Sirodotia amazonica Necchi, N.L.Rossignolo & M.O.Paiano, sp. nov.

(Fig. 3 A-E)

TYPE. — O. Necchi Jr., 27.IX.2010, (holo-, SJRP [SJRP 31924]).

TYPE LOCALITY. — Brazil, Mato Grosso, River Rosana, Route BR- 163, between Sinop and Sorriso; 11°57’26”S, 55°31’01”W.

ADDITIONAL SPECIMENS EXAMINED. — SJRP 32139, SJRP 32140, SJRP 32576, SJRP 32577, and SJRP 32578 (Appendix 1).

ETYMOLOGY. — The species epithet indicates that the alga occurs in the Amazonian region in Brazil.

DISTRIBUTION. — South America: Brazil (mid-western and northern Brazil).

REPRESENTATIVE DNA SEQUENCES. — COI-5P (KF010489, KF010490, MW053464), rbc L (KC951866, KC951867, MW053480) and LSU (BR14, BR15, MW053499).

Description

Plants monoecious or dioecious; whorls 249-491 µm in diameter; primary fascicles, 4-8 cells; proximal cells cylindrical or ellipsoidal; distal cells spherical, subspherical, obovoidal or ellipsoidal; secondary fascicles abundant, covering the entire internode; spermatangia spherical or obovoidal, 1-3 in a group, few or abundant on primary or secondary fascicles, 6-9 µm in diameter; carpogonial branches composed of 1-4 disc- or barrel shaped cells, arising from periaxial or proximal cells of primary fascicles, rarely on the secondary fascicles or cortical filaments, short, 8.5-25 µm in length; carpogonia with sessile, elongate cylindrical (with wave margins) or fusiform trichogynes, 35-58(-62) µm in length, 8-14(-15) µm in diameter; gonimoblast initial developing from the protuberant side of the carpogonium; gonimoblast filaments prostrate with erect branches of 1-4 cells; carposporangia obovoidal or subspherical, 10-18(-19) µm in length, (7-)8-13 µm in diameter.

Remarks

The phylogeography study by Paiano & Necchi (2013) showed the existence of two cryptic species in Brazil. No morphological characteristics were observed to distinguish them, but a high interspecific divergence (2.3-3.0% for rbc L and 4.4-6.2% COI-5P). We conclude they are distinct. Sirodotia amazonica Necchi, N.L.Rossignolo & M.O.Paiano, sp. nov. is very similar to two species found in Brazil, S. delicatuliformis Necchi, N.L.Rossignolo & M.O.Paiano, sp. nov. and S. cryptica Necchi, N.L.Rossignolo & M.O.Paiano, sp. nov., overlapping for most morphometric and morphological characters. However, S. amazonica Necchi, N.L.Rossignolo & M.O.Paiano, sp. nov. is distinguishable from S. delicatuliformis sp. nov. based on the wider carposporangia (8-13 versus 6-8.5(-9.5) µm in diameter).