Actinocyclus comparison

Ali, Naseri, Mostafa, Noroozi & Blanco, Saúl, 2025, A checklist of diatoms with four endemic records and phytogeographical distribution from water habitats of Iran, Phytotaxa 695 (2), pp. 150-206 : 201

A comparison between Brachysira species from Iran and Europe

In this study, Iranian species of the genus Brachysira were compared with several European species of the same genus (Van de Vijver et al., 2021a, b, c). The Iranian Brachysira includes four species, one of which is shared with Europe, namely Brachysira microcephala . B. styriaca (Grunow) R. Ross was reported by Mehrani-Adl et al. in 2020 from the Kordan River. B. vitrea (Grunow) R. Ross was identified 44 years ago by Compère as Anomoeoneis vitrea (Grunow) R. Ross , a cosmopolitan species found in the deserts of Iran. B. exilis (Kützing) Round & D. G. Mann was reported by Compère in 1981 from Nehbandan to Zahedan City (pH 6) as a cosmopolitan species under the name Navicula cryptocephala var. exilis . It was also referred to as Navicula exilis Kützing (1844) by Zarei-Darki in 2011 in the context of Iran’s diatom flora. Brachysira microcephala (Grunow) Compère was reported by Zarei-Darki in 2011 as Navicula microcephala Grunow , recognized as the only common species within the Brachysira genus, and typically found in oligotrophic and acidic environments. These habitat conditions for B. microcephala (Grunow) Compère align with Van de Vijver’s observations regarding the species’ habitat (Van de Vijver et al., 2021a). Morphologically, B. microcephala (Grunow) Compère is characterized by a lanceolate valve outline lacking convex margins, with protracted, rostrate to non-protracted, acutely rounded apices (Van de Vijver et al., 2021a).

Other European Brachysira species include B. neoexilis Lange-Bertalot , which is commonly found in oligotrophic lakes and rivers with pH levels ranging from slightly acidic to distinctly alkaline (Van de Vijver et al., 2021b). B. liliana Lange-Bertalot and B. neglectissima Lange-Bertalot are freshwater species characterized by a high density of striae and individual striae, preferring calcium bicarbonate, oligotrophic, and alkaline lakes (Van de Vijver et al., 2021a). B. styriaca (Grunow) R. Ross and B. zellensis (Grunow) Round & D. G. Mann were described by Grunow from Lake Erlauf (Van de Vijver et al., 2021b).

Based on an analysis of type material, as well as additional historic and modern specimens, it has been revealed that the majority of B. styriaca (Grunow) R. Ross populations from northern Europe belong to a different taxon (Van de Vijver et al., 2021b). This taxon was originally described 70 years ago by Cleve-Euler as Anomoeoneis decipiens A. Cleve and has recently been recombined as B. decipiens (A. Cleve) Van de Vijver & Kusber.

B. styriaca and B. decipiens can be differentiated based on several distinct morphological and ecological preferences (Van de Vijver et al., 2021b). B. styriaca (Grunow) R. Ross is typically found in alkaline lakes and calciumbicarbonate, oligotrophic conditions, whereas B. decipiens prefers acidic environments.

B. rylandsiana B. Van de Vijver, D. M. Williams & Ector , another European species of Brachysira , is distinguished from B. zellensis (Grunow) Round & D. G. Mann by features such as parallel valve margins, cuneately rounded apices, and various smaller ultrastructural details (Van de Vijver et al., 2021b).

The B. serians (Brébisson) Round & D. G. Mann and B. brebissonii R. Ross intermedia complex are typically found in oligotrophic and acidic habitats. The largest species within this complex are Brachysira serians (Brébisson) Round & D. G. Mann and B. wygaschii Lange-Bertalot , which exhibit distinct Voigt incompatibility. Although these species often coexist, they can be differentiated by their valve design and dimensions (Van de Vijver et al., 2021c).