Undaria pinnatifida (Harvey) Suringar, 1873

Belleza, Dominic Franco C., Tateishi, Hiroto, Tanimae, Shin-Ichiro, Kobayashi, Taishun, Aota, Tomoyuki, Urasawa, Toshiki & Nishihara, Gregory N., 2025, An annotated list of brown seaweeds (Phaeophyceae) from Nakadori Island (northern Goto Islands, Nagasaki, Japan), Phytotaxa 694 (1), pp. 1-24 : 16-17

Undaria pinnatifida (Harvey) Suringar, 1873

Japanese name: ワカメ (wakame)

Basionym: Alaria pinnatifida Harvey, 1860

Type locality: —Shimoda, Shizuoka Prefecture, Japan

Description and remarks: —Specimen is 32 cm tall with the blade attached on a 2.5 cm long stipe, 2 mm in diameter. The blade contains a midrib that connects to the stipe. The blade margins are deeply pinnate at the base but are shallower closer to the apex. The specimens collected are young and do not yet have the reproductive sporophyll structures at the base. This species is ubiquitous in early to mid spring along the study sites, especially in Naname where they form understory forests below the S. horneri canopy. However, this species has gradually declined in Yokoura together with other canopy-forming species like Sargassum macrocarpum and Ecklonia cava subsp. kurome .

This species is indigenous to the northwest Pacific coast and grows along the shallow rocky subtidal zone and is also cultivated in Japan, South Korea and China for food ( Wu & Meng 1997, Tanaka et al. 2020). In recent decades, its appearance along the coasts of north and south America, Europe and the southern hemisphere was due to accidental introduction probably through shipping or with the introduction of cultured Pacific oysters ( Hay & Luckens 1987, Floc’h et al. 1991, Casas & Piriz 1996, Casas 2020). In the Atlantic, U. pinnatifida is highly invasive and rapidly expanding its range, outcompeting native species and causes fouling of submerged structures ( Minchin & Nunn 2014). Strategies have been formulated towards controlling its spread and local eradication ( Marine Pest Sectoral Committee 2015, Gnanalingam & Hepburn 2019) but total extermination may be futile.

Materials examined: —18ECS1-119 (1, 3, 4)

Family Lessoniaceae