Modulating effects of orally supplied Euglena gracilis on the physiological responses of the freshwater mussel Diplodon chilensis, exposed to sewage water pollution in a Patagonian river (Argentina).

BIANCHI, V.; CASTRO J.M.; ROCCHETTA I.; CONFORTI V.; PASCUAL M; LUQUET CM

FISH & SHELLFISH IMMUNOLOGY

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2016 vol. 51 p. 17 - 21

1050-4648

In order to test if orally supplied Euglena sp. cells modulate the physiological status of bivalves duringbioremediation procedures, we evaluated the effect of Euglena gracilis diet on the immune response,oxidative balance and metabolic condition of Diplodon chilensis exposed to sewage water pollution.Mussels were fed for 90 days with E. gracilis (EG) or Scenedesmus vacuolatus (SV, control diet), and thenexposed for 10 days at three sites along the Pocahullo river basin: 1) an unpolluted site, upstream of thecity (control, C); 2) upstream (UpS) and 3) downstream (DoS) from the main tertiary-treated sewagedischarge, in the city of San Martín de los Andes, Northwest Patagonia, Argentina. Our results show thatthe total hemocyte number decreases while pollution load increases along the river course for both, EGand SV mussels. Phagocytic activity is higher in EG mussels than in SV ones under all conditions. Reactiveoxygen species (ROS) production in hemocytes increases with the increase in the pollution load, beingsignificantly higher for EG mussels than for SV ones at DoS; no changes are observed for total oxyradicalscavenging capacity (TOSC). Hemocytes´ viability is increased for E. gracilis diet at C and remains unchangedin this group of mussels when exposed at the polluted sites. Lysosomal membrane stability ishigher in EG mussels than in SV ones for all conditions, although it is decreased at polluted sitescompared with that at C. Antioxidant (catalase) and detoxifying (gluthatione S-transferase) defenses aregenerally lower in gills and digestive gland of EG mussels than in SV ones. Lipid peroxidation (TBARS) isevident in gills of EG mussels at C, and in digestive gland of the same group, at all the sites. Gill massfactor (GF) is affected by the E. gracilis diet; it is increased at C and decreased at polluted sites whencompared with that of SV ones. Digestive gland mass factor (DGF) is higher in EG mussels than in SVones. In D. chilensis, continuous and long term feeding with E. gracilis cells favors immune response andreduces the damage caused by sewage pollution exposure on hemocytes. Nevertheless, diet and transplantation procedures may produce negative effects on the oxidative balance of gills and digestivegland and should be taken into account for bioremediation strategies.