The invader mudsnailPotamopyrgus antipodarumin the Tiber River basin (Central Italy)

Abstract

Although the New Zealand mudsnail Potamopyrgus antipodarum has been observed in Italy since 1961, no investigations have gone beyond recording its presence. In this study, populations from three Italian watercourses with different environmental features were comparatively analysed with a view to shedding light on the relationships between habitat type and reproduction. At the study sites, populations were exclusively composed of females. Ultra-structural details showed that egg growth takes place through the accumulation of stored materials, which are essentially constituted by translucent vesicles (lipids) and by electron-dense granules with a darker rim (proteins), the latter deriving from the confluence of smaller granules of the same type. The egg surface displays numerous microvilli, which interdigitate with those emerging from both adjacent eggs and bordering cells. Our comparative analysis shows that the populations differ slightly in fecundity, whereas the number of brooded embryos/female markedly decreases, in parallel with the mean density, in running-water habitats lacking aquatic vegetation. Statistical analysis confirms that P. antipodarum positively selects biological substrates, such as beds of Vaucheria sp. and even, on occasion, dead leaves and wood floating on the water surface. The results suggest that biological substrates constitute one of the key factors favouring the massive spread of P. antipodarum in watercourses.

Long-term population fluctuations of the exotic New Zealand mudsnail Potamopyrgus antipodarum and its introduced aporocotylid trematode in northwestern France

“…Females were reproductively mature at shell height from 2.5 to 3.0 mm, with up to 74 embryos in the largest females. These results are also consistent with observations for other introduced populations, which mature at size between 2.5 and 3.5 mm, and have maximum brood size ranging from 60 to 89 embryos (e.g., Strzelec & Serafinski, 1996;Gaino et al, 2008;McKenzie et al, 2013).…”

“…The lack of sexual reproduction is consistent with what is seen for introduced P. antipodarum from Europe, Australia, and America, where males are rare or completely absent (e.g., Wallace, 1978Wallace, , 1985Hughes, 1996;Schreiber et al, 1998;Gaino et al, 2008;McKenzie et al, 2013;Collado, 2014). increased from March to May in each year, and also increased with snail size, as previously demonstrated (e.g., Winterbourn, 1970;Gérard & Poullain, 2005;Gaino et al, 2008;McKenzie et al, 2013).…”

“…According to Neiman (2006), a nearly twofold increase in the embryo number per female was observed in low versus high density populations maintained in the laboratory with similar food availability, suggesting that reproductive output may be influenced by intraspecific competition. In contrast, the reproductive output of P. antipodarum was much higher in high versus low density conditions in other experiments with no food limitation (Neiman et al, 2013), as also observed in the Italian Topino River (Gaino et al, 2008). Thus, further investigations are needed for a more comprehensive view of the complex connections between environmental quality, resource availability, density, and fecundity of parthenogenetic females, and how they may influence the e.…”

Dynamics of natural populations of the dertitivorous mudsnail Potamopyrgus antipodarum (Gray) (Hydrobiidae) in two interconnected Lakes differing in trophic state

“…The populations investigated in this study only consisted of females and clones unlikely differed in genotype, especially since the lakes are located close to each other (<1 km) and they are interconnected. Moreover, passive transport of P. antipodarum by adherence to fish and waterfowl has been observed (Gaino et al 2008 and references therein; Miura et al 2011 ) and in both lakes, gulls ( Larus ridibundus ) are frequent visitors. Major differences between the two lakes are trophic state, food quantity and quality, which may thus have contributed considerably to the observed variation in population dynamics.…”

“…Morley 2008 ). Throughout Europe, however, males and sexual populations seem to be very rare and genotypic diversity is extremely low (Wallace 1985 ; Hauser et al 1992 ; Jokela et al 2003 ; Gaino et al 2008 ). The populations investigated in this study only consisted of females and clones unlikely differed in genotype, especially since the lakes are located close to each other (<1 km) and they are interconnected.…”