Favnistični zapiski / Faunistical notes
MICRONECTA POWERI (DOUGLAS & SCOTT) IN SLOVENIA (HETEROPTERA: CORIXIDAE)
Andrej Gogala
Prirodoslovni muzej Slovenije, Prešernova 20, p.p. 290, 1001 Ljubljana
Abstract - A lesser boatman species Micronecta poweri (Douglas & Scott, 1869) was discovered in the Višnjica stream near Krka in the pre-Dinaric region of Slovenia. This is the first reliable record of the species in Slovenia.
Key words: Heteroptera, Corixidae, Micronecta, fauna, Slovenia
Izvleček - MICRONECTA POWERI (DOUGLAS & SCOTT) V SLOVENIJI (HETEROPTERA: CORIXIDAE)
Micronecta poweri (Douglas & Scott, 1869), vrsta pritlikave veslavke, je bila najdena v potoku Višnjica pri Krki v preddinarskem območju Slovenije. To je prva zanesljiva najdba te vrste v Sloveniji.
Ključne besede: Heteroptera, Corixidae, Micronecta, favna, Slovenija
Species of the genus Micronecta are the smallest water bugs. Usually they are included in the family Corixidae (water boatmen), but Nieser (2002) put them in their own family Micronectidae due to several morphological differences. Their behaviour is also different from other corixids in many respects. They are found in stagnant or slowly flowing waters, usually along shores with little (or without) vegetation. They live in small to very large swarms. Their food is not known, but they can be kept alive just with fresh bottom material from their habitats (Jansson, 1986). They breathe the oxygen dissolved in water and do not come for the air to the surface. So they cannot live in oxygen-poor waters and are hard-hit by pollution. They overwinter as larvae and reach the adult stage in early summer. In warmer areas, they can have two to three generations in a season. The males stridulate very loudly for their small size during courtship.
The Micronecta species in Slovenia are not well known. Micronecta scholtzi (Fieber, 1860) is a common species in Prekmurje (sub-Pannonian region). Micronecta griseola Horvath, 1899 was recorded from the Cerkniščica river (Dinaric region). Jansson (1995) listed Slovenia among countries where Micronecta poweri (Douglas & Scott, 1869) is present. But we do not know the source of this record and the exact locality. On the map of distribution published by Jansson (1986) no locality in Slovenia is marked, so it is possible that some records from Slovakia were mistakenly attributed to Slovenia in the Catalogue (Gogala, 2003). However, the species was found in Slovenia in 2008, and the find is presented here.
Micronecta poweri (Douglas & Scott, 1869) Record from Slovenia:
Krka, Trebnja Gorica, r. Visnjica, 14°47'E 45°53'N, UTM: VL88, 23. 5. 2008, A. Gogala leg.
I noticed a large swarm of corixid larvae at the shore of the Visnjica stream near its confluence with the Krka river already on May 8, 2008. Many of the larvae were half-burried into the loose, muddy bottom in shallow water. As I expected to find adult Micronecta specimens later, I visited the same spot on May 23, and successfully collected many specimens. I photographed some specimens in natural environment as well, as I did also with the larvae before. The colour pattern of the adults was typical for Micronecta poweri and the identification was proved by the examination of the genitalia.
The Visnjica stream is a slowly flowing, meandering brook in an agricultural landscape. Not far from the collecting spot it fuses with the Krka river, which has a source nearby. This is a karstic river with karstic springs. The banks of both streams near the village Krka are similar and are suitable habitats for Micronecta species. Any pollution or regulation of the stream flow, however, would threaten the exis-tance of the Micronecta population.
Fig. 1: The Visnjica stream near the village Trebnja Gorica, at the place where the Micronecta specimens were found.
Fig. 2: Larvae of Micronecta poweri, photographed in the natural environment of the Visnjica stream, May 8, 2008.
Fig. 3: Adult specimen of Micronecta poweri in its environment, May 23, 2008.
References
Gogala, A., 2003: Heteroptera of Slovenia, I: Dipsocoromorpha, Nepomorpha, Gerromorpha and Leptopodomorpha. Annales, Annals for Istrian and Mediterranean Studies, Series historia naturalis, 13 (2): 229-240.
Jansson, A., 1986: The Corixidae (Heteroptera) of Europe and some adjacent regions. Acta Entomol. Fennica, 47: 1-94.
Jansson, A., 1995: Family Corixidae Leach, 1815 - water boatmen. In: Aukema, B., Ch. Rieger: Catalogue of the Heteroptera of the Palaearctic Region, Volume 1. The Netherlands Entomological Society, Amsterdam.
Nieser, N., 2002: Guide to aquatic Heteroptera of Singapore and Peninsular Malaysia. IV. Corixoidea. The Raffles Bulletin of Zoology, 50 (1): 263-274.
Received / Prejeto: 20. 3. 2009