Cosmarium redimitum Borge var. acroscrobiculatum G.J.P.Ramos, I.B.Oliveira & C.W.N.Moura, 2021

Ramos, Geraldo José Peixoto, Oliveira, Ivania Batista De & Moura, Carlos Wallace Do Nascimento, 2021, Taxonomic updates and a new variety of Cosmarium redimitum from South America, Phytotaxa 514 (1), pp. 77-84 : 79-83

Cosmarium redimitum Borge var. acroscrobiculatum G.J.P.Ramos, I.B.Oliveira & C.W.N.Moura , var. nov. ( Figs 1–2 )

Diagnosis —It differs from the nominate variety by having scrobicles between tubercles from the apical crown. Those tubercles are most flattened than those in the nominate variety, almost on the same level as hexagonal intumescences from the face of the cell wall, in a number of 14-15 generally. Tubercles of the apical margin are rounded or generally elongated. Zygospores are globose-ellipsoid. Cell dimensions: length 60–75 μm, breadth 35–45 μm, breadth of isthmus 10–15 μm. Zygospore dimension: 60 μm diameter.

Holotype — Material numbered ( HUEFS 244149 !) [pro parte] deposited at Herbarium of State University of Feira de Santana, Brazil. Population partially illustrated here in LM ( Fig. 1 ) and SEM ( Fig. 2 ).

Paratype —Material numbered ( HUEFS 155610 ) [pro parte] deposited at Herbarium of State University of Feira de Santana, Brazil .

Etymology: acro - = top, - scrobiculatum = scrobicles; referring to the scrobicles between apical tubercles. Material examined — BRAZIL. Bahia State, Piatã, Barragem da Fazenda Dragão, 13°05’48” S, 41°51’02”W, 14 July 2017, G.J.P.Ramos et al. s/n. (HUEFS 244149); Mata de São João, Imbassaí River, 12º26’24”S, 37º57’01.5”W, 11 January 2009, I.B.Oliveira & C.W.N. Moura . s/n. (HUEFS 155610), Olho d’água, 12º17’42,8”S, 37º51’25,2”W, 14 March 2009, I.B. Oliveira & C.W.N. Moura s/n. (HUEFS 155704); Entre Rios, Subaúma river, 12º 03’32.5”S, 37º44’45,4”W, 15 February 2009, I.B.Oliveira & C.W.N. Moura s/n. (HUEFS 155636), Lagoon-road, 12º12’58,6”S, 37º47’50,9”W, 26 July 2009, I.B.Oliveira & J. T. Farias s/n. (HUEFS 155756); Esplanada, Subaúma lagoon, 12º12’58,4”S, 37º47’51,6”W, 4 February 2009, I.B.Oliveira & C.W.N. Moura s/n. (HUEFS 155612), Lagoon -Km 96, 11º53’03,8”S, 37º38’58,6”W, 26 July 2009, I.B.Oliveira & J.T.Farias s/n. (HUEFS 155742); Conde, Barra do Itariri river, 11º57’45,3”S, 37º40’12,6”W, 28 February 2009, I.B.Oliveira & C.W.N. Moura s/n. (HUEFS 155648), Baixios, Lagoa Azul, 12º06’33,4”S, 37º42’05,3”W, 14 March 2009, I.B.Oliveira & C.W.N. Moura s/n. (HUEFS 155692), Sítio do Conde-Poças, 11º49’32,5”S, 37º33’08,6”W, 2 August 2009, I.B.Oliveira & C.W.N. Moura s/n. (HUEFS 155815).

Note —We have found a bunch of specimens of C. redimitum var. acroscrobiculatum in some areas of the Bahia State, especially at a dam (Fazenda Dragão dam) from Piatã, Chapada Diamantina region. In a sample from there (HUEFS 244149), an ellipsoid-subglobose zygospore of C. redimitum var. acroscrobiculatum was found, representing the first record of this structure to the species. Cells dividing were rather common in that sample too. Abiotic water parameters that were mensurated in the sample were water temperature (21ºC), pH (7.8), conductivity (10 μS. cm-1), dissolved oxygen (9.2 mg.L- 1).

We have noticed minor morphological variations of specimens from Bahia, such as apical margin which could be somewhat truncate (most common) or slightly rounded, and the tubercles from apical crown, which could be rounded or elongated (most common).

Among the South America records of C. redimitum , those considered representatives of C. redimitum var. acroscrobiculatum are: Couté & Tell (1981: 91, Pl. XV, figs. 3- 4) from Argentina, Duque et al. (2013, Appendix 1, Fig. C) from Colombia, Salazar & Guarrera (2000, Fig. 48) from Venezuela. Taxon illustrated by Förster (1964: Pl. 45, Fig. 8) from Conceição, Goyaz, Brazil (currently, Tocantins State), although it is not possible to see the scrobicles, it is rather similar to those found in Bahia, with apical crown flattened, almost like papillae.

Borge (1925) also reported the occurrence of C. redimitum in Brazil (Sepotuba River, State of Mato Grosso). However, he did not provide any figure neither information on cell wall, as he has not seen empty cells. Therefore, it was not possible to restudy this taxon to consider whether it is from the typical variety or var. acroscrobiculatum .

Current status of all records of Cosmarium redimitum and their distribution in South America have been updated as represented in Fig. 3 and Table 1.

Cosmarium pseudoredimitum Coesel & Van Geest (2017:340) is another interesting species, known also from the Tropical region ( Zambia, Africa) and rather similar to C. redimitum . However, C. pseudoredimitum differs from the latter by having no apical crown of tubercles, semicells are broadly elliptic in apical view, and the cell wall is covered with large pore fields that are arranged in hexagons, whereas C. redimitum has circular outline in apical view, and the cell wall is ornamented with punctations surrounding the intumescences. In addition, C. redimitum has one pyrenoid by chloroplast ( Grönblad 1945, Förster 1969), whereas C. pseudoredimitum has two pyrenoids ( Coesel & van Geest 2017).

Figures

FIGURE 1. Cosmarium redimitum var. acroscrobiculatum var. nov. (LM). A–D. Frontal view E.Apical view; arrowheads—scrobicles. F. Cell division G. Zygospore; arrowheads—elongated tubercles of the mother cell.

FIGURE 2. Cosmarium redimitum var. acroscrobiculatum var. nov. (SEM). A–B. Frontal view C. Cell division F. Cell wall details; white arrowheads—flattened tubercles; yellow arrowheads—scrobicles. E. Apical view.

FIGURE 3. Updated distribution of Cosmarium redimitum in SouthAmerica. 1—Borge 1899; 2—Thérézien 1985; 3—Oliveira 2000; 4— Coesel 1992; 5—Duque et al.2013; 6—Salazar & Guarrera 2000; 7—Couté &Tell 1981; 8—Borge 1925; 9—Grönblad 1945; 10—Förster 1964; 11—Förster 1969; 12—Thomasson 1971; 13—Sophia & Dias 1996; 14—Pereira 2011; 15—Bicudo et al. 2019; 16—Saturtino et al. 2020; * New records from Bahia.