First Report of Capitella sp. (Annelida: Polychaeta) from the south Caspian Sea

Polychaetes assemblages were studied in the south Caspian Sea shallow waters. The sediment samples collected by a Van-Veen grab (0.0625 m2) from Gomishan, Gorgan bay, Tonekabon, Kiashahr and Astara coastal areas (Depts 1, 3 and 5 m) in winter & summer, 2017. The sediments were screened by sieves (mesh sizes: 0.5, 1 and 2 mm), and the worm specimens were fixed in glutaraldehyde 4% solution. The morphological investigation was showed the presence of Capitella sp. (Capitelidae) populations in Gomishan, Gorgan bay and Tonekabon. The Capitellid worms, had no branchia and eyes; prostomium was short and conic; thorax was consisted of a pristomium lacking any appendages, accompanied to nine chaetigers with capillary chaetae. Also, the thoracic chaertigers 1-7, 1-8 or all of them had several capillary chaetae. But, abdomen was only equipped to hooded hooks. Pygidium lacking any appendages. Genital spines of males and genital pore of females were between the thoracic segments 8-9. This is the first report of the genus Capitella and the family Capitellidae from the Caspian Sea.