Dictyota spinulosa Hooker f. & Arnott, 1838

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 : 9

* Dictyota spinulosa Hooker f. & Arnott, 1838

Japanese name: ハリアミジグサ (hariamijigusa)

Type locality: —“Loo-Choo” [Okinawa, Ryukyu Retto, Japan]

Description and remarks: —Specimens are 15–16 cm tall and slender. Thalli are dichotomously branched with spinose margins. The upward-facing spines are denser in the apical branches and are sparse in the middle parts of the thallus, but the lower and basal parts are usually smooth. Branch apices generally have acute angles, appearing pointed and serrated along with the small marginal spines, but gradually become obtuse and rounded when branching.

This species of Dictyota was collected from sheltered areas in the Mushima old port and is easily distinguishable for its spinose margins especially in branches near the apex. Other Dictyota species which also have dentate structures (i.e., D. ciliolata , D. crenulata , D. crenulata var. canariensis , D. menstrualis , D. jamaicensis , and D. kohlmeyeri ) compose the “ Dictyota ciliolata – crenulata complex” but are restricted mostly to the Pacific region of Central America and the Caribbean Sea of the Atlantic ( Tronholm et al. 2013). D. spinulosa also occurs in the South China Sea ( Phang et al. 2016) and Taiwan ( Lewis & Norris 1987)

Materials examined: —18ECS1-77 (1 to 2)