Entomologica Romanica Vol. 19 / 2014


Thus they range from simple shallow dishes, plastic containers, Petri dishes, Erlenmeyer flasks, beakers or trays (Kaushik and Hynes 1968, Knispel et al. 2006, Kobayashi and Ando 1990, Nagell 1977a, 1977b, O’Donnell 2009, Taylor and McPherson 2003) through more ingenious devices, like aerated water tanks equipped with polyethylene bags, glass beakers, plastic tubes or rearing cages, miniature stream chambers (Elliott 1978, 2009, Finlay 2001, Fremling 1967, Keiper and Foote 1996, Mackay 1981, Tsuruishi et al. 2006), to complicated systems such as model streams, flow-through or recirculating systems, stream microcosms (Cobo 2005, DeKozlowski and Bunting 1981, Funk et al. 2008, Gallepp 1974, Lauff and Cummins 1964, Lieske and Zwick 2007, 2008, Olsen and Watzin 2009, Pennuto 2003, Schloss 2002, Sudia 1951). The aim of the present study is to introduce and adapt an old water filtration and aeration technique used by aquarists (Horn and Zsilinszky 2005, Józsa 1958) into the macrozoobenthos-related research and to test the efficiency of this method on lotic mayflies. They were chosen for two reasons: 1. constitute a diverse and abundant group of the macroinvertebrate community of running waters; 2. young instar nymphs are difficult to rear to imagines under laboratory conditions. Material and methods Chamber design The rearing chambers (Fig. 1) were constructed from 5 1 plastic soft drink recipients with plain bottom, cut at the level where the sides start to converge to the lid. A plastic funnel with a small hole on the conical surface and 4-5 triangular cuttings located at the edge of the mouth-like part was placed into each rearing chamber with the wider side down and fixed with washed, coarse sand. Aquarium tubing with 0.4 mm interior diameter was introduced into the funnel throughout the hole located at the conical surface of it. The other side of the tubing was connected to an aquarium air pump. Stream water was filled into the rearing chambers till it totally covered the funnel. This setup ensures water circulation in the system during the air pump is switched on. Thus bubbles from the air-line pull water through the funnel up and this current drags water from the rearing chamber down through the sand which filters it. Water enters the funnel via the triangular cuttings. Each chamber was equipped with a dried Rubus idaeus twig and 1 or 2 small and thin pieces of Styrofoam, which served as a platform for the specimens during emergence. In order to prevent the escape of the freshly emerged subimagines, chambers were covered with a silky white material. Testing the rearing chambers The efficiency of the rearing facility was tested in 2008 and 2009. Last instar mayfly nymphs belonging to several taxa were sampled every second week from early spring till autumn and reared in the adapted devices. Additionally, the suitability of the “reversed funnel” method for long-term rearing of especially sensible lotic mayflies was assessed in 2009 with immature Ecdyonurus nymphs. Specimens were collected from 3 creeks of the Eastern Carpathians (Aita, upstream Aita Medie: 45°58’28.49”N 25°37’36.26”E, 530m a.s.L; Cormoș, upstream Filia: 46°10’33.48”N 25°37’39.68”E, 554m a.s.l. and Ozunca, upstream Bățanii Mari: 46° 5’37.73”N 25°43’20.85”E, 533m a.s.l) and a river (Râul Negru, Chichiș: 45°45’45.80”N 25°47’34.08”E), along with visible biofilm-covered stones as food supply and water. Samples were transported in refrigerator bags. The rearing experiment was set up in an empty room. During hot summer days the rearing chambers were moved to the stairs of the cellar. This setup continuously ensured less than 16 °C rearing temperature regime, temperature being measured daily, late in the afternoons. Chambers received natural light. Fourteen rearing chambers were attached to a single Boyu S-2000 air pump with the aid of aquarium airline T-joints equipped with air control taps. A total of 350 undamaged last instar individuals and 45 intact immature Ecdyonurus nymphs were macroscopically identified and accommodated to the habitat temperature. A maximum of 5 last instar mayfly nymph of different taxonomic units or the Fig. 1. Rearing chambers. 6