A taxonomic and karyological study of the Codium geppiorum complex (Chlorophyta) in southern Taiwan, including the description of Codium nanwanense sp. nov

Morphological variations of the Codium geppiorum complex from southern Taiwan were examined, and their karyotypes were studied by microspectrophotometry. Morphological analysis distinguished three prostrate Codium species, including C. edule P.C. Silva, C. geppiorum O.C. Schmidt, and a new taxon, C. nanwanense. Although these species show an anatomical continuum as the length of their utricles increases with the thickness of the branches, there are some apparent differences of thallus type and utricle form. The utricles of C. edule are about 1000 μm or more in length, and with abundant hair scars on the utricle tip. Codium geppiorum has a typical pyriform utricle, which is often less than 500 μm in length. The utricles of C. nanwanense are cylindrical and mediumsized, between C. edule and C. geppiorum. Karyological study on the three Codium species also showed an obvious divergence in nuclear size and relative fluorescent unit (RFU). Codium edule has the largest nucleus (8.90 μm in average length) and expectedly the highest RFU among the three species. The ratio of nuclear long axis vs. width is about 3.01, 1.46 and 1.00 for C. edule, C. geppiorum, and C. nanwanense. This paper summarizes the taxonomic characters of these species and provides microfluorescence data useful in distinguishing members of the Codium geppiorum complex.