Xanthidium concinnum var. longispinum M. A. Santos & C. W. N. Moura 2022, var. nov.
Creators: name: Santos, Maria Aparecida Dos
name: Ramos, Geraldo José Peixoto
name: Moura, Carlos Wallace Do Nascimento
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Charophyta
Conjugatophyceae
Zygnematales
Desmidiaceae
Xanthidium
Xanthidium concinnum
Xanthidium concinnum var. longispinum m.a.santos &amp; c.w.n.moura

description: Xanthidium concinnum var. longispinum M.A.Santos & C.W.N.Moura var. nov. (Figs 2, 17–24)   
 Diagnosis:—It differs from the nominate variety by having a long spine in each lateral margin, a pair of minute spines on the apical margin, and the face of the semicells has a central protrusion, ornamented with a spine with an inflated base. Cell dimensions: length without spines 11–13 μm, with spines 12–16 μm, width without spines 9–14.6 μm, with spines18–23 μm, thickness 8–9 µm, isthmus 3–4 μm, lateral spines 3.5–5.3 μm long.   
 Holotype:—Material numbered (HUEFS 253751!) [pro parte], deposited at Herbarium of State University of Feira de Santana. Population partially illustrated here (Figs. 2, 17–24).   
 Paratypes:—Material numbered (HUEFS 253744, HUEFS 253747) [pro parte], deposited at Herbarium of State University of Feira de Santana.   
 Type locality:— BRAZIL. Bahia: Andaraí, Marimbus do Baiano, Lagoa do Baiano, Lat. 12°45’33.2” S, Long. 41°18’29.1” W, 18 February 2018, M. A . Santos, J. T. X. Neto & F. M. Costa s/n (HUEFS 253751).   
 Habitat:—The new species was rarely found in the study area, occurring generally associated to periphyton of Cabomba caroliniana and Utricularia foliosa; EC 0.01 mS. cm-1 (±0.01); DO 6.4 (±0.7); TDS 0.02 (±0.02); pH 6.9 (±0.4); T 32° C (±0.5); WT 63 cm (±20.7).   
 Etymology:—The varietal epithet refers to the long spines present in the lateral margins of semicells.   
 Differential diagnosis:—Morphologically, the newly described variety resembles Xanthidium concinnum var. boldtianum West (1892: 167, as ‘ boldtiana ’) and Xanthidium concinnum var. scottii C.E.M.Bicudo in Prescott et al. (1982: 62). However, the former differs by having no short apical spines on each apical angle and central obtuse protrusion on the face of semicells, whereas the latter differs by having downward-projected spines at the lateral margins and the mid-region of the semicells.   
 Xanthidium concinnum var. longispinum should be compared to X. concinnum var. guyanense Thérézien (1985: 121), an endemic variety from French Guiana, which differs mostly by lacking the crown of small spines surrounding the lateral spine.   
We also observed variation in spines dimensions in the apical angles, from longer (2.5–3 μm long) to shorter (0.3–1 μm long), which is difficult to view. The spine on the lateral margin of the semicells can be slightly or widely converging, and sometimes measuring approximately 1/3 of the width of the cell.  
 In addition to Bahia, the var. longispinum has been registered in the State of Mato Grosso do Sul by Paula et al. (2014: 428, figs. 50, 51), but as a misapplied name X. concinum W. Archer (1883: 285), based on specimens collected from the Upper Paraná River floodplain.
description: Published as part of Santos, Maria Aparecida Dos, Ramos, Geraldo José Peixoto & Moura, Carlos Wallace Do Nascimento, 2022, Taxonomic notes on genera Bourrellyodesmus and Xanthidium (Zygnematophyceae) from Chapada Diamantina, Bahia, Brazil, pp. 228-242 in Phytotaxa 536 (3) on pages 231-236, DOI: 10.11646/phytotaxa.536.3.3, http://zenodo.org/record/6331876