Boccardiella ligerica, an exotic polychaete in a Southwestern Atlantic coastal lagoon: Morphology and abundance variations

Abstract

Boccardiella ligerica (Ferronniere, 1898) is an exotic polychaete introduced to the southwestern Atlantic Ocean. The species was described for the region 36 years ago, and no updating revision was reported to date. Here, we addressed a detailed study on morphology and abundance variations of B. ligerica in the Mar Chiquita coastal lagoon. We found that B. ligerica from Mar Chiquita shares the diagnostic characters with specimens from the original description (France), and was associated with the reef-like structures ("reefs") of the invader polychaete Ficopomatus enigmaticus (Fauvel, 1923). B. ligerica was not found in sediments, and its distribution in reefs was independent of certain habitat features (i.e., deep or macroalgae), but seasonally, reaching the highest abundances in warm seasons (December). Our results suggest that environmental features might drive the B. ligerica population dynamic, while the substrate offered by F. enigmaticus might support B. ligerica population abundance. The present study updates the known geographic distribution of this nonindigenous species in brackish waters from the SW Atlantic Ocean and shows its association with an invasive habitat-forming species.