Teslenko V.A.
В журнале Entomological Review
Год: 2015 Том: 94 Номер: 2 Страницы: 334-345
The life cycles and production of populations of the predatory stoneflies Skwala compacta, Stavsolus manchuricus, and Kamimuria exilis were studied in the Kedrovaya salmon stream (the Kedrovaya Pad Reserve, the south of Primorskii Territory). Skwala compacta and S. manchuricus are univoltine with direct embryonic development and slow nymphal growth during 311 and 294 days, respectively, including winter growth at low water temperatures. The life history of S. compacta was characterized by synchronous emergence and population recruitment, an uninterrupted increase in the nymphal body weight from May to September, rapid growth in October–November, and a sustained weight gain during the winter months until emergence in April–May. The life history of S. manchuricus was characterized by an extended period of emergence in May–July and recruitment from July to September, as well as by a wide range of size-age parameters, presumably related to the specificity of the reproductive system in adults and an external growth delay at early nymphal instars caused by high water temperatures in late summer and early autumn. Nymphs of S. manchuricus grew actively at 0.2°C during winter, which gave this species a competitive advantage over S. compacta and K. exilis whose growth was slow or absent in winter months. The semivoltine life cycle of K. exilis included a 9-month embryonic diapause and lasted about 4 years with periods of winter nymphal quiescence from December to February. Extended emergence and oviposition were recorded from the end of July to September. The population of K. exilis had a complex structure comprising 3 cohorts whose size ranges overlapped due to the extended flight period and recruitment of the new-generation nymphs in the spring of the next year. Nymphs of K. exilis grew fast during the warm period, when S. compacta and S. manchuricus were only appearing in the stream or underwent growth delay at relatively high water temperatures. The annual production of three species varied from 0.045 to 0.383 g/m2 dry mass, P/Bmean was 1.1–6.9; P/Bcoh = 6.2–9.1, and P/Byear = 4.1–9.4. Low values of P/Bmean and P/Byear were found in the semivoltine K. exilis, and high ones, in the univoltine S. compacta. The latter had a higher cohort-specific growth rate while its specific production was 0.026 day−1. The population of K. exilis had low values of the cohort-specific growth rate (0.013 day−1) and specific production (0.004 day−1). The highest production was observed in the population of S. manchuricus where nymphs grew at a specific rate of 0.023 day−1 while their mean density reached 59 ind./m2.
