Epipyxis fenheensis J. Hao, J. Feng, S. Xie, 2025

Hao, Jun-Xue, An, Ya-Lu, Nan, Fang-Ru, Lv, Jun-Ping, Liu, Qi, Liu, Xu-Dong, Xie, Shu-Lian & Feng, Jia, 2025, Epipyxis fenheensis sp. nov., a new species of the genus Epipyxis (Chrysophyceae), PhytoKeys 260, pp. 115-138 : 115-138

Epipyxis fenheensis J. Hao, J. Feng, S. Xie sp. nov.

Figs 2 , 3 , 4

Type.

China • Shanxi Province, Taiyuan City, the Fenhe River ; 37°50.12'N, 112°32.13'E; 9 Oct. 2023; Yalu An and Junxue Hao leg.; phytoplankton; Holotype: SXU -SX 231009 ; GenBank: PQ 364874 , PQ 364873 , PQ 368406 and PQ 374158 .

Description.

Cells are small, loricate monads with two heterokont flagella, and encased within a lorica. The lorica is tubular, measuring 28.3–43.2 µm in length and 4.78–10.63 µm in width, with subparallel lateral margins. The upper opening of the lorica exhibits a slight expansion or remains parallel. The posterior end of the lorica is slightly constricted and attached to a long thick root, the same length as lorica. The lorica surface is smooth, adorned with oval or elliptical scales, arranged in an obliquely parallel, imbricate pattern. The protoplast is spindle-shaped, with dimensions ranging from 7.27–26.7 μm long and 3.6–10.56 μm wide. It possesses two unequal flagella and a red stigma. The longer flagellum matches the length of the protoplast, whereas the shorter flagellum is approximately one-third of its length. The posterior end of the protoplast is acutely pointed, tapering at the base into a delicate stalk, which does not form a stipe. The stalk measures 7.07–12 μm in length, slightly shorter than the protoplast. Cells are epiphytic and tend to form clumpy colonies. Younger individuals are typically attached to the inner surface of the maternal lorica.

Etymology.

The species epithet refers to the type locality (the Fenhe River, Taiyuan City, Shanxi Province, China).

Authentic strain.

SXU -SX 231009 . Deposited in Herbarium of Shanxi University ( SXU), Shanxi University, Taiyuan, Shanxi Province, China.

Figures

Figure 2. Morphological structures of Epipyxis fenheensis sp. nov. observed by light microscope (LM) A. Morphology of colony; B, C. Scattered protoplasts and loricae; D. Protoplast with a red stigma, as indicated by arrows; E. Protoplast with two red stigma, as indicated by an arrow; F. Protoplast spindle, the posterior end of the protoplast is obviously pointed, tapering at the base to a delicate stalk, as indicated by an arrow; G. Long, tube-like lorica, the junction of loricae is indicated with an arrow; H. Two unequal flagella as indicated by an arrow; I. Reproducing cell; J. The posterior end of lorica with a long thick root, as indicated by an arrow. Scale bars: 50 μm (A); 20 μm (B, C); 10 μm (D – J).

Figure 3. Light micrographs of Epipyxis fenheensis sp. nov. after staining A. Cell colony; B – D, F. Loricae with scales; E. Falling oval and elliptical scales; G. Cell colony; H. Loricae with scales arranged diagonally and parallel; I. Smooth lorica surfaces. Scale bars: 20 µm (A – C); 10 µm (G – I); 5 µm (D – F).

Figure 4. Life history of Epipyxis fenheensis sp. nov. A. A single cell; B. Single cell division; C. Division of a single cell into two cells; D. Separation of two protoplasts; E. Multiple cells; F. Colony. Scale bars: 5 µm (A – D); 10 µm (E); 20 µm (F).