sinensis found in other brackish

waters. For example, Sunitinib order in the Guadalquivir Estuary (Spain), where the salinity is 5 PSU at the time of reproductive migration, only immature females in stages G2 and G3 were caught ( Garcia-de-Lomas et al. 2010). The collection time of females in gonad maturity stages G4 and G5, i.e. in autumn and winter, is also characteristic of the reproduction cycle of E. sinensis. According to Peters (1938) and Anger (1991), copulation in European populations of this species takes place in autumn. Afterwards ovigerous females migrate to the sea where they bury themselves in the bottom to overwinter. The carapace width of the females was relatively large and similar to that recorded in other waters, e.g. in the River Elbe, the Volga and the Tagus Estuary or even in the waters of North America (Cabral & Costa 1999, Herborg et al. 2003, Rudnick et al. 2003,

2005, Ruiz et al. 2006, Shakirova et al. 2007). Larger females carried a significantly greater mass of eggs on their pleopods than smaller ones. Such a relationship was reported by Czerniejewski & De Giosa (2013). According to these authors the fecundity of E. sinensis female ranges from 141 100 to 686 200 eggs and is much larger than for other grapsid crabs. However, other authors state that females can produce up to one million eggs ( Panning 1939, Cohen & Weinstein 2001, Veilleux & Lafontaine 2007). Since the Chinese mitten crab breeds only once in its lifetime, high female fecundity is one of the keys PR-171 molecular weight to successful invasion. The most significant limiting factor where egg hatching is concerned is low salinity (Panning

1939, Otto & Brandis 2011); however, as shown by Anger (1991), tolerance to this factor increases with temperature. Thus, gravid females usually wait until summer or they move to shallow waters, where temperatures become optimal for hatching, Vasopressin Receptor i.e. 15–25°C (Ingle 1986). On the other hand the optimum salinity for hatching and complete larval development is 20 PSU (Panning 1939, Anger 1991, Montú et al. 1996, Dittel & Epifanio 2009). This is much more than in the southern Baltic Sea, where the salinity is ca 7 PSU (Leppäranta & Myrberg 2009). Taking into account the fact that summer temperatures in the Baltic are in the 18–22°C range, it might be assumed that these conditions do not fit the requirements for the proper larval development of E. sinensis. It was previously speculated that the Baltic Sea is only a migration area for Chinese mitten crabs, which reproduce in the Elbe Estuary/North Sea or in the Kattegat/Skagerrak ( Normant et al. 2000, Normant & Chrobak 2002, Ojaveer et al. 2007). This assumption was supported both by the lack of larvae and juveniles, as well as by genetic studies that showed a similarity between specimens from the southern Baltic Sea and from German rivers ( Żmudziński 1961, Herborg et al. 2007, Czerniejewski et al. 2012). On the other hand it was recently reported by Otto & Brandis (2011) that E.