Two new polychaete species living in the mantle cavity of Calyptogena gallardoi (Bivalvia: Vesicomyidae) at a methane seep site off central Chile (∼36°S)

Two new polychaete species belonging to Nautiliniellidae and Antonbruunidae were found in the mantle cavity of the vesicomyid bivalve Calyptogena gallardoi Sellanes and Krylova, 2005, at a methane seep site off central Chile. Shinkai robusta n. sp. is characterized by having modified parapodia with robust notopodia and nine simple hooks per parapodium on the middle setigers, and an anteriorly truncated sub-triangular prostomium, with a pair of small cirriform antennae. The new species closely resembles Shinkai longipedata Miura and Ohta, 1991, and Shinkai semilonga Miura and Hashimoto, 1996. Antonbruunia gerdesi n. sp. is characterized by having a trapezoidal prostomium, with five sub-equal occipital antennae and a conspicuous pygidium with two short, well-developed digitiform anal cirri. These two new species constitute the first report of polychaetes living in symbiosis with chemosymbiotic bivalves in the south-eastern Pacific.