Achnanthidium lacuslustense, Jüttner & Hamilton & Wetzel & De & Vijver & King & Kelly & Williams & Ector, 2022

Jüttner, Ingrid, Hamilton, Paul B., Wetzel, Carlos E., De, Bart Van, Vijver, King, Lydia, Kelly, Martyn G., Williams, David M. & Ector, Luc, 2022, A study of the morphology and distribution of four Achnanthidium Kütz. species (Bacillariophyta), implications for ecological status assessment, and description of two new European species, Cryptogamie, Algologie 20 (10), pp. 147-176 : 158

Achnanthidium lacuslustense sp. nov.

( Figs 17 ; 18 )

HOLOTYPE. — Germany. Lustsee , 14.IV.2013, I. Jüttner (holo-, NMW [ NMW.C.2013.010.2013]; iso-, BM, BR, CANA).

TYPE LOCALITY. — Germany. Upper Bavaria, Osterseen area, Lustsee, 47°48’33.509”N, 11°17’36.959”E.

HABITAT. — Epiphytic and epipsammic in lake littoral.

ETYMOLOGY. — The species was named after the location where it was found, the Lustsee in Upper Bavaria, Germany.

REGISTRATION. — http://phycobank.org/103380

DESCRIPTION

LM ( Fig. 17 A-M)

Frustules with strongly concave RV and convex RL with recurved poles.Valves lanceolate,margins tapering gradually towards large capitate poles.Width of poles slightly less or as wide as the maximum width at valve centre. Valve dimensions (n = 14): length 15.5-29.0 µm, width at valve centre 3-4 µm.Central area on RV a moderately broad fascia.Raphe filiform, straight.Central pores slightly expanded, terminating at margin of central area.Central area on RL rectangular, bordered by 2 short striae on each side. Axial area narrow linear on both valves. Striae radiate throughout on both valves, 28-30 in 10 µm (RV), 30 in 10 µm (RL).

SEM ( Fig. 18 A-H)

Raphe located on raised sternum, central raphe endings slightly expanded, tear drop-shaped, terminal raphe fissures straight with tear drop-shaped ends, terminating at valve/ mantle junction. Internally, central raphe endings very slightly deflected to opposite sides, terminating on side of central nod - ule, terminal raphe endings form small helictoglossae. Striae straight on RV, composed of 3-4, rarely 2, areolae. Areolae round adjacent to axial area and at poles, others often slit-like. On RL striae straight, slightly curved at poles, composed of 3-4, rarely 2 or 5, areolae. Areolae mostly round adjacent to axial area, elsewhere often transapically elongate, internally occluded by individual hymenes. A row of transapically elongated areolae on mantle separated from areolae on valve face by a hyaline area.

Figures

FIG. 17. — Achnanthidium lacuslustense sp.nov.,specimens from Lustsee,Germany:A-L, LM views of valves;M, LM view of frustule in girdle view.Scale bar:10 µm.

FIG. 18. — Achnanthidium lacuslustense sp. nov., specimens from Lustsee, Germany: A, SEM external view of raphe valve; B, SEM internal view of raphe valve; C, D, SEM external views of frustules in girdle view; E, SEM external view of rapheless valve; F, SEM internal view of rapheless valve; G, SEM internal view of centre of rapheless valve; H, SEM internal view of pole of rapheless valve. Scale bars: A-F, 5 µm; G, H, 3 µm.