Search

Three new species of Merizocotyle Cerfontaine, 1894 (Monogenea: Monocotylidae) are described from the nasal tissues of stingrays collected off Borneo. Merizocotyle macrostrobus n. sp. is described from the dwarf whipray Himantura walga (Muller & Henle) collected in shallow waters off Sematan, Sarawak, Malaysia. This species can be distinguished from the other members of the genus by the morphology of the sclerotised male copulatory organ, which is long with many twists and loops. The vaginae of this species are also long and looped. Merizocotyle papillae n. sp. is described from the roughnose stingray Pastinachus solocirostris Last, Manjaji & Yearsley collected off Sematan and Mukah, Sarawak, Malaysia. It is distinguished from the other species of Merizocotyle by the morphology of the male copulatory organ, which is a sclerotised tube that expands slightly and then tapers at the distal end, and by the presence of papillae on the dorsal edge of the haptor. Merizocotyle rhadinopeos n. sp. is described from the whitenose whip ray Himantura uarnacoides (Bleeker) collected off Manggar, East Kalimantan, Indonesia. It can be differentiated by the male copulatory organ, which is a short, narrow, curved, sclerotised tube tapering distally, and the path of the ovary, which runs anteriorly to the base of the ootype. We also provide details of new host and/or locality records for M. australensis (Beverley-Burton & Williams, 1989) Chisholm, Wheeler & Beverley-Burton, 1995, M. icopae Beverley-Burton & Williams, 1989 and M. pseudodasybatis (Hargis, 1955) Chisholm, Wheeler & Beverley-Burton, 1995.

Relationships between the three classes of Neodermata (parasitic Platyhelminthes) are much debated and restrict our understanding of the evolution of parasitism and contingent adaptations. The historic view of a sister relationship between Cestoda and Monogenea (Cercomeromorphae; larvae bearing posterior hooks) has been dismissed and the weight of evidence against monogenean monophyly has mounted. We present the nucleotide sequence of the complete mitochondrial (mt) genome of Benedenia seriolae (Monogenea: Monopisthocotylea: Capsalidae), the first complete non-gyrodactylid monopisthocotylean mt genome to be reported. We also include nucleotide sequence data for some mt protein coding genes for a second capsalid, Neobenedenia sp. Analyses of the new mt genomes with all available platyhelminth mt genomes provide new phylogenetic hypotheses, which strongly influence perspectives on the evolution of diet in the Neodermata. Our analyses do not support monogenean monophyly but confirm that the Digenea and Cestoda are each monophyletic and sister groups. Epithelial feeding monopisthocotyleans on fish hosts are basal in the Neodermata and represent the first shift to parasitism from free-living ancestors. The next evolutionary step in parasitism was a dietary change from epithelium to blood. The common ancestor of Digenea + Cestoda was monogenean-like and most likely sanguinivorous. From this ancestral condition, adult digeneans and cestodes independently evolved dietary specialisations to suit their diverse microhabitats in their final vertebrate hosts. These improved perspectives on relationships fundamentally enhance our understanding of the evolution of parasitism in the Neodermata and in particular, the evolution of diet.

The morphological based taxonomy of highly derived parasite groups is likely to poorly reflect their evolutionary relationships. The taxonomy of the monogenean family Capsalidae, which comprises approximately 180 species of flatworm parasites that predominantly attach to external surfaces of chondrichthyan and teleost fishes, is based mainly on six morphological characters. The phylogenetic history of the family is largely unknown. We reconstructed the phylogenetic relationships of 47 species in 20 genera from eight of the nine subfamilies, from nucleotide sequences of three unlinked nuclear genes, 28S ribosomal RNA, Histone 3 and Elongation Factor 1 alpha. Our phylogeny was well corroborated, with 75% of branches receiving strong support from both Bayesian posterior probabilities and maximum likelihood bootstrap proportions and all nodes showed positive partitioned likelihood support for each of the three genes. We found that the family was monophyletic, with the Gyrodactylidae and Udonellidae forming the sister group. The Capsalinae was monophyletic, however, our data do not support monophyly for the Benedeniinae, Entobdellinae and Trochopodinae. Monophyly was supported for Capsala, Entobdella, Listrocephalos, Neobenedenia and Tristoma, but Benedenia and Neoentobdella were polyphyletic. Comparisons of the distribution of character states for the small number of morphological characters on the molecular phylogeny show a high frequency of apparent homoplasy. Consequently the current morphological classification shows little correspondence with the phylogenetic relationships within the family.

The phylogeography and host specificity of three monogenean species infecting different sites on the southern fiddler ray, Trygonorrhina fasciata (Rhinobatidae) in South Australia (SA) were studied: Branchotenthes octohamatus (Hexabothriidae: gills), Calicotyle australis (Monocotylidae: cloaca) and Pseudoleptobothrium aptychotremae (Microbothriidae: skin). Five rhinobatid species (Aptychotrema vincentiana, T. fasciata, Trygonorrhina sp. A, Aptychotrema rostrata and Rhinobatos typus) with distributions spanning west, south and east Australian coastal waters, were surveyed for monogeneans resembling the three species documented from T. fasciata in SA. The identities of hosts and parasites collected were investigated using the mitochondrial genes ND4 and Cytochrome b (cytb), respectively, in addition to the nuclear marker, Elongation factor 1-alpha (EF1a) for Pseudoleptobothrium. Genetic analyses confirmed that B. octohamatus is geographically widespread and displays little genetic structure, suggesting high levels of gene flow. It was collected from four rhinobatid species throughout its distribution and is not, therefore, host specific. For C. australis, genetic analyses revealed two discrete populations with a genetic divergence of ∼4%, one population occurring west of Bass Strait on two sympatric host species and the other population on the east coast, also occurring on sympatric host species. Similarly, for Pseudoleptobothrium, specimens collected west of Bass Strait were genetically distinct (∼3.5%) from those collected to the east. However, on the east coast, a third Pseudoleptobothrium population was revealed, separated by a genetic distance of >11%, indicating a morphologically cryptic species. Host preferences were indicated for each Pseudoleptobothrium lineage. These genetic discoveries are discussed in relation to life history characteristics of each monogenean species, highlighting the value of phylogeographic analyses to understand the parasite-host relationship.

Metazoan parasites can threaten the sustainability and profitability of finfish sea-cage aquaculture. It is critical, therefore, to identify local parasite species and determine which are potentially harmful. Although several studies have documented parasite species on wild and farmed fish from aquaculture sites, few have used qualitative risk analyses to determine the likelihood and consequence of parasite transfer from locally found wild fish to farmed fish. Indeed, most risk assessments for marine fish farming identify hazards from diseases reported in other, often distant, countries. The usefulness of this approach is limited if an endemic parasite with potential to cause serious disease is undetected before the establishment of aquaculture. This study performs a qualitative risk assessment for 57 metazoan parasite species found to infect wild yellowtail kingfish (Seriola lalandi) and Samson fish (S. hippos) in southern Australia to determine real risks to local sea-cage aquaculture of S. lalandi in South Australia and for industry expansion elswhere. Risk was estimated by considering the likelihood and consequence of parasite establishment and proliferation in S. lalandi sea-cage farming. Benedenia seriolae and Zeuxapta seriolae (Monogenea) were considered extremely likely to establish and proliferate. B. seriolae is currently recorded as the highest potential negative consequence for cost-effective sea-cage farming of S. lalandi in Australia, should the industry expand elsewhere. However, B. seriolae infections can be managed by bathing fish in either hydrogen peroxide or fresh water. Absence of potential treatment methods for Paradeontacylix spp. (Digenea), Kudoa sp. and Unicapsula seriolae (Myxozoa) suggests that these species may present the highest negative consequences for S. lalandi aquaculture in Australia. However, the presence of myxozoan infection in the flesh of wild South Australian Seriola spp. needs confirmation to determine whether these parasite species present an immediate risk to farmed S. lalandi in South Australia.

Yellowtail kingfish, Seriola lalandi support significant commercial and recreational fisheries as well as aquaculture operations throughout the world. Metazoan parasite infections of S. lalandi are of considerable economic and ecological importance, yet very little is known about wild parasite assemblages. S. lalandi were collected from the east coast and south coast of Australia and examined for metazoan parasites. Forty-three parasite taxa were identified, including 26 new host records. Four of the parasite species recovered have been previously associated with disease or mortality in Seriola aquaculture. Comparisons are made between ectoparasite and endoparasite prevalence and intensity of S. lalandi from New South Wales and Victoria. S. lalandi sampled from the east coast of Australia shared ectoparasites previously documented from this species in New Zealand, providing support that S. lalandi in the Tasman Sea comprise a single stock. Based on previously used criteria to evaluate the suitability of parasites as biological tags, the monogenean Paramicrocotyloides reticularis Rohde and the copepod Parabrachiella seriolae Yamaguti and Yamasu may be potentially useful for stock discrimination.

Egg-laying in Zeuxapta seriolae from the gills of yellowtail kingfish ( Seriola lalandi ) in South Australia was investigated in situ under a controlled lighting schedule. Eggs were collected every 3 h from mature Z. seriolae infecting 4 S. lalandi kept individually for 7 consecutive days exposed to alternating 12 h periods of illumination and darkness (light on 06:00 h; light off 18:00 h) at 18±0.5 °C and 40 ppt salinity. A well-defined egg-laying rhythm was demonstrated for Z. seriolae . A total of 650,153 eggs was collected during all periods of illumination and darkness. Of these eggs, 71.6% (57.4–81.8%) were collected during the first 3 h period following ‘dusk’ at 18:00 h. At the conclusion of the experiment, 179 mature Z. seriolae specimens were recovered with a mean clamp number of 47 (37–53) along the major clamp row and 36 (26–44) along the minor clamp row. Of the 179 specimens examined, 177 were found with eggs in utero: mean 321, range 8–1015. Specimens of Z. seriolae produced on average 21.6 (20.8–23.8) eggs/worm/h over the 7 day experiment. It is suggested that Z. seriolae accumulates eggs in utero over a 24 h period. Eggs extracted from the uteri of worms were joined together by filamentous strands and formed a single continuous ‘egg string’. The well-defined egg-laying rhythm in Z. seriolae may be related to a specific host behaviour associated with ‘dusk’ or darkness.

Decacotyle cairae n. sp. (Monogenea: Monocotylidae) is described from the gills of an unidentified species of Pastinachus collected in the South China Sea off Sematan and Mukah, Sarawak, Borneo, Malaysia. D. cairae can be distinguished from the other six members of the genus by the presence of two simple unsclerotised accessory structures on the dorsal surface of the haptor in combination with a long, narrow, looping male copulatory organ. The host specimens of Pastinachus collected in Borneo also appear to be a new species and the monogenean data support this conclusion. A key to species of Decacotyle is given and their host-specificity is discussed.

The oncomiracidium (larva) of the entobdelline Neoentobdella parvitesticulata (Monogenea: Capsalidae), adults of which parasitise the skin of the stingray Himantura fai (Dasyatidae) at Heron Island, Great Barrier Reef, Queensland, Australia, is described. The larva undergoes precocious development (progenesis) in the freely deposited egg. At600 microm long, the fully embryonated, free-swimming oncomiracidium is more than twice as long as the larva of the related species N. diadema. Furthermore, the larva of N. parvitesticulata has a total of 60 flame bulbs compared with only 18 in N. diadema. The anterior hamuli in the oncomiracidium of N. parvitesticulata have well-developed distal hooks and may already be functional for secure attachment whereas those of N. diadema are rod-shaped, have no distal hook and would be unable to function in this way in newly attached larvae.

The effects of temperature and salinity on the embryonation period and hatching success of eggs of Benedenia seriolae were investigated. Temperature strongly influenced embryonation period; eggs first hatched 5 days after laying at 28 degreesC and 16 days after laying at 14 degreesC. The relationship between temperature and embryonation period is described by quadratic regression equations for time to first and last hatching. Hatching success was >70% for B. seriolae eggs incubated at temperatures from 14 to 28 degreesC. However, no B. seriolae eggs embryonated and hatched at 30 degreesC and

Seven specimens of rays of the genus Himantura which could not be identified to species were collected from waters near Dunwich, Stradbroke Island, Moreton Bay, Queensland, Australia. The five smallest specimens of Himanturasp. (disc width 218-302 mm; four female, one male) had a banded tail and the dorsal surface was uniformly grey/brown. The two largest individuals of Himantura sp. (disc widths 460, 533 mm; female and male, respectively) also had a banded tail but the grey/brown dorsal surface had white spots. Two new monogenean species (Monocotylidae: Monocotylinae) are described from both the ‘plain’ and ‘white-spotted’ specimens of Himantura. Dendromonocotyle lastin. sp. is distinguished from other species in the genus by the number of papillae on the haptor, by the morphology of the male copulatory organ and by the morphology of the proximal portion of the vagina. The muscular sheath which surrounds the male copulatory organ is also unique having sclerotised spines at the distal end. Dendromonocotyle species are skin parasites, but a total of five juvenile specimens of D. lasti were found on the gills of four rays. Monocotyle caseyae n. sp. from the gills is characterised by the morphology of the male copulatory organ and its accessory piece. One specimen of M. spiremae Measures, Beverley-Burton & Williams, 1990, originally described from the gills of Himantura fai Jordan & Seale off Heron Island, Great Barrier Reef, Queensland, Australia, was also found on the gills of one Himantura specimen. The site and host-specificity of the parasites and the identity of the hosts are discussed.

Dendromonocotyle pipinna n. sp. (Monogenea: Monocotylidae) is described from the dorsal skin surface of Taeniura meyeni Muller & Henle from a public aquarium in Mooloolaba, Queensland, Australia. D. torosa n. sp. was found on the dorsal skin surface of a heavily infected specimen of Aetobatus narinari (Euphrasen) during a post-mortem at the Mooloolaba aquarium and on a specimen of A. narinari kept in an aquarium in Cairns. Both of these new Dendromonocotyle species are distinguished from each other and others in the genus by the morphology of the terminal papillary sclerite and the male copulatory organ.

The efficacy of the anthelmintic Praziquantel in removing monocotylid monogeneans (Platyhelminthes) from the branchial tissue (Neoheterocotyle rhinobatidis, N. rhynchobatis, and Troglocephalus rhinobatidis) and nasal tissue (Merizocotyle icopae) of juvenile giant shovelnose rays Rhinobatos typus from Heron Island, Australia, was studied. Although effective in removing monogeneans in vivo from the skin and gills of the teleost yellow stripey Lutjanus carponotatus from the same locality, two 2-h treatments using 20 mg/L Praziquantel was ineffective for the giant shovelnose ray. Adult monocotylids were removed, but many post-oncomiracidia and some juveniles remained attached. Juvenile and adult N. rhinobatidis and T. rhinobatidis reacted similarly when exposed to 20 mg/L Praziquantel during in vitro experiments, exhibiting muscle contractions and dying after 12 and 14 h, respectively. We attribute the failure to remove small monogenean stages in vivo to the structure of the branchial and nasal tissu...

A technique is described to preserve the pigment found in the bodies and the intestine of some brightly coloured and darkly pigmented benedeniine capsalid monogeneans. Previous studies of these pigmented capsalids have proven difficult because the pigmentation usually disappears when the worms are fixed using preservatives containing concentrations of formalin over 5% and/or ethanol, acetic acid, chromic acid, picric acid and mercuric chloride. The technique developed here uses a fixative comprising glycerol, acetone and formalin (GAF). After fixation under light coverslip compression for three minutes, specimens are transferred to absolute acetone for three minutes and cleared in a mixture of nine parts cedar wood oil and one part absolute acetone before mounting in Canada balsam. Processing must be carried out quickly, as these chemicals will cause the pigments to fade if the specimens are exposed to them for too long. Pigmented benedeniines processed using this technique retain the distribution, intensity and colour observed in live worms. The colour and distribution of pigmentation in monogeneans may be of taxonomic importance and this technique aids preparation of whole-mounts suitable for registration as type-material.

Polyclithrum mugilini Rogers, 1967, a parasite of Mugil cephalus Linnaeus, is redescribed from type-material from Lake Seminole, Georgia, USA. Three new species of Polyclithrum Rogers, 1967 are also described: P. alberti n. sp. from M. cephalus from the Albert River, Queensland, Australia; P. boegeri n. sp. from M. platanus Günther from Rio da Guarda, State of Rio de Janeiro, Brazil; and P. corallense n. sp. from M. cephalus from Heron Island, Great Barrier Reef, Australia. The four species can be distinguished by the size and shape of haptoral sclerites, but in particular by accessory bar number 3, the dorsal bar, the marginal hooks and the hamulus point to shaft angle. The validity of Micropolyclithrum parvum Skinner, 1975, a parasite of M. cephalus in Biscayne Bay, Florida, is discussed, and a key to the species of Polyclithrum is presented.

A total of 153 elasmobranchs (46 species), either freshly collected from the Gulf of Mexico, USA and Tasmania, Australia or museum specimens collected from various localities worldwide, were examined for calicotyline (Monocotylidae) monogeneans. Thirty-five elasmobranchs, representing 17 species, were infected with Calicotyle spp. which we identified as the following previously described species: C. asterii (Szidat, 1970) Timofeeva, 1985, C. kroyeri Diesing, 1850, C. macrocotyle Cordero, 1944, C. similis (Szidat, 1972) Timofeeva, 1985, C. splendens (Szidat, 1970) Timofeeva, 1985, C. stossichi Braun, 1899 and C. urolophi Chisholm, Beverley-Burton & Last, 1991. The Calicotylinae, which comprises the genera Calicotyle and Dictyocotyle, is revised based on supplementary material as well as deposited type-material. We consider 14 of the 17 nominal Calicotyle spp. to be valid. C. rosinae Kusnetzova, 1970 is synonymised with C. macrocotyle, C. sjegi Kusnetzova, 1970 is considered a species inquirenda and C. inermis Woolcock, 1936 a species incertae sedis. Additional data and illustrations to show the morphological features of the hamuli and male copulatory organ, the form of the intestinal caeca, vaginae and ovary and the distribution of the vitellarium are provided for all valid species. The distribution of the 14 hooklets in the adult haptor of Dictyocotyle coeliaca Nybelin, 1941 is illustrated for the first time. We provide new host and locality records for C. asterii, C. kroyeri, C. macrocotyle and C. stossichi and new locality records for C. similis and C. splendens. A key to species of the Calicotylinae is also included. Host-specificity, geographical distribution and the need for information regarding the development of individuals from juvenile to adult are discussed.

The oncomiracidia of the following six species of monocotylids are described: Monocotyle helicophallus and M. spiremae from the gills and Merizocotyle australensis from the nasal fossae of Himantura fai; Neoheterocotyle rhinobatidis and Troglocephalus rhinobatidis from the gills and Merizocotyle icopae from the nasal fossae of Rhinobatos typus. With these descriptions, larvae from 17 described monocotylids representing 11 genera from five subfamilies are now known. The distribution, types of secretions, and possible functions of the anteromedian, lateral and posterior gland-cells are discussed. The distribution of flame-cells and other characters which may help distinguish between oncomiracidia of monocotylids are also tabulated and discussed.

Tonkinopsis transfretanus Lebedev, 1972 is redescribed and illustrated based on new material from the gills of Diagramma labiosum from Heron Island, Australia. This represents a new host and locality record for this monogenean species. The generic diagnosis is revised to include details of the buccal suckers, the male copulatory organ and the common genital atrium. A description of the oncomiracidium, which is unciliated, is also included.

The genus Dendromonocotyle contains seven previously described species: D. octodiscus Hargis, 1955; D. taeniurae Euzet and Maillard, 1967; D. kuhlii Young, 1967; D. cortesi Bravo-Hollis, 1969; D. akajeii Ho and Perkins, 1980; D. californica Olson and Jeffries, 1983; and D. centrourae Cheung and Whitaker, 1993. An eighth species, D. ardea sp. nov., is described from the dorsal body surface of the ray Pastinachus sephen (Forsskal) from Heron Island, Queensland, Australia. Dendromonocotyle ardea is distinguished from other species in the genus by the distinctive morphology of the terminal papillar sclerite, distal portion of the male copulatory organ and proximal portion of the vagina. An accessory chamber which may serve as a second seminal receptacle is also a differentiating character. Dendromonocotyle octodiscus, the type species of the genus, is redescribed and illustrated, and supplementary data and illustrations for features of the other species of the genus are provided. A key to the species of the g...

The five anterior tentacles and the single posterior attachment organ of the temnocephalan flatworm Craspedella sp. perform important roles in locomotion and attachment. Craspedella sp. moved using a low ‘looping’ motion by alternately attaching the ventro-distal regions of the central three tentacles and the ventral surface of the posterior attachment organ. Secretion from the tentacles is by rod-shaped rhabdites produced in rhabditogen cells. There are more rhabdites and pores in the region of the distal concavity on each of the central three tentacles. It was not possible to determine the presence or not of suction at the distal concavities. The posterior attachment organ has true suctorial ability, can create a reduced pressure and a marginal valve appears to prevent influx of water. However, the ‘sucker’ is also supplied with a granular secretion from posterior gland cells which can leave a conspicuous, annular footprint on glass surfaces. The posterior secretion enables the worms to attach to surfaces by only a small proportion of the surface area of the ventral surface of the posterior disc. The musculature of the anterior tentacles and the posterior attachment organ is described. These means of attachment provide Craspedella sp. with the ability to attach to various surfaces inside the branchial chamber of Cherax quadricarinatus such as the flat, smooth body wall and also irregular and often moving substrata like the gill filaments and associated structures (gill cleaning setae and branchiostegite).

A benedeniine monogenean, Benedenia rohdei n. sp., is reported from the gills of the stripey Lutjanus carponotatus (Richardson, 1842) (Lutjanidae) from Heron Island and Lizard Island, Queensland, Australia. The oncomiracidium of the new species is also illustrated. B. rohdei n. sp. differs from all known species of the genus in the possession of a sclerite at the tip of the penis. Examination of type-specimens of B. jaliscana Bravo-Hollis, 1952 has shown that the three penis ‘hooks’ described by Bravo-Hollis are unsclerotised conical papillae.

Benedenia lutjani sp. nov. is described from the body surfaces and fins of the marine teleost, Lutjanus carponotatus (Richardson 1842) from Heron Island and Lizard Island, Queensland, Australia. The vaginal pore of the parasite opens on the dorsal surface anterior to the common genital aperture. There is a pair of lobes associated with the common genital aperture and a single lobe close to the vaginal opening. The diagnoses of the following taxa are amended: Benedeniinae and Benedenia. This is the first record of a species of Benedenia from the Lutjanidae. The oncomiracidium of B. lutjani is described. Evidence from freshly caught fishes and from a heavily infected aquarium-held host indicates that adult specimens of B. lutjani have a preference for the pelvic fins of L. carponotatus.

The monocotylid monogenean Empruthotrema dasyatidis n. sp. is reported from the olfactory sacs of the brown stingray, Dasyatis fluviorum Ogilby, 1908, from Moreton Bay, Queensland, Australia. This is the first record of Empruthotrema from the family Dasyatidae. E. dasyatidis n. sp. differs from other species of Empruthotrema by possessing eye pigment, which may be scattered, and by its small size. The generic diagnosis for Empruthotrema is amended.

Pseudopolystoma australensis is redescribed from new material from the Australian lungfish Neoceratodus forsteri (Dipnoi) from a natural population in Queensland, Australia. It is transferred to a new genus, Concinnocotyla, as Concinnocotyla australensis n. comb. in a new subfamily, the Concinnocotylinae. The genus Concinnocotyla differs from all other polystome genera in each of the following characters: haptoral suckers bilaterally symmetrical rather than radially symmetrical, with elaborate skeleton of sclerites rather than no sclerites; hamuli, a single pair between marginal hooklets I and II rather than between II and III; a pocket posteriorly on each caecum that opens dorsally; sperm-filled sac between pockets; testes numerous, discrete, cylindrical; seminal vesicle large, discrete, muscular; penis elongate, muscular, unarmed, extensile; penis-bulb large, muscular, with intrinsic glands; host, a dipnoan. A detailed description of the adult parasite is presented and its unique features are discussed. The absence of a true oral sucker is noted. Confirmation of a polystome from a natural population of Australian lungfish has interesting evolutionary implications.

The anatomy and behaviour of the oncomiracidia ofKuhnia scombri, K. sprostonaeandGrubea cochlear, related mazocraeid monogeneans from the gill chamber of the mackerel,Scomber scombrus, caught off Plymouth are compared.K. sprostonaeandG. cochlearare new records at Plymouth. The most important anatomical difference between these larvae is that those ofKuhniaspp. possess a pair of pigment-shielded eyes which are lacking in G.cochlear. The freshly hatched larvae ofKuhniaspp. are strongly photopositive but this response wanes after about 1 h inK. scombriand 1–5 h inK. sprostonae. No response to light was detected in larvae of G.cochlear. Most older larvae ofKuhniaspp. and of G.cochlearswim continuously upwards and downwards, even in ‘darkness’, indicating an alternation between positive and negative geotropism. The larvae ofKuhniaspp. possess angular cells (?) of unknown function close to the pharynx. The larvae of all three species contain prominent anterior glands and lipid droplets; the latter are depleted during their long free-swimming lives (up to 36 h inKuhniaspp. at 13–14°C).

Empruthotrema kearni n. sp. and Thaumatocotyle pseudodasybatis Hargis, 1955 (Monogenea: Monocotylidae) are reported from the nasal fossae of the spotted eagle ray, Aetobatus narinari Euphrasen, 1790, from Moreton Bay, Queensland, Australia. The discovery of E. kearni n. sp. is the first record of this genus from the Myliobatidae and a new geographical record for the genus. A comparison of T. pseudodasybatis from Florida, USA and from Queensland, Australia revealed morphometrical and microhabitat differences. The discovery of T. pseudodasybatis in Australian waters is a new geographical record for this species.

The anterior adhesive areas of Benedenia rohdei from the gills and B. lutjani from the pelvic fins of Lutjanus carponotatus at Heron Island, Australia, were studied using scanning and transmission electron microscopy. All specimens were fixed when detached from host tissue. Both monogenean species have two disc-like anteroventral attachment organs, each of which has an anterolateral adhesive area divided into three adjacent zones by tegument from the ventral surface of the attachment organ. A rod-shaped secretion and a smaller, roughly spherical secretion are associated with the anterior adhesive areas in both species; a third type of secretion occurs anteriorly but outside these adhesive areas. The electron-dense spherical secretory bodies released onto the anterior adhesive zones in these Benedenia spp. are of a single type and differ ultrastructurally from those previously reported in monogeneans living on teleost hosts. A correlation, therefore, between secretion morphology and host type is not supported. No relationship was found between parasite microhabitat and secretion morphology.

Accurate identification of fishes and their parasites is fundamental to the development, management and sustainability of fisheries and aquaculture worldwide. We examined three commercially and recreationally exploited Australian arripid species (Pisces: Arripidae), namely Australian herring (Arripis georgianus), eastern Australian salmon (A. trutta) and western Australian salmon (A. truttaceus), to determine their metazoan parasite assemblages and infection parameters. We identified 49 parasite species including 35 new parasite–host records and recognised seven ambiguous parasite–host records in the literature, largely a consequence of unsubstantiated host identifications in previous studies. Morphological and molecular methods confirmed a new western extension for the range of A. trutta, ∼1000 km west of the previous record. Confusion about host identification and the range extension documented here has implications for the management of these economically important arripid species in southern Australian waters. Our examination of an endemic Australian fish family emphasises that accurate identification of fishes and their parasites is a fundamental pre-requisite for efficient and sustainable resource management.

The presence and ultrastructure of distinctive nuclear bodies in a mature 'egg cell' of a Gyrodactylus sp. are described. These electron-dense granular bodies, which appear in section as open or closed rings or as a solid mass are not membrane-bound and lie in clusters close to the nucleolus. The nuclear bodies are compared with the nuclear-inclusion bodies previously reported in platyhelminths. The possible origin, significance and role of the nuclear bodies in this Gyrodactylus sp. are discussed.

Calicotyle australis Johnston, 1934 is reported from a new host species, the common shovel-nosed ray, Rhinobatos batillum, caught in Moreton Bay, Queensland. The parasite inhabits the cloaca and rectum (microhabitat in type host, Trygonorhina fasciata, unknown): parasites were also found on the ventral skin of R. batillum, but these specimens may have migrated to this site after the death of the host. Since Johnston's description was based on a single specimen, the anatomy of the parasite has been redescribed and the validity of the species established. This redescription has determined the presence of diffuse ocellar pigment granules and the absence of marginal hooklets. C. australis is distinguished from its closest relatives, C. kroyeri Diesing, 1850 and C. mitsukurii Goto, 1894, by the shape and length of the penis-tube. The so-called ‘oral sucker’ in some Calicotyle species is discussed.

Graphical abstract Hundreds of dicyemid parasites (white, fuzzy strands) attached to the renal appendage (in red) of a cuttlefish individual., Highlights • Parasites as biological tags to assess host population structure. • Recent molecular advances support incorporation of parasite genetic data. • Guidelines for selection of a parasite species as a tag candidate updated. • Holistic approach allows for robustness and support of observed result., We review the use of parasites as biological tags of marine fishes and cephalopods in host population structure studies. The majority of the work published has focused on marine fish and either single parasite species or more recently, whole parasite assemblages, as biological tags. There is representation of host organisms and parasites from a diverse range of taxonomic groups, although focus has primarily been on host species of commercial importance. In contrast, few studies have used parasites as tags to assess cephalopod population structure, even though records of parasites infecting cephalopods are well-documented. Squid species are the only cephalopod hosts for which parasites as biological tags have been applied, with anisakid nematode larvae and metacestodes being the parasite taxa most frequently used. Following a brief insight into the importance of accurate parasite identification, the population studies that have used parasites as biological tags for marine fishes and cephalopods are reviewed, including comments on the dicyemid mesozoans. The advancement of molecular genetic techniques is discussed in regards to the new ways parasite genetic data can be incorporated into population structure studies, alongside host population genetic analyses, followed by an update on the guidelines for selecting a parasite species as a reliable tag candidate. As multiple techniques and methods can be used to assess the population structure of marine organisms (e.g. artificial tags, phenotypic characters, biometrics, life history, genetics, otolith microchemistry and parasitological data), we conclude by commenting on a holistic approach to allow for a deeper insight into population structuring.