Relict Mayfly
Ameletus inopinatus Eaton, 1887
Order Mayflies (Ephemeroptera)
Family Rallidentid mayflies (Rallidentidae)
Conservation status: in Bulgaria: Critically endangered CR [B2a; C2a].
General distribution. Norway, Sweden, Finland, Northern and Central Russia, Ireland, Scotland, England, France, Germany, Switzerland, Poland, the Czech Republic, Slovakia, Romania and Bulgaria. A glacial relict with a boreomontane distribution. In Central and Southern Europe, it inhabits only mountains.
Distribution and abundance in Bulgaria. Known from Rila and Pirin mountains. It was recorded in July and August in Borovets (1939), Breznishki Lakes (1968) and Argirovo Lake (1981) with few specimens [1]. From a stream near Ropotamo River (Strandzha Mts.), nymphs are reported (1940) [2]. There are no current data of finding the species.
Habitats. Adults occur near clean and cold water bodies in the mountains with lower temperatures of the water during a long period of the year [1]. The nymphs inhabit small mountainous streams and lakes with stony bottoms without organic load. An indicator of xenosaprobic waters [3, 4, 5].
Biology. One generation yearly with overwintering in nymphal stage. Before metamorphosis, the last instar nymphs usually crawl out during the day onto the stones and vegetation near the water surface. The males fly over the water in the afternoon hours. The period of emergence of the adults is long, from May to August. The eggs hatch from September to February [3]. The nymphs feed by filtrating or collecting organic detritus from the sediments [4]. They stick to the stones and the underwater vegetation or swim fast.
Negative factors. Climatic changes leading to an increase of the water temperature. Increase of the risk of organic pollution of the water bodies. Destruction of the river beds by hydrotechnical building and degradation of habitats. Elimination of the shore vegetation, on which the adult emerges, reduces the possibility for successful reproduction.
Conservation measures taken. The localities in Pirin Mts. are included in the Pirin National Park.
Conservation measures needed. Protection of the habitats of the species from organic pollution. Preservation of the vegetation along the river and lake banks with a view to ensuring places for emerging of the adult.
References. 1. Russev, Vidinova, 1994; 2. Russev, 1960; 3. Gledhill, 1959; 4. Elliot et al., 1988; 5. Sladecek, 1973.
Author: Yanka Vidinova
