Achnanthidium lucectorii E.Morales & Manoylov, 2023

Morales, Eduardo A. & Manoylov, Kalina M., 2023, Achnanthidium lucectorii sp. nov. and A. enigmaticum sp. nov., novel diatoms (Bacillariophyta, Achnanthidiaceae) from Texas, U. S. A., Phytotaxa 592 (1), pp. 1-20 : 3-6

publication ID	https://doi.org/ 10.11646/phytotaxa.592.1.1
DOI	https://doi.org/10.5281/zenodo.7845227
persistent identifier	https://treatment.plazi.org/id/9A0E87F0-FF91-FFC7-FF2C-D6CCFBBCFC3F
treatment provided by	Plazi
scientific name	Achnanthidium lucectorii E.Morales & Manoylov
status	sp. nov.

Treatment

Achnanthidium lucectorii E.Morales & Manoylov sp. nov. Figs 1–36 View FIGURES 1–36 (LM), 37–42 (SEM)

Description:— Frustules apically sigmoidally arched (in an open V-shaped girdle view), producing a raphe valve with a concave valve center ( Figs 22, 23 View FIGURES 1–36 ). Valves elliptic with swollen central area and subcapitate apices ( Figs 1–21, View FIGURES 1–36 24–36), less noticeable in smaller valves. Length: 10.2–35.7 µm, width: 3.1–4.3 µm, stria density 26–28 (up to 30 toward apices) in 10 µm in RV, and 26–27 (up to 32 toward apices) in 10 µm in SV, 1–4 areolae per stria on both valves. Hymenes, girdle bands and plastids not determined.

RV with narrow, lanceolate, raised axial area (externally [ Figs 37–39 View FIGURES 37–42 ] and internally [ Fig. 40 View FIGURES 37–42 ]), tapering into a pointy end at valve apex, becoming enlarged in central area where it connects with the central stauros ( Figs 37–40 View FIGURES 37–42 ). Central stauros with bow-tie shaped fascia (rarely apically rhomboid in some larger valves) ( Figs 1–21 View FIGURES 1–36 ), with raised central nodule in external view ( Figs 37–39, 41 View FIGURES 37–42 ), flat in internal view ( Fig. 40 View FIGURES 37–42 ). Virgae wider than striae except at valve ends where they become slender and rod-shaped, straight or zig-zagged due to polygonal shape of areolae ( Figs 38, 39 View FIGURES 37–42 ). Virgae lower with respect to axial area and at same level as striae in internal and external views ( Figs 37–40 View FIGURES 37–42 ). Raphe uniformly filiform and straight, with proximal ends opposite to each other ( Figs 37–39 View FIGURES 37–42 ). Distal fissures straight and extending over striation regions at both poles ( Fig. 39 View FIGURES 37–42 , white arrows). Internally, proximal raphe ends with a small capitate terminus ( Fig. 40 View FIGURES 37–42 , white arrows) and distal ends terminating in low helictoglossae fused with a low thickening of valve apex ( Fig. 40 View FIGURES 37–42 , black arrow). Striae varying from convex toward valve central area (striae frequently lacking or being shorter on central stauros) becoming extremely convex and noticeably denser toward apices ( Figs 37–39, 41 View FIGURES 37–42 ). Areolae round or elliptic toward the central sternum, becoming transapically elongated toward valve face/mantle transition, and densely packed and polygonal at valve extremes ( Fig. 38 View FIGURES 37–42 , open arrows), usually with two large areolae on both sides of distal raphe end ( Figs 37, 39 View FIGURES 37–42 ). A single row of slit-like areolae present on valve mantle, stopping short of the very apex (unclearly seen in Fig. 40 View FIGURES 37–42 ). A clear area runs around edge of the face/mantle junction ( Figs 37–39 View FIGURES 37–42 ).

SV ( Figs 41, 42 View FIGURES 37–42 ) with wider, flat (only observed in internal view) lanceolate axial area, more or less broad at valve ends. Central nodule is only slightly raised internally. Virgae of same characteristics as in RV, but at same level as striae and axial area (only internal views available). Striae of same general characteristics as those of RV, except they are evenly spaced (some are short) at valve central area, they become less convex toward the valve apices, and single row of elongated striae on the valve mantle are continuous around valve apex. The clear area around edge of the face/mantle junction is less noticeable.

Type:— U.S.A. Texas, Uvalde County, Sabinal River , 29.491 N, 99.493 W, NAWQA, August 7 th, 1996 (holotype slide ANSP GC 102382 a = Fig. 10 View FIGURES 1–36 ) GoogleMaps

Etymology:— The species epithet honors our late colleague Luc Ector. Luc promoted a major advancement in the taxonomy of the genus Achnanthidium through a series of courses and workshops that were the foundation of the taxonomy used in the European Water Framework Directive. The special issue in Algological Studies (2011: 136/137), edited by Luc and the result of one of those workshops, presented critical analyses of type material and new species in Achnanthidium from around the world, a foundation for current studies in this genus.