Pseudorhabdosynochus venus n. sp. (Monogenea: Diplectanidae) from Epinephelus howlandi (Perciformes: Serranidae) off New Caledonia

Pseudorhabdosynochus venus n. sp. is described from specimens collected from the gills of Epinephelus howlandi off Nouméa, New Caledonia, South Pacific. The male sclerotised quadriloculate organ of P. venus, 61-101 microm in internal length, has an anterior chamber with a thin anterior wall, a very short cone and a short posterior tube. The sclerotised vagina, 50-67 microm in total length, is composed of an anterior open trumpet, an S-shaped canal, a tear-shaped principal chamber and a spherical accessory chamber; all parts are heavily sclerotised. The two squamodiscs have 10-11 rows of separate rodlets and no central closed row of rodlets. P. venus is differentiated from all other species of Pseudorhabdosynochus by the spectacular morphology of its sclerotised vagina. It is the first diplectanid described from E. howlandi.     

The ‘Pseudorhabdosynochus cupatus group’ (Monogenea: Diplectanidae) on Epinephelus fasciatus, E. howlandi, E. rivulatus and E. merra (Perciformes: Serranidae) off New Caledonia, with descriptions of Pseudorhabdosynochus cyathus n. sp. and P. calathus n. sp.

Pseudorhabdosynochus cupatus (Young, 1969) is characterised by small lamellosquamodiscs made up of central telescopic rings and peripheral rows of rodlets, and a sclerotised vagina in the shape of a thin-walled coiled tube with three accessory chambers. Two new species of Pseudorhabdosynochus are herein described from epinepheline fish off New Caledonia, South Pacific, and are considered part of the 'P. cupatus group'. P. cyathus n. sp. from Epinephelus howlandi has lamellosquamodiscs made up of four telescopic rings and four rows of separate rodlets; there are dorsal tegumental scales. This species was found only in young hosts; older hosts harbour P. venus Hinsinger & Justine, 2006. P. calathus n. sp. from Epinephelus rivulatus has lamellosquamodiscs made up of four telescopic rings and five rows of separate rodlets; the tegument is smooth. The three species, P. cupatus, P. calathus and P. cyathus, are strictly species specific; although morphologically very similar, they can be distinguished by features of the tegumental scales and measurements of the vagina and haptoral hard parts. P. melanesiensis (Laird, 1958) from E. merra is close to the 'P. cupatus group' according to the morphology of its sclerotised vagina but is distinguished by its squamodiscs which lack telescopic rings. Rare specimens found in E. merra are tentatively attributed to P. coioidesis Bu et al., 1999. A paratype of P. coioidesis is figured for comparison. E. merra, E. fasciatus, E. rivulatus and E. howlandi each have a Pseudorhabdosynochus species of the P. cupatus lineage: these are the dominant species in each host. In addition, E. merra, E. fasciatus and E. howlandi harbour a rare species of Pseudorhabdosynochus, respectively P. cf. coioidesis, P. caledonicus Justine, 2005 and P. venus; these rare species are morphologically unrelated to each other and to the 'P. cupatus group'.     

Species of Pseudorhabdosynochus Yamaguti, 1958 (Monogenea: Diplectanidae) from Epinephelus fasciatus and E. merra (Perciformes: Serranidae) off New Caledonia and other parts of the Indo-Pacific Ocean, with a comparison of measurements of specimens prepared using different methods, and a description of P. caledonicus n. sp.

Species of Pseudorhabdosynochus were studied from fresh specimens collected from Epinephelus fasciatus and E. merra off New Caledonia, South Pacific, and specimens deposited in Museums. Experiments on two species demonstrated that the sclerotised hollow organs, such as the quadriloculate male copulatory organ and the vagina, may show differences in measurements of up to 50% when flattened. P. caledonicus n. sp. is described from E. fasciatus in New Caledonia, on which it is relatively rare; it is distinguished on the basis of the quadriloculate organ, which has a very thin anterior wall, the sclerotised parts of the vagina in form of a straight tube with a star-shaped lateral structure, and the squamodiscs composed of 11 open rows of rodlets. P. cupatus (Young, 1969) is redescribed from abundant material from E. fasciatus off New Caledonia (new geographical record) and compared with paratype specimens from Australia (from E. fasciatus and E. merra) and specimens from E. fasciatus in the Red Sea (both herein redescribed and figured); a specimen was also found on a slide from E. merra off Vanuatu. P. melanesiensis (Laird, 1958) is redescribed from material from E. merra off New Caledonia (new geographical record) and compared with type-specimens (herein redescribed and figured) from the same host off Vanuatu. The structure of the sclerotised vagina in P. cupatus and P. melanesiensis is very similar, with a thin-walled tube and a heavily sclerotised structure with three loculi. P. vagampullum (Young, 1969) is redescribed from the paratypes from E. merra from Australia, but was not found in New Caledonia; specimens included among its paratypes (from E. merra in Australia), but different, are herein attributed to Pseudorhabdosynochus sp. 3. P. lantauensis (Beverley-Burton & Suriano, 1981) is redescribed from the paratype specimens from E. longispinis off Hong-Kong. A specimen found among the paratypes of P. cupatus belongs to a different species, herein designated as Pseudorhabdosynochus sp. 1. Specimens from E. longispinis off Hong-Kong, previously attributed to P. cupatus, are attributed to another species, Pseudorhabdosynochus sp. 2. The three species P. cupatus, Pseudorhabdosynochus sp. 1 and Pseudorhabdosynochus sp. 2 have in common a 'lamellosquamodisc' composed of central telescopic lamellae and peripheral rows of rodlets; they can be distinguished by the shape of the sclerotised vagina and measurements of the haptoral hard-parts. Specimens from E. longispinis off Hong-Kong, previously attributed to P. vagampullum, probably belong to a different species. Consequently, after these modified determinations, P. cupatus parasitises only E. fasciatus and E. merra, and P. melanesiensis and P. vagampullum parasitise only E. merra. With their wide geographical distribution and different species of Pseudorhabdosynochus in different localities, E. fasciatus and E. merra appear to represent excellent models for investigating monogenean biogeography in the Indo-Pacific Ocean.     

Diplectanids (Monogenea) parasitic on the gills of the coralgroupers Plectropomus laevis and P. leopardus (Perciformes, Serranidae) off New Caledonia, with the description of five new species and the erection of Echinoplectanum n. g.

Echinoplectanum n. g. is erected for diplectanids which have a male copulatory organ comprising a tubular sclerotised penis with a muscular reservoir at its proximal extremity and an protrusible cirrus, often with spiny ridges, at its distal extremity, and a female copulatory organ comprising a sclerotised vaginal sac, often with two thin tubes. All species have similar squamodiscs made of rows of rodlets, with the central rows forming closed circles, and haptoral parts with a similar shape but different measurements; they are distinguished on the basis of the size and morphology of the male copulatory organ and sclerotised vagina. Five new species are included in Echinoplectanum and are all parasites of coralgroupers, Plectropomus spp., off New Caledonia, South Pacific. Two are from P. laevis (Lacépède): E. laeve n. sp. (type-species) has a large elongate penis, 53[Formula: see text]m in length, a cirrus with spiny ridges and a spherical vagina with two long thin tubes; and E. chauvetorum n. sp. has a large elongate penis, 51[Formula: see text]m in length, a cirrus with thin spiny ridges, and a pear-shaped vagina with two short thin tubes. Three species are from P. leopardus (Lacépède): E. leopardi n. sp. has an elongate penis, 36[Formula: see text]m in length, an unspiny cirrus and a triangular vagina; E. pudicum n. sp. has a very small elongate penis 14[Formula: see text]m in length and no visible vagina; and E. rarum n. sp. has a short thick penis 18[Formula: see text]m in length and a ring-shaped vagina with two thin tubes. In addition, Diplectanum plectropomi Young, 1969, from P. maculatus off Western Australia, and D. echinophallus Euzet & Oliver, 1965 from Epinephelus marginatus in the Mediterranean Sea and Senegal, West Africa, both herein redescribed from the type-specimens, are transferred to Echinoplectanum, as E. plectropomi n. comb. and E. echinophallus n. comb., respectively. Six of the seven species of Echinoplectanum are parasitic in members of Plectropomus from the South West Pacific, but one (E. echinophallus) is a parasite of Epinephelus marginatus and has been recorded only from the Mediterranean and East Atlantic; it is suggested that Echinoplectanum is associated with Plectropomus, a basal genus among the epinephelines, and that host-switching to Epinephelus marginatus occurred, whose distribution extends from Europe to the Indian Ocean. Morphological characteristics of the copulatory organs suggest that a "chastity belt versus spiny penis" sperm competition pattern prevails in Echinoplectanum spp.     

Pseudorhabdosynochus venus n. sp. (Monogenea: Diplectanidae) from Epinephelus howlandi (Perciformes: Serranidae) off New Caledonia

Pseudorhabdosynochus venus n. sp. is described from specimens collected from the gills of Epinephelus howlandi off Nouméa, New Caledonia, South Pacific. The male sclerotised quadriloculate organ of P. venus, 61–101 μm in internal length, has an anterior chamber with a thin anterior wall, a very short cone and a short posterior tube. The sclerotised vagina, 50–67 μm in total length, is composed of an anterior open trumpet, an S-shaped canal, a tear-shaped principal chamber and a spherical accessory chamber; all parts are heavily sclerotised. The two squamodiscs have 10–11 rows of separate rodlets and no central closed row of rodlets. P. venus is differentiated from all other species of Pseudorhabdosynochus by the spectacular morphology of its sclerotised vagina. It is the first diplectanid described from E. howlandi.

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Résumé Pseudorhabdosynochus venus n. sp. est décrit à partir de spécimens collectés sur les branchies de Epinephelus howlandi, pêché au large de Nouméa, Nouvelle-Calédonie, Pacifique Sud. L’organe tétraloculé sclérifié mâle de P. venus (longueur interne 61–101 μm), possède une chambre antérieure avec une fine paroi antérieure, un cône très court, et un tube postérieur court. Le vagin sclérifié, long de 50–67 μm, est composé d’une trompette antérieure ouverte, d’un canal en S, d’une chambre principale en larme, et d’une chambre accessoire sphérique; toutes les parties sont fortement sclérifiées. Les deux squamodisques ont 10–11 rangées d’osselets séparés, sans rangée centrale fermée. P. venus se différencie de toutes les autres espèces de Pseudorhabdosynochus par la morphologie spectaculaire de son vagin sclérifié. Il s’agit du premier Diplectanidae décrit chez E. howlandi.

     

Four species of Pseudorhabdosynochus (Monogenea: Diplectanidae) from the camouflage grouper Epinephelus polyphekadion (Perciformes: Serranidae) off New Caledonia

Gill diplectanid monogeneans from the camouflage grouper Epinephelus polyphekadion (Bleeker) collected in the coral reef lagoon of New Caledonia, South Pacific, comprise four species. Very few monogeneans were found in most fish examined. Pseudorhabdosynochus dionysos n. sp. has a sclerotised vagina with a robust trumpet, a robust primary canal and two chambers of similar size; it is close to P. bacchus Sigura, Chauvet & Justine, 2007. P. viscosus n. sp. has a sclerotised vagina with a robust trumpet, long primary canal with an extremely thin wall and two small chambers, and a male quadriloculate organ with a characteristic thickening at the extremity of its cone. P. crassus n. sp., the most abundant species, has a sclerotised vagina with a thin-walled trumpet, thin-walled primary canal which is always coiled anteriorly and two small chambers. P. huitoe Justine, 2007, P. manifestus Justine & Sigura, 2007 and P. crassus have very similar sclerotised vaginae; however, species of this 'huitoe complex' can be distinguished by measurements of the haptoral hard parts. A few diplectanid specimens found in a single specimen of E. polyphekadion were attributed to P. huitoe, a species originally described from E. maculatus (Bloch) and also rarely found in E. cyanopodus Richardson in New Caledonia; specimens from these three fish species are morphologically indistinguishable.     

<Emphasis Type="Italic">Pseudorhabdosynochus hirundineus</Emphasis> n. sp. (Monogenea: Diplectanidae) from <Emphasis Type="Italic">Variola louti</Emphasis> (Perciformes: Serranidae) off New Caledonia

Pseudorhabdosynochus hirundineus n. sp. is described from specimens collected from the gills of Variola louti off Nouméa, New Caledonia, South Pacific. No diplectanid was found on V. albimarginata from the same location. The male sclerotised quadriloculate organ of P. hirundineus is 42 μm in internal length, with a long posterior tube; and the sclerotised vagina, 36 μm in length, is composed of a long tube with anterior open trumpet and two posterior, heavily sclerotised chambers. The two squamodiscs, each with 11–15 rows of rodlets and no central closed row of rodlets, are dissimilar in shape, the ventral being round and the dorsal being oval. By the morphology of its sclerotised vagina, P. hirundineus appears close to P. epinepheli (Yamaguti, 1938) but it is differentiated from it by the shape of its squamodiscs. Pseudorhabdosynochus spp. previously recorded from epinephelines are parasites of species of Epinephelus and Mycteroperca; this is the first species from a species of Variola.

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Résumé Résumé Pseudorhabdosynochus hirundineus n. sp. est décrit de spécimens récoltés sur les branchies de Variola louti au large de Nouméa, Nouvelle Calédonie, Pacifique sud. Aucun Diplectanidae n’a été trouvé chez V. albimarginata de la même origine. L’organe mâle sclérifié tétraloculé de P. hirundineus mesure 42μm de longueur interne et a un long tube postérieur, et le vagin sclérifié, long de 36μm, est composé d’un long tube avec une trompe antérieure et deux chambres postérieures très sclérifiées. Les deux squamodisques, chacun avec 11–15 rangées d’osselets et sans rangée close, sont de formes différentes, le ventral rond et le dorsal ovale. Par la morphologie de son vagin sclérifié, P. hirundineus semble proche de P. epinepheli (Yamaguti, 1938), mais s’en distingue par la forme de ses squamodisques. Les espèces de Pseudorhabdosynochus mentionnées auparavant chez les Epinephelinae étaient parasites d’espèces des genres Epinephelus et Mycteroperca; ceci est la première espèce chez Variola.

     

<Emphasis Type="Italic">Pseudorhabdosynochus quadratus</Emphasis> n. sp. (Monogenea: Diplectanidae) from the white-streaked grouper <Emphasis Type="Italic">Epinephelus ongus</Emphasis> (Bloch) (Perciformes: Serranidae) off New Caledonia

Gill diplectanid monogeneans from the camouflage grouper Epinephelus polyphekadion (Bleeker) collected in the coral reef lagoon of New Caledonia, South Pacific, comprise four species. Very few monogeneans were found in most fish examined. Pseudorhabdosynochus dionysos n. sp. has a sclerotised vagina with a robust trumpet, a robust primary canal and two chambers of similar size; it is close to P. bacchus Sigura, Chauvet & Justine, 2007. P. viscosus n. sp. has a sclerotised vagina with a robust trumpet, long primary canal with an extremely thin wall and two small chambers, and a male quadriloculate organ with a characteristic thickening at the extremity of its cone. P. crassus n. sp., the most abundant species, has a sclerotised vagina with a thin-walled trumpet, thin-walled primary canal which is always coiled anteriorly and two small chambers. P. huitoe Justine, 2007, P. manifestus Justine & Sigura, 2007 and P. crassus have very similar sclerotised vaginae; however, species of this ‘huitoe complex’ can be distinguished by measurements of the haptoral hard parts. A few diplectanid specimens found in a single specimen of E. polyphekadion were attributed to P. huitoe, a species originally described from E. maculatus (Bloch) and also rarely found in E. cyanopodus Richardson in New Caledonia; specimens from these three fish species are morphologically indistinguishable.     

Monogeneans from <Emphasis Type="Italic">Epinephelus chlorostigma</Emphasis> (Val.) (Perciformes: Serranidae) off New Caledonia,with the description of three new species of diplectanids

Gill monogeneans from the brownspotted grouper Epinephelus chlorostigma (Val.) collected in deep water off the coral barrier reef of New Caledonia, South Pacific, comprise seven species. These include the ancyrocephalid Haliotrema sp., the capsalid Allobenedenia cf. epinepheli Yamaguti, 1968, and five diplectanids, namely Pseudorhabdosynochus epinepheli (Yamaguti, 1938), reported in a previous paper, P. cyanopodus Sigura & Justine, 2008 and P. podocyanus Sigura & Justine, 2008, two species originally described from E. cyanopodus Richardson, P. stigmosus n. sp., P. exoticoides n. sp. and Diplectanum femineum n. sp. P. stigmosus is characterised by a sclerotised vagina with a straight primary canal, large ovoid primary chamber and spherical secondary chamber. P. exoticoides is a highly aberrant species, with a thick-walled male quadriloculate organ and a discoid sclerotised vagina with an exceptional structure. Interestingly, P. exoticoides resembles P. exoticus Sigura & Justine, 2008, a species from E. cyanopodus, and P. stigmosus resembles P. cyanopodus and P. podocyanus, also both from E. cyanopodus, suggesting close relationships between the diplectanid faunae of these two fish species. D. femineum belongs to a group of diplectanids, provisionally classified as ‘Diplectanum’ Diesing, 1858, which all share a small funnel-shaped male copulatory organ. In contrast to other members of this group which have no sclerotised vagina, D. femineum has a sclerotised vagina with the same organisation as those of species of Pseudorhabdosynochus Yamaguti, 1958. This suggests that the species of ‘Diplectanum’ from groupers are closer to Pseudorhabdosynochus than suggested by the structure of the male organs.     

Pseudorhabdosynochus spp. (Monogenea: Diplectanidae) from the gills of Epinephelus spp. in Brazilian waters

Pseudorhabdosynochus sulamericanus n. sp. from the gills of Epinephelus niveatus has a reniform proximal region of the cirrus-bulb which is divided in four chambers and contains a large, round reservoir of the male accessory glands, a partly sclerotised vagina which is enclosed in a muscular funnel cap and squamodiscs with 15–16 open concentric rows of elements. P. beverleyburtonae (Oliver, 1984) is redescribed from E. marginatus with additional morphological data. These are the first reports of Pseudorhabdosynochus spp. in South American Atlantic waters, where the potentiality for the mariculture of Epinephelus spp. is currently being evaluated. Pseudorhabdosynochus hargisi (Oliver & Paperna, 1984) n. comb. is proposed for Diplectanum hargisi.     

Pseudorhabdosynochus argus n. sp. (Monogenea: Diplectanidae) from Cephalopholis argus, P. minutus n. sp. and Diplectanum nanus n. sp. from C. sonnerati and other monogeneans from Cephalopholis spp. (Perciformes: Serranidae) off Australia and New Caledonia

Monogeneans from three species of Cephalopholis, namely C. argus, C. sonnerati and C. boenak, are described from fish caught off New Caledonia, South Pacific, with comparisons with material from off Queensland, Australia. Pseudorhabdosynochus argus n. sp. from C. argus is present off New Caledonia and Australia; it is characterised by its male quadriloculate organ with very elongate cone, and its sclerotised vagina with anterior trumpet, coiled primary canal and distal part with two chambers and an accessory part. C. boenak has no monogeneans off New Caledonia, but off Australia it harbours Pseudorhabdosynochus sp., a new species which is morphologically related to P. argus. P. minutus n. sp. from C. sonnerati is characterised by its minute body and a sclerotised vagina with two spherical chambers. Diplectanum nanus n. sp. from C. sonnerati is characterised by its very small funnel-shaped male copulatory organ and minute body. A new species, Haliotrema sp. from C. sonnerati is characterised by a very elongate tubular penis; it is distinct from H. cromileptis Young, 1968 (redescribed herein from specimens collected from Cromileptes altivelis off New Caledonia). The species described here include the first members of Pseudorhabdosynochus and the first diplectanids described from species of Cephalopholis. There is no evidence for a clade of Pseudorhabdosynochus species specific to members of Cephalopholis, since the species described here share similarities with other species from Epinephelus. However, it is suggested that the gill structure of Cephalopholis spp. imposes selection toward small body sizes for monogeneans.     

Parasite biodiversity in a coral reef fish: twelve species of monogeneans on the gills of the grouper Epinephelus maculatus (Perciformes: Serranidae) off New Caledonia, with a description of eight new species of Pseudorhabdosynochus (Monogenea: Diplectanidae)

Coral reefs are known for their high level of biodiversity, but parasite biodiversity has not been evaluated. Cases such as Epinephelus maculatus, described here, show that the numerical estimation of parasite biodiversity in coral reefs could reach more than ten times the number of fish species; consequently, the extinction of certain fish species from endangered coral reefs would result in the co-extinction of at least ten times the number of parasite species. E. maculatus is a grouper of intermediate size (1-2 kg) and common in the coral reefs of New Caledonia, South Pacific. Based on the examination of more than 800 monogenean specimens, 12 species of monogeneans (ten diplectanids and two ancyrocephalids) were differentiated on the gills. These species of diplectanids have not been found in other epinephelines in the same area and thus are considered as specific to this host. In addition, three species of copepods, and isopod larvae, are present on the gills; E. maculatus thus has a total of 16 species of gill ectoparasites, which can be found together on a single individual fish. Diplectanids include Laticola dae Journo & Justine, 2006, which is the most abundant species representing about 50% of the specimens, and nine species which are rare, each representing 2-7% of the specimens: Diplectanum uitoe n. sp. and eight species of Pseudorhabdosynochus Yamaguti, 1958. D. uitoe, provisionally attributed to Diplectanum Diesing, 1858, is characterised by a small conical penis with internal walls. Pseudorhabdosynochus auitoe n. sp., P. buitoe n. sp., P. cuitoe n. sp., P. duitoe n. sp., P. euitoe n. sp. and P. fuitoe n. sp. are differentiated on the basis of the morphology of the sclerotised vagina, but are very similar in other characteristics; P. guitoe n. sp. is characterised by a quadriloculate organ with very thick walls and a very small sclerotised vagina; and P. huitoe n. sp. is characterised by its sclerotised vagina and by very long ventral and dorsal haptoral bars. Two rare (2-3% of specimens) ancyrocephalids, Haliotrema epinepheli Young, 1969 and Haliotrema sp., are briefly described in relation to the male copulatory organs and haptoral bars; H. epinepheli is apparently a generalist species found in various epinephelines and other fish species. A table of the 50 species of diplectanids (Pseudorhabdosynochus, Laticola Yang et al., 2006, Echinoplectanum Justine & Euzet, 2006 and Diplectanum) from serranids is provided.     

A new species of Pomphorhynchus (Acanthocephala: Palaeacanthocephala) in freshwater fishes from central Chile

This study describes a new species of Pomphorhynchus collected from Percilia gillissi Girard, 1855 from the Za?artu canal, between the sister basins of the Itata and Laja rivers, in central Chile. Pomphorhynchus moyanoi n. sp. is characterized by an asymmetrical, well-differentiated subspherical bulb and 12-14 longitudinal rows of 13-14 hooks; the third and the fourth hook in each row are stout. Among South American species, P. moyanoi n. sp. shows some similarities to the Chilean species P. yamagutii Schmidt & Hugghins, 1973, but it differs in having a longer neck, larger bulb, and different proboscis armature arrangement. Pomphorhynchus moyanoi n. sp. differs from P. patagonicus Ortubay, Ubeda, Semenas & Kennedy 1991, in the bulb shape (protuberances), number of rows, fourth hook size and basal hook size. Pomphorhynchus moyanoi n. sp. also differs from P. sphaericus in the arrangement of hooks (number of rows and hooks per row), length and width of the proboscis, neck width, and symmetry of the bulb.     

<Emphasis Type="Italic">Diplectanocotyla</Emphasis> Yamaguti, 1953 (Monogenea: Diplectanoidea) from <Emphasis Type="Italic">Megalops cyprinoides</Emphasis> (Broussonet) (Teleostei: Megalopidae) off Peninsular Malaysia

Two known and two new species of Diplectanocotyla Yamaguti, 1953 (D. gracilis Yamaguti, 1953, D. megalopis Rakotofiringa & Oliver, 1987, D. langkawiensis n. sp. and D. parva n. sp.) were collected from Megalops cyprinoides (Megalopidae) off Langkawi, Kedah and Matang, Perak, Peninsular Malaysia. All four species possess similar types of sclerotised male and female reproductive structures and similar soft anatomical features. The squamodisc sclerites of all four species have spine-like projections with varying degrees of visibility and shapes (sharp-pointed to triangular). In D. megalopis and D. langkawiensis n. sp. the spines are sharp-pointed and distinct on sclerites from rows 5–6 onwards. In D. gracilis and D. parva n. sp. the sclerite spines are triangular, lightly sclerotised and occur on almost all of the sclerites. D. parva n. sp. has comparatively the smallest set of anchors, bars, squamodiscs and squamodisc suckers. The anchors and bars of the other three species are almost similar in overall size, and the main distinguishing feature is the relative lengths of the inner and outer roots of the ventral anchors. In D. gracilis the outer root is very much smaller than the inner root and they are disposed almost at a right angle to each other. In D. megalopis the outer root is usually about half the length of the inner root and the roots are inclined at c.60° to each other. In D. langkawiensis n. sp. the roots are inclined at c.40° degrees and the outer root is of a similar length or only slightly shorter than the inner root. The openings of the two squamodisc suckers of all four Diplectanocotyla species are surrounded by tiny scale-like spines. Bifid tegumental spines are found in the posterior region of all four species, differing only in their extent: in D. parva n. sp. the tegumental spines are only distributed in the peduncular region and not beyond, whilst in the other three species the tegumental spines extend from the posterior level of the testis to the end of the peduncle. An amended diagnosis of Diplectanocotyla and a key to its species are appended.     

Diplectanids (Monogenea) on the archerfish Toxotes jaculatrix (Pallas) (Toxotidae) off Peninsular Malaysia

Two new and two previously described species of diplectanid monogeneans (Heteroplectanum flabelliforme n. sp., Diplectanum sumpit n. sp., D. jaculator Mizelle & Kritsky, 1969 and D. toxotes Mizelle & Kritsky, 1969) were collected from archerfish Toxotes jaculatrix off the Island of Langkawi, Kedah and off Perak, Malaysia. The reproductive systems and squamodiscs of D. jaculator and D. toxotes are described for the first time. D. sumpit n. sp. differs from D. toxotes and D. jaculator in a having a small curved copulatory tube with a distinct accessory piece, compared to the long, tubular copulatory tube of D. jaculator and the slender tube of D. toxotes. D. sumpit n. sp. also differs from D. toxotes in having a larger ventral bar and larger squamodiscs. H. flabelliforme n. sp. differs from all known Heteroplectanum species in the shape and size of the squamodiscs, the arrangement of the sclerites in the squamodiscs, the extremely large ventral bar and the short, curved, non-spinous copulatory tube.     

Sciadicleithrum juruparii n. sp. (Monogenea: Ancyrocephalidae) from the gills of Satanoperca jurupari (Heckel) (Osteichthyes: Cichlidae) in the Guamá River, Amazon Delta, Brazil

Sciadicleithrum juruparii n. sp. is described from the gills of the Neotropical cichlid fish Satanoperca jurupari (Heckel) caught in the Guamá River, in the delta of the Amazon River, at Belém, Pará State, Brazil. Diagnostic characters of the new species are a basally articulated male copulatory organ with clockwise coils and an accessory piece; a ventral bar with a median process; similar hooklets; vagina in the form of a sclerotised tube; and a sinistral vaginal aperture with a sclerotised papilla lying in a small surface depression. It is the only species of Sciadicleithrum Kritsky, Thatcher & Boeger, 1989 with a medial projection on the ventral bar.     

Revision of Potamotrygonocotyle Mayes, Brooks & Thorson, 1981 (Platyhelminthes: Monogenoidea: Monocotylidae), with descriptions of four new species from the gills of the freshwater stingrays Potamotrygon spp. (Rajiformes: Potamotrygonidae) from the La Plata river basin

The only known monocotylid genus to parasitise Neotropical freshwater stingrays (Potamotrygonidae) is Potamotrygonocotyle Mayes, Brooks & Thorson, 1981, a monotypic genus erected to accommodate P. tsalickisi Mayes, Brooks & Thorson, 1981. For more than 20 years, no other species has been recognised in this genus, but new efforts to survey the diversity of parasites inhabiting potamotrygonids have revealed the existence of new species and the need to redefine the genus. Here, the generic diagnosis of Potamotrygonocotyle is amended, P. tsalickisi is redescribed and four new species are recognised and described based on samples collected from the gills of freshwater potamotrygonids from the La Plata river basin: Potamotrygonocotyle chisholmae n. sp. and P. dromedarius n. sp. from Potamotrygon motoro; Potamotrygonocotyle eurypotamoxenus n. sp. from Potamotrygon cf. motoro (type-host), P. castexi, P. falkneri and P. histrix; and Potamotrygonocotyle uruguayensis n. sp. from Potamotrygon brachyura. Potamotrygonocotyle is characterised by species possessing: (1) slightly sinuous sclerotised ridges on all septa; (2) two pairs of the dorsal haptoral accessory structures associated with the four posterior peripheral loculi and with anterior dorsal haptoral accessory structure bilobate or semicircular; and (3) male copulatory organ without an accessory piece.