Experimental Studies On The Feeding Rates And Oxygen Consumption Rates Of Four Freshwater Mollusks

The influences of environmental factors on feeding rates (FR) and oxygen consumption rates (OC) of four freshwater mollusks: Cristaria plicata, Anodonta woodiana, Corbicula fluminea, Bellamya aeruginosa were studied through laboratory experiments, meanwhile the influences of different algal composition on the FR and feeding preference were considered using the same methods.The feeding results showed that: (1) As body weight increased, FR of four mollusks decreased, which were accorded with the power function: FR= aW^b; (2) temperature had significant effect on FR of four molluscous species and FR reached maximum after gradually increasing at agreeable temperature, whereas decreased while the temperature rose higher; C plicata, A. woodiana, C. fluminea and B. aeruginosa had peek value at 25℃, 25℃, 20℃, 35℃respectively; (3)An optimal algal concentration range caused the rise of FR of four species; however, when the algal concentration was out of the optimal range, FR decreased; C. plicata, A. woodiana and C. fluminea all had peek value at algal concentration of 5×10⁵cells/ml while B. aeruginosa had at 3×10⁵cells/ml; (4)FR of four species had day and night rhythm: FR of four mollusks all reached the first peek value at 04:00, then fell; C. plicata and C. fluminea had second peek value at 04:00 and 16:00 respectively, while B. aeruginosa and A. woodiana had at 20:00.The oxygen consumption results showed that: (1) OC was negatively correlated with the dry body weight, following the power function: OC=aW^b; (2) OC of four mollusks were positively correlated with the agreeable water temperature; C. plicata, A. woodiana, C. fluminea and B. aeruginosa had OC peek value at 30℃, 25℃, 25℃, 35℃respectively; (3) hyperbolic model OC=DO/( K₁+K₂×DO) was used to quantify the ability of mollusks to maintain OC in low DO, The higher the K₁/K₂ value was, the stronger the oxygen-control ability would be. B. aeruginosa had the highest K₁/K₂ value in our experiment.B. aeruginosa has highest FR when feeding on mono-algae, and four species of mollusks show no feeding preference on mono-Scenedesmus obliquus and mono-Microcystic aeruginosa, that was the FR of each species on Scenedesmus obliquus or Microcystic aeruginosa,had no significant difference; When feeding on multi-algae, four species showed feeding preference: FR of C plicata, A. woodiana and C. fluminea increase significantly and FR on M. aeruginosa were higher than which on C. plicata whereas the feeding on M. aeruginosa of B. aeruginosa was suppressed.In conclusion, mollusks had fluctuation of FR according to different body weight and some environmental factors and difference in tolerating the undesirable situation, which provided theoretical basis for selecting biomanipulation freshwater mollusks.