MORPHOLOGY AND TAXONOMY OF<i>CHAETOCEROS COMPRESSUS</i>LAUDER VAR.<i>HIRTISETUS</i>VAR. NOVA, WITH PRELIMINARY CONSIDERATION OF CLOSELY RELATED TAXA

Abstract

During the fall Chaetoceros blooms of 1985–1988, an unusual taxon was observed in Narragansett Bay, and its morphological structure was studied from both field-collected and cultured material. It shares some conservative characters with the section Compressa species C. compressus Lauder and C. coruortus Schütt, and section Furcellata species C. radicans Schütt, but possesses a unique combination of characters. Preliminary examination and comparison of material from the Indo-West Pacific and North Atlantic suggests that Gran & Yendo's (1914) synonomy of C. compressus Lauder and C. contortus Schütt was erroneous; the two are in fact clearly delineated species. Our Narragansett Bay taxon is most clearly affiliated with C. compressus Lauder (non Schütt, non Gran & Yendo), originally described from Hong Kong Harbour, and is described herein as C. compressus Lauder var. hirtisetus var. nov.