Entomologica Romanica Vol. 19 / 2014

2014-2015

Ecdyonurus species the adapted rearing facility turned to be an optimanal device. Contrary to last instar mayfly nymphs, the rearing of young instars of Ecdyonurus species showed modest results. Their mortality in the aquatic stage exceeded more than 2 times the mortality of last instar Ecdyonurus nymphs’. Moreover 61.54% of the total deaths in the aquatic stage were recorded till the completion of the first 2 moults. Giberson and Rosenberg (1994) also experienced higher mortality for smaller nymphs of Hexagenia limbata and H. rigida (Ephemeridae), whereas Rosillon (1988) and Gupta et al. (1993) reared with remarkable success less sensitive young instar lotic and lenitic mayflies (Ephemerella ignita, Cloeon sp.). We speculate that the low maintenance activities, precisely the scarce food supply and probably the lack of at least one total water replacement had a major influence on the success of the young instar rearing experiment. Weekly water exchange was recommended by Keiper and Foote (1996), but a 50% water replacement was also found to be adequate for waste elimination and nutrient addition for promoting algal growth. Visual examination of the food source was also suggested, which often implied food addition. As in similar systems used in aquaculture, wastes and accumulated organic matter were reported to be trapped in the sediment during water recirculation (Horn and Zsilinszky 2005), where a microbial community was established (Jozsa 1958), we presumed that sediment filtration and biodegradation occurring in the substrate can substitute water replacement, in consequence waste removal and can ensure the necessary amount of nutrients for periphyton growth. Previous studies also sustain indirectly the necessity of food supply by confirming that Ecdyonurus species, like other members of the feeding guild reduce periphyton biomass and change community composition by sweeping with their brush-like mouthparts the more accessible algal physiognomies (Wellnitz and Ward 1998, 2000). The mortality of mayflies in the field highly exceeds our findings. According to a previous study more than 90% of Baetis rhodani died during aquatic life stages, while the prereproductive female adult mortality of B. vernus attained even 98.8% (Werneke and Zwick 1992). Rosillon (1988) found similar results for the mortality of the group-reared Ephemerella ignita and mortality registered in the field. Contrary to natural habitats, where a large number of factors influence the survival of mayflies both in aquatic and aerial stages and limit population size, the controlled conditions, experimental design, especially the developmental stage of the specimens employed in the experiment (exclusion of eggs and first instars after hatching from eggs), are responsible to our better results. In conclusion, the established system, despite of the simplicity and easiness of construction, is adequate for obtaining adults for species identification and description. We expect that it will also provide a wider access to a vast range of experiments upon mayflies and other lotic taxonomic units. Acknowledgements The first author is grateful for the assistance in the field work provided by her parents and brother as well as for the insurance of the space required for the emplacement of the rearing experiment. Gratitude is also expressed to dr. Miklós Bálint for useful comments on an early version of the manuscript. The comments of two anonymous referees highly improoved the manuscript. References Aurich M. (1992) The life-cycle of Apetenie fimbriata Pictet in the Breitenbach. Hydrobiologie 239(2): 65-78. Ball S. L. (2001) Tychoparthenogenesis and mixed mating in natural populations of the mayfly Stenonema femoratum. Heredity 87(3): 373-380. Bauernfeind E. and Humpesch U.H. (2001) Die Eintagsfliegen Zentraleuropas - Bestimmung und Ökologie. Verlag des Naturhistorischen Museums Wien, Wien, 240 pp. Bauernfeind E. and Soldán T. (2012) The Mayflies of Europe: (Ephemer opt er a). Apollo Books, Ollerup, 781 pp. Bohle H.W. (1972) Die Temperaturabhängigkeit der Embryogenese und der embryonalen Diapause von Ephemerella ignita (Poda) (Insecta, Ephemeroptera). Oecologia 10(3): 253-268. Bonada N., Zamora-Munoz C., Rieradevall M. and Prat N. (2004) Ecological profiles of caddisfly larvae in Mediterranean streams: implications for bioassessment methods. Environmental Pollution 132(3): 509-21. Cobo F. (2005) Maintenance of schredders in the laboratory. In Gra^a M.A.S., Bärlocher F. and Gessner M.O. (Eds.): Methods to Study Litter Decomposition. Springer Netherlands, 291-295. DeKozlowski S.J. and Bunting D.L.I. (1981) A laboratory study on the thermal tolerance of four Southeastern stream insect species (Trichoptera, Ephemeroptera). Hydrobiologie 79(2): 141-145. Echols B.S., Currie R.J. and Cherry D.S. (2010) Preliminary results of laboratory toxicity tests with the mayfly, Isonychie bicolor (Ephemeroptera: Isonychiidae) for development as a standard test organism for evaluating streams in the Appalachian coalfields of Virginia and West Virginia. Environmentei monitoring end essessment 169(1-4): 487-500. Elliott J.M. (1978) Effect of temperature on the hatching time of eggs of Ephemerelle ignite (Poda) (Ephemeroptera: Ephemerellidae). Freshweter Biology 8(1): 51-58. Elliott J.M. (2009) Inter- and intra-specific differences in the number of larval instars in British populations of 24 species of stoneflies (Plecoptera). Freshweter Biology 54(6): 1271-1284. Enders G. and Wagner R. (1996) Mortality of Apetenie fimbriete (Insecta: Trichoptera) during embryonic, larval and adult life stages. Freshweter Biology 36(1): 93-104. 9

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