1. Nearly all Potamopyrgus antipodarum, like this one, are female, lacking a penis behind the head. From stream just above tidal limit. September 2012. Llanfihangel y Traethau, Merionydd, Wales.
2. Nearly all Potamopyrgus antipodarum, like this one, are female, lacking a penis behind the head. From stream just above tidal limit. September 2012. Llanfihangel y Traethau, Merionydd, Wales.

Nearly all Potamopyrgus antipodarum, like this one, are female, lacking a penis behind the head. From stream just above tidal limit. September 2012. Llanfihangel y Traethau, Merionydd, Wales.