Nitzschia fenestralis: A new diatom species abundant in the Holocene sediments of an eastern African crater lake

Abstract

Nitzschia is common in the phytoplankton of several East African lakes. A new species, Nitzschia fenestralis, sp. nov. D. Grady, D.G. Mann et Trobajo was encountered at numerous depths in a 16 m sediment core from Lake Babogaya, Ethiopia and is described using light and scanning electron microscopy. It is compared with several other morphologically similar taxa described from East and Central Africa (especially N. aequalis, N. mediocris, N. obsoleta and N. fabiennejansseniana), and from Europe (N. fruticosa). An unusual feature of some of these species (N. fenestralis, N. obsoleta and N. fabiennejansseniana) is that in the raphe canal each stria is represented by two narrower areolae (alternatively interpreted as a single subdivided areola). It is this feature that suggested the name of the new species (through the resemblance to a series of sash windows). Another characteristic of N. fenestralis and N. obsoleta, apparently never reported previously in any diatom, is that the more advalvar bands end approximately halfway along the frustules, rather than at the poles. In most respects (shape and size, stria and fibula densities, valve and girdle structure), N. fenestralis and N. obsoleta are very similar, but confusion is unlikely because they differ in whether central raphe endings are present (N. fenestralis) or absent (N. obsoleta). In Nitzschia fenestralis, and perhaps to a lesser extent in N. obsoleta, the striae usually become strongly radiate towards the poles. A preliminary assessment, based on the literature, suggests that N. fabiennejansseniana may be synonymous with N. obsoleta, which was described earlier.

A polyphasic approach to the study of the genus Nitzschia (Bacillariophyta): three new planktonic species from the Adriatic Sea

“…1986, Grady et al. 2020) are spicular, as is N. inordinata among the species described here. Less elongate and squat Nitzschia species are generally benthic and either adhere to surfaces, or live free, moving through sediments.…”

“…2013, Grady et al. 2020). Most of these Nitzschia species are needle‐shaped ( N. lacustris , N. bacata , N. nyassensis , N. kavirondoensis , N. rusingae, N. fenestralis, N. aequalis, N. mediocris, etc.…”

“…2013, Grady et al. 2020). In marine phytoplankton, Nitzschia has historically been camouflaged within a category of “small pennate diatoms.” Among these are a number of small, single‐celled, more or less bicapitate Nitzschia species (including N. bicapitata , N. curvilineata , N. bifurcata , N. braarudii , N. capitata , N. ikeanae , N. reimersenii , N. schaunslandii, and N. subinflata; Kaczmarska et al.…”

Exploring the Community Structure of Plankton in the Maricultures Sites of Kodek Bay, Lombok Island

“…The abundance of Thallasiosira and Nitzchia at all sampling sites revealed their natural ability to adapt. Nitzchia is the second largest genus of Diatom (Mann, 1986) and can be composed of more than 30 to 100% Diatom community (Grady et al, 2020;Sitoki et al, 2013), whereas Thallassiosira ranges in size to fit the available nutrient in the environment. Therefore, these genera strive in freshwater, brackish water, and seawater (Lange-Bertalot et al, 2017;Lobban et al, 2019).…”

Nitzschia anatoliensis sp. nov., a cryptic diatom species from the highly alkaline Van Lake (Turkey)

“…( Patrick, 1936 ). Other examples of such extreme environments are some African crater lakes (also with high pH), whose sediments have proven to be very rich in several Nitzschia species, including a very abundant new species, Nitzschia fenestralis ( Grady, Mann & Trobajo, 2020 ).…”