Predation of Prochilodus lineatus (Valenciennes, 1836) post-larvae by dragonfly (Pantala Fabricius, 1978) fry in different development phases - DOI: 10.4025/actascibiolsci.v25i1.2105

Abstract

The aim of this experiment was to evaluate the predation of dragonfly (Pantala sp.) fry in different development phases by the Prochilodus lineatus post-larvae (Characiformes, Prochilodontidae). Fifty-four dragonfly fry were distributed among eight length groups (2.54, 3.89, 6.37, 9.67, 10.98, 12.81, 18.50 e 24.50 mm), then they were also distributed among 27 aquarium (1.0 L), with constant illumination by fluorescent lamps (40 watts), and two dragonfly fry of similar size were put in each experimental unit. The P. lineatus post-larvae (Lt: 6.20±0.22 mm and Wt: 0.91 mg). 15 P. lineatus post-larvae were distributed in each aquarium (18:00h), each three- hour-interval (21.00, 0.00, 3.00, 6.00, 9.00, 12.00, 15.00 e 18.00h), the live post-larvae were counted and the dead ones were replaced. The physical and chemical parameters pH, dissolved oxygen, electric conductivity and temperature was measured in the beginning and in the end of the experiment, the average values of these ones were 7.83±1.11, 6.57±1.23 mg/L, 212.71±3.93 µS/cm and 27.19±0.27ºC, respectively. A quadratic effect of the dragonfly fry size on the total number of P. lineatus post-larvae eaten with maximum point with dragonfly larvae of 24.46mm. was observed. And a decrease in the number of post larvae eaten in time of the experimental period was also observed. It may be concluded that there was an increase in the number of P. lineatus post-larvae eaten with a size increase of dragonfly fry