On the Preference of Roaches (Leuciscus rutilus) for Trinitrophenol, Studied with the Fluviarium Technique

Abstract

The fluviarium, first described by Höglund (1951), has been improved in several respects.The reaction of roaches in stepped concentration gradients of 2,4,6-trinitrophenol has been studied in the fluviarium; all gradients used were of 10 equal steps, the lowest step being always pure tapwater. Preliminary experiments showed that specimens of this species are attracted by this substance in concentrations lower than 3 × 10−4 molar. However, their responsiveness varies very much, and seems to depend on length as well as on age, the smaller fishes reacting more promptly than the larger ones, and the older fishes more promptly than the younger ones. These differences are probably caused by different activity of the fishes.When the steepness of the gradients is increased the reaction of the fishes also increases, up to the gradient with maximal concentration about 8 × 10−5 molar. Then the reaction remains unaltered up to a maximum of at least 28 × 10−5 molar. Still steeper gradients cause a decrease in the reaction.The weakest gradient causing a reaction of the roaches has been estimated by statistical extrapolation to be one with maximum concentration of 0.38 × 10−5 molar.