The family Xystonellidae (Ciliophora, Tintinnina) in the Adriatic Sea

Abstract

This paper reports quantitative, horizontal and vertical distribution data of the 11 species of the family Xystonellidae found in the Adriatic Sea and in the Strait of Otranto. The samples were collected in coastal and open waters, with a plankton net equipped with a closing system, in the period from 1973 to 1986. At the deeper stations of the South Adriatic Pit, hauls were taken in eight vertical layers, while at other stations sampling depended on the respective depth of each station. Xystonellidae are oceanic tintinnines, mainly present in the South Adriatic and the Strait of Otranto throughout the year. They are characteristic of South Adriatic and Eastern Mediterranean water masses. Horizontal distribution of lower mesopelagic species is limited by the 200 m isobath. Only sparse individuals of the upper mesopelagic and epipelagic species were found in the Jabuka Pit, probably due to the late autumn and winter current. These species were not registered to the north of this region. They were registered below the 200 m depth as dominant tintinnines, while in summer they represented an average of 81% of the total tintinnine population.