First record of the invasive North American gastropod Ferrissia fragilis (Tryon, 1863) from the Pripyat River basin, Belarus

The invasive North American gastropod Ferrissia fragilis (Tryon, 1863) has been recorded for the first time in August 2007 at three sites on the Pripyat River basin (the Belarusian part of the inland European “central invasion corridor”). This species occurs in the onshore shallow zone (depth 0.2-0.3 m) with dense aquatic vegetation and temperature from 21.8 to 23.7°C. Maximal abundances of this species have been observed in Mykashevichy port bay. Most likely, this invasive gastropod entered the River Pripyat basin from the Ukrainian territory where it was found early in cooling reservoir of Chernobyl Nuclear Power Station; however invasion pathways through the western (Poland) and ornamental trade are also likely.

In August 2007 invasive North American gastropod Ferrissia fragilis (Tryon, 1863) was found in hand net samples taken during a survey of the Pripyat River basin Annex).A typical biotope where F. fragilis was found is onshore shallow zone (depth 0.2-0.3m) with dense aquatic vegetation (Ceratophyllum spp.and Potamogeton spp.) and temperature from 21.8 to 23.7°C.Oxygen content and pH in the biotopes were between 4.8-6.9 and 7.73-7.77mg l -1 , respectively.Maximal abundance of F. fragilis pointed out in Mikashevichy port bay.In this site F. fragilis inhabit simultaneously with the other alien invasive species -Lithoglyphus naticoides (Pfeiffer, 1828) In Central and Northern Europe F. fragilis inhabit mostly artificial warm-water habitats (reservoirs-coolers, ponds), but in Southern Europe and in the Pripyat River it lives under natural temperature conditions.In Southern Ukraine (Dniestr Delta) F. fragilis survived outside its native range during the winter when the air temperature reached minus 10°C (Son 2007).Therefore F. fragilis can be characterised as the eurythermal species.
The invasive North American gastropods F. fragilis are distributed in Black Sea Region (Son 2007), Central (Manas 1970;Strzelec 2005), Northern (Falkner and Proschwitz 1995), Western and Southern Europe (Lill 1990;Van Der Velde 1991;Cianfanelli et al. 2007) and East Asia (Walther et al. 2006).No data about distribution F. fragilis in the Dnieper reservoirs on Ukrainian territory (Alexandrov et al. 2007) but this species was recorded in the continental waters of Northern Black Sea Region (Dnieper and Dniestr Deltas and Lake Beloje) (Son 2007).The problem of the genus Ferrissia (Walker, 1903) origin in Europe can be approached from several viewpoints however, an idea has been suggested that this gastropod appears a cryptic invader of European ecosystems (Beran and Horsak 2007;Son 2007).
There are two possible ways of invasion F. fragilis to the Prypyat River: from the Dnieper River and Poland territory where it was found in some lakes and ponds in central and northern part (Strzelec 2005).The first way is more probable since this species most numerous in the Mykashevichy port bay and distributed in cooling reservoir of Chernobyl Nuclear Power Station which connected with the Pripyat River by canal, but the western way (Poland) also can be probable such as this species was found in western part of the Pripyat River basin: near Pinsk town.The ornamental introduction F. fragilis to the cooling reservoir of Pinsk Power Station is also possible.

Figure 1 .
Figure 1.Map of Belarus with records of Ferrissia fragilis (see also Annex 1).

Figure 2 .
Figure 2. Overlook view of Ferrissia fragilis (body size from 2 to 4 mm), recorded on 11 August 2007 in the Mykashevichy port bay (Photograph by Laenko).