BEHAVIOUR AND MANIPULATION CAPACITY OF THE SHRIMP PENAEUS SUBTILIS PÉREZ-FARFANTE, 1967 (CRUSTACEA, PENAEIDAE) FED WITH PELLETIZED DIET IN LABORATORY

Abstract

The study investigated the behavior and manipulation capacity of three groups (G₁ = 4.0 - 6.9 g; G₂ = 7.0 - 9.9 g; and G₃ = 10.0 - 13.9 g) of the shrimp Penaeus subtilis, using a pelletized dry feed with similar chemical composition, but of three different pellet sizes (P₁ = 1.904 mm í­Ëœ, P₂= 1.314 mm long and P₃ = 5.503 mm long). In laboratory, shrimps were classified in relation to their body size, and starved in aquariums for 36 hours. Preceding the experiment, each shrimp was individually acclimated for 30 minutes in a 3,760 L aquarium, with constant aeration and artificial light. The aquarium was suspended in an aluminium rectangular structure, with a glass on the top. On its bottom, a video camera was installed to film shrimp feeding behavior. The experiment started administering a dry pelletized feed in excess. Each pellet size was tested separately for each shrimp group. Later, shrimp images were analyzed and the following data processed: number of tries to capture feed pellets or particles (T), number of feed pellets or particles conducted to the mouth or pre-oral cavity (C_D) and number of feed pellets or particles partially or completely ingested (C_S). Shrimp manipulation capacity was determined by the following formulas: Manipulation Capacity Index (ICM) = [(C_D/T)+(C_S/C_D)]/2; Capture Efficiency (EC_P) = (C_D x 100)/T and Consumption Efficiency (EC_S) = (C_S x 100)/C_D. A total of 101 images of different shrimps were analyzed. The Analysis of Variance (ANOVA) of ICM showed statistically significant differences (P < 0.05) between shrimp groups G₁, G₂ and G₃, which had ICM varying from 0.4583 (G₁ for P₂) to 0.6442 (G₃ for P₃). EC_P varied from 40.81 (G₁ for P₃) to 69.44% (G₃ for P₁) showing statistically significant differences (P < 0.05; MANOVA) between shrimp groups and pellet sizes. EC_S varied from 43.61 (G₁ for P₂) to 77.69% (G₃ for P₃). Analysis of Covariance (ANCOVA) revealed that the main factor responsible for the variation in the indices ICM, EC_P and EC_S between shrimp groups was the body size of each animal, and not that of the pellet.