The American brine shrimp as an exotic invasive species in the western Mediterranean

The hypersaline environments and salterns present in the western Mediterranean region (including Italy, southern France, the Iberian Peninsula and Morocco) contain autochthonous forms of the brine shrimp

Artemia

, with parthenogenetic diploid and tetraploid strains coexisting with the bisexual species

A. salina

. Introduced populations of the American brine shrimp

A. franciscana

have also been recorded in these Mediterranean environments since the 1980s. Based on brine shrimp cyst samples collected in these countries from 1980 until 2002, we were able to establish the present distribution of autochthonous brine shrimps and of

A. franciscana

, which is shown to be an expanding invasive species. The results obtained show that

A. franciscana

is now the dominant

Artemia

species in Portuguese salterns, along the French Mediterranean coast and in Cadiz bay (Spain). Co-occurrence of autochthonous (parthenogenetic) and American brine shrimp populations was observed in Morocco (Mar Chica) and France (Aigues Mortes), whereas

A. franciscana

was not found in Italian cyst samples. The results suggest these exotic

A. franciscana

populations originate as intentional or non-intentional inoculations through aquacultural (hatchery effluents) or pet market activities, and suggest that the native species can be rapidly replaced by the exotic species.