New data on distribution, morphology and taxonomy of phoronid larvae (Lophophorata: Phoronida)

Abstract

Phoronids have worldwide distribution and are found in almost all seas of the World Ocean. Frequently phoronid larvae (actinotrochs) comprise a significant proportion of the total zooplankton biomass that makes their studies a very important source of information for ecologists, planktonologists, and zoologists. Investigations of phoronid larvae are interesting due to their relation to affiliation of this phylum and other main groups of Bilateria. Identification of all species and stages is difficult due to the paucity of published information regarding phoronid larvae. The descriptions of morphology and microscopic anatomy of actinotrochs found in Mediterranean and Black seas, Sea of Okhotsk, Sea of Japan, close to Reunion Island and in the Puget Sound are given. For the first time, the larvae that presumably belong to Phoronopsis albomaculata and P. californica are described. The morphological and behavioral features of two main types of actinotrochs are formulated. A complete key for identification of all actinotrochs known by now is developed.