Cylindrospermopsis africana J.Komárek & H.Kling, 1991

Li, Xiao-Chuang, Huo, Shou-Liang, Cai, Fang-Fang, Yang, Yi-Ming, Xi, Bei-Dou & Li, Ren-Hui, 2017, The taxonomy and phylogeny of the genus Cylindrospermopsis (Cyanobacterium) evaluated by adding five new records from China, Phytotaxa 316 (3), pp. 224-238 : 229-230

Cylindrospermopsis africana J.Komárek & H.Kling (1991: 38, 33, fig. 10)

Strains:— CHAB 353, CHAB 355 and CHAB 359 from Lake Wenshan in Shenzhen City, Guangdong Province; CHAB 482 and CHAB 485 from Lake Nan in Wuhan City, Hubei Province; CHAB 1394 from Lake Chidong in Huanggang City, Hubei Province; CHAB 3411 from a pond in Qingdao City, Shandong Province

Habitat:— In lakes, reservoirs and ponds, planktonic.

Description:— Trichomes solitary, free floating, straight or rarely irregularly spirally coiled, without sheath, constricted at the cross-walls, uniformly wide along whole trichome length ( Fig. 1R–V ). Cells cylindrical, slightly attenuated towards the ends, 4.0–11.2–17.8 μm long, 1.5–4.4–5.3 μm wide (L:W ratio 1.2–4.3–7.9), apical cells cylindrical and rounded at the ends. Heterocytes cylindrical or slightly narrowed towards ends, widely rounded at the ends, 3.2–8.1–12.4 μm long, 1.7–5.1–7.6 μm wide (L:W ratio 1.0–2.8–4.6). Akinetes cylindrical to ellipsoidal, rounded at the ends, usually solitary, 5.4–14.6–24.3 μm long, 2.3–7.3–9.6 μm wide (L:W ratio 1.5–3.0–5.4).

Notes:— C. africana was characterized by its straight trichomes, apical cells cylindrical and rounded at the ends, and distinct constrictions at the cross-walls.

Morphology:— During the survey on many freshwater bodies in China, over 100 Cylindrospermopsis unialgal strains have been isolated and maintained at the HAB. Five new records, C. taverae , C. helicoidea , C. philippinensis , C. catemaco and C. africana were morphologically identified based on mainly the shape of filament ends, heterocytes and akinetes, and trichome coiling. Dimension of vegetative cells, heterocytes and akinetes for the upper five Cylindrospermopsis species was shown in Table S4. The majority of strains isolated belonged to C. raciborskii , whereas strains from other Cylindrospermopsis species were rarely found. Key to six Cylindrospermopsis species described in the study was shown in Fig. 2 .

Molecular phylogeny:— Inferred from 16S rRNA phylogeny ( Fig. 3 ), three Raphidiopsis subclades were formed, together with Cylindrospermopsis strains, grouped into a larger cluster that separated from clusters composing strains of other heterocytous cyanobacteria. Phylogenetic analysis based on four gene loci, 16S rRNA ( Fig. 4 ), ITS-L ( Fig. 5 ), cpcBA-IGS ( Fig. S1 ), rpoC1 ( Fig. S2 ), and multi-gene analysis (Fig. 7) indicated that strains of six Cylindrospermopsis species were intermixed, and not grouped into separate subclades.Some strains, such as C. ellipsoidea , C. philippinensis , C. catemaco and C. africana , were separated into more than two subclades, while C. raciborskii strains were scattered through the whole phylogenetic tree ( Figs. 4 –7, S1–S2). Furthermore, high 16S rRNA gene sequence (99.1%–100%) similarities were shared among strains of the six Cylindrospermopsis species ( Table 3). Similar results were observed in sequences similarities of ITS-L (97.7%–100%) ( Table 4), cpcBA-IGS (96.7%–100%) (Table S6) and rpoC1 (99.4%– 100%) (Table S7). Only one strain, C. catemaco CHAB 1390 , showed greater genetic differences when compared to other Cylindrospermopsis strains (five remaining C. catemaco strains contained), respectively with 87.9%–88.4%, 94.1%–94.6% and 94.7%–95.1% similarities for ITS-L, cpcBA-IGS and rpoC1.

Figures

FIGURE 1. General morphological aspects of five Cylindrospermopsis new records species from China. A–C. C. taverae CHAB 143. D–G. C. helicoidea CHAB 357. H–K. C. philippinensis CHAB 5180. L. C. philippinensis CHAB 5182. M. C. catemaco CHAB 148. N–O. C. catemaco CHAB 151. P. C. catemaco CHAB 155. Q. C. catemaco CHAB 220. R. C. africana CHAB 359. S. C. africana CHAB 485. T–V. C. africana CHAB 1394. Scale bars = 10 μm. Note: C. = Cylindrospermopsis.

FIGURE 2. Key to six Cylindrospermopsis species described in the study.

FIGURE 3. Maximum likelihood (ML) phylogenetic tree based on the 16S rRNA gene sequences from thirty-six strains of six Cylindrospermopsis species described in the study, together with sequences from other heterocytous cyanobacteria obtained from NCBI. Bootstrap values greater than 50% are given in front of the corresponding nodes for neighbor-joining (NJ) and ML analyses followed by Bayesian posterior probabilities (over 0.5 are illustrated).

FIGURE 4. ML phylogenetic tree based on the 16S rRNA gene sequences (1268 bp) from thirty-six strains of six Cylindrospermopsis species described in the study, with Anabaena variabilis ATCC 29413 as the outgroup.Bootstrap values greater than 50% are given in front of the corresponding nodes for NJ and ML analyses followed by Bayesian posterior probabilities (over 0.5 are illustrated).

FIGURE 5. ML phylogenetic tree based on the ITS-L sequences (510 bp) from thirty-six strains of six Cylindrospermopsis species described in the study, with Anabaena variabilis ATCC 29413 as the outgroup. Bootstrap values greater than 50% are given in front of the corresponding nodes for NJ and ML analyses followed by Bayesian posterior probabilities (over 0.5 are illustrated).