BURYING AND MOLTING OF PINK SHRIMP,PENAEUS DUORARUM(CRUSTACEA: PENAEIDAE), UNDER SELECTED PHOTOPERIODS OF WHITE LIGHT AND UV-LIGHT

Abstract

1. Shrimp activity was inversely related to the amount of light exposure. 2. Shrimp responded to a 12-hour photophase of white light and UV-light in a similar manner. The light-dark transition is apparently the Zeitgeber, and the burying rhythm can be readily changed with a change in the light-dark transition. 3. A circadian burying rhythm was found for shrimp kept in continuous white light; no rhythm was found for shrimp kept in continuous darkness or UV-light. 4. Evidence was obtained to support a lunar influence, with shrimp of Group V being more active during the new and first-quarter moon. 5. Burying activity between the first and last four weeks of the experiment was similar. 6. No significant differences among the groups' overall growth rates or molt rates were found for the four two-week periods. 7. The photoperiod influenced the time rather than the rate of molting. Groups II and III molted highly significantly more during the scotophase. Group I with no light molted highly significantly more during the time interval corresponding with the scotophase of Groups II and III, indicating presence of an endogenous molt rhythm. 8. Molt rate did not decline in the latter half of the experiment as did the growth rate. 9. Deaths approached 50% for all groups at the end of eight weeks.