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Polylabris lingaoensis sp. n. is described from the gills of the bald glassy, Ambassis gymnocephalus (Chandidae), from the Gulf of Tonkin (South China Sea), near Lingao, Hainan Province, China. The new species is characterized by a midventral vaginal pore, comparatively few (5-7) testes, and 2 parallel rows each comprised of 30-43 microcotylid clamps in the haptor. Polylabris lingaoensis is the only member of the genus known to parasitize a chandid host. Polylabris cf. mamaevi is described from the gills of the mottled spinefoot, Siganus fuscescens (Siganidae), from the South China Sea, which represents new host and locality records for the helminth. The gill parasites from S. fuscescens are tentatively assigned to P. mamaevi pending new collections and restudy of microcotylid species from siganid fishes.

Glochidia are the larval stage of freshwater unionid mussels that parasitize the fins and gill apparatus of fish. A total of 22 fish species were examined for the presence of glochidia whose distribution on individual hosts was studied on three common fish species, the roach Rutilus rutilus (L.), perch Perca fluviatilis L. and bitterling Rhodeus sericeus (Pallas). Between 1997 and 1999, the fish were obtained from the rivers Morava and Kyjovka and surrounding water pools in the Czech Republic. The glochidia of two genera, Unio and Anodonta, were found. Anodonta glochidia were observed on 10 fish species, Unio glochidia on 17 fish species. There was a difference in spatial distribution of glochidia on the body of the host fish. Unio glochidia were predominantly located on the gills, whereas most Anodonta glochidia were found on the fins, with the highest numbers of glochidia were observed on the margin of the pectoral fins. For the gill apparatus, Unio glochidia were found predominantly on the second and third arch. Anodonta glochidia were predominantly found during winter and spring (November-May), whereas Unio glochidia were more abundant during May and June. The number of glochidia was positively correlated with fish length in perch highly infected by Anodonta glochidia and perch infected by Unio glochidia. Of the three fish species, the highest occurrence of parasites was found on perch with fewer observed on roach. In spite of the close relationship between bitterling and unionid mussels, glochidiosis was rare on this fish species.

Microhabitat preference of the monogenean Discocotyle sagittata (Leuckart, 1842) was determined in late spring and late autumn in rainbow trout, Oncorhynchus mykiss (Walbaum), reared in the Isle of Man, UK. Discocotyle sagittata exhibits a preference for attachment to anterior gill arches: 29% of all worms occurred on gill arch I, 28% on II, 25% on III and 18% on IV. This distribution pattern on the introduced salmonid species is the same as reported for its native European host, the brown trout Salmo trutta (L.). Previous experimental work suggested that invasion is a passive process followed by post-invasion migration to anterior gill arches; the present work provides evidence of equivalent site selection taking place in fishes maintained under conditions promoting continuous reinfection in aquaculture. Migration may be density-dependent, since a significant inverse association was found between the intensity of mature parasites and their proportion on anteriormost gill arch I.

Lyme borreliosis (LB) is a serious infectious disease of humans and some domestic animals in temperate regions of the Northern Hemisphere. It is caused by certain spirochetes in the Borrelia burgdorferi sensu lato (s.l.) species complex. The complex consists of 11 species (genospecies). Borrelia burgdorferi sensu stricto (s.s.), Borrelia garinii and Borrelia afzelii are the major agents of human disease. Borrelia burgdorferi s.l. species are transmitted mainly by ticks belonging to the Ixodes ricinus species complex plus a few additional species not currently assigned to the complex. B. burgdorferi infections may produce an acute or chronic disease with a wide array of clinical symptoms such as erythema migrans (EM), carditis, arthritis, neuroborreliosis, and acrodermatitis chronica atrophicans (ACA). Differences in LB spirochetes 'genospecies' and strains/isolates determine the occurrence and severity of this multi-system disease. Accurate and reliable identification of the LB spirochetes in ticks as well as knowledge of their prevalence are essential for prevention against the disease and development of an effective vaccine. An overview of the knowledge of molecular factors with emphasis on potential protein-carbohydrate interactions in the tick-borrelia system is the main focus of this review.

A new species, Prosorhynchus maternus sp. n., is described from the serranid fish Epinephelus malabaricus (Bloch et Schneider) in the waters off New Caledonia. It belongs to a group of Prosorhynchus species from serranids in which the uterus is restricted to the postovarian region. Its distinguishing features include the vitellarium relatively distant from the rhynchus, the cirrus-sac relatively distant from the posterior testis, the distinctly pre-equatorial mouth and several other somatic ratios. New records of Prosorhynchus longisaccatus Durio et Manter, 1968 from Epinephelus cyanopodus (Richardson) and Prosorhynchoides lamprelli Bott et Cribb, 2005 from Caranx papuensis Alleyne et Macleay off New Caledonia are also included.

The first ultrastructural description of Ceratomyxa tenuispora Kabata, 1960 (Myxozoa, Bivalvulida) from Madeira Island (Portugal), a parasite found in the gall bladder of the commercially important black-scabbard fish, Aphanopus carbo Lowe is presented. This parasite possesses spherical to ellipsoidal disporous trophozoites. Spores have a central crescent-shaped body averaging 11.0 µm in length, 28.5 µm in thickness and 12.1 µm in width. The valves have two long opposite lateral processes (ribbon-like structures or tails), each averaging 173 µm in length. The total thickness of the spore averages 375 µm. The spore has two sub-spherical polar capsules (∼5.2 × 4.1 µm), each with a polar filament with 7 to 8 coils. Some ultrastructural aspects of the sporogonic stages are described. The trophozoites develop without contact with epithelial cells. The cytoplasmic membrane has numerous evenly distributed external slender projections about 0.3 to 0.7 µm long. The sporogenesis produces two spores without pansporoblast formation. In the matrix of the capsular primordium, microtubules with an unusual organisation were observed. A binucleate sporoplasm that contains several sporoplasmosomes and dense bodies fills the spore cavity and extends to the tails without penetrating them.

A greater blue-eared glossy starling Lamprotornis chalybaeus Ehrenburg from a large flight aviary in Hong Kong was found on post mortem to be infected with Plasmodium octamerium Manwell, 1968, Plasmodium cf. relictum (Grassi et Feletti, 1891) and Haemoproteus cf. pastoris Mello, 1935. Descriptions of their morphology are provided as none of the examined parasites fully concord with their type (or neotype) material descriptions. Plasmodium octamerium has been recorded in avian hosts from geographically distant locations, suggesting that infection in imported hosts may persist in a chronic state for a long period. This Plasmodium species as well as P. relictum are evidently not fastidious in choice of passeriform hosts and are transmitted by ubiquitous domestic mosquito vectors, apparently facilitating their proliferation among zoo and aviary inhabitants. The Haemoproteus infection appears to be conspecific with H. cf. pastoris reported from a myna (Acridotheres tristis) in Singapore. Mynas are also common in Hong Kong, which suggests a possible cross-transmission of infection between these two starlings.

A study of the actinosporean fauna of oligochaetes from a freshwater salmon farm in Northern Scotland was carried out from October 1996 to August 1998. Following the examination of 28,387 oligochaete worms belonging to the families Tubificidae, Lumbriculidae, Naididae and Enchytraeidae, five types of echinactinomyxon (four previously described), six types of raabeia (five previously described), three types of synactinomyxon (all previously described), four types of aurantiactinomyxon (three previously undescribed), one type of triactinomyxon (previously described), one type of neoactinomyxum (previously undescribed) and one type of siedleckiella (previously undescribed) were identified. The triactinomyxon type was released from unidentified immature oligochaetes. Of the twenty-one types of actinosporeans found, thirteen types were released from Tubifex tubifex (Müller), three types were released from Lumbriculus variegatus (Müller), three types from both L. variegatus and T. tubifex and two types from immature oligochaetes.

Experimental activation of peritoneal macrophages by interferon gamma (IFN-γ) resulted in the inhibition of Encephalitozoon cuniculi replication. However, E. cuniculi could replicate either in a non-activated cell line of murine macrophages PMJ2-R or in IFN-γ-activated PMJ2-R cells. Moreover, activation with IFN-γ led to faster replication of E. cuniculi in these cells. Opsonisation of E. cuniculi spores with anti-E. cuniculi polyclonal antibody did not affect E. cuniculi replication in both, non-activated and activated murine macrophages. In contrast, opsonisation of E. cuniculi spores caused the most effective replication of E. cuniculi in activated PMJ2-R cells. However, production of nitric oxide by these cells was significantly more intensive than that in non-activated, infected cells, where the parasite replicated to a much lesser extent. Our results support the hypothesis that E. cuniculi uses phagocytosis for the infection of host cells. They also indicate that the mechanism by which spores of E. cuniculi are killed by macrophages is not dependent on nitric oxide and they reveal that PMJ2-R cells cannot substitute peritoneal murine macrophages in immunological studies on E. cuniculi.

Cuculisyringophilus crotophaginus gen. n. et sp. n. is described from the guira cuckoo Guira guira (Gmelin) from Paraguay and also was collected from the groove-billed ani Crotophaga sulcirostris Swainson from Colombia and Mexico. This new genus is closely related to Neoaulobia Fain, Bochkov et Mironov, 2000 but is distinguished by the following characters: propodosomal setae sce are situated distinctly anterior to level of setae d1, leg setae vs'II are absent, apodemes I are divergent.

Bothitrema bothi (MacCallum, 1913), a monopisthocotylean monogenean (Bothitrematidae) found on gills and occasionally on the olfactory rosette within the nares of the bothid flounder, Scophthalmus aquosus (Mitchill, 1815), is distributed along the Atlantic coast of the USA from Woods Hole, Massachusetts to Delaware Bay. This study details aspects of the morphology, microecology and biology of the oncomiracidium, juvenile and adult. Adult worms occur almost exclusively between rakers on the first and second gill arches while juveniles occupy secondary gill filaments. Analysis of variance revealed significant arch, side and position effects. Worm attachment and position is maintained largely by suction generated by a circular seal using its 54 radially arranged accessory haptoral sclerotised elements and a marginal valve. A small anterior appendix with two marginal hooks lies dorsal to a deep anteromedian cleft in the haptor, which, together with wall muscles, creates and releases the negative pressure required for attachment. Four pairs of gland openings in the ventrolateral margins of the anterior adhesive area produce secretions for attachment. Operculate eggs with four rounded protuberances and a filament are laid individually at four-minute intervals at 22ºC. Hatching occurs in five days at 20°C. Oncomiracidia have two pairs of eyes, with the posterior pair fused, show both positive and negative phototaxis and swim at a mean rate of 5.2 mm/s at 22°C. Larvae have a circle of 16 hooks and a pair of hamulus primordia. Other accessory haptoral sclerotised structures arise de novo in juveniles after attachment to the host. These data will help to resolve more clearly the relationships of the Bothitrematidae within the Monopisthocotylea.

Host-parasite interactions of Pomphorhynchus laevis (Müller, 1776) in naturally infected amphipod, Echinogammarus stammeri (Karaman), from the Brenta River (northern Italy) are described. A fully developed acanthocephalan larva occupies a large portion of an amphipod's haemocoelic space; thus, the parasite frequently induces displacement of host digestive tract and other internal organs. However, no apparent damage to the host's internal structures was observed. Within the haemocoel of E. stammeri, each larva of P. laevis is surrounded with a membranous layer, formed by microvilli, which maintains intimate contact with the amphipod's internal organs and haemocytes. Three types of circulatory haemocytes were identified based upon their distinct appearance: hyaline cell, semi-granular cell and granular cell. Echinogammarus stammeri haemocytes surrounded acanthocephalan larvae and in some instances a partially and/or totally melanized P. laevis larva was noticed. Interestingly, no melanized larvae were found in E. stammeri parasitized with other acanthocephalans namely Echinorhynchus truttae (Schrank, 1788), Polymorphus minutus (Goeze, 1782) and Acanthocephalus clavula (Dujardin, 1845).

Ailinella gen. n. (Pseudophyllidea: Triaenophoridae) is proposed to accommodate Ailinella mirabilis sp. n. from Galaxias maculatus (Jenyns, 1842), a freshwater fish inhabiting the Andean lakes in Argentinean Patagonia. Ailinella belongs to the Triaenophoridae because it has a marginal genital pore, a follicular vitelline gland, and a ventral uterine pore. The new genus can be distinguished from other triaenophorids by the following combination of characters: a small body size, a low number of proglottides, which are longer than wide, a truncated pyramidal to globular scolex, a rectangular apical disc, presence of the neck, lack of internal longitudinal musculature separating the cortex from the medulla, testes distributed in one central field surrounding the ovary laterally and posteriorly, the vagina predominantly anterior to the cirrus sac, vitelline follicles circum-medullary, the genital pores post-equatorial, a saccate uterus, and operculate eggs. Blade-like spiniform microtriches were present on all tegument surfaces, and tumuli on all surfaces of the scolex and the anterior surface of the neck. Microtriches were characterized according to their size and density, and tumuli according to their size, inter-tumulus distance and density. Ailinella mirabilis is the first cestode described from G. maculatus and the second triaenophorid species recorded from a South American freshwater fish.

New strains of non-vannellid flattened amoebae isolated from fish, an invertebrate and the marine environment were studied together with Flabellula citata Schaeffer, 1926 selected by morphology as a reference strain. The study revealed a paucity of features distinguishing individual strains at the generic level, but clearly evidenced mutual phylogenetic relationships within the assemblage of strains as well as their affiliation to the Leptomyxida. In this study, the SSU rDNA dataset of leptomyxids was expanded and a new branching pattern was presented within this lineage of Amoebozoa. Sequences of three newly introduced strains clustered in close relationship with the type strain of F. citata, the type species of the genus. Three strains, including one resembling Flamella sp., were positioned within a sister-group containing Paraflabellula spp. Results of phylogenetic analysis confirmed doubts of previous authors regarding generic assignment of several Rhizamoeba and Ripidomyxa strains.

During October 2003, a specimen of Amblyrhynchotes honckenii (Bloch, 1795) was captured at low tide, with a hand net, in a rock pool at Koppie Alleen, De Hoop Nature Reserve, South Africa. This fish was heavily parasitized by unidentified gnathiid praniza larvae, caligid copepods identified as Caligus tetrodontis Barnard, 1948, cymothoid isopods identified as Cinusa tetrodontis (Schioedte et Meinert, 1884), and the blood protozoan Haemogregarina koppiensis Smit et Davies, 2001. Giemsa-stained blood smears from this fish revealed new and unusual stages of merogony for H. koppiensis that included small, rounded, likely intraerythrocytic merozoites arranged in circles of eight around the host nucleus. Host cells appeared ghost-like and enlarged compared with normal erythrocytes. Identical merozoites, usually in clusters of up to 16, were also observed free of host cells. The pattern of merogony seen in H. koppiensis is unusual for a fish haemogregarine.

Myxobolus diaphanus (Fantham, Porter et Richardson, 1940) was found in banded killifish Fundulus diaphanus (Lesueur) at several freshwater localities in Nova Scotia, including the type locality at the mouth of the Salmon River, Guysborough County. The new material, the first to be reported in 64 years, was used to supplement information on spore morphology, to document the site of development in the tissue, and to compare sequence data of the 18S rDNA to other studied myxobolids. Plasmodia with developed spores occurred in loose connective tissue of the head, the dermis (particularly in the roof of the mouth and at the base of fins), surface of the brain and ovary, muscle epimysium, and the submucosa of the intestine. Developed plasmodia containing spores were also found free in the lumen of the vena cava and within fluid-filled spaces of the skull, mandible and lower jaw. A phylogenetic analysis using 18S rDNA (878 bp) placed M. diaphanus in a terminal clade containing certain freshwater species of Henneguya, all of which occur in North America and have elongate spore bodies.

Myxidium biliare sp. n., a new myxosporean species parasitizing the gall bladder of Galaxias maculatus (Jenyns), in Patagonia, is described. Its coelozoic plasmodia were floating free in the bile. Spores are fusiform 13.7 ± 0.9 µm long and 6.9 ± 0.6 µm wide, with rounded ends in frontal view and slightly pointed ends in sutural view; shell with ridges and sinuous sutural line. Both maximum prevalence and maximum percentage of immature plasmodia occurred in summer. In winter the prevalence and the percentage of immature plasmodia fell to their lowest values. Prevalence was independent of host sex but increased with host length. Prevalence in 15 Patagonian Andean lakes (situated from 39°25'S to 41°30'S) ranged between 4.2% and 70%.

Haematophagous larvae of a gnathiid isopod were collected from the gills, nares and buccal cavity of a single leopard catshark Poroderma pantherinum (Smith, 1838) at Jeffreys Bay and five puffadder shysharks Haploblepharus edwardsii (Voight, 1832) and one blackspotted electric ray Torpedo fuscomaculata Peters, 1855, at the De Hoop Nature Reserve on the South African south coast. Larvae were kept in fresh seawater until their moult into adult stages. The morphology of the adult males did not conform to that of any known species and they are therefore described as Gnathia pantherina sp. n. The descriptions of the adult male, female and praniza larva are based on light and scanning electron microscopy observations. Characteristic features of this species include the large size of all the final life-cycle stages, the deeply divided mediofrontal process of the male, the morphology of the pylopods and maxillipedes of the female, and the number of teeth on the mandibles (eight) and maxillules (seven) of the praniza larvae.

Over the past 40 years, much has been published on the ultrastructure and cellular development of embryonic structures in a wide range of cestodes. However, the literature contains many discrepancies in both terminology and interpretations because of the facts that these organisms are phylogenetically diverse within their respective orders and families, the habitats that affect embryonic envelope structure are diverse, and the work has been done in various laboratories around the world. This review and synthesis was initiated by a working group of biologists from around the world convened at the Fifth International Workshop on Cestode Systematics and Phylogeny in České Budĕjovice, at the Institute of Parasitology of the Biology Centre, Academy of Sciences of the Czech Republic. It brings together the data from published work and establishes a uniform terminology and interpretation based on the data as they are presented. A consensus was reached for standardised definitions of the oncosphere, hexacanth, coracidium, embryonic envelopes, outer envelope, inner envelope, embryophore, vitelline capsule, shell, and outer coat. All of these are defined as components of the embryo or its vitellocyte-derived or uterine-derived coatings.

The epizootiology, transmission dynamics, and survival strategies employed by two mosquito-parasitic microsporidia that utilize copepods as intermediate hosts are examined in relation to the biological attributes of their hosts and the environments in which they inhabit. Amblyospora connecticus Andreadis, 1988, a parasite of Ochlerotatus cantator (Coquillett) and Acanthocyclops vernalis (Fischer) is found in an unstable salt marsh environment that is subject to periodic flooding and drying. Both hosts have distinct non-overlapping generations. A. connecticus exhibits a well-defined seasonal transmission cycle that relies heavily on maternal-mediated transovarial transmission by female O. cantator during the summer, and horizontal transmission via the copepod host during the spring (copepod to mosquito) and fall (mosquito to copepod). Its survival strategies include: delayed virulence, low pathogenicity and high tissue specificity that allow for transstadial transmission of horizontally acquired infections and maximum spore production, reliance on living hosts throughout most of its life cycle with overwintering in the copepod, polymorphic development that is well synchronized with host physiology, and production and dissemination of infectious spores that are coincident with the seasonal occurrence of susceptible stages in each host. Hyalinocysta chapmani Hazard et Oldacre, 1975, a parasite of Culiseta melanura (Coquillett) and Orthocyclops modestus (Herrick) is found in a comparatively stable, subterranean habitat that is inundated with water throughout the year. Copepods are omnipresent and C. melanura has overlapping broods. H. chapmani is maintained in a continuous cycle of horizontal transmission between each host throughout the summer and fall but lacks a developmental sequence leading to transovarial transmission in the mosquito host. It relies on living hosts for most of its life cycle and overwinters in diapausing mosquito larvae. Transstadial transmission does not occur and there is no dimorphic development in the mosquito host. The spatial and temporal overlap of both mosquito and copepod hosts during the summer and fall affords abundant opportunity for continuous horizontal transmission and increases the likelihood that H. chapmani will find a target host, thus negating the need for a transovarial route. It is hypothesized that natural selection has favoured the production of meiospores in larval female mosquitoes rather than congenital transfer of infection to progeny via ovarian infection as a strategy for achieving greater transmission success. Analysis of the molecular phylogeny data suggest that (1) transovarial transmission and the developmental sequence leading to ovarian infection have been secondarily lost in H. chapmani, as they occur in all other closely related genera, (2) the ancestral state included complex life cycles involving transovarial transmission and an intermediate host, and (3) mosquito-parasitic microsporidia are adjusting their life cycles to accommodate host ecological conditions.

Sequencing of SSU rDNA showed that actinospores of the tetractinomyxon type, which develop in Chone infundibuliformis Krøyer (Annelida, Polychaeta, Sabellidae) from the northern Øresund, Denmark, are identical with Ceratomyxa auerbachi Kabata, 1962 (Myxozoa, Ceratomyxidae). This myxosporean was found in the gallbladder of the Atlantic herring Clupea harengus L. from the northern Øresund, Denmark, and from the Bergen area, western Norway. The pansporocysts and actinospores of C. auerbachi are described. This is the third elucidated two-host life cycle of a marine myxozoan, and the first involving a marine ceratomyxid.

Systemic ciliatosis caused by histophagous ciliates constitutes a serious disease of cultured turbot. Six ciliate isolates were obtained from parasitized turbot during six epizootics at four different farms located in Spain, France and Portugal. Axenic cultures of the six isolates were obtained by periodical subculturing in ATCC 1651MA or supplemented L-15 media. In basal media or seawater, the parasites could survive starving for long periods with no apparent proliferation. In adequate media, growth kinetics was found to be very similar for isolates A and B, with a clear influence of temperature. Morphological studies demonstrated that all isolates share common features that allows their assignment to either Philasterides Kahl, 1931 or Miamiensis Thompson et Moewus, 1964. However, statistically significant differences were evident in pairwise comparisons of the isolates from the four farm sites in 16 taxonomically relevant morphometric features. This could allow the discrimination of different species or strains. Virulence of isolates A and B for healthy turbot was tested in several experiments. Differences in the virulence were especially evident after long-term in vitro culturing, isolate A being clearly attenuated after 35-42 passages, whereas isolate B became more virulent after 20-42 passages. The need of further studies to confirm such virulence variability and its implications in pathogenesis and prevention of turbot scuticociliatoses is stressed.

Seven species of fishes, Catostomus commersonii (Lacépède), Etheostoma nigrum Rafinesque, Micropterus dolomieu Lacépède, Notemigonus crysoleucas (Mitchill), Notropis hudsonius (Clinton), Perca flavescens (Mitchill), and Percina caprodes (Rafinesque) from the St. Lawrence River, Quebec, Canada, were found infected with progenetic specimens of Neochasmus spp. in the orbits and/or the body musculature. Worms displayed varying degrees of maturation. Eggs occupied the entirety of the worm in late stages of development and persisted as distinct clusters in situ after worm death. Populations of parasites were studied monthly in E. nigrum from one site between May and October in order to follow parasite recruitment, development and maturation. Recruitment of parasites was observed in young-of-the-year fish primarily in July and continued through October. Worms matured rapidly, displaying egg production within a month. Later developmental stages, in which eggs occupied most of the worm, and clusters of eggs became abundant by September. Infections in overwintered fish collected in May consisted mainly of worms in early stages of egg production and of clusters of eggs. When hatched artificially, eggs from the clusters released viable miracidia, indicating that they survive beyond the lifespan of the adult worm. It is suggested that progenesis is a fixed characteristic of the life cycle of these species, that egg dispersal requires the death of the host and that it is facilitated by predation. All prior records of Neochasmus spp. are examined, leading us to conclude that the role of the putative definitive host (primarily basses) has been reduced to that of a dispersal agent. Current hypotheses concerning the evolution and maintenance of progenesis are considered, but it is concluded that they do not apply to this host-parasite system.

The adults of Trichosurolaelaps dixous Domrow, 1972 are redescribed from a population of Trichosurus cunninghami Lindenmayer, Dubach et Viggers, 2002 in south-eastern Australia. The nymphal stages are described for the first time. Morphologically, T. dixous is similar to Trichosurolaelaps crassipes Womersley, 1956. Morphological differences between the pre-female deutonymphs and adult females of the two mite species are the presence of a single large ventral spur on tibia I of T. dixous. Males of T. dixous could not be distinguished from T. crassipes morphologically and the idiosomal length of male T. dixous was variable (475-683 μm). Protonymphs of the two mite species differed only in size, with that of T. dixous being larger. Although T. crassipes was prevalent in a sympatric population of Trichosurus vulpecula and has been reported from other populations of T. cunninghami in southern Australia, it was never recovered from the population of T. cunninghami studied.

This paper reviews past, current and likely future research on the fish haemogregarine, Haemogregarina bigemina Laveran et Mesnil, 1901. Recorded from 96 species of fishes, across 70 genera and 34 families, this broad distribution for H. bigemina is questioned. In its type hosts and other fishes, the parasite undergoes intraerythrocytic binary fission, finally forming mature paired gamonts. An intraleukocytic phase is also reported, but not from the type hosts. This paper asks whether stages from the white cell series are truly H. bigemina. A future aim should be to compare the molecular constitution of so-called H. bigemina from a number of locations to determine whether all represent the same species. The transmission of H. bigemina between fishes is also considered. Past studies show that young fish acquire the haemogregarine when close to metamorphosis, but vertical and faecal-oral transmission seem unlikely. Some fish haemogregarines are leech-transmitted, but where fish populations with H. bigemina have been studied, these annelids are largely absent. However, haematophagous larval gnathiid isopods occur on such fishes and may be readily eaten by them. Sequential squashes of gnathiids from fishes with H. bigemina have demonstrated development of the haemogregarine in these isopods. Examination of histological sections through gnathiids is now underway to determine the precise development sites of the haemogregarine, particularly whether merozoites finally invade the salivary glands. To assist in this procedure and to clarify the internal anatomy of gnathiids, 3D visualisation of stacked, serial histological sections is being undertaken. Biological transmission experiments should follow these processes.

About 300 species belonging to four superfamilies (Gnathostomatoidea, Habronematoidea, Physalopteroidea and Thelazioidea) of the nematode suborder Spirurina are known as the adult parasites of freshwater, brackish-water and marine fishes. They are placed in four families, of which the Gnathostomatidae, including Echinocephalus with a few species and the monotypic Metaleptus, are parasites of elasmobranchs, whereas Ancyracanthus contains one species in teleosts; the Physalopteridae is represented in fish by four genera, Bulbocephalus, Heliconema, Paraleptus and Proleptus, each with several species in both elasmobranchs and teleosts. The majority of fish spirurines belongs to the Rhabdochonidae, which includes 10 genera (Beaninema, Fellicola, Hepatinema, Heptochona, Johnstonmawsonia, Megachona, Pancreatonema, Prosungulonema, Rhabdochona and Vasorhabdochona) of species parasitizing mainly teleosts, rarely elasmobranchs, and the Cystidicolidae with about 23 genera (Ascarophis, Caballeronema, Capillospirura, Comephoronema, Crenatobronema, Cristitectus, Ctenascarophis, Cyclozone, Cystidicola, Cystidicoloides, Johnstonmawsonoides, Metabronema, Moravecnema, Neoascarophis, Parascarophis, Prospinitectus, Pseudascarophis, Pseudoproleptus, Salvelinema, Similascarophis, Spinitectoides, Spinitectus, Sterliadochona), with many species parasitic in teleosts only. Because of difficulties in studying fish spirurines, associated with their morphological and biological peculiarities, most species of these parasites are poorly known. It is apparent that their present classification system does not reflect phylogenetic relationships and a taxonomic revision of this nematode group, based on detailed morphological (including SEM and TEM), life history and molecular studies of individual species, is quite necessary. In Cystidicolidae, several genera have been based on details in the cephalic structures visible only with the aid of SEM, but it will be evident whether or not these tiny features are of generic importance only when more cystidicolids are described using SEM and comparative molecular data become available. Data on the biology of fish spirurines are scarce. In known cases, their life cycles involve aquatic arthropods (crustaceans or insects) as intermediate hosts, in which, sometimes, the larvae undergo a precocious development and may even attain adulthood and become gravid in these invertebrates; sometimes, fish paratenic hosts are known to occur in cystidicolids parasitizing as adults piscivorous definitive hosts. Some spirurine species are pathogenic and are known as causative agents of serious fish diseases. Consequently, further detailed studies on fish spirurines are significant not only from the theoretical viewpoint, but they may also have practical implications.

Little is known about the viability of myxozoan actinospore stages after harvest from laboratory cultures of infected oligochaete worms. The viability and reactivity of actinospores of three myxozoan species was evaluated after short-term storage at 4°C and 12°C. Two methods of determining actinospore viability were compared: differential fluorescent staining and direct microscopic observation of morphological indicators of spore integrity. Spore reactivity was quantified by measuring polar filament discharge rates in a micro-assay with fish mucus substrate and mechanical stimulation by vibration. The age-dependent viability of the three species showed clear differences. Myxobolus cerebralis actinospores had the shortest effective life span whereas Henneguya nuesslini actinospores survived significantly longer. Storage at lower temperatures yielded higher viability in all species. Myxobolus pseudodispar actinospores were significantly robust up to 12°C when assessed by staining, but showed similar viability characteristics as H. nuesslini when analyzed morphologically. Evaluation of spore viability by fluorescent staining correlated with morphological assessment, although fewer viable actinospores were usually detected microscopically. Polar filament discharge activity of morphologically intact actinospores did not significantly decrease until the third day of storage compared to freshly harvested samples. The results indicate that durability and reactivity trends during storage of actinospores differ among myxozoan species.

Two little-known nematode species of the genus Spinitectus Fourment, 1883, S. petrowi Belous, 1965 (prevalence 25%, intensity 1-8) and S. gigi Fujita, 1927 (prevalence 10%, intensity 2-3), were collected from the gastrointestinal tract of the yellow catfish, Pelteobagrus fulvidraco (Richardson), from Liangzihu Lake, Hubei Province, central China, in September of 2002. The light and scanning electron microscopical examination of this material, supplemented by a few museum specimens of S. gigi collected from the catfish Clarias fuscus (Lacépède) in southern China, made it possible to study in detail the morphology of these parasite species and to redescribe them. The first species, whose correct name is S. petrowi Belous, 1965, exhibits some morphological features (e.g., unusually short vestibule, shape of pseudolabia and of the left spicule) not found in most other congeners; a unique feature is the presence of peculiar pairs of transversely oriented peg-like cuticular spines with rounded ends on the ventral surface of the female tail. Spinitectus gigi was found to have 28-31 cuticular spines in the first ring, relatively long distances between the 2nd-7th rings of spines, and anterior rings divided into 2 sectors; the excretory pore is located at the level of the 4th ring of cuticular spines; males posses 4 pairs of preanal- and 6 pairs of postanal caudal papillae and a pair of small phasmids. Spinitectus bagri Wang, Wu et Yu, 1993 and S. wulingensis Yu et Wang, 1997 are considered junior synonyms of S. petrowi, whereas S. clariasi Ky, 1971, S. ophicephali Ky, 1971 and S. yuanjiangensis Wang, Wu et Yu, 1997 are regarded to be junior synonyms of S. gigi. Spinitectus petrowi was not previously reported from China.

Henneguya pilosa sp. n., a new species of myxosporean from the gill filaments of the white piranha, Serrasalmus altuvei Ramirez, 1965 (Characidae), a freshwater teleost fish collected in the Zoological Garden of the city of Teresina (Piauí), Brazil, is described from light and transmission electron microscope observations. This myxosporean produced small plasmodia (up to 0.2 mm in diameter), each one containing all life-cycle stages of the parasite, including numerous spores. The spores, laterally compressed, averaged 54.2 (52.3-56.0) µm in total length and consisted of two unequal valves adhering together along the suture line and two caudal processes. The spore body measured 21.1 (20.0-23.1) µm in length, 5.9 (5.5-6.3) µm in width, and 2.2 (1.9-2.6) µm in thickness. The two equal ellipsoidal polar capsules of 7.4 (7.1-7.6) µm long and 1.2 (1.0-1.3) µm wide possessed a polar filament with 11-12 (rarely 13) turns. All surfaces of the spores were covered with a tightly adherent complex network of numerous densely ramified granulo-fibrillar masses, the longest measuring 1.5 µm long, observed around the caudal processes. The prevalence of infection was 30%. The taxonomic affinities of this parasite with other of the same genus in freshwater South American fish species are discussed.