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Accurate identification of parasite species and strains is crucial to mitigate the risk of epidemics and emerging disease. Species of Neobenedenia are harmful monogenean ectoparasites that infect economically important bony fishes in aquaculture worldwide, however, the species boundaries between two of the most notorious taxa, N. melleni and N. girellae, has been a topic of contention for decades. Historically, identifications of Neobenedenia isolates have overwhelmingly been attributed to N. melleni, and it has been proposed that N. girellae is synonymous with N. melleni. We collected 33 Neobenedenia isolates from 22 host species spanning nine countries and amplified three genes including two nuclear (Histone 3 and 28S rDNA) and one mitochondrial (cytochrome b). Four major clades were identified using Maximum Likelihood and Bayesian inference analyses; clades A-D corresponding to N. girellae, N. melleni, N. longiprostata and N. pacifica respectively. All unidentified isolates and the majority of Neobenedenia sequences from GenBank fell into clade A. The results of this study indicate that N. girellae is a separate species to N. melleni, and that a large proportion of previous samples identified as N. melleni may be erroneous and a revision of identifications is needed.The large diversity of host species that N. girellae is able to infect as determined in this study and the geographic range in which it is present (23.8426° S and 24.1426° N) makes it a globally cosmopolitan species and a threat to aquaculture industries around the world.

SUMMARYDicyemids, poorly known parasites of benthic cephalopods, are one of the few phyla in which mitochondrial (mt) genome architecture departs from the typical ~16 kb circular metazoan genome. In addition to a putative circular genome, a series of mt minicircles that each comprises the mt encoded units (I–III) of the cytochromecoxidase complex have been reported. Whether the structure of the mt minicircles is a consistent feature among dicyemid species is unknown. Here we analyse the complete cytochromecoxidase subunit I (COI) minicircle molecule, containing theCOIgene and an associated non-coding region (NCR), for ten dicyemid species, allowing for first time comparisons between species of minicircle architecture, NCR function and inferences of minicircle replication. Divergence inCOInucleotide sequences between dicyemid species was high (average net divergence = 31·6%) while within species diversity was lower (average net divergence = 0·2%). The NCR and putative 5′ section of theCOIgene were highly divergent between dicyemid species (average net nucleotide divergence of putative 5′COIsection = 61·1%). No tRNA genes were found in the NCR, although palindrome sequences with the potential to form stem-loop structures were identified in some species, which may play a role in transcription or other biological processes.

Accurate identification of parasite species and strains is crucial to mitigate the risk of epidemics and emerging disease. Species of Neobenedenia are harmful monogenean ectoparasites that infect economically important bony fishes in aquaculture worldwide, however, the species boundaries between two of the most notorious taxa, N. melleni and N. girellae, has been a topic of contention for decades. Historically, identifications of Neobenedenia isolates have overwhelmingly been attributed to N. melleni, and it has been proposed that N. girellae is synonymous with N. melleni. We collected 33 Neobenedenia isolates from 22 host species spanning nine countries and amplified three genes including two nuclear (Histone 3 and 28S rDNA) and one mitochondrial (cytochrome b). Four major clades were identified using Maximum Likelihood and Bayesian inference analyses; clades A-D corresponding to N. girellae, N. melleni, N. longiprostata and N. pacifica, respectively. All unidentified isolates and the majority of Neobenedenia sequences from GenBank fell into clade A. The results of this study indicate that N. girellae is a separate species to N. melleni, and that a large proportion of previous samples identified as N. melleni may be erroneous and a revision of identifications is needed. The large diversity of host species that N. girellae is able to infect as determined in this study and the geographic range in which it is present (23.8426°S and 24.1426°N) makes it a globally cosmopolitan species and a threat to aquaculture industries around the world.

Ten Southern Hemisphere cephalopod species from six families collected from six localities in western, southern and eastern Australia were examined for dicyemid parasites. A total of 11 dicyemid species were recorded, with three cephalopod species uninfected, four infected by one dicyemid species and three infected by multiple dicyemid species. Dicyemid species prevalence ranged from 24-100%, with observed infection patterns explored due to host size, host life history properties, host geographical collection locality and inter-parasite species competition for attachment sites, space and nutrients. Left and right renal appendages were treated as separate entities and four different patterns of infection by asexual and sexual dicyemid stages were observed. The detection within a single host individual of asexual dicyemid stages in one renal appendage and sexual dicyemid stages in the other renal appendage supported the notion that developmental cues mediating stage transition are parasite-controlled, and also occurs independently and in isolation within each renal appendage. Our study exploring dicyemid parasite fauna composition in relation to cephalopod host biology and ecology therefore represents a thorough, broad-scale taxonomic analysis that allows for a greater understanding of dicyemid infection patterns.

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.

Acanthocotyle urolophi sp. nov. is described from the skin of the banded stingaree, Urolophus cruciatus (Lacepede, 1804). This is the first acanthocotylid to be described from Australian waters. Acanthocotyle urolophi sp. nov. is distinguished from other species of Acanthocotyle by a combination of the number of vitelline follicles 38 (33-46) and the number of rows 35 (32-37) of sclerites on the pseudohaptor. In addition, Acanthocotyle urolophi sp. nov. has no germarial appendix and no uterine "arm". A uterine receptaculum seminis was not identified in whole mounts. There is no penis papilla and no penis sclerite associated with the male reproductive opening. A brief description of the larva is provided. The diagnosis of the Acanthocotylidae Price, 1936 is amended and we review the Allacanthocotylinae Yamaguti, 1963, Lophocotylinae Yamaguti, 1963 and Pseudacanthocotylinae Yamaguti, 1963. We deem that these subfamilies are invalid and that the family now comprises only the subfamily Acanthocotylinae and the genus Acanthocotyle. The validity of species previously assigned to the Acanthocotylidae (sensu Yamaguti, 1963) is discussed and a key to what we consider to be the valid species in the family is also provided.

Species of Entobdella Blainville in Lamarck, 1818, from skin (less commonly gills) of teleost flatfishes and occasionally from round-bodied teleosts are reviewed, with special reference to the nominal (type) species “Entobdella hippoglossi (Muller, 1776) Blainville, 1818” (Monogenea: Capsalidae: Entobdellinae) and to E. pugetensis Robinson, 1961. In the late 20th century the following 5 species were synonymised with E. hippoglossi: E. brattstroemi Brinkmann, 1952; E. curvunca Ronald, 1957; E. rosaceus Crane, 1972; E. squamula (Heath, 1902) Johnston, 1929; E. steingroeveri (Cohn, 1916) Johnston, 1929. We have shown that E. brattstroemi and E. squamula are valid, E. curvunca is a synonym of E. hippoglossi and E. rosaceus and E. steingroeveri are species inquirendae. Specimens of E. steingroeveri, first described in 1916 by Cohn, have been re-examined. Parasites from the Pacific Ocean on Hippoglossus stenolepis Schmidt, 1904 (Pacific halibut) and Eopsetta jordani (Lockington, 1879) (Petrale sole) (Pleuronectiformes: Pleuronectidae) and parasites geographically isolated in the Atlantic Ocean on H. hippoglossus (Linnaeus, 1758) (Atlantic halibut) and Reinhardtius hippoglossoides (Walbaum, 1792) (Greenland halibut) (Pleuronectiformes: Pleuronectidae) have all been regarded as E. hippoglossi. We confirm that E. hippoglossi sensu stricto is a parasite of the Atlantic halibut, but is accompanied on the same host by a second entobdelline species, E. vanbenedeni n. sp. It differs from the type species, E. hippoglossi in the anatomy of the distal region of the vagina and in the number, distribution and shape of papillae on the ventral surface of the haptor. Parasites from H. stenolepis are morphologically similar to E. hippoglossi on H. hippoglossus (no second species has been found on H. stenolepis), but differences in the number and shapes of haptor papillae support proposal of the parasites from H. stenolepis as a distinct species, E. stenolepis n. sp. Our anatomical studies of these parasites, with the exception of E. pugetensis, have revealed a cluster of several seminal receptacles opening into the ovo-vitelline duct. Previous reports of a single seminal receptacle in E. stenolepis (as E. hippoglossi) and E. steingroeveri are erroneous. Furthermore, reports of the vagina opening proximally into the alleged single seminal receptacle are also incorrect; direct and indirect evidence suggests that in all these parasite species, including E. pugetensis, the vagina opens proximally into the vitelline reservoir. Entobdella squamula from Paralichthys californicus (Ayers, 1859) (California flounder) (Pleuronectiformes: Paralichthyidae) differs from E. stenolepis, E. hippoglossi and E. vanbenedeni in the relative lengths of the accessory sclerites and anterior hamuli. Parasites originally identified as E. squamula from Hippoglossina macrops Steindachner, 1876 (Bigeye flounder) (Pleuronectiformes: Paralichthyidae), caught off the coast of Chile by the Lund University Chile Expedition (1948 – 49), differ from E. squamula in the shapes of the accessory sclerites and are regarded as a new species, E. brinkmanni n. sp. E. aegyptiacus Amer, 1990 must be regarded as a species inquirenda. A key to the 7 valid species of Entobdella recognised by us is included. Entobdella pugetensis differs in the following ways from all other species of Entobdella: the parasite is found on gills (less commonly on skin) of Atheresthes stomias (Jordan & Gilbert, 1880) (Arrowtooth flounder) (Pleuronectiformes: Pleuronectidae); the penis sac has a thick, possibly muscular, wall; the vagina is a relatively wide, short, straight tube with a conspicuous opening; no seminal receptacles have been observed; there are no papillae on the ventral surface of the haptor. We regard these distinctions as sufficient to erect a new genus, Branchobdella n. gen. to accommodate B. pugetensis n. comb. Assimilation of spermatophores in skin-parasitic Entobdella spp. and in the gill parasite B. pugetensis is discussed.

We investigated the efficacy of praziquantel (PZQ) administered orally to yellowtail kingfish (Seriola lalandi in sea-cage aquaculture in South Australia) against the monogeneans Zeuxapta seriolae and Benedenia seriolae infesting gills and skin, respectively. PZQ was administered to fish by surface-coating feed pellets (Trial 1) or by direct intubation of the stomach (Trial 2). In both trials 4 daily doses were administered: 50 and 75 mg kg(-1) body weight (BW) d(-1) for 6 d, and 100 and 150 mg kg(-1) BW d(-1) for 3 d. Mean parasite intensity was compared between medicated fish and unmedicated control fish. In Trial 1, fish fed lower daily doses of PZQ for 6 d (50 and 75 mg kg(-1) BW d(-1)) had fewer Z. seriolae and B. seriolae than fish fed higher daily doses for 3 d (100 and 150 mg kg(-1) BW d(-1)). Fish rejected feed pellets surface-coated with PZQ, suggesting PZQ affected palatability of feed, and may explain differences in efficacy between treatments. In Trial 2, where PZQ was administered by intubation, there were fewer Z. seriolae and B. seriolae in medicated fish than control fish. Intubated PZQ was also effective against newly recruited Z. seriolae and B. seriolae. PZQ could be developed as a useful treatment for Z. seriolae and B. seriolae parasitising S. lalandi in sea-cage aquaculture if suspected palatability problems are resolved.

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.

There are three major groups of parasitic platyhelminths (flatworms). The digeneans and cestodes are endoparasites, while the monogeneans are ectoparasites mostly on the gills or skin of fishes. Monogeneans are hermaphrodite and, with the exception of the gyrodactylids, mostly protandrous, the male reproductive system maturing before the female system. Their ectoparasitic life-style provides unique opportunities to observe the reproductive biology of living platyhelminths, opportunities restricted in digeneans and cestodes by their endoparasitic habits. Moreover, the male copulatory organs (MCOs) of monogeneans are of special interest because of their perplexing diversity, ranging from sclerotised penis tubes, many with accessory sclerites, to cirruses and genital atrium armature (hooks and spines). The relatively few accounts in the literature of mating in monogeneans are reproduced in this review, together with consideration of the following aspects of sperm transfer: structure and function of MCOs; self-insemination; spermatophores and pseudospermatophores; “hypodermic” and transtegumental insemination; tissue fusion; glands associated with MCOs and vaginae; finding a mating partner.

The elongated encased spermatophores of the capsalid (entobdelline) monogeneans Neoentobdella diadema (Monticelli, 1902) Kearn et Whittington, 2005 and N. apiocolpos (Euzet et Maillard, 1967) Kearn et Whittington, 2005 have been found attached by their proximal ends to the region of the vaginal opening, with the bulk of the spermatophore projecting from the vagina and therefore lying outside the body. In spite of previous reports, no spermatophores were found projecting from the common genital opening and if spermatophore exchange is as rapid as it is in the related entobdelline Entobdella soleae, then the chances of finding a spermatophore in this location are small. In N. diadema and N. apiocolpos it is likely that sperm enters the vagina through the open proximal end of an attached spermatophore, after which the empty spermatophore case is probably discarded. There is no evidence for a previous proposal that the whole spermatophore is engulfed by the vagina followed by digestion of the case to release the sperm. Three specimens of N. diadema were found each with two spermatophore cases projecting from the vagina and a specimen of N. apiocolpos carried three cases. Assuming that each parasite is able to donate or receive only one spermatophore at each mating, then the presence of one spermatophore does not prevent a further mating and acceptance of a fresh spermatophore. In spite of differences between the spermatophores of E. soleae and N. diadema/N. apiocolpos, the events of spermatophore exchange may be similar.

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.

Calicotyle australis Johnston, 1934 (Monogenea Monxocotylidae) is redescribed from the cloaca of the type-host, the southern fiddler ray Trygonorrhina fasciata (Rhinobatidae) off Adelaide, South Australia. Lobed glands joining the oötype are reported for the first time and may be characteristic of the genus. The presence of an appendix associated with the seminal vesicle in C. australis, previously reported as absent, is confirmed. The anatomy of the oncomiracidium of C. australis is described from observations of live larvae, and the number and distribution of ciliated epidermal cells and sensilla, revealed by silver staining larvae, is also described. Use of larval characters to distinguish between species of Calicotyle Diesing, 1850 and other closely related monocotylids is discussed.

Branchotenthes octohamatus sp. n. (Monogenea: Hexabothriidae) is described from the gills of the southern fiddler ray, Trygonorrhina fasciata Müller et Henle (Elasmobranchii: Rhinobatidae), off Adelaide, South Australia. It is distinguished from the type species, Branchotenthes robinoverstreeti Bullard et Dippenaar, 2003, by producing eggs that are joined end to end forming a chain, in the morphology of the male copulatory organ that has a pronounced constriction in duct diameter between proximal and distal regions, the possession of a thin muscular layer surrounding the proximal part of the male copulatory organ and distal region of the vaginae, and by the absence of a raised process on the shaft of the hamulus. An amended generic diagnosis is provided and the reliability of sperm duct number as a generic character is discussed. The oncomiracidium of B. octohamatus is also described and is the first monogenean to be described with only eight hooklets in the larval haptor. This discovery of eight hooklets may be important for higher-level monogenean evolutionary hypotheses.

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 monogeneans Decacotyle lymmae and D. tetrakordyle (Monocotylidae: Decacotylinae), from gills of the dasyatid stingrays Taeniura lymma and Pastinachus sephen, respectively, have a single aperture for adhesive secretion on each side of the anterior ventrolateral region. Rod-shaped bodies (S1) and electron-dense spherical secretion (S2) exit through specialised ducts opening adjacent to one another within these apertures. The S1 bodies are 230 +/- 11 nm wide and greater than or equal to4 mum long in D. lymmae and 240 +/- 9 nm wide and greater than or equal to3.3 mum long in D. tetrakordyle. The S2 bodies have a diameter of 88 +/- 7 nm in D. lymmae and 65 +/- 6 nm in D. tetrakordyle. The apertures are unusual in being extremely small (internal diameter, 3-5 mum). Each aperture has a slit-like surface opening as small as 160 nm wide, surrounded by muscle fibres indicating that they may be opened and closed. The aperture is also surrounded and underlain by muscle fibres that may aid in secretion from, or even eversion of, the tissue within the aperture. Sensilla/cilia are also found within the apertures. Additional secretions from anteromedian and anterolateral glands (body glands), each containing granular secretions, occur in profusion and exit anteriorly and posteriorly to the position of the apertures, through duct openings in the general body tegument. These granular secretions do not appear to be associated with anterior adhesion. Both species show similarities in aperture, underlying tissue, sense organ, and secretion detail, in accordance with findings from other monogenean genera, and which supports the importance of such data for phylogenetic studies.

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 species (Monogenea: Monocotylidae) are the only monocotylids to parasitize the skin of chondrichthyan hosts. Currently 11 species are recorded from the skin of ray species in the Dasyatidae, Myliobatidae and Urolophidae. There have been increasing reports of Dendromonocotyle outbreaks on rays kept in public aquaria. This paper provides a broad review of Dendromonocotyle that should assist taxonomists and aquarists with species identification and help decisions on potential control methods for Dendromonocotyle infections. The taxonomy and host-specificity of Dendromonocotyle are discussed and a key to current species is provided. We summarise what little is known about the biology of Dendromonocotyle including egg embryonation and hatching, feeding, camouflage and reproduction. The efficacy of freshwater baths, chemical treatments and biological control measures such as the use of cleaner fish for Dendromonocotyle is also discussed. We demonstrate that effective control of Dendromonocotyle on captive rays is hampered by the lack of basic biological data on the life cycle of the parasites. A case history is provided outlining the success of a public aquarium (Underwater World, Mooloolaba, Queensland, Australia) in managing D. pipinna infections on captive Taeniura meyeni without chemical intervention simply by taking measures to reduce host stress.

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.

Experimental infections were used to track the fate of the dorsal sensilla of Merizocotyle icopae (Monogenea: Monocotylidae) from nasal tissue of the shovelnose ray, Rhinobatos typus (Rhinobatidae). Scanning and transmission electron microscopy revealed that 3 types of uniciliate dorsal sensilla exist at different times in the development of the monogenean. Type 1 sensilla have little or no invagination where the cilium exits the distal end of the dendrite and possess a ring of epidermis surrounding the cilium distal to the invagination. Type 2 sensilla have a deep invagination where the cilium exits the dendrite. Type 3 sensilla can be distinguished from the other types by the shape of the dendrite. The larvae have predominantly Type I dorsal sensilla, most of which are lost approximately 24 h after infection and a few Type 2 sensilla, which are retained. Additional Type 2 sensilla (termed Adult Type 2 sensilla), which are slightly different morphologically from the Type 2 sensilla of the larvae, form in later stages of development. Numerous Type 3 sensilla are unique to the dorsal surface of adults. Loss of all Type I sensilla upon attachment to the host, R. typus, suggests that these may be chemo- or mechanoreceptors responsible for host location by the swimming infective larvae. Type 2 sensilla appear to be important in the larvae, juveniles, and adults whereas the modality mediated by Type 3 is specific to adults. (C) 2003 Wiley-Liss, Inc.

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...

Secreted anterior adhesives, used for temporary attachment to epithelial surfaces of fishes (skin and gills) by some monogenean (platyhelminth) parasites have been partially characterised. Adhesive is composed of protein. Amino acid composition has been determined for seven monopisthocotylean monogeneans. Six of these belong to the Monocotylidae and one species, Entobdella soleae (van Beneden et Hesse, 1864) Johnston, 1929, is a member of the Capsalidae. Histochemistry shows that the adhesive does not contain polysaccharides, including acid mucins, or lipids. The adhesive before secretion and in its secreted form contains no dihydroxyphenylalanine (dopa). Secreted adhesive is highly insoluble, but has a soft consistency and is mechanically removable from glass surfaces. Generally there are high levels of glycine and alanine, low levels of tyrosine and methionine, and histidine is often absent. However, amino acid content varies between species, the biggest differences evident when the monocotylid monogeneans were compared with E. soleae. Monogenean adhesive shows similarity in amino acid profile with adhesives from starfish, limpets and barnacles. However, there are some differences in individual amino acids in the temporary adhesive secretions of, on the one hand, the monogeneans and, on the other hand, the starfish and limpets. These differences may reflect the fact that monogeneans, unlike starfish and barnacles, attach to living tissue (tissue adhesion). A method of extracting unsecreted adhesive was investigated for use in further characterisation studies on monogenean glues.

The current classification of the Monocotylidae (Monogenea) is based on a phylogeny generated from morphological characters. The present study tests the morphological phylogenetic hypothesis using molecular methods. Sequences from domains C2 and D1 and the partial domains C1 and D2 from the 28S rDNA gene for 26 species of monocotylids from six of the seven subfamilies were used. Trees were generated using maximum parsimony, neighbour joining and maximum likelihood algorithms. The maximum parsimony tree, with branches showing less than 70% bootstrap support collapsed, had a topology identical to that obtained using the maximum likelihood analysis. The neighbour joining tree, with branches showing less than 70% support collapsed, differed only in its placement of Heterocotyle capricornensis as the sister group to the Decacotylinae clade. The molecular tree largely supports the subfamilies established using morphological characters. Differences are primarily how the subfamilies are related to each other. The monophyly of the Calicotylinae and Merizocotylinae and their sister group relationship is supported by high bootstrap values in all three methods, but relationships within the Merizocotylinae are unclear. Merizocotyle is paraphyletic and our data suggest that Mycteronastes and Thaumatocotyle, which were synonymized with Merizocotyle after the morphological cladistic analysis, should perhaps be resurrected as valid genera. The monophyly of the Monocotylinae and Decacotylinae is also supported by high bootstrap values. The Decacotylinae, which was considered previously to be the sister group to the Calicotylinae plus Merizocotylinae, is grouped in an unresolved polychotomy with the Monocotylinae and members of the Heterocotylinae. According to our molecular data, the Heterocotylinae is paraphyletic. Molecular data support a sister group relationship between Troglocephalus rhinobatidis and Neoheterocotyle rhinobatidis to the exclusion of the other species of Neoheterocotyle and recognition of Troglocephalus renders Neoheterocotyle paraphyletic. We propose Troglocephalus incertae sedis. An updated classification and full species list of the Monocotylidae is provided.

The Gyrodactylidae is a diverse family of predominantly viviparous monogeneans (for familial status of oviparous genera see Boeger W.A, Kritsky D.C, Belmont-Jegu E. 1994: J. Helminthol. Soc. Wash. 61: 34-44) found on a wide variety of fish taxa globally. Gyrodactylids are thought to be more common in high latitude environments and conversely less common in low latitude environments such as the Great Barrier Reef (GBR) (Rohde K. 1985: Hydrobiologia 127: 197201). Most research on gyrodactylids has been carried out in temperate areas of Europe and North America, but the gyrodactylid fauna of the Indo-Pacific Ocean remains comparatively unknown. In Australia, for example, few of the estimated 3000 coastal marine fish species (Kuiter R.H. 1996: Guide to Sea Fishes of Australia. New Holland, Sydney, 433 pp.) have been examined thoroughly for small ectoparasites such as gyrodactylids. There is the potential, therefore, for a diverse, undiscovered gyrodactylid fauna on Australian marine fishes. This note presents the results of a survey for these parasites from coastal marine fishes from Queensland, Australia. Our survey has resulted in the discovery of several new gyrodactylid species, and descriptions of some of these have already been published (Ernst I., Whittington I.D., Jones M.K. 2000: Syst. Parasitol. 45: 61-73; Ernst I., Jones M.K., Whittington I.D. 2001: J. Nat. Hist. 35: 313-340). Fishes were collected between 1995 and 2000 by beach seine, cast net, line fishing, anaesthetic (clove oil) or spearfishing. On the GBR, fishes were collected at Heron and Wistari Reefs (23°27’S, 151°55’E) in the southern region and Eagle Islet (14°42’S, 145°23’E) and Lizard Island (14°40’S, 145°28’E) in the northern region. Fishes were collected in south-east Queensland at Amity Point (27°45’S, 153°26’E), Dunwich (27°30’S, 153°24’E), Manly (27°28’S, 153°11’E), Redcliffe (27°14’S, 153°07’E), Wellington Point (27°28’S, 153°11’E), Noosa (26°23’S, 153°07’E), Nudgee Beach (27°21’S, 153°06’E) and Southport Broadwater (27°58’S, 153°25’E). Fishes were identified using the books of Randall et al. (Randall J.E., Allen G.R., Steene R.C. 1990, 1998: Fishes of the Great Barrier Reef and Coral Sea. Editions 1 and 2. Crawford House Press, Bathurst, 507 pp. and 557 pp.), Kuiter (Kuiter R.H. 1993: Coastal Fishes of South-Eastern Australia. Crawford House Press, Bathurst, 437 pp.) and Myers (Myers R.F. 1991: Micronesian Reef Fishes. Coral Graphics, Guam, 298 pp.). Live fish of the same species were placed in individual containers of seawater for transport to the laboratory where they were held in separate aquaria until dissection. Fish were killed and dissected and worms were mounted as described in Ernst et al. (2000, op. cit.). Specimens are deposited in the Queensland Museum (QM), P.O. Box 3300, Brisbane, Queensland 4101, Australia. We examined 501 marine teleosts comprising 104 species in 37 families (Table 1). Gyrodactylids were found on 20 fish species (19% of those examined) from 9 families. At least 16 different species of gyrodactylids were found in this survey including: 7 species of Gyrodactylus von Nordmann, 1832, 7 species of Acanthoplacatus Ernst, Jones et Whittington, 2001, 1 species of Anacanthocotyle Kritsky et Fritts, 1970 and 1 species of Polyclithrum Rogers, 1967 (Table 2). Due to insufficient material, the specific status could not be determined for a single specimen of Gyrodactylus from a goby and specimens of Acanthoplacatus from two siganid species (Table 2). It is possible that these specimens represent three additional gyrodactylid species. Therefore, the gyrodactylids collected in this survey represent between 16 and 19 species. Those specimens ascribed specific status (Table 2) are considered to be new species (see also Ernst et al. 2001, op. cit.) and constitute a major addition to the known gyrodactylid fauna of the world which is estimated to include over 400 species (see Harris P.D. 1993: Bull. Fr. Peche Piscic. 328: 546). When interpreting these data, two sources of bias should be borne in mind. First, we did not examine species in some potential host families that have been studied for monogeneans previously and which are not reported as hosts of gyrodactylids (e.g. Lethrinidae, Serranidae; see Whittington I.D. 1998: Int. J. Parasitol. 28: 1481-1493). Secondly, only a few specimens of some fish species were examined (Table 1). Of 104 marine fish species examined in this survey, 33 species are represented by 5 or more specimens and only 13 species are represented by 10 or more specimens (Table 1). With sample sizes of 5 and 10 individuals, parasite prevalences of up to 45 and 26%, respectively (95% confidence limit) could go undetected (see Post R.J., Millest A.L. 1991: Parasitol. Today 7: 141). Therefore the reported absence of gyrodactylids from some fish species should be interpreted cautiously because only relatively prevalent gyrodactylid species are likely to have been detected. This is not the first survey for monogeneans in marine waters of Australia. Rohde (1985, op. cit.) presented the results of surveys for monogeneans from the northern GBR where he examined 239 specimens of 56 fish species, the southern GBR where he examined 392 specimens of 74 fish species and northern New South Wales (NSW) where he examined 1859 specimens of 45 fish species. Gyrodactylid species were poorly represented, with only one or two unidentified species recorded from the southern GBR and one unidentified species recorded in northern NSW. Rohde (1985, op. cit.) compared these results with surveys for monogeneans from other geographic areas. He presented data showing that FOLIA PARASITOLOGICA 48: 165-168, 2001

Benedenia Diesing, 1858, a genus of capsalid (benedeniine) monogeneans, is redefined. The generic diagnosis is amended to include: the path of tendons in the haptor from extrinsic muscles in the body; presence and form of the marginal valve; a penis occupying a penis canal with weakly muscular wall; a weakly muscular accessory gland reservoir proximal to the penis and enclosed by a proximal extension of the wall of the penis canal; male and female genital apertures usually common, rarely separate; vagina with pore usually close to the common genital pore but may open in mid body between the germarium and the common genital pore, or anterior to the common genital pore. A conservative approach is adopted and the generic diagnosis is clarified and broadened to accommodate species that display some variation in reproductive anatomy, especially of the female system. We argue against potential alternative actions such as defining Benedenia strictly to contain species with separate male and female genital apertures and against recognition of a separate genus, Tareenia Hussey, 1986, for species with a vaginal pore anterior to the common genital pore. Under our conception, Benedenia comprises 21 species: B. sciaenae (van Beneden, 1856) Odhner, 1905 (type species); B. acanthopagri (Hussey, 1986) comb. nov.; B. anticavaginata Byrnes, 1986; B. bodiani Yamaguti, 1968; B. elongata (Yamaguti, 1968) Egorova, 1997; B. epinepheli (Yamaguti, 1937) Meserve, 1938; B. hawaiiensis Yamaguti, 1968; B. hendorffi(von Linstow, 1889) Odhner, 1905; B. hoshinai Ogawa, 1984; B. innobilitata Burhnheim Gomes and Varela, 1973: B. jaliscana Bravo-Hollis, 1952; B. lolo Yamaguti, 1968; B. lutjani Whittington and Kearn, 1993: B. monticellii (Parona and Perugia, 1895) Johnston, 1929; B. ovata (Goto, 1894) Johnston. 1929: B. pompatica Burhnheim, Gomes and Varela, 1973; B. rohdei Whittington, Kearn and Beverley-Burton, 1994; B. scari Yamaguti, 1968; B. sekii (Yamaguti, 1937) Meserve, 1938; B, seriolae (Yamaguti, 1934) Meserve, 1938; and B. synagris Yamaguti, 1953. The type species, B. sciaenae, is redescribed based on new material from Australia. No types for this taxon were designated and we have assigned a series of voucher specimens. Tareenia acanthopagri Hussey, 1986 becomes B. acanthopagri (Hussey, 1986) comb. nov. and T. anticavaginata (Byrnes, 1986) Egorova, 1997 and T. lutjani (Whittington and Kearn, 1993) Egorova, 1997 are returned to Benedenia as B. anticavaginata and B. lutjani Benedenia akaisaki Iwata, 1990 is considered a synonym of B. ovata and B. kintoki Iwata, 1990 is considered a synonym of B. elongata. Two species, B, madai Ishii and Sawada, 1938 and B. pagrosomi Ishii and Sawada, 1938, are considered species inquirendae. Based on the redefinition of Benedenia, the diagnosis for the Benedeniinae is amended. Tareenia is synonymized with Benedenia but Menziesia Gibson, 1976 is recognized and its generic diagnosis amended to include: anterior attachment organs tending to form a 'hooded' appearance; prominent anterior gland cells between the pharynx and the anterior margin of the body: long penis, tapering proximally, occupying a penis canal with weakly muscular wall: penis canal and penis describe a sigmoid; accessory gland reservoir dorsal and alongside, or posterior and lateral to, proximal end of the penis and enclosed by a proximal extension of the wall of the penis canal. Under this conception. Menziesia comprises: M. noblei (Menzies. 1946) Gibson, 1976 (type species); M. malaboni (Velasquez. 1982) comb. nov.: M. merinthe (Yamaguti, 1968) Gibson. 1976: M. ovalis (Yamaguti, 1968) Gibson, 1976: and M. sebastodis (Yamaguti, 1934) comb, nov. A key to valid species of Benedenia and Menziesia is provided and a list is presented of published records of undescribed or unattributed species of Benedenia. Some protocols are suggested for preparation of benedeniine material to enhance future taxonomic studies and comparisons. The host-specificity and geographic distribution of species in these revised genera are discussed. The composition of the Capsalidae is discussed and some difficulties in defining and distinguishing between its different subfamilies are considered.

Dendromonocotyle colorni sp. n. (Monogenea: Monocotylidae) is described from the dorsal skin surface of two specimens of Himantura uarnak (Forsskål) kept at the Eilat Underwater Observatory in Israel. Dendromonocotyle colorni is distinguished from the other eight species in the genus by the morphology of the terminal papillar sclerite on the haptor, the distal portion of the male copulatory organ and the morphology of the vagina. The development of the male copulatory organ is detailed for D. colorni and the adaptations of species of Dendromonocotyle to life on the dorsal skin surface of rays are discussed. Dendromonocotyle octodiscus Hargis, 1955 was identified from the dorsal skin surface of the southern stingray Dasyatis americana Hildebrand et Schroeder off Bimini, Bahamas and represents a new host record.

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.

The monogenean Neobenedenia melleni (Mac- Callum, 1927) Yamaguti 1963 is a well-known and virulent pathogen in culture conditions recorded from the skin of many teleost fish species worldwide. Until now, N. melleni has not been reported from wild or cultured fish in Australian waters. This study documents a recent outbreak of N. melleni that occurred on Lates calcarifer (barramundi) cultivated in sea cages in Hinchinbrook Channel between Hinchinbrook Island and mainland Queensland, Australia, which resulted in the loss of 200 000 fish (50 tonnes). The origin of this outbreak is unclear because N. melleni has not been recorded from any wild host species in Australia and strict quarantine regulations exclude the possibility of its introduction on imported fish. We propose that N. melleni occurs naturally on wild populations of some teleost species in Australian waters and that the few surveys of wild fish conducted along the eastcoast have failed to report this species. The possibility that uncharacteristically low water temperatures led to the outbreak is discussed.

Eggs of Neoheterocotyle rhinobatidis, Troglocephalus rhinobatidis and Merizocotyle icopae (Monogenea: Monocotylidae) from the shovelnose ray Rhinobatos typus (Rhinobatidae) have a distinct hatching pattern linked to light periodicity. Larvae of these 3 monogenean species emerge only during daylight when exposed to natural illumination or when incubated in alternating 12 h periods of light and dark (light on 06.00 h, light off 18.00 h). N. rhinobatidis larvae emerge with a distinct peak during the first 2 h of light; this peak is not as pronounced in T. rhinobatidis or M. icopae. Eggs of N. rhinobatidis incubated in a reverse light/dark cycle (light on 18.00 h, light off 06.00 h) hatched only during periods of illumination, again with a peak during the first 2 h of light. Evidence suggests that the hatching patterns observed in all 3 species represent true circadian rhythms because eggs incubated in 24 h light or 24 h dark conditions continued to hatch with a rhythm. Shadows, disturbance and host tissue did not promote hatching in N. rhinobatidis or T. rhinobatidis but there were indications that host tissue may promote hatching in M. icopae. The hatching patterns observed are discussed with respect to their adaptive responses to host behaviour and predation pressure.

Heliocotyle ewingi sp. n. (Monogenea: Monocotylidae) is described from the gills of Myliobatis australis Macleay, 1881 (Myliobatididae) collected from Norfolk Bay near Hobart, Tasmania, Australia. Heliocotyle ewingi can be distinguished readily from the only other species in the genus, Heliocotyle kartasi Neifar, Euzet et Ben Hassine, 1999, by the presence of a single pseudoseptum on each of the peripheral loculi except the posteriormost, eyespots and by the morphology of the male copulatory organ which is a short, straight sclerotised tube which lacks a sclerotised accessory piece. The generic diagnosis is revised to accommodate the new species and the anterior glands are discussed.

Monogeneans (flatworms) are among the most host-specific of parasites in general and may be the most host-specific of all fish parasites. Specificity, in terms of a restricted spatial distribution within an environment, is not unique to parasites and is displayed by some fungi, insects, birds, symbionts and pelagic larvae of free-living marine invertebrates. The nature of cues, how "habitats" are recognised and how interactions between partners are mediated and maintained is of interest across these diverse "associations". We review some experiments that demonstrate important factors that contribute to host-specificity at the level of infective stages (larvae of oviparous monogeneans; juveniles of viviparous gyrodactylids) and adult parasites. Recent research on immune responses by fish to monogenean infections is considered. We emphasise the critical importance of host epidermis to the Monogenea. Monogeneans live on host epidermis, they live in its products (e.g. mucus), monopisthocotyleans feed on it, some of its products are "attractants" and it may be an inhospitable surface because of its immunological activity. We focus attention on fish but reference is made to amphibian hosts. We develop the concept for a potential role in host-specificity by the anterior adhesive areas, either the specialised tegument and/or anterior secretions produced by monogeneans for temporary but firm attachment during locomotion on host epithelial surfaces. Initial contact between the anterior adhesive areas of infective stages and host epidermis may serve two important purposes. (1) Appropriate sense organs or receptors on the parasite interact with a specific chemical or chemicals or with surface structures on host epidermis. (2) A specific but instant recognition or reaction occurs between component(s) of host mucus and the adhesive(s) secreted by monogeneans. The chemical composition of fish skin is known to be species-specific and our preliminary analysis of the chemistry of some monogenean adhesives indicates they are novel proteins that display some differences between parasite families and species.

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.

Empruthotrema tasmaniensis sp. nov. is described from the nasal fossae of the southern eagle ray, Myliobatis australis Macleay (Myliobatidae), from the east coast of Tasmania. Empruthotrema tasmaniensis is distinguished from others in the genus by the presence of an accessory piece associated with the male copulatory organ; no other species of Empruthotrema Johnston and Tiegs, 1922 has an accessory piece. Merizocotyle urolophi sp. nov. is described from the nasal fossae of the sparsely spotted stingaree, Urolophus paucimaculatus Dixon (Urolophidae), and is distinguished from other members of the genus by 12 marginal loculi on the haptor; this is the only species of Merizocotyle Cerfontaine, 1894 that has this configuration. Squalotrema llewellyni Kearn and Green, 1983, described previously from Squalus acanthias Linnaeus (Squalidae) from the English Channel, is recorded from the same host species caught off the east coast of Tasmania. We found Triloculotrema japanica Kearn, 1993, which was described origi...

Ultrastructural details of reproductive epithelia in the viviparous monogenean Gyrodactylus kobayashii are described. Specimens of G. kobayashii were fixed for transmission electron microscopy in glutaraldehyde in sodium cacodylate buffer followed by either 1% aqueous osmium tetroxide or 1% aqueous osmium tetroxide reduced with 1.5% potassium ferricyanide. All reproductive epithelia are underlain by a fibrillar basal matrix. The uterine basal matrix is electron-opaque after potassium ferricyanide reduced osmium tetroxide fixation suggesting the presence of carbohydrate-containing materials. With potassium ferricyanide reduced osmium tetroxide fixation, two prominent membrane systems were distinguished in the uterine epithelium. Basal invaginations are short infoldings of the basal membrane. The basal invaginations are common in other reproductive epithelia and tegument and probably enhance transport of materials by these epithelia. Laminated membranes are membrane stacks, resembling endoplasmic reticulum stacks. These membranes were abundant at the apical membrane. The birth plug is a solid cytoplasmic layer, lacking a lumen, and rich in cytoplasmic vesicles. This layer connects the tegument and the uterine epithelium.

There are approximately 25,000 species of fishes known in the world. The Monogenea are believed to be among the most host-specific of parasites and if each species of fish is host to a different species of monogenean, there could be almost 25,000 monogenean species on Earth. Currently, I estimate that between 3000 and 4000 of these are described. Australia has a rich marine fish fauna with approximately 3500 species of teleosts. If the same formula of one monogenean species per host fish species is applied, Australia marine fishes could host potentially 3500 species of monogeneans. The first monogenean species described from Australia was Encotyllabe pagrosomi MacCallum, 1917 and approximately 300 more species have since been described from the continent. Even in a region of Australia such as Heron Island on the Great Barrier Reef that has been a focus of sustained research on these parasites, only about 85 species are described from 40 of the most common, easily-caught species of fish. Reasons are discussed for the relatively small numbers of monogenean species described so far from Australia. Endemicity is difficult to judge, but only one is certain: Concinnocotyla australensis (Polystomatidae) from Neoceratodus forsteri (Dipnoi). Despite reductions in research funding, the value of parasite taxonomy must not be underestimated, particularly in regions of the world that have a rich diversity of potential hosts.

The anterior adhesive areas of a monocotylid monogenean, Merizocotyle australensis (Merizocotylinae), were investigated. They comprise 6 ventral apertures in 2 groups of 3 arranged at the anterolateral margins of the head. These regions are also well supplied with groups of cilia. Each aperture is 13.8 to 15.8 μm wide and contains multiple tubular projections that are covered with microvilli through which open 2 types of secretory cell ducts that carry either rod-shaped or spherical secretory bodies. The gland cell bodies that produce these 2 types of secretions co-occur at the anterior end. The 2 types of secretory bodies occur adjacent to one another and both are present in the extruded adhesive. The membranes of rod-shaped bodies are retained in the extruded glue. Rod-shaped bodies are 390 ± 18 nm wide, at least 10.9 pm long, and show 2 types of internal periodic banding: 10.6 nm and 143 ± 3 nm. The spherical vesicles are 130 ± 6 nm in diameter and are electron-dense. A third secretion is present in separate ducts that also open anteriorly but emerge through the tegument between the ventral apertures. This secretion does not appear to be part of the adhesive secretion. The bodies of the third secretion are elongate, electron-dense, and 374 ± 23 nm long. Inside the 'lip' of the aperture, general body tegument abuts tegument specific to the aperture. The general body tegument is thicker, contains electron-dense vesicles, and has a ridged surface devoid of microvilli. Where the 2 kinds of tegument meet, they are connected by septate desmosomes.

Monocotylid monogeneans inhabit a wide diversity of sites on their chondrichthyan hosts including the skin, gills, nasal fossae, urogenital system and coelom. The large variation in the morphology of the haptor appears to reflect this diversity in attachment sites. We demonstrate that the complexity of the haptor can be related to the habitat of the parasite. Generally, those parasites which live in habitats subject to strong water currents such as the gills and dorsal skin surface have more complex haptors than those in environments exposed to weaker or no water currents including the nasal fossae, urogenital system and body cavity. However, there can be considerable variation in haptoral components, even among congeners, living on the ‘gills’ of their hosts. The microhabitat was determined for Monocotyle helicophallus and M. spiremae, both from the gills of the pink whipray, Himantura fai, and M. corali from the gills of the cowtail ray, Pastinachus sephen. We demonstrate that differences in the morphology of the hamuli and the number and morphology of septal sclerites and marginal papillae among these species of Monocotyle can be related directly to their microhabitat. It also appears that different haptoral structures are important for attachment to the host at different stages in the development of the parasite, based on studies on the development and distribution of Neoheterocotyle rhinobatidis from the gills of the common shovelnose ray Rhinobatos typus.

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.

Rhinobatos typus and Rhynchobatus djiddensis were collected from Heron Island, Australia and examined for monocotylid parasites. Specimens of Neoheterocotyle rhinobatidis (Young, 1967) Chisholm, 1994 and N. rhynchobatis (Tripathi, 1959) Chisholm, 1994 were collected from the gills of Rhinobatos typus . This represents both a new host and new locality record for N. rhynchobatis. Neoheterocotyle bychowskyi (Timofeeva, 1981) Chisholm, 1994, N. nagibinae (Timofeeva, 1981) Chisholm, 1994 and N. rhinobatis (Pillai & Pillai, 1976) n. comb. were identified from the gills of Rhynchobatus djiddensis from Australia and are all new locality records. We consider N. djiddensis (Pillai & Pillai, 1977) n. comb. a species inquirenda and synonymise N. trilobata Timofeeva, 1981 with N. rhinobatis . Therefore, there are 7 valid species in the genus, including N. bychowskyi, N. forficata, N. inpristi, N. nagibinae, N. rhinobatidis, N. rhinobatis and N. rhynchobatis . The larvae of N. rhinobatis and N. rhynchobatis are described and the anterior glands of the larvae are related to those of the adults. The development of the male copulatory organ of N. rhinobatidis is described. Host-specificity and geographic range of the genus are also discussed and a key to species is provided.

Observations with the light microscope and the scanning and transmission electron microscopes have shown that the anterior end of Monocotyle spiremae has 8 slit-like apertures on the ventrolateral margins at each side of the mouth. Gland cells located next to the pharynx produce rod-shaped secretory bodies that are conveyed in ducts that open on to the surfaces of rounded lobes inside “reservoirs” behind each ventral, slit-like aperture. Rod-shaped secretory bodies are extruded into the “reservoirs” and appear to combine and form a homogeneous secretion which may bond the ventrolateral regions of the head of the parasite to a substrate. At no stage, however, were intact rods observed outside the duct endings. Gland cells that produce an ovoid secretory body also supply the head of M. spiremae , but ducts from these open dorsal and anterior to the mouth in a region where the parasite is not known to attach. There appears to be little or no chance for the ventral rods and the dorsal ovoid secretion to mix. This is the first record of a monogenean parasite with a single type of secretion supplying the ventral surfaces of the anterior end. The rods in M. spiremae differ in some respects from the rod-shaped bodies recorded previously among gyrodactylid, dactylogyrid, capsalid and acanthocotylid monogeneans.

This review examines briefly the reproductive capacity of representatives of the 4 principal groups of platyhelminths, the "Turbellaria", Monogenea, Digenea and Cestoda. Of the flatworms, 3 main groups are wholly parasitic (monogeneans; digeneans; cestodes). Among the largely free-living "Turbellaria", there are several parasitic representatives in some families (Umagillidae; Graffillidae; Pterastericolidae; Fecampiidae; Acholadidae). Endoparasitic platyhelminths with complex life-cycles produce large numbers of eggs and numbers of offspring are increased further in the digeneans and a few cestodes by asexual multiplication. Like their free-living relatives, most ectosymbiotic and ento- and ectoparasitic flatworms ("turbellarians" and monogeneans) produce, on the whole, far fewer eggs and progeny but are still successful organisms in terms of their numbers of species and diversity. Estimates of parasite fecundity from in vivo experiments are needed for representatives from all flatworm groups. For those parasites that are host-specific, the particular species of host provides a predictable target to be located. Adaptations displayed by the eggs and infective stages of some flatworms increase their chances of finding and recognising their specific host and these are reviewed: attachment of eggs to their "host"; egg hatching in response to host chemicals; rhythmical emergence; special behaviours of infective stages; host recognition.

Spontaneous hatching of eggs of Benedenia lutjani and B. rohdei occurred after incubation for 4–6 days and 6–10 days, respectively, at a constant temperature in the range 22–28°C when exposed to natural illumination or to alternating 12-h periods of light and darkness (LD12:12; light on, 06.00 h; light off, 18.00 h). Under these conditions, hatching of the eggs of both species was rhythmical, all larvae emerging only during periods of illumination. Hatching was not confined to particular times within the illuminated period. Evidence for an endogenous component to the rhythm was revealed by transfer of eggs from LD12:12 to continuous darkness (DD) near the end of the incubation period. Hatching also occurred only during periods of illumination when eggs of each species were incubated under a DL12:12 regime (i.e. period of illumination 18.00 h to 06.00 h; period of darkness 06.00 h to 18.00 h). When the eggs of B. lutjani and B. rohdei were laid and incubated in DD or continuous illumination (LL), some degree of rhythmicity persisted, raising the possibility that the eggs inherit circadian rhythmicity from their parent. The hatching patterns of these 2 species of monogeneans are discussed in relation to host finding, host behaviour and limited observations on the behaviour of the oncomiracidia after hatching.

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.