Environmental Contaminants and the Prevalence of Hemic Neoplasia (Leukemia) in the Common Mussel (Mytilus edulisComplex) from Puget Sound, Washington, U.S.A.

Abstract

The relationship between hemic neoplasia, a blood cell disorder in bivalve molluscs, and chemical contaminants was evaluated in the common mussel (Mytilus edulis complex). Hemic neoplasia (HN) is endemic to mussel populations in Puget Sound. The prevalence of hemic neoplasia ranged from 0 to 30% in mussels from nine sites in Puget Sound, Washington. Organic chemical contamination in sediment from these sites range from 0.1 to 64.0 ppm of polycyclic aromatic hydrocarbons (PAHs) and 0.07 to 0.50 ppm chlorinated hydrocarbons. No relationship between the body burden of environmental contaminants and the prevalence of HN in mussels was identified. To evaluate the shortterm ability of chemical contaminants to induce HN in mussels, mussels, from a site where mussels were previously determined to be HN free, were fed microencapsulated PAHs (composed of a mixture of phenanthrene, flouranthene, and benzo[a]pyrene) or PCBs (Aroclor 1254) and the prevalence of HN was assessed after 30 days of exposure. Although an apparent increase in HN prevalence (20 to 30%) was observed in all treatments groups except the untreated controls, no significant difference in the prevalence of HN was observed between the control group of mussels fed corn oil (vehicle) and mussels fed either PAHs or PCBs in corn oil. A long-term (180-day) exposure study was conducted to evaluate the influence of PAHs or PCBs in modulating the prevalence of HN in a mussel population already exhibiting a moderate HN prevalence. Mussels, from a site where mussels were previously determined to exhibit a background prevalence of HN, fed microencapsulated PAHs, PCBs, and corn oil (vehicle) over a long time period (180 days), revealed an apparent increased prevalence of HN (30 to 40%) above the low levels (20%) initially present. However, no significant difference in the prevalence of HN was observed between the control group of mussels fed corn oil (vehicle) and mussels fed either PAHs or PCBs in corn oil. Although chemical contaminants have been proposed as a modulating factor in the development and promotion of HN in bivalve molluscs from environmentally stressed and degraded habitats, we find no evidence that chemical contaminants induce or promote the development of HN in the mussel M. edulis complex. Academic Press

Identification and phylogenetic comparison of p53 in two distinct mussel species (Mytilus)

“…Other authors (Krishnakumar et al, 1999) were unable to link chemical exposure to onset of haemic neoplasia. We and others have demonstrated that the p53 gene and its family member, p73, are implicated in the onset of molluscan leukemia (Barker et al, 1997;Kelley et al, 2001;Stephens et al, 2001).…”

Influence of disseminated neoplasia, trematode infections and gametogenesis on surfacing and mortality in the cockle Cerastoderma edule

“…Neoplasms in C. edule were initially recorded in 1982 in Cork Harbour, Ireland, and in that same year they were also reported in Brittany, France (Twomey & Mulcahy 1988, Twomey 1994, Villalba et al 2001, Romalde et al 2007, Le Grand et al 2010. Disseminated neoplasia is a proliferative disorder of the haemocytes and is of unknown origin; it is characterised by very large, mitotically active, pleomorphic and highly invasive cells (Twomey 1994, Krishnakumar et al 1999, Collins & Mulcahy 2003, Barber 2004, Ciocan et al 2006, Le Grand et al 2010, Díaz et al 2011.Throughout their range Cerastoderma edule are known to act as the first or second intermediate host for at least 16 digenean parasites from 7 different families, of which the family Echinostomatidae is the most dominant (de Montaudouin et al 2009). A recent study along the southwest coast of Ireland found 8 species of digenean parasites in C. edule, and Meiogymnophallus minutus (synonym Parvatrema minutus, Scholz 2002) was the most common in terms of prevalence and intensity of infection (Fermer et al 2009).…”

Assessment of Seasonal Variability of Cytochemical Responses to Contaminant Exposure in the Blue Mussel Mytilus edulis (Complex)

“…To determine the prevalence of HN, 0.2-0.5 ml of hemolymph was drawn from the posterior adductor muscle of 20 mussels per month per site. Hemolymph was collected with a 23-gauge needle into a 3-cc syringe containing 0.5 ml Tris-EDTA hemocyte buffer (Krishnakumar et al 1999). The contents of the syringe were then placed on a poly-L-lysine slide in a moist chamber and incubated at room temperature for 30 min.…”