No abstract

No abstract

Five decapod crustacean species were examined for presence of the parasitic dinoflagellate Hematodinium spp. (Alveolata, Syndinea) by morphological methods (colour and pleopod methods) as well as by PCR and nested PCR with Hematodinium-specific primers. Nephrops norvegicus, Pagurus bernhardus and Liocarcinus depurator were sampled by trawling in Danish waters and Chionoecetes opilio and Hyas araneus were sampled by trapping off the west coast of Greenland. The existence of Hematodinium has not previoiusly been documented in Danish waters, but it was detected in all 3 decapod species examined in the present study. Hematodinium sp. was also detected for the first time in H. araneus and the existence of Hematodinium sp. in Greenlandic C. opilio was documented by PCR. Analyses of 26 Hematodinium sp. ITS1 sequences, including sequences from all 5 host species sampled, revealed more than 95% sequence similarity between 24 of the sequences. Two Hematodinium sp. ITS1 sequences from C. opilio were only 81% similar to the 24 other ITS1 sequences. The nested PCR approach resulted in the highest reported percentages of positive samples for Hematodinium sp.in the hosts investigated (between 45 and 87.5%). However, no decapods were found to be infected with Hematodinium sp. based on morphological methods. Consequently, Hematodinium sp. may be more common than previously believed, and, assuming that the DNA found originated from viable and infectious parasite cells, infections may not always be fatal. We suggest that the hosts investigated may have been subject to latent infections that could develop into a fatal disease only if the hosts were physiologically stressed due to other factors. KEY WORDS: Hematodinium · Latent infections · ITS1 · Parasitic dinoflagellates · PCR detection Resale or republication not permitted without written consent of the publisherDis Aquat Org 92: [59][60][61][62][63][64][65][66][67][68] 2010 dinium sequences may warrant species status (Small et al. 2007b,c, Jensen et al. 2010. Different Hematodinium genotypes were related to different host species (Small et al. 2007b, Hamilton et al. 2010, Jensen et al. 2010) and geographical regions (Hamilton et al. 2010). It is also clear, however, that a single Hematodinium genotype may infect more than one host species (Hamilton et al. 2007, Small et al. 2007a, Jensen et al. 2010. However, so far only one other species of Hematodinium has been formally described, namely H. australis, which was described on the basis of morphology, host species, and austral location (Hudson & Shields 1994).In some host species, advanced infections lead to a discoloration of the carapace from reddish-brown to a reddish 'cooked' appearance (e.g. in Nephrops norvegicus and Chionoecetes opilio) and this may be used for detection of the disease (colour method; Meyers et al. 1987, Field et al. 1992. Rapid logarithmic growth of parasitic cells in the host's haemolymph causes a colour change from bluish-transparent to milky-white (e.g. Shields & Squyars 2000) and aggregat...

Northern shrimp (Pandalus borealis) represents one of the most important fisheries in the Northwest Atlantic Ocean, but few studies have considered connectivity among different management units (i.e., stocks). Using a biophysical model, we investigated potential larval dispersal among North Atlantic Fisheries Organization (NAFO) divisions and its interannual variability during the long pelagic larval phase of P. borealis (∼3 months). Overall, we found a largely stable, stream-like larval connectivity system driven by the main currents that flow over both the Greenland and Canadian continental shelves, with a relatively low but consistent exchange of larvae between Greenland and Canada across the Baffin Island continental shelf. We observed highest potential settlement densities on the northwestern Greenland and Newfoundland shelves, representing retention areas that correspond to highest abundances of adult shrimp. Intermittent and variable larval exchanges of lower magnitude also occurred between populations less obviously associated with the major circulation features. Our study improves understanding of northern shrimp stock–recruitment relationships at the metapopulation level, which could help determine the appropriate spatial scale to improve management strategies.