DISTRIBUTION AND ECOLOGY OF THE REPRESENTATIVES OF SOME EPHEMEROPTERAN FAMILIES IN BULGARIA YANKA VIDINOVA & BORIS RUSSEV Institute of Zoology, Bulgarian Academy of Sciences, Blv. Tzar Osvoboditel 1, Sofia The distribution of 23 species belonging to the families Heptageniidae (Epeorus, Iron, Electrogena, Heptagenia), Ephemerellidae, Polymitarcyidae, Ephemeridae and Potamanthidae is shown on a map. The data are based on samples gathered in 40 years of research on the hydrobiology and saprobiology of Bulgarian rivers. The established ecological data for each species is discussed. INTRODUCTION A survey of the literature and the established species from this order in Bulgaria was made by RUSSEV (1993). To the established 102 species RUSSEV & VIDINOVA (1994a) added other 3. The investigations which have been carried out during the last 40 years on the hydrobiology and saprobiology of the Bulgarian rivers amassed rich material for the establishment of distribution and ecology of Ephemeroptera species in Bulgaria. The first publications in this sphere were on the family Palingeniidae for the species Palingenia longicauda (OLIV.), by RUSSEV (1987) and the families Siphlonuridae, Rallidentidae, Ametropo- didae, Oligoneuriidae and Isonychiidae by RUSSEV & VIDINOVA (1994b). The subject of the present report are the 23 species, established in Bulgaria belonging to the families Heptageniidae (the genera Epeorus, Iron, Heptagenia, Electrogena), Ephemerellidae, Poly- mitarcyidae, Ephemeridae and Potamanthidae. METHODS Hydrochemical analyses are made by methods recommended by the Council of Economic Mutual Aid (1977). The saprobiological state of the rivers is determined with the help of the method of saprobic valences of ZELINKA & MARVAN (1961) and ROTHSCHEIN (1962). RESULTS AND DISCUSSION HEPTAGENIIDAE Epeorus sylvicola (PICTET, 1865) is widely spread mainly in the purest xenosaprobic and oligosaprobic mountainous and foothill rivers and streams in the epi-, meta- and hyporhithral (even up to 1900 m above sea level), but it is more rarely met in the midcurrent of the ß- mesosaprobic plane rivers (epipotamal) above 200 m above sea level (Fig. 1, NN 44,45,47-50,52, 71,74,75,84,87,88,95-100, 103-110, 113-115, 121, 133, 140, 142, 144, 148, 156-161, 171, 176-179, 181, 185, 188, 190, 209, 212, 214, 269, 295-298, 300-302, 305, 317, 318, 320-322, 326, 327, 329, 333, 336, 337, 340, 344, 346-352, 354-356, 363-372, 374-378, 383-385, 390, 394-404, 406, 407, 409, 410, 415-418, 420-422, 425, 435, 444, 445, 449- 451, 453, 455, 456, 458, 460, 461, 464-466, 477, 499-501, 503, 506, 508, 510, 515, 534, 536, 538, 549, 552). It mainly inhabits the rocky and stony bottom in the middle of streams and rivers at current speeds from 0,32 up to 1,95 m/s and water temperatures usually from 0°C up to 17°C, but we have found nymphs several times at tH 2 O from 17,8°C to 23,3°C. Its resistance to changes in hydrochemical surrounding is comparatively high. We have found it with a content of water dissolved oxygen from 7,17 up to 14,0 mg/1 and oxygen saturation from 70,02 up to 150%; oxidability (by K 2 Cr 2 O 7 ) from 0,24 up to 9,15 mg/lO 2 ; BOD 5 (biological demand for oxygen) from 1,0 to 17,0 mg/l O 2 ; CHDO (chemical demand for oxygen) from 1,97 up to 21,89 mg/1 etc. (Table 1). The species has been found at saprobiological index (the integral state of river saprobity with the help of bioindicators from all groups of invertebrates) SR from 51,70 (ß-mesosaprob- ity) up to 82,24 (xenosaprobity). The imago of this species has also been found in Rila and the Rhodopes mountains. SAMAL (1939) raised the question about the group Epeorus-Iron. BRAASCH (1980a, b) stu- died it, using the larva of the Caucasian species in order to differentiate the two genera. © MTL, Fribourg - 1997. P. Landolt & M. Sartori (Eds). Enhemeroptera & Plecoptera: Biology-Ecology-Systematics. 139