Abstract
Brazilian specimens of Branchiosyllis cf. exilis, B. tamandarensis sp. n., Haplosyllis lattigae sp. n., H. loboi, Opisthosyllis brunnea and O. viridis are described and illustrated herein, from recently collected material; also, the distributions of Haplosyllis amphimedonicola and H. rosenalessoae are expanded to other localities in the states of Paraíba and Pernambuco. Branchiosyllis tamandarensis sp. n. was found associated with sponges and is characterized by having a flattened, ribbon-like body, with longitudinal line of mid-dorsal papillae, peristomium dorsally inconspicuous, branchiae with up to six lobes, branchiae and ungulae on all parapodia, and falcigers absent. Haplosyllis lattigae sp. n. is characterized by having two kinds of chaetae with different sizes and shapes per parapodium, papillate dorsum from midbody, and midbody dorsal cirri alternating in length. Additionally, we provide keys to the Brazilian species of Branchiosyllis, Haplosyllis and Opisthosyllis, comparative tables of the new species described herein and selected similar congeners, and the first record for Trypanosyllis zebra in the states of Espírito Santo and Paraíba.