Lemanea fucina Bory

Résumé fourni par la source

Lemanea fucina Bory Fig. 2 A – F Homotypic synonyms. Lemanea mamillosa var. fucina (Bory) Kützing; Sacheria fucina (Bory) Sirodot. Heterotypic synonyms. Lemanea mamillosa Kützing; Sacheria mamillosa (Kützing) Sirodot. Type locality. la route de Fougères à Vitré (Bretagne) (Bory de Saint-Vincent 1808). Previous records in Italy. There are no reports available for Italy. Sampling site. Monte San Nicola. Herbarium specimen. Deposited in CAT Herbarium – sectio Algae (HERB 00123). Morphology. The thalli formed tufts ranging from light to dark green in colour and measured approximately 10–13 cm in length. They were stalked, becoming gradually narrower toward the base, and had many branches, often with secondary ones, while “ false ” branches were rarely observed where the thallus had broken off (Fig. 2 a). Nodes and internodes were easily distinguished (Fig. 2 b). The nodal basal portion was 524–714 μm, the nodal median portion was 643–809 μm, and the nodal apical portion was 619–786 μm. The internodal basal portion was 405–524 μm, the internodal median portion was 476–524 μm, and the internodal apical portion was 430–476 μm. The nodal-internodal ratio varied between 1.4 and 1.6. The central axial cell was not surrounded by a cortex and bore T-shaped ray cells (Fig. 2 e, f). The thalli were monoecious. In the fertile thalli, the spermatangial papillae were distributed in circular patches on nodes, while the carposporophytes were borne on the inner portion of the cortex (Fig. 2 c). The carposporangia, borne in chains, ranged in length between 35 and 40 μm with a diameter varying from 20 to 30 μm (Fig. 2 d). The Chantransia stage was not found. Ecology and associated species. L. fucina was found exclusively at Monte San Nicola, a site characterised by natural rapids formed by erosive processes. In this location, the species colonised the surfaces of volcanic rocks, specifically within micro-habitats such as concavities shaped by the high-energy, turbulent flow, which provided optimal substrates for thallus attachment. Only a few thalli of L. fucina were observed within a community dominated by P. catenata. In this site, other associated taxa included cyanobacteria (i. e., Nostoc sp.) and some macroalgae (i. e., Cladophora sp., Vaucheria sp.). These species were abundant in areas with lower hydrodynamic stress and during the summer period, when reduced river discharge produced less turbulent flow conditions and the subsequent desiccation of L. fucina.

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