Observations on the SilicoflagellateDictyocha SpeculumEhrenb. From The Firth of Clyde

Abstract

Occasional reference to the sporadic appearances of silicoflagellates (commonlyDictyochaspp.) are to be found in a number of seasonal studies of phytoplankton in the coastal waters of the British Isles. The silicoflagellates are rarely described in any detail since they usually form a small component of the annual phytoplankton. The autumnal occurrence of silicoflagellates in the Firth of Clyde was briefly described by Marshall (1924) in an account of the food ofCalanus, and further seasonal observations on silicoflagellates in European coastal waters are to be found in the works of Margalef (1965), Nival (1965), Travers & Travers (1968) and Ignatiades (1970). Numerous studies on silicoflagellates have been concerned with their taxonomy, particularly the plasticity of form shown by their tubular siliceous skeletal structures and the many taxa (fossil and living) so far described. The confusion which has arisen through the differing views of palaeontologists studying fossil material, and botanists working with live populations and their seasonal abundances, has been highlighted recently in a culture study ofDictyocha fibula, in which skeletal variations in a single clone were matched with a number of other entities, fossil and living (Van Valkenburg & Norris, 1970).