Mussel histopathology: effects of season, disease and species

Abstract

ABSTRACT:We assessed seasonal histological changes as markers of health status in mussels Mytilus spp. sampled from Southampton Water, Hampshire, UK and the River Exe, Devon, UK between November 2004 and October 2005. A total of 29 health parameters related to pathogens, inflammatory and non-specific pathologies, and reproductive and physiological condition were recorded monthly from individual mussels collected from these 2 sites. We then assessed the diffential prevalence of these health parameters according to species. M. edulis, M. galloprovincialis and their hybrids were identified using the Glu-5' gene and the ME15 and ME16 primer sets that distinguish alleles specific to M. edulis (180 bp), M. galloprovincialis (126 bp) and hybrids (180 bp/126 bp). Although no overall annual differences were observed between species with respect to median levels of adipogranular (ADG) tissue and reproductive status, specific differences in reproductive status were observed within individual months. During these months (August to October), M. edulis exhibited a relatively lower reproductive status compared to M. galloprovincialis and hybrids. With respect to all remaining health parameters (pathogens, inflammatory and non-specific pathology), principal components analysis revealed no overall differences between species throughout the year. However, greater differences were observed between species during the autumn and winter than during the spring and summer, thus indicating that species differences may be exacerbated by season. This study highlights how species can affect the accurate interpretation of histopathology data collected during biological effects monitoring programmes. Whether species can also affect the biomarker response of Mytilus mussels to contaminated environments remains to be shown. The results are discussed in the context of biological effects monitoring utilising mussels.

Effect of age on liver pathology and other diseases in flatfish: implications for assessment of marine ecological health status

“…Recently published work has suggested that these types of disease may be better utilised as so-called 'phenotypic anchors' (with sex, species, etc.) against which contaminant-related biomarker (or disease) expression can be assessed (Bignell et al 2008). It should be noted that we do not advocate that the recording of grossly visible diseases (including pathogens and parasites) has no value in monitoring the health of fish within the ocean.…”

“…They stated that at least some of this stable pattern may be explained by life-history features of specific subsets of the metapopulation (e.g. the age of fish sampled at a particular site) and further that marine monitoring programmes that utilise fish disease data must take these life-history parameters into account when assessing site-level impacts, a process termed 'phenotype anchoring' in several recent studies attempting to utilise disease as a marker for assessing marine health status , Ward et al 2006, Hines et al 2007, Bignell et al 2008.…”

Effects of various pollutant mixtures on immune responses of the blue mussel (Mytilus edulis) collected at a salinity gradient in Danish coastal waters

“…Previous studies showed that histological changes in mussel tissues are sound markers of health status (Bignell et al, 2008;Sunila, 1987). However, altered haemocyte morphology has not been reported yet.…”

Site-specific disease profiles in fish and their use in environmental monitoring

“…Quantification and documentation of these life history parameters have been termed phenotype anchoring in recent studies that have attempted to align biomarker responses with higher-level health indicators (such as disease) in fish and molluscs , Ward et al 2006, Hines et al 2007, Bignell et al 2008. By using this approach, the disease(s) per se may either be considered as a direct marker of environment status (e.g.…”