Myrmecia Printz.

Myrmecia is a coccoid alga with spherical, ovoid, or pear-shaped cells that can form multicellular aggregates. The cell wall may be locally thickened. The chloroplast is parietal, cup-shaped, wavy at the edges, and usually divided into 2–4 lobes (Fig. 2). It reproduces asexually by zoospores, aplanospores or autospores (Ettl & Gärtner 2013). From the nine taxonomically accepted species (Guiry & Guiry 2022) only two ( M. biatorellae and M. israelensis) have so far been confirmed as photobionts of Psora, Placidium and Heteroplacidium from the family Verrucariaceae (Thüs et al. 2011; Moya et al. 2018).

Free-living M. biatorellae is often reported from arid regions (Flechtner et al. 1998; Vinogradova et al. 2004; Flechtner et al. 2008; Venter et al. 2015). However, there are also records from the tundra in north-eastern Russia (Andreyeva 2005). This species has been reported quite frequently from caves (Roldán et al. 2004; Vinogradova et al. 2009). For instance, Roldán & Hernández-Mariné (2009) isolated M. biatorellae from a biofilm on the surface of stalactite in Collbató Cave (Spain). The granite walls of historic buildings in Galicia (Spain) are also a substrate inhabited by this alga (Rifón-Lastra & Noguerol-Seoane 2001). In addition to rocks (Vinogradova et al. 2004), this species often inhabits soil (Khaybullina et al. 2010; Bakieva et al. 2012), tree bark (Khaybullina et al. 2010), sand (Schulz et al. 2016) and survives on serpentinite soils (Venter et al. 2015).