Four novel species from the genus Hantzschia Grunow (Bacillariophyta: Bacillariaceae) from rural areas of Southeast Asia Author Mateusz, Rybak 0000-0001-8998-9537 University of Rzeszów, Department of Agroecology and Forest Utilization, Ćwiklińskiej 1 a, 35 - 601, Rzeszów, Poland & matrybak 91 @ gmail. com; https: // orcid. org / 0000 - 0001 - 8998 - 9537 matrybak91@gmail.com Author Natalia, Kochman-Kędziora 0000-0003-1006-1715 University of Rzeszów, Department of Ecology and Environmental Protection, Zelwerowicza 4, 35 - 601, Rzeszów, Poland & nkochman @ ur. edu. pl; https: // orcid. org / 0000 - 0003 - 1006 - 1715 nkochman@ur.edu.pl Author Muzaky, Luthfi Oktiyas University of Brawijaya, Department of Marine Science, Jl. Veteran Malang, East Java Indonesia & University of Szczecin, Institute of Marine and Environmental Sciences, Mickiewicza 16 A, 70 - 383 Szczecin, Poland text Phytotaxa 2022 2022-10-07 567 3 207 221 http://dx.doi.org/10.11646/phytotaxa.567.3.1 journal article 10.11646/phytotaxa.567.3.1 52e28e8a-d989-48c3-8a9f-189556756f59 1179-3163 7156659 Hantzschia minima M.Rybak sp. nov. ( Figs 1–15 , 46–52 ) LM observations ( Figs 1–15 ) : — Valves dorsiventral with straight or almost straight dorsal margin. Ventral margin weakly concave in middle, becoming slightly convex near apices.Apices abruptly protracted, small and clearly capitate, slightly deflected towards dorsal side. Valve dimensions (n=20): length 17.5–38.5 μm, width 3.5–4.5 μm. FIGURES 1–27. LM microphotographs of Hantzschia minima sp. nov. (1–15) and H. tokarczukiana sp. nov. (16–27) in size diminution series, scale bar = 10 µm. FIGURES 28–45. LM microphotographs of Hantzschia malaysiana sp. nov. (28–37) and H. beksinskii sp. nov. (38–45) in size diminution series, scale bar = 10 µm. FIGURES 46–52. SEM microphotographs of Hantzschia minima sp. nov. , scale bar = 10 µm (46–48), 2 µm (49–52). Fibulae 5–8 in 10 μm, unequally spaced, middle two fibulae clearly more distant. Striae equidistant, weakly radiate in middle, 22–25 in 10 μm. In some specimens, striae in valve middle slightly more spaced than others ( Figs 10, 14 ). Areolae not discernible. SEM observations ( Figs 46–52 ) : — Valves on the ventral side bordered by a clearly thickened keel ( Figs 46, 47 ). Striae composed of round areolae occluded by individual hymens. 49–60 in 10 µm ( Figs 47, 51 ). External central raphe endings slightly deflected, very close together ( Fig. 51 ). Distal raphe endings clearly hooked ( Fig. 49 ). Internally central raphe endings deflected to opposite directions ( Fig. 52 ). Striae forming narrow, deep, parallel grooves ( Figs 48, 52 ). Each fibulae connected to 1–4 transapically costae ( Fig. 48 ). Type :— Indonesia , Kairatu , West Seram , Molouki , 3°21’46.5”S 128°22’19.48”E , coll. date. 28 June 2018 , holoslide no. SZCZ28484 ! and the unmounted material with the same number at the Szczecin Diatom Collection ( University of Szczecin , Poland ), iso - slide no. 2018/445 and the unmounted material with the same number at the University of Rzeszów , Poland . The type population is illustrated on Figs 1–15 and 46–52 . Etymology:— The species epithet “ minima ” refers to its small size. Hantzschia minima sp. nov. is one of the smallest species in the genus. Distribution:— So far, the species was only observed from the type locality. Associated diatom flora:— The most abundant taxa in assemblage were: Hantzschia minima sp. nov. , Humidophila contenta (Grunow) Lowe, Kociolek, Johansen, Van de Vijver, Lange-Bertalot & Kopalová (2014: 357) , H. lacunosa (Moser, Lange-Bertalot & Metzeltin) Lowe et al. (2014: 358) , Luticola intermedia (Hustedt) Levkov, Metzeltin & Pavlov (2013: 138) , L. sublagerheimii Levkov, Metzeltin & Pavlov (2013: 229) and Pinnularia borealis Ehrenberg (1843: 420) . The share of Hantzschia tokarczukiana sp. nov. did not exceed 5% in the assemblages.