Entomologica Romanica Vol. 19 / 2014

2014-2015

19 species (Table 1). 78% of the last instar mayfly nymphs emerged and due to the low subimaginal mortality, the rearing success also attained high levels (68.57%). Species mortality in the subimaginal stage was considerably lower than the nymphal mortality. The rearing success of several species reached the maximum level (Fig. 2). Rearing of young instar Ecdyonurus nymphs Young instar Ecdyonurus nymphs survived up to 130 days in the designed chambers and including the last instar nymphal moult, cast their skins 7 times the most. The high mortality in the aquatic and first alar stage implied a modest rearing success (Fig. 2). Contrary to the subimaginal mortality, the statistical analysis revealed significant differences between the medians of the mortality in aquatic stage (p=0.02498), emergence success (p=0.00564) and rearing success (p=0.00054) of the early and last instar Ecdyonurus datasets. and not differentiated rearing temperature regime like in the mentioned study. Additionally, the low number of sampling sites with relatively comparable mayfly community may also have contributed to the better results. Nevertheless, discrepancies in the biology and ecology of the various taxa led to the variation of the emergence success, subimaginal mortality and rearing success of the mayfly species implied in our experiment. Several species were characterized by maximal rearing success, but, with the exception of Serratella ignita, an eurytopic species colonizing the rhithron of almost all types of running water (Bauernfeind and Soldan 2012), the results are not reliable due to the low number of specimens introduced into the experiment. This is the case for Caenis macrura Discussion Among the advantages of the “reversed-funnel” technique, we highlight the low financial input, the easiness of construction of the entire device, the accessibility both by scientists and enthusiast amateurs without being required well-equipped laboratories, the modest maintenance actions required for optimal function, space efficiency. For all the vast literature of novel rearing facility descriptions (Mackay 1981, Schneider 1967, Sudia 1951), the number of studies assessing the proposed method is considerably lower (Finlay 2001, Keiper and Foote 1996). According to our evaluation, the adapted device yields promising results especially for rearing last instar nymphs. In their case both the rearing success and emergence success fluctuated around 70%, moreover the rearing success highly exceeded the one experienced by Finlay (2001). Our better results might be reflected by the use of freshly collected specimens instead of a cooled stock material and Epeorus assimilis as well, which died in first alar and last nymphal stage. Epeorus assimilis along with Oligoneuriella rhenana are rheophile mayflies colonizing fast flowing, well oxygenated rivers, especially the riffle sections of epi- to metarhithron, respectively hyporhithron and epipotamon (Bauernfeind and Soldan 2012, Fenoglio et al. 2005, Jansen et al. 2000) and despite the low number of specimens introduced into the experiment, we might speculate that the rearing conditions were suboptimal for their requirements. Even so, the rearing success of Oligoneuriella rhenana outreached all our expectations. Despite of the massive mortality during the nearly one hour transportation time, 50% of the reared specimens achieved the final developmental stage. For Habroleptoides confusa and several Rearing success (%) Subimaginal mortality (%) Nymphal mortality (%) 1 Reared nymphs (nr.) Fig. 2. Rearing success, nymphal and subimaginal mortality of the reared young and last instar Ephemeroptera nymphs. 8

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