Hematodinium sp. (Alveolata, Syndinea) detected in marine decapod crustaceans from waters of Denmark and Greenland

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...

Hematodinium infection seasonality in the Firth of Clyde (Scotland) Nephrops norvegicus population: a re-evaluation

“…It is also possible that subpatent infections can persist for long periods in N. norvegicus without manifesting as patent infection. Using a nested PCR approach in a Danish N. norvegicus population with no history of patent Hematodinium infection, Eigemann et al (2010) found prevalence of subpatent Hematodinium infection to be around 65%. Those authors concluded that if the Hematodinium DNA amplified by the PCR was from viable cells, infections may not always be fatal.…”

Advances in our understanding of the global diversity and distribution of Hematodinium spp. – Significant pathogens of commercially exploited crustaceans

“…Recently, Eigemann et al (2010) have documented the presence of Hematodinium in N. norvegicus, P. bernhardus, and L. depurator from Danish waters (Kattegat), in a new host, Hyas araneus, from the west coast of Greenland (Sisimiut area), and in C. opilio from same Greenlandic waters, areas that Hematodinium had not previously been reported from. The presence of Hematodinium was only detected using standard and nested PCR assays (using a combination of previously published primers) as external diagnostic techniques (body color method and pleopod assessment) were negative.…”

“…Although dates and descriptions of the discovery of Hematodinium spp. in the literature are not definitive proof of the parasite's first presence in that host, there is general agreement that Hematodinium infections are increasing in frequency and are being encountered in new hosts and locations (Bower et al, 2003;Eigemann et al, 2010;Morado, 2011;Morado et al, 2010;Ryazanova, 2008;Xu et al, 2007aXu et al, , 2007bXu et al, , 2010.…”

“…of interest (Small et al, 2006(Small et al, , 2007b and are used in combination with other primers in diagnostic assays (Eigemann et al, 2010). In a follow up study, Hudson and Adlard (1996) then sequenced the 3 0 end of the SSU rRNA gene and the 5 0 end of the ITS1 rRNA region from samples of Hematodinium-infected C. sapidus, C. bairdi, C. opillio, and N. norvegicus.…”

“…Shields (personal communication). the genetic relationships between Hematodinium isolates have revealed informative taxonomic affiliations (Eigemann et al, 2010;Hamilton et al, 2007Hamilton et al, , 2009Hamilton et al, , 2010Hudson and Adlard, 1996;Jensen et al, 2010;Pagenkopp Lohan, 2011;Small et al, 2006Small et al, , 2007aSmall et al, , 2007bSmall et al, , 2012. In this paper I will review studies that have generated DNA-based data in an effort to clarify the distribution and taxonomic diversity among members of the genus.…”