Variations in biochemical composition of juvenile Ruditapes philippinarum infected by a Vibrio sp.

Abstract

The biochemical composition of young Rudltapes phlllppinaruln was exanlined in 2 groups of clams, healthy clams and those expenmentally Infected with the pathogenic V~b n o P1 bactenum to document utilization of biochemical reserves in ~n d~v i d u a l s affected by 'brown ring d~s e a s e ' After 1 mo of starvation, refeedlng half of the expenmental clams induced recovery as determined by the absence of v~s u a l slgns of disease D~s e a s e was associated with decreased dry weights In both fed and starved individuals (from 41 down to 30-35 mg clam ' ) Glycogen was found to be the main biochemical reselve used by diseased ~ndlviduals A significant decrease In glycogen (from 45 down to 20-25 my g ' dry wt) was observed in infected clams Lipid and proteln amounts were related to nutritional conditions In refed ~ndividuals, carbohydrate reserves were low In s p~t c of some iecovery These results could Indicate an ~rieversible change of the digestive gland manifested by the inabil~ty to store reserves and distnbute them to other tissues In the field, mass mortal~ties obseived in infected popul a t~o n s could result from the degeneration of metabolic actlvity KEY WORDS Brown rlng disease . Clam . V~b r i o

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

“…These winter mortalities were subsequently attributed to BRD (Paillard, 1992). Our results also confirm the observations of Plana (1995) and Plana et al (1996), who showed that Manila clams experimentally infected by Vibrio tapetis showed a significant decrease in dry weight and glycogen reserves in comparison to uninfected individuals. In marine bivalves, weight loss associated with microparasite infection is a general pattern.…”

“…This value may be overestimated because growth rate value was obtained at 18 • C, temperature which is near to the thermal growth optimum of V. tapetis (Haberkorn, 2005). This rough estimate allows us to conclude that the host energy loss due to the V. tapetis population growth is very low and can not explain the weight loss and reserve depletion observed by Plana et al (1996) and Plana (1995). Choi et al (1989) showed that, for heavily infected oysters Crassotrea virginica, the protozoan parasite P. marinus consumes more energy than the oyster has available after meeting its own metabolic needs.…”

“…Furthermore, Plana et al (1996) and Plana (1995) presented evidence suggesting that starved Manila clams experimentally infected by V. tapetis lost weight at a greater rate than did uninfected control clams. This differential weight loss and energy depletion could not be explained by a difference in energy acquisition since both groups were starved.…”

“…Vibrio tapetis induced development of BRD, weight loss and depletion of glycogen reserves, suggesting an energetic cost of the disease (Plana, 1995;Plana et al, 1996). In the field, Goulletquer (1989) also showed that winter mass mortalities of Manila clams were associated with low condition index and glycogen reserves.…”

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

“…Nevertheless, oysters infected by Vibrio splendidus had a lower level of carbohydrate than oysters free of both pathogens and oysters infected by herpesvirus alone (Table 4). Similarly, young clams Ruditapes philippinarum infected by the pathogen V. tapetis showed a significant decrease in glycogen compared with healthy clams (Plana et al 1996). However, it is still unclear why the level of carbohydrate in oysters co-infected by V. splendidus and herpesvirus was similar to that of oysters free of these 2 pathogens (Table 4).…”