Pachymeniopsis lanceolata (Okamura) Yamada ex Kawabata 1954

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 : 154-156

3.3 Pachymeniopsis lanceolata (Okamura) Yamada ex Kawabata 1954

Pachymeniopsis lanceolata was originally described from Japan, as Aeodes lanceolata Okamura , and is native to Japan ( Okamura 1934; Yoshida et al. 2015), China ( Liu 2008) and Korea ( Lee and Kang 2001). The species was reported in various locations in the Pacific Ocean outside of its natural range through the last decades, such as California ( Aguilar-Rosas et al. 2010), Mexico ( Pedroche and SentÍes 2020) or New Zealand (D’ Archino and Zuccarello 2021). The first European occurrence for P. lanceolata was detected in French waters in the Thau Lagoon ( Verlaque et al. 2005, as Grateloupia lanceolata ) and it was later found in the Gulf of Morbihan ( Le Roux 2018). In August 2020, specimens were collected outside the Gulf of Morbihan on the shore at Penvins, Sarzeau. Individual thalli grew up to 30–40 cm, with a dark to purplishred color ( Figure 6b ). The color turns a distinctive green when aging. Thalli are characterized by the large foliose palmate frond (regularly wider than 10 cm) attenuated at the base (cuneate base, see Figure 6a ). The texture is much more coriaceous and never soft as it is in Grateloupia turuturu . The thickness of the blade is up to 800 µm with a compact cortex and medulla ( Figure 6c ). Locally P. lanceolata can be misidentified with the introduced G. turuturu . The latter species is much more linear, and as shown above, both texture and thickness are good criteria. One has to be vigilant though, as both species were commonly found

2017

Antithamnion hubbsii Botryocladia wrightii

2010 2016 Pachymeniopsis lanceolata

2008 1994 2005 Polyopes lancifolius Polysiphonia morrowii Solieriasp.

0 50 200 km

New record

Previous record

2005

Source:Trait de côte Histolitt © IGN-Shom 2009 Coordinate system: Lambert-93 Symphyocladiella dendroidea

Opposite distichous branching Opposite decussate branching

Antithamnion cruciatum

Antithamnion villosum Figure 4: Antithamnion spp. in the north-east Atlantic,showing the different morphologies of Antithamnion hubbsii segments and the branching patterns.

together in rocky and sandy pools from the upper and mid-shore.

Figures

Figure 6: Pachymeniopsis lanceolata from Brittany: (a) general habit; (b) tetrasporophyte with numerous marginal proliferations (Herbarium T. Burel); (c) longitudinal section. Scale bars: (a–c) 2 cm; (d) 100 µm.