Rhizoclonium umbraticum Ichihara et Miyaji, 2016

Ichihara, Kensuke, Shimada, Satoshi & Miyaji, Kazuyuki, 2016, Two new green algae, Rhizoclonium fractum sp. nov. and R. umbraticum sp. nov., from tropical and subtropical brackish waters of Japan, Phytotaxa 266 (4), pp. 231-249 : 246

Rhizoclonium umbraticum Ichihara et Miyaji sp. nov. ( Figs. 9 , 10 )

Description: Thalli comprising narrow, uniseriate, unbranched, yellowish-green filaments growing on mangroves or in shaded brackish waters. Non-septate rhizoids develop frequently; thalli fragment at the rhizoidal cells. Thalli up to 5 mm long. Cells 20.7–29.3 μm in diameter, 16.5–58.0 μm long, with an L/D ratio of 0.7–2.4. Each cell contains 1–2 nuclei. Spindle- or band-shaped chloroplasts are densely arranged peripherally in the cytoplasm. Each chloroplast contains 3–12 pyrenoids. Pyrenoids polypyramidal, each covered with 2–8 starch plates; 1–4 thylakoid membranes traverse each pyrenoid. Nuclear-encoded SSU rRNA gene sequence: LC042103, nuclear-encoded LSU rRNA gene partial sequence: LC042096.

Holotype: SAP114678 , collected by K. Miyaji on Oct 14, 2012, deposited in the Herbarium of the Faculty of Science at Hokkaido University , Sapporo.

Type locality: Tanotsu, Fukuoka, Fukuoka Pref., Japan (33°37′N, 130°26′E).

Etymology: From the Latin adjective “umbraticus,” meaning “in the shade,” in reference to shady growing environment.

Figures

FIGURE 9. Field-collected specimens of Cladophoraceae sp. 3 (Rhizoclonium umbraticum). (A) Morphologies of field-collected specimens. (B, C) Filamentous thalli with non-septate rhizoids. (D–F) Spindle- and band-shaped chloroplasts with pyrenoids (arrow heads).(G, H)Autofluorescence of chloroplasts.(I)Cells stained with DAPI, showing nuclei.(J) Cells stained with Lugol’s iodine, showing pyrenoids. (K, L) Pyrenoids observed by transmission electron microscopy. Pyrenoids with starch plates. (K) A thylakoid membrane; (L) Three thylakoid membranes traversing a pyrenoid. Scale bars = 80 μm (A–C); Scale bars = 10 μm (D–H); Scale bars = 40 μm (H, J); Scale bars = 0.5 μm (K, L).

FIGURE 10. Cultured material of Cladophoraceae sp. 3 (Rhizoclonium umbraticum). (A, B) Morphology of filamentous thalli. (C) Tip of filamentous thalli. (D) Filamentous thalli with rhizoidal structures. (E–G) Spindle- and band-shaped chloroplasts. (H) Autofluorescence of chloroplasts. (I) Cells stained with DAPI, showing nuclei. (J) Cells stained with Lugol’s iodine, showing the pyrenoids. (K) Detail of hapteroid attachment cell. Scale bars = 10 μm (A, B, D, F–H, K); Scale bars = 20 μm (C, E, J).