Vaucheria macounii (Blum) Vishnyakov, 2024

Vishnyakov, Vasily S. & Moseev, Dmitry S., 2024, Vaucheria macounii comb. et stat. nov. (Vaucheriaceae, Xanthophyceae): first occurrence in Europe and notes on the species, Phytotaxa 676 (3), pp. 287-296 : 289

Vaucheria macounii (Blum) Vishnyakov , comb. et stat. nov. ( Figs 2–13 )

Basionym:— V. longicaulis var. macounii Blum 1971 , Bull. Torrey Bot. Club, 98(4): 193.

Type:— ʻJ. Blum #1977, from open ground in salt marsh, south end of Sequim Bay, Washington, September 25, 1966, in Herb. New York Botanical Garden’.

Morphology:— Filaments dioecious, rarely monoecious, sympodially branched, 32.5–50.0 µm in diam. Gametangia terminal. Antheridia commonly in clusters, separated from filament by wall-bound cavity, fusiform (spindle-shaped), fusiform-cylindrical, sometimes furcate, conical, curved, spirally twisted, 140–265 µm in length, 30–70 µm in diam., opening a terminal pore and 1–7 pores on lateral papillae ( Figs 2–7 ). Antheridial papillae conical, pointed upwards, 2.5–37.5 µm in length. Oogonia club-shaped (pyriform), commonly curved, 220–410 µm in length, 87.5–122.5 µm in diam., without a distinctive fertilization pore ( Figs 8–13 ). Oospores globose or ellipsoid, 92.5–135 µm in length, 77.5–122.5 µm in diam.; smaller lower portion of cytoplasm remaining after fertilization usually degenerates without forming wall material (remaining an amorphous mass in proximal part of the oogonium), leaving thin annular deposit on the oogonial wall, or forming a transverse wall and ultimately an empty cell. Asexual reproduction by club-shaped aplanospores forming in terminal sporangia, 250 µm in length, 130 µm in diam. (rarely seen).

Figures

FIGURES 2–7. Vaucheria macounii from the White Sea, morphology of antheridia (V-988): 2—antheridia of various shapes in short terminal clusters, one spirally twisted antheridium is indicated by arrow; 3—conical antheridia, proliferation of basal antheridium is indicated by arrow, 4—bifurcate antheridium; 5, 6—fusiform antheridia, barely discernible lateral pore is indicated by arrow; 7—fusiformcylindrical, curved antheridium with numerous lateral pores. Scales: 2, 3—100 µm, 4–7—50 µm.

FIGURES 8–13. Vaucheria macounii from the White Sea, morphology of oogonia (V-988): 8, 11—oogonia in lateral position due to pronounced sympodial growth, 9, 10, 12—curved terminal oogonia, residual mass of cytoplasm is indicated by arrows; 13—paired terminal oogonia. Scales: 100 µm.