Streptococcus iniae associated mass marine fish kill off Western Australia.

Streptococcus iniae causes high mortality in cultured and wild fish stocks globally. Since the first report in captive Amazon river dolphins Inia geoffrensis in 1976, it has emerged in finfish across all continents except Antarctica. In March 2016, an estimated 17000 fish were observed dead and dying along a remote 70 km stretch of the Kimberley coastline north of Broome, Western Australia. Affected species included finfish (lionfish Pterois volitans, angelfish Pomacanthus sp., stripey snapper Lutjanus carponotatus, sand bass Psammoperca waigiensis, yellowtail grunter Amniataba caudavittata, damselfish Pomacentridae sp.), flatback sea turtles Natator depressus, and olive (Aipysurus laevis) and black-ringed (Hydrelaps darwiniensis) sea snakes. Moribund fish collected during the event exhibited exophthalmia and abnormal behaviour, such as spiralling on the surface or within the water column. Subsequent histopathological examination of 2 fish species revealed bacterial septicaemia with chains of Gram-positive cocci seen in multiple organs and within brain tissue. S. iniae was isolated and identified by bacterial culture, species-specific PCR, Matrix-Assisted Laser Desorption Ionisation Time-Of-Flight (MALDI-TOF) and biochemical testing. This is the first report of S. iniae associated with a major multi-species wild marine fish kill in Australia. Extreme weather events in the region including a marked decrease in water temperatures, followed by an extended period of above-average coastal water temperatures, were implicated as stressors potentially contributing to this outbreak.

A new genus and species of the trematode family Gyliauchenidae Fukui, 1929 from an unexpected, but plausible, host, Kyphosus cornelii (Perciformes: Kyphosidae).

The Enenteridae Yamaguti, 1958 and Gyliauchenidae Fukui, 1929 exhibit an interesting pattern of host partitioning in herbivorous fishes of the Indo-West Pacific. Enenterids are known almost exclusively from fishes of the family Kyphosidae, a group of herbivorous marine fishes common on tropical and temperate reefs. In contrast, gyliauchenids are found in most of the remaining lineages of marine herbivorous fishes, but until the present study, had never been known from kyphosids. Here we report on the first species of gyliauchenid known from a kyphosid. Endochortophagus protoporus gen. nov., sp. nov. was recovered from the Western buffalo bream, Kyphosus cornelii (Whitley, 1944), collected off Western Australia. Kyphosus cornelii also hosts an enenterid, Koseiria allanwilliamsi Bray & Cribb, 2002, and is thus the first fish known in which enenterids and gyliauchenids co-occur. Molecular phylogenetic analyses place the new species close to those of Affecauda Hall & Chambers, 1999 and Flagellotrema Ozaki, 1936, but there is sufficient morphological evidence, combined with the unusual host, to consider it distinct from these genera. We discuss factors which may have contributed to the host partitioning pattern observed between enenterids and gyliauchenids.

DNA profiling reveals Neobenedenia girellae as the primary parasitic monogenean in global fisheries and aquaculture.

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.

Two species of Neometadena Hafeezullah & Siddiqi, 1970 (Digenea: Cryptogonimidae) from Moreton Bay, Australia, including the description of Neometadena paucispina n. sp. from Australian Lutjanidae.

A survey of the trematode fauna of lutjanid fishes off the east coast of Queensland (QLD), Australia revealed the presence of two species of Neometadena Hafeezullah & Siddiqi, 1970 (Digenea: Cryptogonimidae). Neometadena paucispina n. sp. is described from the intestine and pyloric caeca of Lutjanus fulviflamma (Forsskål) and L. russellii (Bleeker) from Moreton Bay, in southeast QLD. Specimens of the type- and only other species, N. ovata (Yamaguti, 1952) Miller & Cribb, 2008, were recovered from L. carponotatus (Richardson), L. fulviflamma, L. fulvus (Forster), L. russellii, and L. vitta (Quoy & Gaimard) off Lizard Island, on the northern Great Barrier Reef (GBR). Neometadena paucispina is distinguished from N. ovata in having fewer oral spines (55-65 vs 67-80). Alignment of novel molecular data for these two taxa revealed that they differ consistently by 13 nucleotides (1.5%) over the partial large subunit (LSU), 34 nucleotides (6.6%) over the internal transcribed spacer 1 (ITS1), 0 nucleotides over the 5.8S, and 21 nucleotides (7.3%) over the ITS2 rDNA regions. Despite relatively large samples of L. carponotatus, L. fulviflamma and L. russellii from three distinct locations along the east coast of QLD (i.e. Moreton Bay in the south, Heron Island in central QLD and Lizard Island in northern QLD), these two species have been found at only one site each with neither species at Heron Island. These distributions are discussed in the context of the wide distribution of other cryptogonomid species in the same hosts elsewhere in the Indo-West Pacific.

Host Specificity and Ecology of Digenean Parasites of Nassariid Gastropods in Central Queensland, Australia, with Comments on Host-Parasite Associations of the Nassariidae.

Nassariid gastropods are well represented in Australia, and Nassarius dorsatus (Röding), Nassarius olivaceus (Bruguière), and Nassarius pullus (Linnaeus) are common in the intertidal mangroves of the Capricornia region in Central Queensland. A survey of the digenean trematode fauna of nassariids of the region revealed cercariae of 12 species from six trematode families associated with these gastropods. Six species of Acanthocolpidae were found, including three putative species of the genus Stephanostomum. Additionally, two species of Himasthlidae and one species each of Microphallidae, Opecoelidae, Zoogonidae, and Lepocreadiidae were identified. The majority of the trematode species identified were found in only one host species; only four infected more than one species of nassariid. Sixteen new host-parasite combinations were added to the fauna known to infect the Nassariidae. Broader examination of host-parasite associations shows that families using nassariids commonly as first intermediate host are the Acanthocolpidae, Lepocreadiidae, and Zoogonidae, as well as Himasthla spp. from the Himasthlidae. Nassariid gastropods are also the dominant marine first intermediate hosts for the Acanthocolpidae, Lepocreadiidae, and Zoogonidae and one of the three most common first intermediate host families for marine Himasthla spp.

Culture-independent genomics of a novel chlamydial pathogen of fish provides new insight into host-specific adaptations utilized by these intracellular bacteria.

Several Chlamydiales families are associated with epitheliocystis, a common condition of the fish gill epithelium. These families share common ancestors with the Chlamydiaceae and environmental Chlamydiae. Due to the lack of culture systems, little is known about the biology of these chlamydial fish pathogens. We investigated epitheliocystis in cultured Orange-spotted grouper (Epinephelus coioides) from North Queensland, Australia. Basophilic inclusions were present in the gills of 22/31 fish and the presence of the chlamydial pathogen in the cysts was confirmed by in situ hybridization. Giant grouper (Epinephelus lanceolatus) cultured in the same systems were epitheliocystis free. 16S rRNA gene sequencing revealed a novel member of the Candidatus Parilichlamydiaceae: Ca. Similichlamydia epinephelii. Using metagenomic approaches, we obtained an estimated 68% of the chlamydial genome, revealing that this novel chlamydial pathogen shares a number of key pathogenic hallmarks with the Chlamydiaceae, including an intact Type III Secretion system and several chlamydial virulence factors. This provides additional evidence that these pathogenic mechanisms were acquired early in the evolution of this unique bacterial phylum. The identification and genomic characterization of Ca. S. epinephelii provides new opportunities to study the biology of distantly-related chlamydial pathogens while shining a new light on the evolution of pathogenicity of the Chlamydiaceae.

Patterns of specificity and diversity in species of Paraorygmatobothrium Ruhnke, 1994 (Cestoda: Phyllobothriidae) in Moreton Bay, Queensland, Australia, with the description of four new species.

A survey of tapeworms of galeomorph sharks from Moreton Bay (Queensland, Australia) identified a complex of species of Paraorygmatobothrium Ruhnke, 1994 infecting 11 carcharhiniform and two orectolobiform species. Combined morphological and multi-locus molecular analyses (based on the 28S nuclear ribosomal RNA and partial mitochondrial NADH dehydrogenase subunit 1 genes) revealed the presence of 12 species of Paraorygmatobothrium; four species (Paraorygmatobothrium christopheri n. sp., P. harti n. sp., P. sinclairtaylori n. sp. and P. ullmanni n. sp.) are considered to be new to science and are formally described, four represent known species, and four lack sufficient morphological data to allow definitive identification. In contrast to previous records for the genus, four of the species found in this study exhibited low host specificity [P. orectolobi (Butler, 1987) Ruhnke, 2011, P. sinclairtaylori, P. ullmanni and Paraorygmatobothrium sp. 3], three stenoxenic species were each found in two closely-related sharks (P. orectolobi, P. ullmanni and Paraorygmatobothrium sp. 3) and one euryxenic species was found in five species from two shark families (P. sinclairtaylori). One species was found to exhibit mild morphologically plasticity (P. orectolobi), with size range being associated with different shark species. Conversely, collections of almost morphologically indistinguishable specimens from single shark species were found to represent multiple species of Paraorygmatobothrium. The findings of this study indicate that the description of species of this genus on the basis of morphological data alone is problematic and that the inclusion of multi-locus molecular data is essential for future work on Paraorygmatobothrium. Host specificity, morphology and phylogenetic relatedness of species of Paraorygmatobothrium are explored.

Molecular approaches to trematode systematics: 'best practice' and implications for future study.

To date, morphological analysis has been the cornerstone to trematode systematics. However, since the late-1980s we have seen an increased integration of genetic data to overcome problems encountered when morphological data are considered in isolation. Here, we provide advice regarding the 'best molecular practice' for trematode taxonomy and systematic studies, in an attempt to help unify the field and provide a solid foundation to underpin future work. Emphasis is placed on defining the study goals and recommendations are made regarding sample preservation, extraction methods, and the submission of molecular vouchers. We advocate generating sequence data from all parasite species/host species/geographic location combinations and stress the importance of selecting two independently evolving loci (one ribosomal and one mitochondrial marker). We recommend that loci should be chosen to provide genetic variation suitable to address the question at hand and for which sufficient 'useful' comparative sequence data already exist. Quality control of the molecular data via using proof-reading Taq polymerase, sequencing PCR amplicons using both forward and reverse primers, ensuring that a minimum of 85% overlap exists when constructing consensus sequences, and checking electropherograms by eye is stressed. We advise that all genetic results are best interpreted using a holistic biological approach, which considers morphology, host identity, collection locality, and ecology. Finally, we consider what advances next-generation sequencing holds for trematode taxonomy and systematics.

A complex of Cardicola Short, 1953 (Digenea: Aporocotylidae) species infecting the milkfish Chanos chanos Forsskål (Gonorynchiformes), with descriptions of two new species.

Two new species of Cardicola Short, 1953 are described from the milkfish, Chanos chanos Forsskål (Gonorynchiformes: Chanidae), obtained from off Lizard Island on the northern Great Barrier Reef (GBR) and North Stradbroke Island in southeast Queensland. These are the first known blood flukes from this order of fishes. Cardicola suni n. sp. differs from all other Cardicola spp. by a combination of a large ovoid oral sucker surrounding a subterminal mouth, recurved tegumental spines up to 16 µm long, anterior caeca occupying 25.1-31.3% (28.7%) of total body length and a mostly-intercaecal ovary. Cardicola jiigurru n. sp. differs from C. suni n. sp. and all other species of Cardicola by a combination of a narrowly lanceolate body, weakly-muscularised and poorly-demarcated oral sucker, minute tegumental spines <1 µm in length, and anterior caeca occupying 15.9-22.0% (19.4%) of total body length, an almost entirely post-caecal ovary and the male genital pore terminal on a dorsolateral protuberance. A third species, closely resembling C. suni n. sp., was also discovered off Wangetti Beach, north Queensland, but is not described due to lack of material. Molecular phylogenetic analysis, based on both ITS2 and partial 28S rDNA regions, shows that these three species form a clade nested within that formed by existing species of Cardicola.

Molecular and morphological evidence for the widespread distribution of Laticola paralatesi infecting wild and farmed Lates calcarifer in Australia.

Infections with monogeneans of the Diplectanidae can limit productivity of and cause considerable health issues for fish in aquaculture. To date, 9 species of diplectanids have been reported from the Asian sea bass or barramundi Lates calcarifer (Perciformes: Latidae) in the Asia-Pacific region. This study characterised the diplectanid parasite fauna found infecting wild and farmed barramundi from 5 localities in tropical Australia, including north Queensland and Western Australia. A combination of morphometric and comparative genetic analyses of partial 28S ribosomal RNA (28S rRNA) from specimens recovered were used to confirm their identity and to explore relationships with other diplectanids. These data revealed that a single, dominant species of diplectanid, Laticola paralatesi, infects wild and farmed Lates calcarifer in tropical Australia. Laticola lingaoensis Yang, Kritsky, Sun, Jiangying, Shi & Agrawal, 2006 is synonymised with L. seabassi (Wu, Li, Zhu & Xie, 2005) Domingues & Boeger, 2008 based on the combination of the host infected (Lates calcarifer), geographic distribution, distinct morphological similarity, and identical 28S rRNA sequence data identified here. Laticola seabassi is now designated as the type species of Laticola due to nomenclatural priority.

A species pair of Bivesicula Yamaguti, 1934 (Trematoda: Bivesiculidae) in unrelated Great Barrier Reef fishes: implications for the basis of speciation in coral reef fish trematodes.

Combined morphological and molecular analysis shows that a species of Bivesicula Yamaguti, 1934 from four species of Apogonidae Günther [Nectamia fusca (Quoy & Gaimard), Ostorhinchus angustatus (Smith & Radcliffe), O. cookii (Macleay) and Taeniamia fucata (Cantor)] on the Great Barrier Reef is morphologically similar to, but clearly distinct from B. unexpecta Cribb, Bray & Barker, 1994 which infects a sympatric pomacentrid, Acanthochromis polyacanthus (Bleeker). Bivesicula neglecta n. sp. is proposed for the form from apogonids. Novel ITS2 rDNA sequences generated for the two species differ at just one consistent base position, implying that the two species are closely related. The combination of their close relationship, high but distinct specificity and co-occurrence suggests that speciation was driven by a recent host switching event enabled by similar dietary ecomorphology.

A review of the currently recognised zoogonid cercariae, including the identification and emergence ecology of Cercaria capricornia XI (Digenea: Zoogonidae) from Nassarius olivaceus (Gastropoda: Nassariidae) in Central Queensland, Australia.

In the present study, we review the known zoogonid cercariae, summarise their life-cycles and first intermediate host distributions, and present a new cercaria, Cercaria capricornia XI (Digenea: Zoogonidae), which was found in one of three nassariid gastropods, Nassarius olivaceus (Bruguière), surveyed in the intertidal zone in the Capricornia region of Central Queensland, Australia. Morphological data and molecular analysis of the ITS2 rDNA region support placement of this cercaria in the family Zoogonidae but do not allow any further resolution of its identity. There are now fifteen cercariae described as belonging to the Zoogonidae; thirteen of these, including the present species, infect neogastropods as first intermediate hosts and two use vetigastropods. This study reinforces the pattern that the Nassariidae is by far the most commonly reported family for the Zoogonidae. Given its richness we predict that the Nassariidae will prove to harbour many more zoogonid species.

A new species of Plectognathotrema Layman, 1930 (Trematoda: Zoogonidae) from an Australian monacanthid, with a molecular assessment of the phylogenetic position of the genus.

During helminthological examinations of teleost fishes of Ningaloo Reef, Western Australia, a new species of the enigmatic genus Plectognathotrema Layman, 1930 was discovered infecting the pot-bellied leatherjacket Pseudomonacanthus peroni (Hollard). The new species, Plectognathotrema kamegaii n. sp., is formally described, and the status of its four congeners is reviewed. Plectognathotrema hydrolagi Olson, Hanson & Pratt, 1970 is not recognised within the genus, as it differs greatly from its congeners in the form and arrangement of the vitellarium, testes and uterus, and in that it was described from a holocephalan. Plectognathotrema cephalopore Layman, 1930 and P. tsushimaense Kamegai, 1970 are morphologically similar, were described from the same host species and from close geographical localities and are considered synonymous. The new taxon is most similar to P. cephalopore, but differs from it in being much smaller and possessing a distinctly larger oral sucker relative to its body size. The generation of novel partial 28S ribosomal DNA sequences allowed a phylogenetic assessment of the genus and demonstrated that Plectognathotrema clearly belongs in the Zoogonidae Odhner, 1902, rather than in the Fellodistomidae Nicoll, 1909, where it is currently assigned. With the inclusion of Plectognathotrema in the Zoogonidae, there are now three zoogonid genera for which the species are restricted to monacanthid teleosts, i.e. Cephaloporus Yamaguti, 1934, Plectognathotrema and Yamagutiplectognathotrema Parukhin, 1977. Species of these genera share pronounced morphological and ecological affinities and a previously synonymised subfamily, the Cephaloporinae Yamaguti, 1934, is resurrected for them. The host specificity of these trematodes is commented upon.

The sexual adult of Cercaria praecox Walker, 1971 (Digenea: Fellodistomidae), with the proposal of Oceroma n. g.

A sexual adult trematode that is considered to be conspecific with the distinctive larval trematode Cercaria praecox Walker, 1971 is reported from the kyphosid fish Scorpis lineolata Kner in Moreton Bay, Queensland, Australia. The sexual adult is consistent with the cercarial body of Cercaria praecox in having a single caecum with an asymmetrical appendix, symmetrical testes immediately posterior to the ventral sucker, and the ovary and vitellarium both well posterior to the testes. This combination of characters is distinct within the Fellodistomidae Nicoll, 1909 and requires the proposal of a new genus, Oceroma n. g. Analysis of 28S rDNA sequences demonstrates that this species forms a clade with Coomera Dove & Cribb, 1995 within the Fellodistomidae. The life-cycle of the species is predicted to require two hosts and to involve the direct ingestion of the cercaria.

Experimental infections of Orchitophrya stellarum (Scuticociliata) in American blue crabs (Callinectes sapidus) and fiddler crabs (Uca minax).

Outbreaks of an unidentified ciliate have occurred on several occasions in blue crabs from Chesapeake Bay held during winter months in flow-through systems. The parasite was initially thought to be Mesanophrys chesapeakensis, but molecular analysis identified it as Orchitophyra stellarum, a facultative parasite of sea stars (Asteroidea). We investigated the host-parasite association of O. stellarum in the blue crab host. Crabs were inoculated with the ciliate, or they were held in bath exposures after experimentally induced autotomy of limbs in order to determine potential mechanisms for infection. Crabs inoculated with the ciliate, or exposed to it after experimental autotomy, rapidly developed fatal infections. Crabs that were not experimentally injured, but were exposed to the ciliate, rarely developed infections; thus, indicating that the parasite requires a wound or break in the cuticle as a portal of entry. For comparative purposes, fiddler crabs, Uca minax, were inoculated with the ciliate in a dose-titration experiment. Low doses of the ciliate (10 per crab) were sometimes able to establish infections, but high intensity infections developed quickly at doses over 500 ciliates per crab. Chemotaxis studies were initiated to determine if the ciliate preferentially selected blue crab serum (BCS) over other nutrient sources. Cultures grown on medium with BCS or fetal bovine serum showed some conditioning in their selection for different media, but the outcome in choice experiments indicated that the ciliate was attracted to BCS and not seawater. Our findings indicate that O. stellarum is a facultative parasite of blue crabs. It can cause infections in exposed crabs at 10-15°C, but it requires a portal of entry for successful host invasion, and it may find injured hosts using chemotaxis.

Bucephalidae (Platyhelminthes: Digenea) of Plectropomus (Serranidae: Epinephelinae) in the tropical Pacific.

We examined four species of Plectropomus Oken, 1817 (Serranidae: Epinephelinae), Plectropomus areolatus (Rüppell), Plectropomus laevis (Lacepède), Plectropomus leopardus (Lacepède) and Plectropomus maculatus (Bloch) from sites off Heron Island and Lizard Island on the Great Barrier Reef, Australia (GBR), and the Gambier Islands, French Polynesia. Three new species of Neidhartia Nagaty, 1937, five new species of Prosorhynchus Odhner, 1905, and one previously described species, Prosorhynchus freitasi Nagaty, 1937, are characterised. The three species of Neidhartia, Neidhartia haywardi n. sp., Neidhartia plectropomi n. sp. and Neidhartia tyleri n. sp. are readily distinguishable morphologically. Two of the six species of Prosorhynchus (Prosorhynchus lesteri n. sp. and Prosorhynchus wrightae n. sp.) are easily distinguished from their other congeners by morphology but the other four species (P. freitasi, Prosorhynchus heronensis n. sp., Prosorhynchus munozae n. sp. and Prosorhynchus plectropomi n. sp.) are generally similar in morphology and were only distinguished initially by comparing their ITS2 rRNA sequences. Three additional taxa, one from the GBR and two from French Polynesia, were recognised as distinct on the basis that their ITS2 rRNA sequences differed from those of the new taxa described here; these species remain unnamed for the present. Inter-specific divergence observed within these genera in the ITS2 rRNA ranged from 10 to 42 base pairs (4-16 %) for species of Neidhartia and 2-57 base pairs (3-21 %) for species of Prosorhynchus. Inter-generic divergences were 42-55 base pairs (17-21 %). No intraspecific variation in the ITS2 rRNA region was observed for any of the six species for which multiple sequence replicates were obtained. Phylogenetic analysis of 12 operational taxa from Plectropomus together with sequences of three other species from epinepheline serranids demonstrated that Neidhartia and Prosorhynchus were reciprocally monophyletic with the exception that P. wrightae n. sp. fell either within or basal to the Neidhartia species. The richness of bucephalids in species of Plectropomus appears to be exceptional within the Serranidae relative to that observed in other serranid genera in the tropical Indo-West Pacific.

Phylogenetic relationships of the Gorgoderidae (Platyhelminthes: Trematoda), including the proposal of a new subfamily (Degeneriinae n. subfam.).

Phylogenetic analyses of a range of gorgoderid trematodes based on ITS2 and partial 28S rDNA data lead us to propose the Degeneriinae n. subfam. for the genus Degeneria in recognition of its phylogenetic isolation and distinctive morphology and biology. The current concepts of the subfamilies Anaporrhutinae and Gorgoderinae were supported. Within the Gorgoderinae, the large genus Phyllodistomum is shown to be paraphyletic relative to Pseudophyllodistomum and Xystretrum. Notably, the clade of marine Phyllodistomum does not form a clade with the other marine genus, Xystretrum. Distinct clades within the Gorgoderinae correspond variously to identity of first intermediate host, form of cercaria and their marine or freshwater habitat. We are not yet in a position to propose separate genera for these clades.

Dramatic phenotypic plasticity within species of Siphomutabilus n. g. (Digenea: Cryptogonimidae) from Indo-Pacific caesionines (Perciformes: Lutjanidae).

A survey of Indo-Pacific lutjanids of the subfamily Caesioninae revealed the presence of Siphodera gurukun Machida, 1910 and two new cryptogonimid taxa from off Heron and Lizard Islands on the Great Barrier Reef, Australia, Ningaloo Reef, Western Australia and Rasdhoo Atoll, Maldives. A combined morphological and genetic characterisation of these species shows that they form a clade distinct from the type-species of Siphodera Linton, 1910, S. vinaledwardsii (Linton, 1901), and warrants the proposal of a new genus. Here we propose Siphomutabilus n. g. and transfer Siphodera gurukun Machida, 1986 as the type-species, Siphomutabilus gurukun (Machida, 1986) n. comb. Siphodera aegyptensis Hassanine & Gibson, 2005 is transferred to Siphomutabilus as S. aegyptensis (Hassanine & Gibson, 2005) n. comb. based on morphological and ecological similarities. Siphomutabilus raritas n. sp. is described from Caesio cuning (Bloch) off Lizard Island and S. bitesticulatus n. sp. is described from Pterocaesio marri Schultz off Heron Island. The two new species are unique in that they have two testes, making their morphology broadly consistent with that of Metadena Linton, 1910, yet the molecular analyses conducted here indicates that they are unequivocally united with Siphomutabilus gurukun (which has multiple testes) to the exclusion of Metadena lutiani (Yamaguti, 1942), which was sequenced here. The dramatic phenotypic plasticity observed among such closely related species of Siphomutabilus suggests a secondary modification of what is generally considered a robust generic diagnostic character within this and other digenean families, highlighting the need for a combined morphological and molecular diagnostic approach when characterising these taxa. Siphodera Linton, 1910 is amended to include just two species, the type-species S. vinaledwardsii (Linton, 1901) Linton, 1910 and S. cirrhiti Yamaguti, 1970, which are distinguished by their lack of oral spines and multiple testes that are primarily extracaecal. Siphodera ghanensis Fischthal & Thomas, 1968 is considered a species incertae sedis here based on significant morphological and ecological differences compared with species of Siphodera and Siphomutabilus n. g.

Henneguya mauritaniensis n. sp. (Myxozoa) from the arterial bulb of Pagrus caeruleostictus (Valenciennes, 1830) off Mauritania.

We describe a new species of myxozoan, Henneguya mauritaniensis n. sp., extracted from the arterial bulb of the bluespotted seabream, Pagrus caeruleostictus (Valenciennes, 1830), collected in Mauritanian waters. Out of the 209 individuals examined, 30.1 % were infected with this new taxon. Spore total length ranged from 15.0 to 20.5 µm with a mean of 17.9 µm. The two polar capsules were equal in size, and pyriform and caudal appendages joined until mid-length. Morphometric analysis revealed significant differences between H. mauritaniensis n. sp. and morphologically similar species from this region as well as congeners known from other sparid hosts. Phylogenetic analysis of 18 S rDNA indicated that this new species is closely related to Henneguya pagri, reported recently from Pagrus major off Japan. Bayesian inference and maximum likelihood analyses of the 18 S rDNA dataset also revealed that species of marine Henneguya reported forming pseudocysts in the hearts of their fish hosts were closely related. Histological analysis of the H. mauritaniensis n. sp. pseudocysts embedded in the arterial bulb of P. caeruleostictus suggests that these parasites may cause considerable pathology, which may impact negatively on the health of the fish host. Finally, we discussed the importance of a combination of morphological and molecular analysis for species description because of high variability in size within the same taxa.

In vitro culture and developmental cycle of the parasitic dinoflagellate Hematodinium sp. from the blue crab Callinectes sapidus.

Hematodinium is a genus of parasitic dinoflagellates whose species have caused significant mortalities in marine crustacean fisheries worldwide. A species of Hematodinium infects the blue crab, Callinectes sapidus on the eastern seaboard of the USA. The mode of transmission of the parasite in blue crabs is unknown. We established several continuous in vitro cultures of Hematodinium sp. isolated from the haemolymph of infected blue crabs. One isolate has been continuously maintained in our laboratory through serial subcultivation for over 12 months, and is capable of infecting new hosts when inoculated into healthy crabs. Cells of the parasite undergo characteristic developmental changes in vitro consistent with the identifiable stages of Hematodinium sp.: filamentous trophonts, amoeboid trophonts, arachnoid trophonts and sporonts, sporoblasts, prespores and dinospores (macrospores and microspores). Additionally, we describe an unusual shunt in the life cycle wherein presumptive schizonts derived from arachnoid sporonts developed into filamentous and arachnoid trophonts that can then initiate arachnoid sporonts in new cultures. This may explain the rapid proliferation of the parasite in blue crab hosts. We also found that temperature and light intensity affected the growth and development of the parasite in vitro.