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 Author Jüttner, Ingrid Amgueddfa Cymru - Museum Wales, Department of Natural Sciences, Cathays Park, Cardiff, CF 10 3 NP (United Kingdom) ingrid. juettner @ museumwales. ac. uk (corresponding author) Author Hamilton, Paul B. Canadian Museum of Nature, Research Division, Ottawa, ON, K 1 P 6 P 4 (Canada) phamilton @ nature. ca phamilton@nature.ca Author Wetzel, Carlos E. Luxembourg Institute of Science and Technology (LIST), Environmental Research and Innovation Department (ERIN), Observatory for Climate, Environment and Biodiversity (OCEB), 41 rue du Brill, L- 4422 Belvaux (Luxembourg) carlos. wetzel @ list. lu wetzel@list.lu Author De, Bart Van Botanic Garden Meise, Research Department, Nieuwelaan 38, 1860 Meise and University of Antwerp, Department of Biology - Universiteitsplein 1, 2610 Wilrijk bart. vandevijver @ plantentuinmeise Author Vijver Belgium) ECOSPHERE, (Belgium). be Author King, Lydia Limnologie-Phykologie-Diatomologie, Basler Landstr. 54, 79111 Freiburg (Germany) brachysira @ live. com brachysira@live.com Author Kelly, Martyn G. Bowburn Consultancy, 11 Monteigne Drive, Bowburn, Durham, DH 6 5 QB (United Kingdom) and School of Geography, University of Nottingham, Nottingham, NG 7 2 RD (United Kingdom) mgkelly @ bowburn-consultancy. co. uk Author Williams, David M. The Natural History Museum, Department of Life Sciences, London, SW 7 5 BD (United Kingdom) d. m. williams @ nhm. ac. uk williams@nhm.ac.uk Author Ector, Luc Luxembourg Institute of Science and Technology (LIST), Environmental Research and Innovation Department (ERIN), Observatory for Climate, Environment and Biodiversity (OCEB), 41 rue du Brill, L- 4422 Belvaux (Luxembourg) In memory of our friend and colleague Luc Ector (1962 - 2022) text Cryptogamie, Bryologie 2022 2022-10-04 20 10 147 176 journal article 10.5252/cryptogamie-algologie2022v43a10 cfd2fae7-72ba-4fef-9a8e-64d1203a7793 1776-0992 7819378 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.