Faculty Publications

Title

Locomotor rhythms in the fiddler crab, Uca subcylindrica

Document Type

Article

Keywords

Circadian, Fiddler crabs, Locomotor rhythm, Seasonal phase-inversion

Journal/Book/Conference Title

Biological Rhythm Research

Volume

29

Issue

2

First Page

179

Last Page

196

Abstract

The locomotor activities of individual specimens of Uca subcylindrica (Stimpson) collected from semi-arid, supratidal habitats in south Texas and northeastern Mexico were studied in the laboratory using periodogram analysis. When crabs were placed under constant darkness (DD) or constant illumination (LL), free-running circadian rhythms were observed in the activity recordings. The locomotor activity of strongly rhythmic crabs in LL has an average period length of 24.4 h. Crabs held in DD express motor rhythms with periods of approximately 24.0 h. In LL the most common wave form for activity is unimodal, while under DD it is bimodal. Recordings under natural illumination (NL) revealed that both period length and the time of maximum activity (phasing) varied through the year. During winter months, the crabs are primarily diurnal with peaks in activity occurring between 0900 and 2100 h and possess a circadian rhythm with a 23.9 h period. During summer, crabs were nocturnal with maximal activity between 1300 and 0600 and a circadian period closer to 24.0 h. In these experiments, the rhythmic locomotor activities of U. subcylindrica are best described as 'circadian'. This is unusual for a genus known for its expression of circatidal and circalunidian rhythms.

Original Publication Date

6-25-1998

DOI of published version

10.1076/brhm.29.2.179.1448

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