Colour changes associated with the semilunar cycle in the fiddler crab, Uca capricornis

The purpose of the experiment was to examine the colour changes associated with the semilunar cycle in the fiddler crab, Uca capricornis. Experiments were conducted in the East Point Reserve, Darwin from Nov - Jan (04/05 & 05/06).

1m diameter cages were constructed and stocked with 4 crabs of the species Uca capricornis. During one semilunar cycle, from one neap tide to the next, digital photographs were taken of 22 crabs (10 males, 12 females) active in the cages at approximately low tide. Photos were examined to observe any colour changes on a day to day basis.

The results show that Uca capricornis do not rythmically change their colour or pattern between moults. Although some individuals did exhibit a slight variation, by brightening or darkening existing colours, there was no apparent trend in the number of crabs either brightening or darkening with respect to the time in the cycle.

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Published (Metadata Record) 02/03/2026
Last updated 03/03/2026
Organisation Australian Federal Government
License cc-by-2.5
Update Frequency Unknown