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Tail flip escape swimming was measured in the Norway lobster, Nephrops norvegicus (Linnaeus, 1758) up to cessation and following 4 hours recovery, and was compared with that of lobsters infected by the parasitic dinoflagellate Hematodinium sp. Swimming in uninfected lobsters comprised around 65 high-power flips in Phase 1 and a variable number of less powerful flips in Phase 2. Lightly-infected lobsters executed fewer flips in Phase 2, and heavily-infected lobsters produced only a few weak flips. Following 4 hours recovery uninfected lobsters produced 84.3% of the flips produced initially, due to a smaller number of Phase 2 tail flips. Infected lobsters showed less recovery, proportional to the severity of infection. The metabolic basis of the two-phase swimming pattern and the reduced performance during infection by Hematodinium is discussed. Our findings have implication for the catchability of uninfected and infected N. norvegicus, especially on fishing grounds where the fishing effort is high.

Mullowney, D. R., Dawe, E. G., Morado, J. F., and Cawthorn, R. J. 2011. Sources of variability in prevalence and distribution of bitter crab disease in snow crab (Chionoecetes opilio) along the northeast coast of Newfoundland. – ICES Journal of Marine Science, 68: . Bitter crab disease (BCD), caused by a parasitic dinoflagellate of the genus Hematodinium, is a source of mortality in Newfoundland and Labrador snow crab (Chionoecetes opilio). Prevalence and distribution patterns have been spatially and temporally variable since the discovery of BCD in 1990, and controlling factors are poorly understood. Data from a long-term trap survey in two bays along the northeast coast of Newfoundland are analysed, investigating the influences and interactions of various biotic and abiotic factors over BCD. Factors examined include host size and density, temperature, salinity, and depth. The density of small to medium-sized snow crabs was directly related to prevalence and distribution of BCD, whereas all other factors had either an indirect or no effect. Further, much of the spatio-temporal variability in disease expression is a function of variability in host productivity, growth, and movement. The study also considers the impacts BCD can exert on the commercial fishery, and the potential for predicting intermediate to long-term recruitment potential based on BCD prevalence levels.

Hamilton, K. M., Shaw, P. W., and Morritt, D. 2009. Prevalence and seasonality of Hematodinium (Alveolata: Syndinea) in a Scottish crustacean community. – ICES Journal of Marine Science, 66: 1837–1845. Protist parasites of the genus Hematodinium were detected in seven crustacean species (Cancer pagurus, Carcinus maenas, Liocarcinus depurator, Munida rugosa, Necora puber, Pagurus bernhardus, and Pagurus prideaux) from the Clyde Sea in Scotland. Seasonal screening of different tissues with sensitive molecular probes showed average infection of 3–23%, with prevalence reaching almost 60% in hermit crabs (P. bernhardus) and brachyuran hosts in spring and >30% in C. pagurus and N. puber in autumn. During summer, Hematodinium infections were rare. Hematodinium seemed to be present in all host sizes sampled. The infection was equally distributed between males and females in most host species, except C. maenas, where males seemed to be more susceptible to infection. PCR amplification of the Hematodinium ribosomal RNA gene in crustacean tissue detected the parasite most frequently in muscle, gills, and heart throughout the 2-year sampling period.

Stentiford, G. D. 2008. Diseases of the European edible crab (Cancer pagurus): a review. – ICES Journal of Marine Science, 65: 1578–1592. The edible crab (Cancer pagurus) supports an important fishery in European waters. The fishery is increasing in size and in relative importance as stocks of marine finfish decline. Despite its importance, though, studies on the pathogens and parasites of this crab species are relatively lacking compared with studies of commercially exploited finfish and molluscan hosts. Recent basic surveys of C. pagurus stocks from the English Channel carried out by the Cefas laboratory at Weymouth have identified a new viral infection (C. pagurus bacilliform virus, CpBV) in juvenile crabs, and several new species of protistan parasite (Hematodinium sp., Paramarteilia canceri, and Enterospora canceri) in the adult population. The histopathology and prevalence of each of these pathogens suggests that each can induce host mortality and, further, that specific pathogens are differentially prevalent in juvenile and adult cohorts from similar geographic locations and at different times of the year. In this review, these newly discovered pathogens are placed in context with previously described bacterial, fungal, protistan, and metazoan pathogens of C. pagurus, and the potential for these pathogens to impact on the health of individuals and populations within the English Channel fishery is discussed.

Organisms in natural habitats must frequently respond to changes in their environments through various physiological mechanisms. My laboratory has developed several methods for the quantification of stress in crustaceans. An ELISA was developed for the crustacean hyperglycemic hormone (CHH) from the American lobster (Homarus americanus). It is sensitive to as little as 0.2 fmol of peptide. Increases in hemolymph CHH were observed under conditions of acute hypoxia, elevated temperature, and altered salinity. In addition, elevated CHH concentrations were observed in Norway lobsters (Nephrops norvegicus) that were parasitized with the dinoflagellate Hematodinium sp.Stress proteins, also known as heat-shock proteins (HSPs), comprise a highly conserved class of proteins that display elevated transcription during periods of stress. Using homologous molecular probes, my collaborators and I have examined the influence of heat-shock, osmotic stress, and the molt cycle upon HSP expression at the protein and mRNA levels. We observed a significant elevation in HSP mRNA expression after 1 hr of heat-shock or after 0.5 hr of osmotic stress. When comparing claw and abdominal muscles during molting, we observed a tissue-specific HSP response. Quantification of these different stress responses may serve as early indicators of the degradation of environmental health.

The two major field methods (body colour and pleopod index) for the diagnosis of infection in the Norway lobster, Nephrops norvegicus by the dinoflagellate parasite Hematodinium were compared. Using the more reliable method, the pleopod index, which scores infection severity on a four-point scale, infection prevalence data were collected from a single fishing ground in the Clyde Sea area, western Scotland over a continuous period of 31 months. Peak infection prevalence occurs during the spring and is highest in small N. norvegicus [mean carapace length 28.1 (0.67) mm in females and 30.9 (0.50) mm in males] and in females. Mean infection severity increased from 1.050.03 during the low season (July–December) to 2.590.19 by the end of the main infection season (May), highlighting the progressive nature of patent infection over time. Infection prevalence is synchronous between the sexes in some seasons but not in others. Additionally, the proportion of recently moulted, infected males in the late season extends the duration of peak infection prevalence in certain years. Data from two adjacent fishing grounds in the Clyde Sea area also show that infection prevalence depends upon the population structure at a given site – the site with smaller animals showing the higher prevalence. An evaluation of methods for monitoring Hematodinium infection suggests that the pleopod method gives the most accurate estimation of prevalence in field-caught lobsters. 2001 International Council for the Exploration of the Sea

Around Scotland, coastal stocks of the commercially important Norway lobster (Nephrops norvegicus), particularly those within the Clyde Sea Area (CSA), have for some years been known to be infected by syndiniid dinoflagellate endoparasites of the genus Hematodinium. The prevalences of infected Norway lobsters in trawl samples from the CSA are reported for 1992-1995, together with similar data from a range of Scottish west coast sites in 1992, and from the Irish Sea in 1994 and 1995. In the CSA, infection prevalences declined after 1992 and were higher than those recorded in other sampled areas. Infection by Hematodinium was confined to the first half of the year, peaking in the spring and early summer, with medium-sized and female lobsters showng the highest prevalence. Comparison between CSA sites suggests that infection may be influenced by factors directly related to Nephrops age rather than size. In addition to the usual diel variability in catch, in spring male Nephrops showed diel variability in Hematodinium prevalence in trawl samples (being higher in the midnight samples). Females showed no diel variation in prevalence. Underwater television surveys of Nephrops burrow density and data on commercial landings indicate a decrease in Nephrops abundance in the last decade, which might in part reflect the higher levels of infection by Hematodinium during this time.

Ní Chualáin, C., and Robinson, M. 2011. Comparison of assessment methods used to diagnose Hematodinium sp. infections in Cancer pagurus. – ICES Journal of Marine Science, 68: . Endoparasitic dinoflagellates of the genus Hematodinium have recently gained attention as significant pathogens of the brown crab Cancer pagurus in Ireland. Patent infections, which are characterized by a hyperpigmented carapace and moribund condition, are limited to the discrete periods when macroscopic identification is possible. Three methods are assessed for diagnosing Hematodinium sp. infections in brown crab at the times when macroscopic identification is not always possible. Haemolymph smears, histological sections of gill, heart, midgut, hepatopancreas, muscle, and gonad, and a polymerase chain reaction (PCR) assay provided virtually equivalent accuracy in gauging infection prevalence, regardless of season. Sequences of PCR amplicons from the 18S ribosomal RNA gene confirmed the identity of the parasite as belonging to the genus Hematodinium. Infection intensity values (