Impact of Brown Ring Disease on the energy budget of the Manila clam Ruditapes philippinarum

Abstract

Brown Ring Disease (BRD) is a bacterial disease caused by the pathogen, Vibrio tapetis. The disease induces formation of a brown deposit on inner shell of the Manila clam, Ruditapes philippinarum. Development of this disease is correlated with a decrease in the condition index of infected clams. Experiments were conduced in order to assess the effect of the development of BRD on two parameters affecting the energy balance of the clams: the clearance and the respiration rates. Experiments were performed in a physiological measurement system that allowed simultaneous measures of clearance and respiration rates. During both acclimation and measurements clams were fed with cultured T-iso and temperature was close to seasonal field temperature (10 • C). Our results showed that severely diseased clams (conchiolin deposit stage, CDS ≥ 4) are subject to weight loss in comparison to uninfected ones, indicating that BRD induces a desequilibrium in the energy balance. We demonstrated a reduction of the clearance rate of severely diseased clams which led to a decrease in energy acquisition. Respiration rate showed asignificant decrease with BRD symptoms, but evidence in the literature allowed us to hypothesize that energy mobilised for an immune response and lesion repair increases overall organism maintenance costs. Both factors should thus contribute to the degradation of the energy balance of diseased clams. Because effects of BRD on naturally infected clams only appears significant for CDS ≥ 4, when brown ring assumes a significant place on the inner shell, we consider that the Manila clam is tolerant of low disease levels.

Mass mortalities of Pacific oysters Crassostrea gigas reflect infectious diseases and vary with farming practices in the Mediterranean Thau lagoon, France

“…Activity of HK in labial palps of oysters varies with feeding ration (Bacca 2007, p. 123). Therefore, the reduction in HK activity observed in infected oysters may reflect a decrease in feeding activity, which is symptomatic of pathogen infection in bivalves (Flye-Sainte-Marie et al 2007, Genard et al 2011.…”

Physiological and biochemical changes associated with massive mortality events occurring in larvae of American oyster (Crassostrea virginica)

“…Indeed, several studies on marine invertebrates have shown that respiration rate and CS activity were positively correlated (Moran and Manahan 2004;Meyer et al 2007). In juvenile Manila clams, respiration rate decreased with the development of brown ring disease symptoms (Flye-Sainte- Marie et al 2007). These authors observed that the oxygen consumption decrease was correlated with decreased feeding (clearance rate) and could be interpreted as a compensatory reduction of metabolic rate, as was observed by Widdows and Hawkins (1989).…”

Variability of the hemocyte parameters of Ruditapes philippinarum in the field during an annual cycle

“…and can affect both Ruditapes decussatus and R. philippinarum (see Villalba et al, 2004, for a review). Both pathologies can interfere with host energy balance (Ngo and Choi, 2004;Park et al, 2006;Leite et al, 2004;Flye-Sainte-Marie et al, 2007b) and can be responsible for mass mortalities (see e.g. Paillard et al, 1989;Castro et al, 1992;Paillard, 1992Paillard, , 2004bVillalba et al, 2005Villalba et al, , 2004.…”