The morphological comparison, variation and molecular analysis between two green tidal algae Enteromorpha
Ding, Lanping; Teng, Linhong; Lu, Qinqin; Luan, Rixiao; Huang, Bingxin
The common green seaweed Enteromorpha presents extensive morphological plasticity and contains numerous variants, which makes their taxonomic status problematic. Green tidal alga Enteromorpha prolifera, occurring in west China Yellow Sea in recent years, raised widely discussion about the species' taxonomic position. Compared with thalli of E. prolifera grown benthically in nature, the free floating plants of this species exhibited some variations as following: 1) bright green thallus, 2) numerous long and thin branches, 3) branch base nonconstricted but obviously expanded, 4) pyrenoid generally 1 per cell, but up to 2-5 per cell occasionally, 5) some branchlets with entire or partial uniseriate cells. Some of these features (items 2, 4 and 5) overlap with E. clathrata. In this study, we compared the two species from morphological levels, including frond color, hold status, habit, cells shape and arrangement, branching pattern, summarized their differences. Besides, molecular data were used to investigate the genetic relationship of the two species. The pairwise distance and sequence similarity between the two species were 9.2% and 87.5% respectively. Phylogenetic analysis in an alignment with 18 other representatives showed that the two species are separated by different branches, which confirmed genetic divergence at molecular level. Based on these results, people can identify the two species easily and accurately.