Temporal criterion for behavior: Orientation of the young Japanese flounder Paralichthys olivaceus

When considering a behavioral pattern as a specific type of mechanism, an inherent problem is that it is difficult to determine to what extent the mechanism is programmed to behave selectively in individual situations. To probe this question further, we investigated the orientation of the body axis of the young Japanese flounder Paralichthys olivaceus. The pattern of the substrate and the orientation of neighboring fish were recognized as the determining factors for orientation in P. olivaceus. It was expected, therefore, that a group of individuals would exhibit a definite orientation pattern with respect to the striped pattern. However, the global orientation patterns on the striped substrate based on ten individuals could be classified into two categories: perpendicular and cross to the stripe pattern. This suggests that the substrate pattern and the surrounding individuals operated as distinct temporal criteria as stimuli for orientation. Analysis based on the local and global viewpoints reveals the temporality quantitatively.