Studies in the biology of Talitridae (Crustacea, Amphipoda): visual orientation in Talitrus saltator

Abstract

The nocturnal migrations of Talitrus over the sand surface cover considerable distances, frequently taking specimens well below mid-tide level. In spite of this, by day the species occupies burrows in a broad, but fairly well-defined, zone in the region of high-water mark. The nocturnal distribution of the animals can be attributed to a somewhat random search for food, but the question arises (worded anthropomorphically), how do the animals find their way back to the high-water region? Perhaps in an attempt to answer this question, Verwey (1929) states briefly that Talitrus orientates on the beach by mnemotaxis to the wind, sun and direction of the sea, and by menotaxis (compass reaction). Mnemotaxis, or orientation by memory images, has been entirely eliminated from the modern classification of orientation reactions (Fraenkel & Gunn, 1940), so that Verwey's contribution is reduced to a statement without evidence that Talitrus orientates by means of a compass reaction to an unknown stimulus, and no other author mentions the orientation of Talitrus on the beach.