The prevalence of Hematodinium in Nephrops norvegicus from the western Irish Sea

Abstract

Infection of Nephrops norvegicus by a dinoflagellate parasite belonging to the genus Hematodinium, is reported in populations of Nephrops from the Irish Sea. Diseased animals are recognized by an opaque vivid body colour and high densities of parasites in the haemolymph. Infection causes a general morbidity of the host along with a reduction in swimming performance, which eventually leads to the death of the host lobster. Research vessel cruises performed over the period 1994–2001 have shown Hematodinium to occur in populations of Nephrops from the Irish Sea throughout this period. High infection prevalence during the month of April and negligible levels during October agree with published data on seasonal infection levels in Scottish Nephrops stocks. Data on spatial and temporal infection prevalence are presented for the first time for the Irish Sea and show variation between stations and between years. Mean infection prevalence peaked at 18% of captured Nephrops during April 1996 and was followed by a downward trend to 2001. Infection predominates in small Nephrops (<30 mm carapace length) and in females is normally associated with immature animals. Although a positive correlation with seawater salinity was noted, preliminary analysis did not show a relationship between prevalence and other environmental factors.

A review of the parasitic dinoflagellates Hematodinium species and Hematodinium-like infections in marine crustaceans

“…Long-term datasets for the prevalence of infections in Nephrops norvegicus from the Clyde Sea Area, Scotland, have shown that prevalence is highest in winter and spring (Field et al 1992, Field et al 1998, Stentiford et al 2001c, 2001d, reaching as high as 70% in notable epizootics (Field et al 1992). In the Irish Sea prevalences reached 18 and 35% (Briggs & McAliskey 2002), and showed a seasonal pattern with a nadir in the summer and fall. In the Chionoecetes bairdi fishery of southeastern Alaska, the carapace discoloration of infected crabs becomes more pronounced as the epizootics progress into the fall (Meyers et al 1990).…”

“…Thus, the simplest diagnostic method involves an external assessment of the opaquely discoloured carapace that can be performed rapidly in the field. This method has been used as a field diagnostic tool for Hematodinium infection of Nephrops norvegicus in Scottish, Swedish and Irish waters (see Field et al 1992, Tärnlund et al 2000, Stentiford et al 2001c, Briggs & McAliskey 2002, for Cancer pagurus in the English Channel (Stentiford et al 2002), for Chionoecetes bairdi from Alaskan waters (see Meyers et al 1987Meyers et al , 1990) and for C. opilio from Newfoundland (Taylor & Khan 1995, Dawe 2002, Pestal et al 2003, Shields et al 2005. However, while this method remains useful for the detection of advanced cases in heavily infected hosts, it does not detect low-level 'sub-patent' or potentially sub-patent (low-level, tissue-based) infections (see Meyers et al 1987, Shields & Squyars 2000, Stentiford et al 2001c, Pestal et al 2003, nor is it useful for infections in temperate species such as Callinectes sapidus (J. D. Shields pers.…”

“…In this way, castration could be effected through the disruption of the testis or ovary of infected hosts. Infected female Nephrops norvegicus from the Irish Sea do not develop mature gonads (Briggs & McAliskey 2002). However, size at maturity was not presented and would likely confound their analysis because females reach maturity between 21 and 34 mm (Hillis & Tully 1993, Tuck et al 2000.…”

The influence of defined ante-mortem stressors on the early post-mortem biochemical processes in the abdominal muscle of the Norway lobster,Nephrops norvegicus(Linnaeus, 1758)

“…infection Á patently infected animals were selected from the trawled catch on board the vessel by using a rapid method based on body colour and general appearance, as described by Stentiford et al (2001b) and used by Briggs & McAliskey (2002). Moribund animals were discarded.…”

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

“…Epizootics often occur in enclosed hydrological areas like fjords and poorly drained estuaries or other restricted areas (Shields 1994, Pestal et al 2003. However, epizootics actually do occur in open areas (Meyers et al 1996, Field et al 1998, Briggs & McAliskey 2002, Stentiford et al 2002, but in open ocean systems, e.g. the habitats of C. opilio and C. bairdi in the Bering Sea, the prevalence of Hematodinium sp.…”