Fecundity and development of the benthopelagic copepod Pseudocyclops umbraticus: temperature effects

The shallow-living, benthopelagic copepod species Pseudocyclops umbraticus was collected seasonally during night-time in the brackish waters of Lake Faro (north-eastern Sicily). It showed marked seasonal fluctuations in population abundance, with maximum numbers in summer. In the laboratory, the mean daily egg production rates EPR of P. umbraticus were positively correlated with temperature, with values ranging from 2.3 ±6.3 eggs per female per day at 14 °C, to 6.1 ±10.2 eggs per female per day at 24 °C. In terms of the total egg production for the entire female lifespan, maximum values occurred at 14 °C and minimum at 24 °C. At 12 °C and 32 °C, the females were able to survive, but they stopped egg production. Temperature also dramatically affected the female lifespan, which was shorter at higher temperatures. The development time for the eggs decreased with increasing temperature, as did the development time from egg to adulthood. The recruitment rate was low at lower temperatures. The egg-laying behaviour of P. umbraticus is here described for the first time. It might ensure higher survival rates of the egg stages compared to free-spawning and egg-carrying calanoid species. The EPR in P. umbraticus is relatively low compared to other pelagic copepods, but within the ranges reported for egg-carrying species. The greater fecundity at higher temperatures compared to other subtemperate species indicates that P. umbraticus is well adapted to the higher temperatures of coastal brackish basins, where it contributes to enhance the biodiversity of the plankton community at night, when it migrates from the substratum to the water column.