Effect of Pollution History on Immunological Responses and Organ Histology in the Marine Mussel Mytilus edulis Exposed to Cadmium

Abstract

The effect of previous toxicant exposure (i.e., exposure history) on an organism's response to re-exposure to the toxicant is of considerable interest. The marine mussel Mytilus edulis was collected from reference and polluted sites in southwest England, and groups of mussels from each site were exposed to 20 μg/L CdCl2 for 0, 1, 4, and 8 days and compared with unexposed controls. End points evaluated were tissue metal and electrolyte concentrations, haemolymph chemistry, haemocyte characteristics [counts, neutral red uptake (NRU), and phagocytosis], histology, and expression of metallothionein gene (mt10) expression in digestive glands. Field-collected animals differed by collection site for some end points at time zero, at which time tissue Fe and Pb concentrations were greater and NRU and condition index lower in mussels from the polluted site. Subsequent exposure to cadmium (Cd) in the laboratory caused Cd accumulation mainly in digestive gland, but there were no site-specific effects on tissue trace-metal concentrations. NRU, phagocytosis, and haemolymph Na(+) and K(+) concentrations differed among sites and Cd treatment, but there were no clear trends. Exposure to Cd resulted in lower Ca(2+) concentrations in gill, digestive gland, and haemolymph in animals from the polluted site compared with controls (Kruskal-Wallis, p ≤ 0.05). Lesions, including necrosis, inflammation, and neoplasia, were observed in animals from the polluted site, but the frequency of these lesions appeared to decrease unexpectedly after Cd exposure. Expression of mt10 increased 3-fold in Cd-exposed animals from the polluted site compared with all other groups (Kruskal-Wallis, p = 0.01). We conclude that Cd exposure affected some immune responses in M. edulis, but pre-exposure history influenced toxicological outcomes of Cd exposure in the laboratory.

Isoform‐specific responses of metallothioneins in a marine pollution biomonitor, the green‐lipped mussel Perna viridis, towards different stress stimulations

“…The abundance of MT10‐I and MT10‐II gene transcript was normalized to 18S rRNA gene transcript for each sample. A previous study showed that the expression of 18S gene was a suitable reference gene in mussels and its expressions were stable among different chemical treatments . In this study, expressions of the 18S gene were not significantly different for different control and treatment groups (ANOVA, p > 0.05), and thus this gene was considered as a suitable reference.…”

Transcriptomic responses of the endangered freshwater mussel Margaritifera margaritifera to trace metal contamination in the Dronne River, France

“…In bivalves, the digestive gland functions both as a site for metal uptake and as an important reservoir for metal storage; thus, this organ is a main target of metal bioaccumulation (e.g., Sheir et al 2013). Measurements showed significant differences between the two sites and the two times of sampling.…”

Histopathological Alterations in the Gonad of Megapitaria squalida (Mollusca: Bivalvia) Inhabiting a Heavy Metals Polluted Environment

“…), are in some cases related to the effect of pollutants (De Vico and Carella ), as observed in Mytilus edulis chronically exposed to heavy metals (Sheir et al. ). In this sense, the highest prevalence of hemocytic infiltration in Santa Rosalía clams and the absence of granulocytomas and brown cells in clams from San Lucas beach suggest that these inflammatory responses in Santa Rosalía clams is mainly due to pollution, while hemocytic infiltration in clams from San Lucas beach is likely due to a normal clearance process, reabsorption of residual gametes, and postspawning cellular repair (postspawning stage).…”

“…; Sheir et al. ). In Mexico, many coastal ecosystems affected by anthropogenic activities show signs of environmental degradation (García‐Gasca et al.…”

“…; Sheir et al. ). In particular, the deterioration of gonadal tissue and gamete viability is one of the most devastating consequences of marine pollution, as it can reduce the reproductive success and well‐being of organisms (Vaschenko et al.…”