Xanthidium mamillosum var. mediolaeve (Grönblad) Couté & Tell (1981: 197)

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, Phytotaxa 536 (3), pp. 228-242 : 236

Xanthidium mamillosum var. mediolaeve (Grönblad) Couté & Tell (1981: 197) ( Figs 3 , 25–30 )

Basionym: Xanthidium antilopaeum var. mamillosum f. mediolaeve Grönblad (1945: 22 , Pl. 7, fig.149)

Cell dimensions:—length without spines 65–66 μm, with spines 110–120 μm, width without spines 58.6–60 μm, with spines 131–140 μm, thickness 19 µm, isthmus 26 μm, spines 31–40 μm long. Zygospore 100 µm in diameter (including spines), globular in shape and provided with long spines.

Material examined:— BRAZIL. Bahia: Andaraí, Marimbus do Baiano, Lagoa do Baiano. Samples : HUEFS 253745 .

Habitat:—Taxon was rare in Marimbus do Baiano, found associated only to U. foliosa ; EC 0.04 mS. cm-1; DO 6.6; TDS 0.03; pH 7.0; T 31.4 ° C; WT 36 cm;

Taxonomic notes:— This taxon was originally proposed by Grönblad (1945: 22) from specimens collected in Santarém, Pará State, Amazon Basin, as X. antilopaeum var. mamillosum f. mediolaeve . Later, Couté & Tell (1981: 197) raised that form to a varietal level: X. mamillosum var. mediolaeve .

Morphologically, var. mediolaeve differs from the nominate variety by not having a spine in the midregion of semicells, and smallest cell dimensions ( Prescott et al. 1982). It somewhat resembles X. mamillosum var. sexaculeatum (Grönblad) Kurt Förster (1969: 62) , but this latter variety differs by having basal angles of semicells decorated by the single spine, and a ring of pores around a central one, visible in the apical view ( Förster 1969).

Thomasson (1971), studying material from X. mamillosum collected in Maica Lake (Santarém, Pará) and Rio Preto da Eva Lake (Rio Preto da Eva, Amazonas), Amazon Basin, observed that taxa have a typical mamillate base, and some specimens have 1–2 frontal spines. The author considered that all forma under X. mamillosum described by Grönblad (1945), besides X. canadense var. borgei Kurt Förster (1981: 247) , are considered to belong within the morphological range of the species. Until molecular studies to be conducted to verify the delimitation of the varieties of X. mamillosum , we consider more appropriate to maintain var. mediolaeve as a distinct taxon.

The zygospore of X. mammilosum var. mediolaeve analyzed resembles to format observed in X. trilobum , except by absence apical furcated spines.

Details of the scanning electron microscopy ( SEM) of the var. mediolaeve were presented by Couté & Tell (1981: 207, Pl. 3, fig, 7–8), showing smooth facial semicells, punctuated cell walls, and spines with a characteristic mamillate base, similar to the specimens analyzed under photonic microscopy in the present study ( Figs. 25, 28 ).

In Brazil, aside from the type locality, the taxon under discussion has also been reported in Bahia ( Oliveira et al. 2011), Mato Grosso ( De-Lamonica-Freire 1992), Paraná ( Paula et al. 2014), and São Paulo ( Bicudo et al. 2018), all reported as X. antilopaeum var. mamillosum f. mediolaeve .

Figures

FIGURES 1–6. Line drawings. 1. Bourrelyodesmus comperei sp. nov. 2. Xanthidium concinnum var. longispinum var. nov. 3. Xanthidium mamillosum var. mediolaeve. 4. Xanthidium nordstedtii. 5. Xanthidium regulare var. asteptum. 6. Xanthidium trilobum.

FIGURES 8–30. Bourrelyodesmus comperei sp. nov. (8–16): frontal view (8, 11, 13–16), lateral view (9), apical view (10, 12), morphological variation (13–16). Xanthidium concinnum var. longispinum var. nov. (17–24): frontal view (17, 20, 23–24), lateral view (18, 21), apical view (19, 22), morphological variation (23–24). Xanthidium mamillosum var. mediolaeve (25–30): frontal view (25, 28), empty cell after reproduction (26), zygospore (27), lateral view (29), apical view (30). Scale Bar: 10 μm, except Fig. 25, 28–30 (40 μm), Fig. 26–27 (50 μm, horizontal bar).