Sirodotia aquiloamericana Necchi, N.L.Rossignolo & M.L.Vis, sp. nov.

(Fig. 3 F-J)

TYPE. — T.A. Dempster, 24.IV.2011 (holo-, BHO [BHO-0437]).

TYPE LOCALITY. — United States, Arizona, outlet canal of Montezuma; 34°38’57”N, 111°45’08”W.

ADDITIONAL SPECIMENS EXAMINED. — BHO A-0410, MEX 1.

ETYMOLOGY. — The species epithet indicates that the alga is known from North America.

DISTRIBUTION. — North America: Mexico and the United States (Arizona and Texas).

REPRESENTATIVE DNA SEQUENCES. — COI-5P (MW053469, MW053470, EU636739) and rbc L (JN408523, JF344716, AF126414).

Description

Plants dioecious; whorls 408-675 µm in diameter; primary fascicles 7-12 cells; proximal cells cylindrical or ellipsoidal; distal cells subspherical, ellipsoidal or obovoidal; secondary fascicles abundant, covering the entire internode; spermatangia spherical or obovoidal, 1-3, few or abundant on primary or secondary fascicles, 5-7(-8) µm in diameter; carpogonial branches composed of 1-3 disc- or barrel shaped cells, arising from periaxial or proximal cells, short, 11-14 µm long; carpogonia with sessile, elongate cylindrical (with wavy margins) or fusiform trichogynes, 29-42 µm in length, 6-7.5 µm in diameter; gonimoblast initial developing from the protuberant side of the carpogonium; gonimoblast filaments with erect branches of 2-5 cells; carposporangia obovoidal, 10-13 µm in length, 6-8 µm in diameter.

Remarks

This species has been reported as S. huillensis (Necchi et al. 1993; Vis & Sheath 1999; Lam et. al. 2012) from North America. It has been described as having spermatangia arranged in clusters. However, this arrangement was not confirmed in this species and we have observed only abundant spermantangia in some specimens. The true arrangement in clusters in Sirodotia was observed only in S. assamica . S. aquiloamericana specimens are genetically divergent from those of S. huillensis from Africa. Thus, the North American material represents a distinct species that is here described. This species is most closely comparable to S. delicatuliformis Necchi, N.L.Rossignolo & M.O.Paiano, sp. nov. based on the narrow carposporangia, 6-8.5 (-9.5) µm in diameter. However, S. aquiloamericana differs from S. delicatuliformis sp. nov. in having wider whorls (408-675 versus 169-491 µm in diameter) and geographical distribution (arid regions of North America versus southern North American and South America).