Structure and mechanisms of schooling intadpoles of the clawed frog, Xenopus laevis

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The geometric structure and sensory bases of social aggregates in larvae of the clawed frog, Xenopus laevis, were studied using photographic data interpreted with the aid of a computerized image analyser. The system records positional data from photographs and uses this information to assess: (1) extent of parallel orientation between tadpoles that are nearest neighbours, (ii) distance over which significant parallel orientation is maintained (interactive distance), and (iii) extent of clumping or evenness of individuals. o (1) Under all density, size, and illumination conditions, tadpoles show a highly significant tendency to line up parallel (0° between neighbours) and, to a lesser extent, antiparallel (180° between neigh-bours) to their nearest neighbour. (2) Tadpoles in the light show a much greater tendency to orient parallel to nearest neighbours than in the dark. (3) The tendency to orient parallel to nearest neighbours increases slightly with increasing tadpole size and density. (4) In the light, tadpoles have an interactive distance of approximately two body lengths; in the dark, only approximately one body length. (5) Interactive distance shows a slight increase with decreasing tadpole density. (6) Interactive distance is proportional to tadpole size. (7) Spacing between tadpoles is random, but there is a weak tendency toward increased evenness with increasing tadpole size and density; tadpoles in the light position themselves more evenly than in the dark. We propose that Xenopus tadpoles use both visual and lateral line input to school. Lateral line input is presumably necessary for maintaining some degree of parallel orientation in the dark and is augmented by visual information in the light.