Cosmarium knopkirri Levanets & Janse van Vuuren, 2024

Levanets, Anatoliy & Vuuren, Sanet Janse Van, 2024, Cosmarium knopkirri sp. nov. (Desmidiaceae, Zygnematophyceae) from a tropical wetland in northern Mozambique, Phytotaxa 634 (2), pp. 153-158 : 155-156

Cosmarium knopkirri Levanets & Janse van Vuuren sp. nov. Figs. 2–8 .

Description: Cells large, solitary, 1.5–2.0 times longer than wide; in frontal and side view they are approximately ellipsoidal, with a deep median constriction and wide-open sinus ( Fig. 2 ); cells circular in apical view ( Figs. 6, 7 ). Semicells ( Fig. 8 ) rounded to slightly ellipsoidal, with convex apices and strongly convex margins, lower and upper angles rounded.

Cell wall granulated, furnished with small-sized granules, and decorated with four concentric circles of well-developed, large granules. Large granules in each circle/row alternate with those in the adjacent row (alternation distance approximate half of the inter-granular distance). The apical circle consists of 6 finger-like granules. Subapical circle contains 6, median circle 8, and adjacent-sinus circle 10 hemispherical granules ( Figs. 3–5 ). Granules of subapical and median circles are similar in size and larger than the granules located in the circle adjacent to the sinus ( Fig. 5 ).

Chloroplast axial, stellate in end view. Each chloroplast contains a single pyrenoid. Zygospores unknown.

Cell dimensions: Length (excluding granules) 122.7–141.1 μ m, length (including granules) 140.2–150.0 μ m; Width (excluding granules) 61.9–94.9 μ m, width (including granules) 73.5–112.9 μ m; isthmus 33.2–41.7 μ m (n=14).

Type: — MOZAMBIQUE, Cabo Delgado Province, near Palma, collected as a benthic sample (10°49’ 51.00” S, 40°31’ 50.81” E, 14.95 m a.s.l) on 28 February 2012 (holotype: accession number No. 12–434, deposited in South African National Diatom Collection ( SANDC) of the North-West University, Potchefstroom, 2531, Republic of South Africa). Morphology of vegetative cell of the holotype sample is illustrated in Fig. 2 .

Type locality: —Freshwater inland wetland system with soft black peat-like sediment, near Palma, Cabo Delgado Province, Mozambique (10°49’ 51.00” S, 40°31’ 50.81” E, 14.95 m a.s.l).

Registration: —http://phycobank.org/104265

Etymology:— The name is derived from the Afrikaans word knop, meaning “knob” or “ball” and the Khoekhoe or San word kirri, meaning “walking stick”.

Distribution: —Observed from the type locality only.

Differential diagnosis: — Cosmarium knopkirri differs from all other species of the genus by having rounded to slightly ellipsoidal semicells decorated with four concentric circles of well-developed large granules. The position of granules in successive rows alternates with each other.

Only a few species show slight resemblances to Cosmarium knopkirri . C. knopkirri differs from C. welwitschii W.West & G.S. West 1897: 175 , pl. 367, fig. 2, regarding the position, number, size and shape of the granules, as well as having much larger cell dimensions. C. hieronymusii Schmidle 1898: 24 , pl. 1, fig. 19 (Pleurotaeniopsis stuhlmannii Hieronymus in Engler 1895: 20, no fig.; non Cosmarium stulilmannii Hieronymus in Engler 1895: 19, no fig.) also shows resemblances to the newly described species ( C. knopkirri ), but differs with respect to the much smaller cell dimensions, number and position of the granules situated in rings, and especially in the apical ring of granules/tubercles that forms a very distinctive crown. C. mirum Thomasson 1966: 23 ; pl. I, fig. 20; pl. IX, fig. 16–18, also shows similarities in morphology, but its cell wall is covered with short processes, tipped with short spines, arranged in 12 rows ( Thomasson 1966).

Ecology: —A freshwater desmid, rare in occurrence. Co-occurring taxa included the desmids Pleurotaenium multitaeniatum J.A. Rino , Closterium lagoense Nordst. , C. dianae Ehrb. ex Ralfs , Euastrum subcrassum F.E.Fritsch & M.F.Rich , Hyalotheca dissilens (Smith) Bréb. , Cosmarium laeve Rabenh. , C. regnesi Reinsch , and C. scabrum W.B.Turner.

The values of the physico-chemical variables measured at the wetland sampling location were as follows:Dissolved oxygen 1.28–1.75 mg /l, temperature 27.5–30.9˚C, electrical conductivity 15.37–28.87 mS/m, total dissolved solids 77–144 mg /l, salinity 0.07–0.14%, and pH 6.0–6.2 ( Environmental Impact Assessment 2014).

Figures

FIGURES 2–8. Light microscope images of the type material of Cosmarium knopkirri sp. nov. from the wetland system near Palma, Cabo Delgado Province, Mozambique. 2–5. Front view of vegetative cell with younger semicell, 6–7. Apical view, 8. Semicell. Scale bar = 20 μm.