Movement patterns of river crabs (Decapoda, Potamoidea) in the field: predictable and unpredicatable components

Authors

  • S. Barbaresi,

    1. Dipartimento di Biologia Animale e Genetica, Università di Firenze, and Centro di Studio per la Faunistica ed Ecologia Tropicali del CNR, Firenze, Italy
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  • F. Gherardi,

    1. Dipartimento di Biologia Animale e Genetica, Università di Firenze, and Centro di Studio per la Faunistica ed Ecologia Tropicali del CNR, Firenze, Italy
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  • M. Vannini

    1. Dipartimento di Biologia Animale e Genetica, Università di Firenze, and Centro di Studio per la Faunistica ed Ecologia Tropicali del CNR, Firenze, Italy
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    • 2

      Marco Vannini, Dipartimento di Biologia Animale e Genetica, Universiti di Firenze, Via Romana 17, 50125 Firenze, Italy


Abstract

Radio-telemetry was used to investigate locomotor activity rhythms in a field population of the freshwater crab Potamon fluviatile. Fourteen adult specimens were radio-tracked almost continuously over a 13-day period along a hill stream in Tuscany, Italy. A rough nychthemeral movement pattern was found in some animals of both sexes. None of the crabs showed a constant activity on different days, nor did they follow any periodical pattern. Although average displacement amounted to about 5m/d, activity was concentrated over several days at a time, followed randomly by periods of almost total inactivity. On average, only about 3/4 of radio-tagged crabs were active every day and only a small fraction active at the same time. The crabs spent about 60% (females) or 70% (males) of their time out of the water, but there was no regular pattern in land-water preference. The random high variation in locomotor activity on different days seems to be a constant pattern in all decapods that have been studied so far, using individual marking techniques.

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