Symphyocladiella dendroidea (Montagne) Bustamante, B.Y. Won, S.C. Lindstrom

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 : 158

3.7 Symphyocladiella dendroidea (Montagne) Bustamante, B.Y. Won, S.C. Lindstrom

et T. O. Cho 2019

Symphyocladiella dendroidea is a species belonging to the family Rhodomelaceae . It is native to the Pacific ( Bustamante et al. 2016, 2019). The first European record was from the Thau Lagoon in 1995 as Pterosiphonia sp. ( Verlaque et al. 2015). It was then found in 2005 in the Bay of Arcachon ( Verlaque et al. 2008) and in the Gulf of Morbihan ( Le Roux 2018) as Pterosiphonia tanakae Uwai et Masuda , probably introduced by oyster spat. The species has continued to spread northward and is now present in the marinas of the bay of Concarneau, the marinas of Brest and of Perros-Guirec. In this study, all specimens were found attached on pontoons, suggesting an extension through maritime traffic. Symphyocladiella dendroidea is a small dark red to blackish purple Pterosiphonieae growing up to 7 cm ( Figure 10a and b ). Fertile tetrasporophytes were found in Brest, growing tetraspores in series of 8–12 within lateral branchlets ( Figure 10e ). Female specimens were also observed with mature cystocarps ( Figure 10d ). Cystocarps were ovoid, with dimensions equal to 126–136 × 95 µm and were oriented toward apices. Morphologically, S. dendroidea may be easily distinguished from most other native Pterosiphonieae by the pyramidal outline of the thallus ( Figure 10c ). Symphyocladiella dendroidea can still be confused with the local Deltalsia parasitica (Hudson) DÍaz-Tapia et RodrÍguez-Buján which differs by the number of pericentral cells in the axes (8–12 vs. 7–9, respectively) and the cortication (light cortication vs. absence of cortication). Identification can be difficult as cryptic diversity occurs in the latter species as described by DÍaz-Tapia et al. (2022). Further studies are needed to clarify the taxonomic status of the complex Symphyocladiella dendroidea ( DÍaz-Tapia et al. 2018).

Figures

Figure 10: Symphyocladiella dendroidea from Brittany:(a) general habit showing alternate branches and ultimate proliferations; (b) dried specimen from Brest marina (Herbarium of the European Institute for Marine Studies); (c) apex with characteristic pyramidal outline aspect; (d) branches bearing cystocarps; (e) series of tetrasporangia in branchlets. Scale bars: (a and b) 500 µm; (c–e) 200 µm.