Botryocladia wrightii (Harvey) W.E. Schmidt, D.L. Ballantine et Fredericq 2017

Burel, Thomas, Helias, Mathieu & Duff, Michel Le, 2023, Range expansion of some non-indigenous seaweeds along the coasts of Brittany - English Channel, Botanica Marina (Warsaw, Poland) 66 (3), pp. 151-164 : 154

3.2 Botryocladia wrightii (Harvey) W.E. Schmidt, D.L. Ballantine et Fredericq 2017

Botryocladia wrightii is a Rhodymeniaceae originating from the North-West Pacific, initially described from Japan by Harvey in 1860 as Halosaccion wrightii . It was first found outside its native distribution area in 1978 in the Thau Lagoon as Chrysymenia wrightii Harvey ( Ben Maiz 1986) . Botryocladia wrightii was found in 2005 in the North-East Atlantic (Galicia, North-West Spain) under the name Chrysymenia wrightii ( Bárbara et al. 2008) . It was discovered in the Gulf of Morbihan in 2010 ( Le Roux 2018) and reached the coasts of England in 2013 ( Bunker 2014). All specimens found in this study were collected in the lower part of the intertidal zone with a deposit of sand. This species develops a tubular hollow thallus, somewhat gelatinous, more or less cylindrical, with a color from golden orange to purplish ( Figure 5a ). The largest sampled specimens were up to 20 cm, with main axes up to 0.6 cm wide ( Figure 5b ). The thallus is attached to the substratum by a discoid holdfast and shows numerous branches with an irregular branching pattern. In transverse section, the center of the thallus appears hollow with a cortex consisting of small cortical cells and large subcortical cells ( Figure 5c ). Cystocarpic plants were found in Tréveneuc ( Figure 5d ). When present, cystocarps (up to 1000 µm) are numerous and protrude all over the thallus. Specimens of B. wrightii can be confused with the native Dumontia contorta (S. G. Gmelin) Ruprecht , but differ in the branching pattern, the inner structure of the thallus and the arrangement of cystocarps.

Figures

Figure 5: Botryocladia wrightii from Brittany: (a) in situ material from Tréveneuc (picture by F. Gully and M. Cochu); (b) general habit; (c) cortex and subcortex in transverse section; (d) immature cystocarp lacking carpostome in surface view. Scale bars: (a and b) 2 cm; (c and d) 100 µm.