taxonID	type	description	language	source
B2232643595A0574FF402B21FE1AC0AC.taxon	description	Isotype material: — TNS-AL- 58999 m Synonym: Actinocyclus aquae-dulcis Idei in Idei et al. Plos one 7: e 41890: 2. 2012. nom. nud. Type locality: — Lake Akan (43 ° 26 ’ 25.95 ” N, 144 ° 05 ’ 07.05 ” E, Akan-cho, Kushiro-shi, Hokkaido, Japan) (Figs. 1, 2). Description: — Valves circular, 31 – 71 µm in diameter, with concentric undulations (Figs. 4 – 16, 19 – 21). The center of these concentric undulations sometimes deviates slightly from the center of the frustule. Valve face with radially arranged vaguely fasciculate areolae (8 – 10 / 10 µm in a radial areola) (Figs. 16 – 21, Table 1, 2). Shallow mantle, 2 – 5 µm in height, with fine areolae (7 – 9 / 10 µm in an areolar row) (Figs. 6, 16, 19 – 21, Table 1, 2). Areolae with an internal narrow passage, a loculus, and an external cribrum (Figs. 22 – 24). Loculate areolae on the valve face (Figs. 22 – 24). Valve wall without a bullulate structure. Rimoportulae born from valve face / mantle junction. Rimoportula slightly long, about 1 – 2 μm long. Rimoportula internally with a long, wide, and bent (horseshoe-shaped or slightly horseshoe-shaped), ambiguous labium and fan-shaped tube, externally with an elliptical opening on the mantle (Figs. 7 – 15, 17, 18, 25 – 31, Table 1). A single pseudonodulus at the valve face / mantle junction (Figs. 8, 10, 11, 22). The rimoportula of this species appears fan-shaped in LM and SEM observations when observed in valve view; in contrast, when observed in girdle view, it appears horseshoe-shaped under both LM and SEM. The microstructure observed in this study is consistent with that reported by Idei et al. (2012). The number of rimoportulae relative to valve diameter was almost the same in both samples (Lake Akan and Yoneshiro River mouth, Fig. 36); in other words, the number of rimoportulae decreases as the valve diameter decreases. All Japanese Actinocyclus strains in this study and Idei et al. (2012) isolated from Lake Akan, Lake Ogawara, and the Yoneshiro River, fell within a single clade with high bootstrap values (100 for NJ and 100 for ML) (Fig. 37). Thus the rbc L extraction results showed that the diatoms from Lake Akan and the Yoneshiro River mouth sample in this study were the same as those reported by Idei et al. (2012) (Fig. 37). In addition, it was not only confirmed that A. aquae-dulcis and A. normanii (in Lake Kasumigaura) are different species, but also that both are completely different from A. octonarius and A. subtilis. In the culture experiments, Actinocyclus aquae-dulcis from Lake Akan and from the Yoneshiro River mouth were observed to proliferate in salinities of 0 % – 25 ‰ (Table 3). Samples from Lake Akan (n = 20) (Figs. 4 – 31, Table 1) Valve diameter: 31 – 71 μm Areolae density: 7 – 9 / 10 μm Striae density: 8 – 10 / 10 μm Number of rimoportulae: 4 – 8, horseshoe-shaped, somewhat horseshoe-shaped Habitat and sediment type: attached to sand Salinity tolerance: 0 % – 25 % Samples from the Yoneshiro River mouth (n = 20) (Figs. 32 – 35) Valve diameter 33 – 62 μm Areolae density: 7 – 10 / 10 μm Striae density: 8 – 10 / 10 μm Number of rimoportulae: 4 – 8, horseshoe-shaped, somewhat horseshoe-shaped Habitat and sediment type: attached to sand Salinity tolerance: 0 % – 25 %	en	Chiba, Takashi, Osada, Ryosuke, Tuji, Akihiro, Idei, Masahiko (2025): Actinocyclus aquae-dulcis sp. nov. (Coscinodiscophyceae, Coscinodiscales, Hemidiscaeae), a new centric diatom from Lake Akan and northern coasts of Japan. Phytotaxa 687 (1): 65-83, DOI: 10.11646/phytotaxa.687.1.5, URL: https://doi.org/10.11646/phytotaxa.687.1.5
