Micrasterias foliacea var. ornata Nordstedt, 1869

Levanets, Anatoliy & Janse van Vuuren, Sanet, 2023, Morphology, taxonomy, biogeography and ecology of Micrasterias foliacea Bailey ex Ralfs (Desmidiales, Zygnematophyceae), PhytoKeys 226, pp. 33-51 : 33

6. Micrasterias foliacea var. ornata Nordstedt, 1869

Micrasterias foliacea var. ornata Nordstedt, 1869. "Videnskabelige Meddelelser fra den Naturhistorisk Forening i Kjøbenhavn for Aaret" 21: 221, Taf. 2, fig. 16.

Morphology.

Each semicell is rectangular and the cell wall bears one to three small spines along the sinus, as well as on the upper margin of the upper lateral lobe near its base and the lower margin of the lower lateral lobes near the isthmus ( Kim 2013, 2014). The presence of the spines on the upper and lower margins of the lateral lobes, as well as the incision which separates the polar lobe, is regarded as the major difference between this variety and the type ( Nordstedt 1869; Zalocar de Domitrovic 1981).

In Asian specimens of both the specific form and var. Micrasterias ornata ornata a peculiar phenomenon, never seen in any American specimens, was observed. This is a warping of the surface of the filament, resulting in the twisting of the side (edge) view of the chains into a sinusoidal curve which is sometimes quite pronounced. It is caused by the curving and dishing in opposite directions of the right and left lateral lobes of one semicell, those of the other semicell being curved and dished in the reverse manner ( Scott and Prescott 1961). Illustrations of these twisting of the chains can be found in Scott and Prescott (1961).

Distribution.

Although variety Micrasterias ornata is less widespread than var. Micrasterias ornata foliacea , it is also widely distributed throughout the world. Similar to the type, it was not recorded anywhere in Europe and in North America it was only recorded from northwestern Canada and two eastern states of the USA. It is more abundant in South America, Africa, and Asia and it was also recorded from Australia. The distribution of var. Micrasterias ornata ornata is illustrated in Fig. 2 and more details regarding its patterns of distribution are presented in Suppl. material 3.

Habitat and ecology.

Variety Micrasterias ornata was recorded from a wide range of different ecological niches - it was found in different types of freshwaters, both standing (rainwater pools, rock ponds, rice fields, reservoirs, lakes, swamps, wetlands, flooded savannahs and lagoons) and flowing (creeks, moderate to rapidly flowing rivers). It was growing on the leaves of Hymenachne amplexicaulis ( Poaceae ) by Salazár Pereira (1991) and Salazar (2006/2007). It was also found in a coastal area in Nigeria ( Kadiri 2002).

According to Kim (2013) this variety occurs mostly in oligo-mesotrophic, neutral-alkaline water bodies. The variety had a rare abundance in a natural oligotrophic pond on Jeju Island (South Korea), with pH ranging between 6.1 and 7.5 and conductivity between 44 and 108 μS /cm ( Kim 2014). In Venezuela it was found in a flooded savannah which was acidic, with a low salinity and a high biomass of macrophytes ( Salazár Pereira 1991; Salazar 2006/2007).

Figures

Figure 2. Worldwide distribution of different varieties of Micrasterias foliacea.