PHOTOPERIODIC AND TEMPERATURE REGULATION OF DIAPAUSE IN<i>LABIDOCERA AESTIVA</i>(COPEPODA: CALANOIDA)

Abstract

The calanoid copepod Labidocera aestiva was reared in the laboratory to ascertain the effects of photoperiod and temperature on subitaneous and diapause egg production. The results indicate that photoperiod is the primary stimulus regulating the type(s) of eggs produced by a female, but that the temperature regimen can modify this effect. Under short daylength photoperiods (e.g., 8L:l6D) subitaneous egg production is increased by increasing the temperature regimen from 15.0°C or 19.0°C to 25.0°C. However, under long daylength regimens (e.g., 18L:6D) females appear to be unresponsive to temperature changes within the range of 15.0°C to 25.0°C. It is suggested that this response to photoperiod and temperature more accurately couples the life cycle of L. aestiva with seasonal environmental fluctuations.