Nitella capillaris (Krocker) J. Groves & Bullock-Webster

Fig. 5 a – c

Geographical distribution.

N. capillaris is not a widespread species. It has been mainly reported from Europe (Guiry and Guiry 2024) and Africa (Muller et al. 2017). In Italy, it was reported in Lombardy, Veneto, Emilia Romagna, Umbria, Latium, and Sicily (Bazzichelli and Abdelahad 2009; Troia et al. 2018; Guarino et al. 2019; Romanov et al. 2019).

Conservation status.

In Sweden, Slovakia and Great Britain N. capillaris is considered extinct. In North Rhine-Westphalia, Schleswig-Holstein, Brandenburg and Thuringia is considered endangered and, following the revision of the Red List in 2010, in the Balkan countries the species is classified as vulnerable (VU) (Auderset Joye and Schwarzer 2012; Hindáková et al. 2022). In Poland, it is protected by national environmental laws and it is considered a critically endangered species (CR) by IUCN (Urbaniak and Gabka 2014).

Previous reports in Sicily.

Catania, unspecified locality; Palermo, Gurgo di San Ciro (Formiggini 1908 reported as Nitella capitata); Trapani, Anguillara pond (Troia et al. 2018; Guarino et al. 2019; Romanov et al. 2019)

New reports in Sicily.

Monte Soro Lake (LM - Cesarò, Messina).

Morphology.

thalli are about 10–15 cm tall. The axes have a diameter of about 500 μm and the colour of the thalli is green or light green. The internodes are generally 2–3 times longer than the branches. In the whorls, there are generally 6 or more rays, branched once, with 2–3 second-order rays (Fig. 5 a). The rays have pointed unicellular terminal segments (dactyls) (Fig. 5 b). The rays of the lower whorls are usually sterile, while those of the upper whorls are fertile. N. capillaris is a dioecious species. The oogonia are borne in the bifurcations of the rays, generally grouped in pairs, and are about 300 × 280 μm in size, with prominent ridges (Fig. 5 c). Antheridia were not observed in our specimens.