Reproductive plasticity in the invasive -Xenostrobus securis (Bivalvia: Mytiloidea) in northwestern Spain.
The invasive mussel Xenostrobus securis was first recorded from Galicia (NW Spain) in 2007, within an area characterized by the commercial culture of Mytilus galloprovincialis. This study investigated the spatial variability in reproduction of X. securis at three adjacent locations over a period of twelve months and the temporal variation at one location over two consecutive years. This is the first such study conducted outside its native range and in which the influences of temperature and salinity on the reproductive cycle were also tested. The invader exhibited rapid gametogenesis, accumulation of mature gametes and an extended spawning period interspersed with gonad recovery, without resting periods. The onset of gametogenesis varied both spatial and temporally, starting 15-days later at the innermost location than at the outermost one. Such spatial variability resulted in an almost continuous breeding season (10 months), in contrast to the 7-8 months observed in the native range. Although the spatial variability in maturation and spawning in the native location is mainly attributable to variations in salinity, the variability in the Ría de Vigo was probably caused by temperature acting as a trigger for maturation and spawning. The almost continuous breeding season exhibited by X. securis potentially results in planktotrophic larvae being present in the water column for almost 10 months of the year. The reproductive plasticity of X. securis and the potential to adapt to local environmental conditions highlight the need for specific monitoring programmes focused on early detection in potential invasion hotspots.