non-overlapping features with our specimens, namely P. atlanticus,    (Table 6). We consider that our specimens conform to the species P. longisaccatus, a species originally reported from a ''leche'', a serranid from off New Caledonia [9]. Later, we [5] considered our specimens from E. cyanopodus as this species and then [19] reported E. areolatus, and E. maculatus as hosts; all these reports are from New Caledonia. In the latter paper we reported the specimen from C. urodeta as Prosorhynchus sp. Prosorhynchus atlanticus Manter, 1940 is an Atlantic species, originally described in the serranids, the black grouper Mycteroperca bonaci (Poey), the gag Mycteroperca microlepis (Goode & Bean) and the yellowfin grouper Mycteroperca venenosa (Linnaeus) off Florida [25]. The ovary is, apparently, always pre-testicular, the uterus almost never reaches anteriorly to ovary (only slightly in 1 of 29) and the cirrus-sac reach is generally smaller ( Table 6).
Prosorhynchus epinepheli Yamaguti, 1939 was originally described from the Hong Kong grouper Epinephelus akaara (Temminck & Schlegel) (Serranidae) from the Inland Sea of Japan [52]. The name has been widely used subsequently for Prosorhynchus specimens from serranids [8], although some may be misidentified. P. longisaccatus is closely similar to P. epinepheli. We believe that either P. epinepheli or P. longisaccatus is the most appropriate identification, particularly as the variable position of the ovary, which is anterior to (and overlapping) the testes or between the testes in our specimens is similar to that described for both of these species. Yamaguti [52] described the position of the ovary in P. epinepheli as ''overlapping right testis or entirely on its dorsal side (in the type it lies anterodorsal to the right testis, but may be dorsal, dorsolateral or posterodorsal to it)''. Durio & Manter [9] found that in P. longisaccatus the ovary is ''to the right of, or partly posterior to, anterior testis''. This sheds some doubt on the generic classification of the worm, the variation of which includes a characteristic feature of the genus Neidhartia Nagaty, 1937, which according to Overstreet & Curran [33] is ''Ovary at level between testes''. Durio & Manter [9] compared their new species to P. epinepheli, using Yamaguti's [52] original description and new material reported from the honeycomb grouper Epinephelus merra Bloch, 1793 off Heron Island, southern Great Barrier Reef. It should be noted, however, that Bott & Cribb [2] examined one of Durio & Manter's ''P. epinepheli'' specimens and considered that it belonged to their new species P. jexi, and that the host was most probably not E. merra, but the similar species, the longfin grouper Epinephelus quoyanus (Valenciennes), which is much commoner in the waters around Heron Island (see also [20]). Durio & Manter [9] summarised the differences between P. epinepheli and P. longisaccatus as ''(1) the uterus does not extend even to midatrial level, whereas in all specimens of P. epinepheli it extends postatrially; (2) the rhynchus is wider, and the arrangement of muscles at its anterior edge gives a distinctive appearance''. The first distinction probably relies just on the amount of eggs produced and the second is rather vague and difficult to assess. It seems quite possible that these species are synonymous. There appear to be no morphological criteria for separating these species and we are recognising this species based on the locality of collection, and expect the status of this worm to be elucidated or at least clarified by molecular studies at present in progress.
Prosorhynchus lafii Bott & Cribb, 2009 from the brownmarbled grouper Epinephelus fuscoguttatus (Forsskål) from off Heron Island, Great Barrier Reef [2] differs from P. longisaccatus in the vitelline fields which are ''tight lateral clusters at level of caecum''. It is probably a more slender worm than P. longisaccatus ( Table 6). The ovary is anterior to, but overlapping, the anterior testis.
Suriano & Martorelli [45] reported P. longisaccatus in the Remo flounder Oncopterus darwinii Steindachner (Pleuronectidae) off Buenos Aires Province, Argentina. It is larger than previously described for this species, with a shorter post-testicular region and cirrus-sac reach, and probably a shorter rhynchus (Table 6). In agreement with Etchegoin et al. [12] we believe that these worms are not conspecific with the worms from serranids in the Pacific Ocean.

Description
It should be noted that the uterus reaches anteriorly beyond the ovary. Measurements and ratios are given in Table 7.

Discussion
Prosorhynchus serrani is known previously only from the yellow-edged lyretail Variola louti (Forsskål) (Serranidae) from the Red Sea and off New Caledonia [9,29]. Our specimens appear indistinguishable from those described by these authors.
This species is very similar to several other species and their relationships will probably only be resolved by molecular means. However, there seem to be minor morphological features which may allow the continued recognition of the Variola parasites as distinct (Table 8). Of those with no distinction in the parameters used in the visual key two can immediately be distinguished by other features.
P. attenuatus Siddiqi & Cable, 1960 from the Atlantic bumper Chloroscombrus chrysurus (Girard) (Carangidae) off Puerto Rico was described with a ''spherical, suckerlike'' rhynchus and it certainly looks like a sucker in the illustration. The pars prostatica is described as ''tubular'' and appears straight in the illustration [43], thus indicating that it may have been placed in the wrong subfamily.
Other similar species are: Prosorhynchus caballeroi Gupta & Ahmad, 1976 known from one specimen from the shrimp scad Alepes djedaba (Forsskål) (as Caranx kalla Cuvier) (Carangidae) in the Bay of Bengal [17] grows larger than P. serrani, with a smaller rhynchus and a longer previtelline distance.
Prosorhynchus conorjonesi Bott & Cribb 2009 from the barramundi cod Cromileptes altivelis (Valenciennes) (Serranidae) on the Great Barrier Reef [2] grows larger than P. serrani, is much narrower, with a more anterior mouth and a shorter cirrus-sac reach.
Prosorhynchus jexi has a more anterior mouth than P. serrani and a longer post-testicular region [2,9].
Prosorhynchus thapari Manter, 1953 was based on 17 specimens from the spotted coralgrouper Plectropomus maculatus (Bloch) (Serranidae) from off Fiji [26]. We can detect no morphological distinctions from P. serrani and retain the species as separate based on host distinction, and the knowledge that as yet unpublished studies indicate some specificity and cryptic speciation in the genus. Nevertheless, it may well be that this is the oldest valid name for this species.
Prosorhynchus truncatus Verma, 1936 is based on two specimens, one ovigerous and lost and the other without eggs, from the intestine of the river catfish Cephalocassis jatia (Hamilton) (as Arius j.) (Ariidae) off Puri, Bay of Bengal [49]. It has a more posteriorly situated mouth and a shorter cirrus-sac reach.  Table 9 measurements, Table 10 comparisons. In terms of the parameters used in the visual key there are no differences between our specimens from Plectropomus laevis and Prosorhynchus freitasi as described from ''Serranus guttatus'' from the Red Sea [29]. According to Froese & Pauly [15] S. guttatus is now known as the peacock hind Cephalopholis argus (Bloch) (Serranidae). It has also been reported in Epinephelus sp. and the spotted coralgrouper Plectropomus maculatus (Bloch) (Serranidae) from off New Caledonia [9] and Plectropomus leopardus and Plectropomus laevis from the Great Barrier Reef [3]. It has an unusual morphology in that all the internal organs are restricted to the posterior half of the body and the rhynchus is relatively small.

Prosorhynchus freitasi
Bott et al. [3] described six Prosorhynchus species from Plectropomus spp. on the Great Barrier Reef, five of which are new and one, P. freitasi already known. They are mostly distinguished by minor morphological characters and by analysis of ITS2 rDNA sequences. P. lesteri is distinguished by its distinctly larger rhynchus. P. wrightae differs in the pre-uterine extent, being the only one of these species where the uterus extends well beyond the vitellarium anteriorly. P. heronensis also has a larger rhynchus, although not as large as in P. lesteri, and a distinct U-shaped seminal vesicle. In P. plectropomi the uterus extends to, or just anterior to the anterior extent of the vitellarium, apparently forcing the anterior follicles apart, breaking up the continuous arc found in other related species. P. munozae is a rather small worm, but with larger eggs. Our specimens agree closely with Bott et al.'s [3] description of P. freitasi. Velasquez, 1959 (Figures 15, 16) urn:lsid:zoobank.org:act:25F350A1-F852-4CA9-91D8-A28 8F9B3F7DD

Discussion
No species are identical to these two specimens according to the visual key (Tables 12, 13). As only one specimen is in good condition, the worms have not been described as new, but the very elongate rhynchus seems to be a distinguishing feature. Also note that the ovary lies beside the anterior testis.
One species, Prosorhynchus epinepheli, has one major distinguishing feature in the visual key, i.e., width (Table 13). Minor distinguishing features are the pre-mouth distance and the egg-size.

Conclusions
The molecular evidence presented by Bott et al. [3] indicated that there are many distinct, but very similar species of prosorhynchines in serranids, especially Epinephelus and Plectropomus. The morphological similarity of these forms has led to many problems in identification, and some unlikely combinations of hosts in the literature, as for example the quoted hosts for Neidhartia neidharti, which in addition to serranids, includes a belonid and a freshwater siluriform. Recent molecular studies of a wide range of digeneans have indicated that most species exhibit oioxenous or stenoxenous specificity and ''that no euryxenous host distribution should be accepted on the basis of morphology only'' [28]. Although it is dangerous to identify parasites solely on the basis of their hosts, consideration should be taken of the relatedness of the hosts and the geographical distribution.
Cribb et al. [8] discussed the digenean fauna of epinepheline serranids and found that Prosorhynchus was the commonest parasite, both in the Atlantic/Eastern Pacific region and the Indo-West Pacific Region, and is the only bucephalid genus which has ''apparently strongly radiated within the Epinephelinae''. Since that paper [8] our knowledge of epinepheline bucephalids has increased markedly [2,3,5] reinforcing that point, but suggesting that Neidhartia has also radiated, at least in the Indo-West Pacific region. The morphological distinctions between Prosorhynchus and Neidhartia are minor, but molecular evidence [3] indicates that these distinctions are reflected by the molecules. Those species of Prosorhynchus with a variable ovary configuration (e.g., P. epinepheli, P. longisaccatus) may invalidate this distinction, or may belong to either monophyletic genus.