New records of the benthic medusa Ptychogastria polaris Allman, 1878 (Trachylida, Hydroidea) in the Barents Sea and off the Kurile Islands (Pacific Ocean)

Abstract

This paper reports new records of the benthic trachymedusa Ptychogastria polaris Allman, 1878 in grab samples taken off the Kurile Islands (Pacific Ocean). Photographs showing habitats of P. polaris on the seabed were obtained in the southeastern Barents Sea in 1988. The new material, as well as collections of the Russian Academy of Sciences, allowed a revised morphological description. The cnidom of this species is described for the first time. The cold-water nature of the medusa is confirmed. However, its occurrence in temperate waters of the Atlantic and Pacific Oceans allows classification of the distribution area of P. polaris as boreal-arctic or, possibly, bipolar, according to Kramp.