Morphology and Taxonomy of Chaetoceros contortus Schütt 1895, with Preliminary Observations on Chaetoceros compressus Lauder 1864 (Subgenus Hyalochaete, Section Compressa)

Chaetoceros Ehrenberg, subgenus Hyalochaete Gran, section Compressa contains the species Ch. compressus Lauder 1864 and Ch. contortus Schütt 1895. On the basis of apparent intermediate forms, they were synonymized by Gran and Yendo. Rines and Hargraves suggested that they might be distinct taxa. Light and electron microscopy studies of a wide range of material supports that opinion, although further study of Ch. compressus sensu Lauder from the Indo-West Pacific is needed. Differences of opinion as to whether these taxa should be combined or considered distinct can be attributed to increased knowledge of the biology of diatoms, and advances in systematic theory.