Rhizoclonium fractum 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 : 245-246

Rhizoclonium fractum Ichihara et Miyaji sp. nov. ( Figs. 5 , 6 )

Description: Narrow, uniseriate, unbranched, filamentous alga growing on mangrove bark. Thalli are green, rarely with non-septate rhizoids, up to 5 mm long. Apical cells sometimes enlarged and swollen. Cells 22.9–43.9 μm in diameter, 18.6–86.4 μm long, with L/D ratios of 0.7–2.9. Each cell contains 2–13 nuclei. Spindle- or band-shaped chloroplasts located peripherally in the cytoplasm. Chloroplasts containing 3–12 pyrenoids. Pyrenoids polypyramidal, each covered with 4–12 starch plates; 2–10 thylakoid membranes traverse each pyrenoid. Nuclear-encoded SSU rRNA gene sequence: LC042104; nuclear-encoded LSU rRNA gene partial sequence: LC042102.

Holotype: SAP114670 , collected by K. Miyaji on Feb 27, 2012, deposited in the Herbarium of the Faculty of Science at Hokkaido University , Sapporo.

Type locality: Kesaji, Azuma, Okinawa Pref., Japan (26°36′N, 128°08′E).

Etymology: From the Latin adjective “fractus,” meaning “break, fragment,” referring to the formation of short thalli by fragmentation.

Figures

FIGURE 5. Field-collected specimens of Cladophoraceae sp. 1 (Rhizoclonium fractum). (A, B) Field-collected specimens. (C–E) Range of morphological types in field-collected specimens.(E)Arrowhead pointing to rhizoidal structure.(F, G) Cells of field-collected materials. (H, I) Spindle- or band-shaped chloroplasts. Arrowheads indicate pyrenoids. (J, K) Autofluorescence of chloroplasts. (L) Cells stained with DAPI, showing nuclei. (M) Cells stained with Lugol’s iodine, showing the pyrenoids. (N) Polypyramidal pyrenoid observed by transmission electron microscopy. Scale bar = 5 mm (A, B,); Scale bars = 20 μm (C–F, L, M); Scale bar = 10 μm (G–K).; Scale bar = 0.5 μm (N).

FIGURE 6. Cultured material of Cladophoraceae sp. 1 (Rhizoclonium fractum). (A–D) Morphologies of growing filamentous thalli. (A, B) Some of the thalli have rhizoidal structures. (E, F) Chloroplasts with many starch granules. (G) Autofluorescence of chloroplasts. (H) Cells stained with DAPI, showing nuclei. (I) Cells stained with Lugol’s iodine, showing the pyrenoids. Scale bar = 20 μm (A–C, E–G); Scale bars = 40 μm (D); Scale bars = 10 μm (H, I).