Cyclicity
Circadian clocks have evolved in all forms of life (Rosbash 2009). In several species of crustaceans, rhythmicity is apparent in behaviour, development, physiological and sensory processes (Palmer 1971; Strauss and Dircksen 2010). Although a master clock has not been identified in crustaceans, clock, period and cryptochrome-gene products are present in the central nervous system and other organs (Strauss and Dircksen 2010).
To test whether locomotor activity in O. cordimanus is governed by day/night cycles, an experiment was performed in which 14 individuals were put into a tank and subjected to normal day/night cycles (Tank A) while 14 individual in another tank (Tank B) were subjected to reversed light cycles (12 hours out of phase) over a 24 hour period. Results showed that animals subjected to an out of phase day/night cycle were not significantly more, nor less, active than animals subjected to normal day/night cycles (Fig 2. unpublished data). This finding correlates with previous studies that demonstrated the the the tendency for O. cordimanus to maintain autonomous locomotor rhythms (Palmer 1971).
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