First record of the invasive medusa Blackfordia virginica in the Río de la Plata estuary, Argentina-Uruguay.

GENZANO, G.; MIANZAN, H.W.; ACHA, E.M.; GAITÁN, E.

REVISTA CHILENA DE HISTORIA NATURAL

Año: 2006 vol. 79 p. 257 - 261

0716-078X

Blackfordia virginica is a well-known invasive medusa inhabiting estuarine areas. It was recently detected in northern Argentina, constituting the first record of invasive hydromedusa for the Argentine Sea. In this work more than 1500 plankton samples in the Southwestern Atlantic Ocean (34-55º S) from 1983 up to 2000 were analyzed. More than 5000 specimens per sample of B. virginica were found in Río de la Plata estuary for the first time in February 2000. This river is one of the large waterways of South America with an intense nautical traffic and several exotic species has been recorded here, mainly due to trans-oceanic shipping traffic. It is important to point out that we found medusae of both sexes (therefore this species could be introduced in either the medusa or the polyp stages or both), different size classes (including very small juveniles) and maturation stages, and in such high numbers that would suggest local reproduction. For this reason the recent finding of this hydromedusa could represent the starting point of an successful introduction.