Reproductive behavior and role in maintaining an aggregative form of the freshwater green alga Marimo, Aegagropila linnaei, in Lake Akan, Hokkaido, Japan

Abstract Aegagropila linnaei is a unique freshwater green alga that develops into spherical aggregations known as “lake balls”, “Cladophora balls” or “Marimo”. Loss of this species progressing globally, and there concern over threats its conservation. As part the study which aims to conserve endangered species, zoosporogenesis A. in Lake Akan, designated Special Natural Monument Japan, was investigated. Materials encompassing three growth forms linnaei: aggregative, free-floating, epilithic, were collected at five sites around lake regular intervals from spring autumn 2017 2018. Quadriflagellate zoospores observed (one aggregative two epilithic) mid-August early September with reproducibility, but not one free-floating). Percentages zoospore-producing filaments extremely low (maximum 1.3 %), result statistical analysis by generalized linear model showed no significant difference among periods both years. These results indicated linnaei, has been thought be an rare event past, occurs regularly even though being percentage. Such appears provide few initials for ensuing generations contribute maintaining form through continuation vegetative growth.