Individual differences determine the morphogenesis pattern and reproductive uniqueness of the invasive green macroalga, Chaetomorpha valida, with possible implications for its habitat adaptation

The marine green algae genus Chaetomorpha is a common source of “green tide” and is widespread on coasts around the world. In this study, based on invasive Chaetomorpha valida collected from the Shandong Peninsula, the morphogenesis and reproductive characteristics of two strains that are morphologically different from each other, were observed using experimental biology methods. The main results are as follows: (1) significant difference in the size of reproductive cells produced by Strains 1 and 2; (2) gametes produced by Strain 2 are isogamous and same gametangial during the binding process of gametes, whereas those of Strain 1 are isogamous but hetero-cystic; (3) progeny from Strain 1 has rhizoidal holdfast, whereas that of Strain 2 has discoid holdfast; (4) gametophytic “branching” was found in Strain 1. These results could validate the high phenotypic plasticity of macroalgae and offered an interpretation of habitat adaptation. Furthermore, this study innovatively provided fundamental research on the selection of macroalgal traits and explored competitive strategies for the dominant survival of macroalgae from a new perspective.