Abstract This study aimed to review previous records of Polydora species from Brazil, as well as provide new records, mainly from the Southeast and South regions of the country. In total, 11 species were distinguished and a key to their identification is given. Polydora cornuta , P. nuchalis , and a new species from the state of Rio de Janeiro, P. nonatoi sp. nov. were found to occur in silty sand tubes in soft sediments; six species were found to be opportunistic commensals boring in shells of various molluscs; P. colonia was found to only bore in sponges; and a new species, P. paulolanai sp. nov., was found to bore in both sponges and oyster shells in Paraná state. Adults of P. nonatoi sp. nov. have black stripes on the palps, black spots on the peristomium and 3−4 anterior chaetigers, short occipital antenna, falcate spines of chaetiger 5 with a large lateral tooth connected to main stem by thin sheath, and only capillary chaetae in the posterior notopodia. Adults of P. paulolanai sp. nov. have black bands on the palps, short occipital antenna, falcate spines of chaetiger 5 with transverse subdistal collar on concave side, and numerous needle-like spines loosely held in tufts in addition to capillary chaetae in the posterior notopodia. Polydora caeca Webster, 1879 is resurrected and treated here as a senior subjective synonym of P. neocaeca Williams & Radashevsky, 1999. Shell-boring worms from Brazil earlier identified as P. neocaeca or P. cf. haswelli Blake & Kudenov, 1978 are referred to P. caeca . The urgent need of molecular data for the correct identification of Polydora species from Brazilian waters is highlighted. country total 1 given P Janeiro sp nov sediments molluscs palps 34 3 4 3− chaetigers antenna sheath notopodia side needlelike needle like Webster 187 Radashevsky 1999 Shellboring Shell cf Kudenov 197 highlighted 18 199 19

Novo gênero e nova espécie de Clausiidae (Crustacea, Copepoda) parasita de Dipolydora armata (Polychaeta, Spionidae) no Brasil: Descrição e ilustração de novo gênero e nova espécie de um copépodo parasita (Clausiidae), Spionicola mystaceus, associado ao poliqueto Dipolydora armata (Spionidae). O novo copépodo tem um corpo alongado, antenula penta articulada , ramos biarticulados nos pereiópodos um e dois, dois espinhos representando o pereiópodo 3, pereiópodo 4 ausente, pereiópodo 5 muito desenvolvido e estruturas dos apêndices bucais reduzidas. O hospedeiro é um perfurador de conchas de moluscos coletado ao largo da Ilha de São Sebastião, Estado de São Paulo, Brasil.

A new genus and species of parasitic copepod (Clausiidae), Spionicola mystaceus, associated with the polychaete Dipolydora armata (Spionidae) is described and figured. The new copepod has an elongate body, 5-segmented antennule, 2-segmented rami on legs 1 and 2, 2 spines representing leg 3, no leg 4, leg 5 well developed and reduced armature elements on feeding limbs. The host is a mollusk-shell borer, collected off São Sebastião Island, State of São Paulo, Brazil.