In this paper, we report 10 species of Syllidae, collected in the Socotra Archipelago (Indian Ocean). They belong to eight different genera in four subfamilies namely, Syllinae: Haplosyllis Langerhans, 1879, Megasyllis San Martín, Hutchings Aguado, 2008, Opisthosyllis Langerhans, 1879, Trypanosyllis Claparède, 1864; Eusyllinae: Eusyllis Malmgren, 1867, Odontosyllis Claparède, 1863; Exogoninae: Salvatoria McIntosh, 1885; and Autolytinae: Myrianida Milne Edwards, 1845. Trypanosyllis mercedesae n. sp., is here formally described and distinguished from congeners. Trypanosyllis richardi Gravier, 1900 is re-described, adding important taxonomic information to the original description, based on specimens collected from Djibouti (Gulf of Aden). We provide new insight into the reproduction of Megasyllis heterosetosa (Hartmann-Schröder, 1991) with the description of a specimen with an attached female dicerous stolon, full of oocytes. Odontosyllis polycera (Schmarda, 1861) is described because it is newly recorded for the Indian Ocean. We also provide some remarks about Myrianida pachycera (Augener, 1913), collected with a chain of stolons.
Keywords: Annelida, Trypanosyllis mercedesae n. sp., Trypanosyllis richardi, redescription, Megasyllis heterosetosa, reproduction, new records, taxonomy, morphology.