taxonID	type	description	language	source
EE038124FFC0FE5FF482F093FE14FB75.taxon	materials_examined	Type: — RUSSIA. Ivankovskoe Reservoir (Volga Reservoirs Series), Russia, September, 1972, leg. S. Genkal, slide no. C 10 (holotypus illustrated in Fig. 13, in collection S. Genkal, I. D. Papanin Institute for the Biology of Inland Waters of the Russian Academy of Sciences (IBIW RAS ))	en	Genkal, Sergei, Kulikovskiy, Maxim (2012): Cyclotella horstii sp. nov. (Bacillariophyta) from Ivankovskoe reservoir (Volga reservoirs, Russia). Phytotaxa 59 (1): 55-63, DOI: 10.11646/phytotaxa.59.1.3, URL: http://biotaxa.org/Phytotaxa/article/view/phytotaxa.59.1.3
EE038124FFC0FE5FF482F093FE14FB75.taxon	distribution	Distribution: — From type locality only.	en	Genkal, Sergei, Kulikovskiy, Maxim (2012): Cyclotella horstii sp. nov. (Bacillariophyta) from Ivankovskoe reservoir (Volga reservoirs, Russia). Phytotaxa 59 (1): 55-63, DOI: 10.11646/phytotaxa.59.1.3, URL: http://biotaxa.org/Phytotaxa/article/view/phytotaxa.59.1.3
EE038124FFC0FE5FF482F093FE14FB75.taxon	etymology	Etymology: — Named after and dedicated to our colleague and friend Professor Horst Lange-Bertalot. Observations: — Cyclotella horstii can be usefully compared to С. kuetzingiana Thwaites (1848: 169), C. kuetzingiana var. planetophora and C. ocellata. Comparison with С. kuetzingiana reveals some similarities but С. kuetzingiana has valve depressions in short radial rows and often has papillae and marginal fultoportulae situated on recessed costae. The known diameter of initial valves is 25 – 27 µm (Houk et al. 2010: Tab. 189, fig. 6; Tab. 190, fig. 6). Relevant data for the valve diameter of C. kuetzingiana var. planetophora is absent from many published accounts (e. g. Cleve-Euler 1951, Hustedt in Huber-Pestalozzi 1942, Kozirenko et al. 1992) but for the original illustrations, Fricke presented images of valves with diameter ranges of 13.3 – 16.6 µm (in A. Schmidt 1900: Taf. 222, figs 9 – 12), while other accounts, derived from specimens in the Hustedt collection (BRM), illustrate valves with diameters ranges 6 – 16.6 µm (Krammer & Lange-Bertalot 1991, Taf. 51, figs 2 – 4, Houk et al. 2010, Tab. 198, figs 1 – 13). Hustedt illustrated an account of C. kuetzingiana var. planetophora with images of valves c. 20 µm in diameter (Hustedt in Huber-Pestalozzi 1942: Abb. 491). In contrast, the diameter of the vegetative valves of Cyclotella horstii has a range of 18 — 47 µm. The valve diameter of C. ocellata is 3 – 27 µm (Zabelina 1951, Genkal & Kuzmin 1979, Klee & Steinberg 1987, Krammer & Lange-Betalot 1991, Schmidt 1993, Kiss et al. 1996, 1999, Hegewald & Hindakova 1997, Acs & Padisak 2001, Håkansson 2002, Houk et al. 2010); only a population found in Lake Khubsugul, Mongolia, was recorded with valve diameters of 43 – 44 µm (Edlund et al. 2003; Genkal & Popovskaya 2008). Both С. kuetzingiana and C. ocellata have marginal fultoportulae on recessed costae and papillia outside; C. ocellata has 3 (rarely 4 to 7) depressions (Wunsam et al. 1995, Kiss et al. 1996, 1999, Genkal & Popovskaya 2008, Houk et al. 2010). Many (4 – 7) of the large depressions in Cyclotella horstii are situated along the periphery of the central part of the valve, sometimes with small depressions irregularly situated on the valve face. A few rows of granules are found along the marginal edge. Initial valve diameter of C. ocellata has a size range of 10 – 28.8 µm (Genkal & Zagorenko 1987, Schmidt 1993, Kiss et al. 1996, Hegewald & Hindakova 1997, Rojo et al. 1999), only in Lake Khubsugul were initial valves found measuring 43 – 48.5 µm in diameter (Edlund et al. 2003, Genkal & Popovskaya 2008). Initial valves of Cyclotella horstii are 51 – 60 µm diameter, 14 striae in 10 µm, and central fultoportulae are absent. Moreover, the maximal size of the lacunas in Cyclotella horstii is between 1 – 2.2 µm; in C. ocellata it is 0.7 – 1.0 µm (Klee & Steinberg 1987, Wunsam et al. 1995, Kiss et al. 1996, 1999, Håkansson 2002, Houk et al. 2010). Further features of Cyclotella horstii, such as the number of striae in 10 µm, the number of central fultoportulae and satellite pores, the arrangement of marginal fultoportulae with number of satellite pores, the number of rimoportulae and its arrangement in comparison to those in Cyclotella kuetzingiana and C. ocellata have been tabulated (Table 1).	en	Genkal, Sergei, Kulikovskiy, Maxim (2012): Cyclotella horstii sp. nov. (Bacillariophyta) from Ivankovskoe reservoir (Volga reservoirs, Russia). Phytotaxa 59 (1): 55-63, DOI: 10.11646/phytotaxa.59.1.3, URL: http://biotaxa.org/Phytotaxa/article/view/phytotaxa.59.1.3
