Fecundity and development of the bentho-pelagic copepod Pseudocyclops umbraticus: effects oftemperature

摘要

The shallow-living, bentho-pelagic copepod species Pseudocyclops umbraticus was collected seasonally during nighttime in the brackish waters of Lake Faro (north-eastern Sicily). It showed marked seasonal fluctuations in population abundance, with maximum numbers occurring in summer. In the laboratory, mean daily egg production rates (EPR) of P. umbraticus were positively correlated with temperature, with values ranging from (mean ± SD) 2.3 ± 6.3 eggs female-1 d"1 at 14°C to 6.1 ± 10.2 eggs female-1 d-1 at 24°C. In terms of total egg production over the entire female lifespan, maximum values occurred at 14°C and minimum at 24°C. At 12 and 32°C, females were able to survive, but they stopped egg production. Temperature also dramatically affected female copepod lifespan, which was shorter at higher temperatures. Development time for the eggs decreased with increasing temperature, as did development time from egg to adulthood. Recruitment rate was low at lower temperatures. The distinctive egg-laying behaviour of P. umbraticus is described here for the first time. The EPR in P. umbraticus is relatively low compared to other pelagic copepods, but within the ranges reported for egg-carrying species. 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 the biodiversity of the plankton community at night as it migrates from the substratum into thewater column.