Acinetospora asiatica Yaegashi, Yamagishi et Kogame sp. nov. (Figure 3A–H)

Diagnosis

Plants are sparsely branched uniseriate filaments up to 30 cm or more in length, forming entangled tufts on rocks and other seaweeds (e.g. Sargassum spp. and Scytosiphon lomentaria). Erect filaments have scattered meristematic zones consisting of short cells. Crampons are formed on erect filaments at right angles. Cells of erect filaments are 20–77 µm in length and 18–30 µm in width and contain many discoid chloroplasts. Plurilocular zoidangia are ectocarpoid, 90–135 µm in length and 25–40 µm in width, sessile or with one- or two-celled pedicels.

Holotype

SAP112509 (Figure 3A, collected on 15 June 2010) deposited in the Herbarium (SAP), the Faculty of Science, Hokkaido University, Sapporo, Japan.

Isotypes

SAP112510-112512 deposited in SAP.

Type locality

Oshoro (43°12′39″ N, 140°51′35″ E), Otaru, Hokkaido, Japan.

In samples collected from Oshoro, Shinori and Muroran, Hokkaido, scattered meristematic zones, crampons and plurilocular zoidangia were observed (Figure 3B–E). Plurilocular zoidangia were not observed, however, in samples collected from Oohamacho, Innoshima, Hiroshima Pref. In Oshoro, plants were collected in May and June but were not found in April and August. In Innoshima, plants were found from January to June. Unilocular sporangia were not found in any of the samples.

In culture, zoids from plurilocular zoidangia germinated unipolarly, forming a germ tube, and developed into branched prostrate filaments (Figure 3F). Cells of prostrate filaments became globular, while cells of erect filaments were cylindrical (Figure 3F, G). Prostrate filaments formed erect filaments which tapered slightly to a pseudohair or a hair with short cells (like those of meristems) near their base and longer pale cells in the upper portion. Plurilocular zoidangia were formed on prostrate filaments and the lowermost portion of young erect filaments (Figure 3G) at 10–20°C, 2–3 weeks after germination. Erect filaments grew longer than prostrate filaments and formed plurilocular zoidangia (Figure 3H) and scattered meristems. Cells of erect filaments were 23–78 µm in length and 20–32 µm in width. Heterokont zoids from plurilocular zoidangia possessed an eyespot. Settled zoids from plurilocular zoidangia were round and 9.3–10.8 µm in diameter. Unilocular sporangia were not found in any culture condition. In two strains, no reproductive organs were formed at all (Table 1).

Molecular analyses

Rbc L sequences were determined for Acinetospora filamentosa (17 samples) and A. asiatica (16 samples). Alignment length was 1476 bp. BI and ML trees were similar and highly supported clades corresponded between the trees. Samples of A. filamentosa formed a fully supported clade, which was sister to the European sample of A. crinita (Figure 4). Samples of A. asiatica clustered with full support, and formed a clade with Feldmannia irregularis (Kützing) Hamel and Hincksia sp. The latter clade was sister to the A. filamentosa - A. crinita clade, and both clades were included in the Acinetosporaceae clade. Sequence differences (p-distances) between A. filamentosa and A. crinita were 3.0–3.3%, those between A. asiatica and A. crinita were 4.6–4.7%, and those between A. filamentosa and A. asiatica were 4.0–4.6%.

Partial cox 1 sequences (658 bp) were determined for A. filamentosa (four samples) and A. asiatica (four samples). In the NJ tree of cox 1 (Figure 5), the two species of Acinetospora from Japan as well as A. crinita from Europe (Greece and Brittany, France) formed three separate clades, each with full support. The clade of A. asiatica consisted only of Japanese samples while the A. filamentosa clade included one unidentified sample from Greece (LM995369). Sequence differences (p-distances) were 11.3–16.3% among the three species and <2.7% within each species.