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Free keywords:
egg development; incubation periods; temperature dependence; interspecific variation; congeneric species; Protonemura
Abstract:
Embryonal development of the five congeners Protonemura auberti Illies, 1954, P. hrabei Rauser, 1956, P. meyeri (Pictet, 1841), P. nitida (Stephens, 1835), and P. praecox (Morton, 1894) was studied under various laboratory temperatures and different photoperiods. Mean number of eggs in field collected batches was between 470 (P. praecox ) and 1211 (P. auberti ). Spring species had smaller egg batches than autumn species. Mean hatching success in the laboratory was 50-100% at 2-18°C. In most species hatching success decreased slightly with increasing temperature. None of the eggs incubated at 24°C developed. Hatching pattern followed an asymmetric frequency distribution. In general, the hatching periods were the shorter the higher the incubation temperature.
