Thorea gaudichaudii is a fresh water alga originally known from Guam in the Mariana Islands. In Japan, this species has been confirmed only from Ryukyu Islands including Okinawa, Miyako, Hateruma and Yoron Is, and can be found in small freshwater springs used by local inhabitants.
This species was reported from Yoron Is. in early spring (Suzawa et al. 2010). Today, we visited there to confirm its status in summer season.
Two other freshwater algae,
Nemalionopsis tortuosa and
Thorea okadae, generally occur in winter and disappear by summer in Kagoshima Prefecture. However, it was present today in Yoron Is.
シマチスジノリは熱帯から亜熱帯にかけての湧水地に生育する淡水紅藻で,環境省のレッドリストでは絶滅危惧I類(CR+EN)に記載されています。日本で確認されている生育地のほとんどは沖縄県ですが,その多くで群落が消失しています。