Effects of temperature on development, molting, and population growth of Yuukianura szeptyckii Deharveng & Weiner, 1984 (Collembola: Neanuridae)

Neanuridae is one of the most diversified families of Collembola, but its biology and ecology are poorly understood. This is, to our knowledge, the first report on the biology of the neanurid species Yuukianura szeptyckii Deharveng & Weiner. Y. szeptyckii individuals were collected near a stream in Korea, and maintained on OECD artificial soil. This species showed a better reproductive performance on an artificial soil-based substrate than on charcoal-based substrate, and thus the soil-based substrate was used for investigating its biology. The sex ratio of Y. szeptyckii was found to be biased toward females (88.0%), and its mode of reproduction was sexual. The development, survival, longevity, reproduction, molting, and life table parameters of Y. szeptyckii were evaluated at 15, 20, 25, and 30 °C. Individual growth was estimated by measuring head capsule widths. Mean developmental period from egg to adult decreased with increasing temperature from 73.7 d at 15 °C to 25.6 d at 30 °C. In the adult stage, ovipositional periods decreased with temperature from 273 d at 15 °C to 45.5 d at 30 °C, but senile periods increased at temperatures above 20 °C. The developmental zero temperature was estimated to be 7.88 °C. Median survival time (ST50s) and mean longevity decreased with temperature from 228 d at 15 °C to 98.0 d at 30 °C and from 401 d at 15 °C to 177 d at 30 °C, respectively. The maximum and minimum total number of eggs produced per individual were observed at 20 °C (73.8 eggs) and 30 °C (6.9 eggs), respectively. The head capsule width at first oviposition was significantly smaller at 25 and 30 °C (0.30-0.31 mm) than that at 15 and 20 °C (0.45-0.46 mm), while the head capsule width at last oviposition was smaller at 30 °C (0.55 mm) than that at 15 to 25 °C (0.63-0.64 mm). The molting rate (per individual per week) increased with temperature from 0.50 at 15 °C to 1.43 at 30 °C, but the total number of molts during the life span varied only slightly, ranging from 29.1 at 25 °C to 33.2 at 30 °C. The population reared at 20 °C had the highest intrinsic rate of increase (0.060) and net reproductive rate (84.5), indicating that the optimal temperature for Y. szeptyckii population growth is 20 °C. This study demonstrated that temperature can profoundly affect the development, molting, and population growth of Y. szeptyckii.