Spirotaenia filiformis G.J.P.Ramos, C.E.M.Bicudo & C.W.N.Moura, 2017

Ramos, Geraldo José Peixoto, Bicudo, Carlos Eduardo De Mattos & Moura, Carlos Wallace Do Nascimento, 2017, Taxonomic notes on Spirotaenia (Mesotaeniaceae, Zygnematophyceae) from a Brazilian phytotelm habitat: new species and new records, Phytotaxa 309 (3), pp. 265-270 : 268

Spirotaenia filiformis G.J.P.Ramos, C.E.M.Bicudo & C.W.N.Moura , sp. nov. ( Figs. 19–24 ).

Cells 17–31 times longer than broad, elongate-cylindrical, narrowed toward the poles, poles rounded. Cells straight or slightly curved. Chloroplast a parietal ribbon making 3.5–8.5 turns, pyrenoids in series, one per turn. Conjugation not observed. Cell dimensions: length 26–94 μm, breadth 1.5–3 μm.

Type material: — BRAZIL. Bahia: Santa Teresinha, Serra da Jiboia, 12°51’06.8”S, 39°28’35.5”W, 18-VII-2015, G. J. P. Ramos, C. W. N. Moura & D.D. S. Reis s.n (Holotype: HUEFS 155348!).

Habitat:— bromeliad tanks ( Alcantarea nahoumii ); water temperature 22–27ºC. pH 5.3–6.1. electric conductivity 0.01–0.12 mS. cm-1. total dissolved solids 0.01–0.06 ppt. dissolved oxygen 6.9–7.3 mg.L- 1.

Etymology:— The epithet derives from filiform (thread-like).

Differential diagnosis:— Spirotaenia filiformis differs from all other species in the genus in its narrower cells (1.5–3 μm), 17–31 times longer than broad, elongate-cylindrical, rounded poles, the parietal chloroplast making 3.5– 8.5 turns. The newly described Spirotaenia species resembles S. turfosa West & G.S. West (1898: 331) , however, the latter is different by having a chloroplast broader with 1.5–2 turns, and wider cells (7.5–8.5 μm) ( Prescott et al. 1972).

The new species is very different when compared to S. condensata , which was so far the only Spirotaenia species ever reported from Brazil. Spirotaenia condensata differs from S. filiformis by having cells 5–12 times longer than broad and broadly rounded poles ( Prescott et al. 1972). Oliveira et al. (2013) reported S. condensata from Conde’s county, Bahia, and recently, we found it in a temporary lagoon at Parque das Dunas, Salvador ( Fig. 25 ).

A population of about 100 individuals was analyzed. Some morphological variation was observed in the newly described species such as the presence of about straight cells (more common), and sometimes presenting curved cells. Slightly sigmoid cells or with irregular curvature also were observed, but both were less common in the samples. In the bromeliad tanks Spirotaenia filiformis was found associated with cyanobacteria ( Chroococcus sp , Pseudanabaena sp. , Leptolyngbya sp. ) and other desmids such as Netrium digitus (Brébisson ex Ralfs) Itzigsohn & Rothe in Rabenhorst (1856: 508) and Closterium sp.

Spirotaenia species are predominantly found in acidic waters, the specimens mingled with other desmids ( Prescott et al. 1972, Brook et al. 2011). Due to some probably optimal conditions such as acidic water and low electric conductivity, bromeliad tanks are quite favorable for the development of Spirotaenia species. In addition, the bromeliads inhabiting the top of the Monte da Pioneira, north of Serra da Jiboia, are continuously exposed to high insolation, which may also play an important condition for the growth of desmids in the phytotelm habitat ( Sophia et al. 2004). In the same bromeliad where the three species were found, gelatinous masses were observed mainly composed of cyanobacteria, coccoid green algae and other desmids.

From this study, the knowledge on genus Spirotaenia in Brazil has been expanded to four species currently confirmed: Spirotaenia closteridia , S. condensata , S. endospira , and S. filiformis . Finally, the find of those Spirotaenia species support the notion that bromeliad tanks may be an interesting habitat for rare desmids or even new species ( Ramos et al. 2017), inviting further examination of that biotope.

Figures

FIGURES 3–25. Spirotenia species occurring in Brazil. 3–10. Spirotaenia closteridia. 11–18. Spirotaenia endospira 19–24. Spirotaenia filiformis sp. nov. 25. Spirotaenia condensata. Scale Bars: 10 μm.