Aphanta asiatica X. L. Wang, Z. M. Sun & G. C. Wang 2020, sp. nov.
Creators: name: Wang, Xulei
name: Sun, Zhongmin
name: Xia, Bangmei
name: Wang, Guangce
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Plantae
Rhodophyta
Florideophyceae
Nemaliales
Pterocladiaceae
Aphanta
Aphanta asiatica

description: Aphanta asiatica X.L. Wang, Z.M. Sun & G.C. Wang, sp. nov. (Figs 1–22)
Type:— CHINA. Hainan Province: Sanya City, Hongtang Bay (N: 18°18′08.85′′, E: 109°15′56.77′′), on subtidal rocks, August 30, 2019, X.L. Wang, holotype SY94- 1 in AST (Marine Biological Museum, Chinese Academy of Sciences, Qingdao, China), isotype SY94-2, paratypes SY94-3, CJ5-1, CJ5-2, CJ5-3, SY134-1, SY134-2, SY134-3, JPN-X5-1, JPN-X5-2, and JPN-X5-3.
Thalli were 1.8–3.0 cm high, purple-red, comprising a prostrate system and erect fronds (Fig. 1). The prostrate system comprised robust, irregularly branched terete stolons bearing peg-like haptera (Fig. 2). Stolons were 439.7–1,045.5 μm in diameter with a mean of 711.4 μm. Several uprights sometimes corresponded to the main hapteron on the dorsal side (Fig. 3), and a single upright usually developed from the stolon without a dorsal hapteron (Fig. 4). Uprights were sometimes anastomosed to the stolon by very short (~ 1 mm long) cylinders (Fig. 4), resulting in the fronds being interweaved. Erect axes were lanceolate or ligulate, flattened, 1.4–3.9 mm wide with a mean of 2.0 mm, and 145.0–370.4 μm thick with a mean of 230.8 μm. Young branches were cordate (Fig. 5), becoming lanceolate or ligulate when mature, with obvious basal constrictions (Fig. 6). Branches were subpinnate to pinnate or lateral in a regular or irregular pattern, with one to two orders (Fig. 6). The apex of branches was usually emarginate (Fig. 7).
Cross-sections of the central axis showed ovate or elongate cortical cells of two to three layers, and round, angular, or elongate medullary cells (Fig. 8). The rhizoidal filaments were grouped at the two distal ends of each axis and on the inner cortex, but were sparsely distributed in the medulla (Fig. 8). The outermost cortical cells were regularly arranged, 3.8–8.5 × 1.6–5.4 μm, with a mean of 5.9 × 2.9 μm, whereas the inner cortical cells were arranged loosely, 4.3–14.1 × 2.1–8.8 μm with a mean of 7.8 × 3.8 μm. Medullary cells were uneven in size (17.6–36.3 × 12.3–26.1 μm, with a mean of 26.7 × 17.5 μm). The rhizoidal filaments were round in transection, and 2.9–4.3 μm in diameter, with a mean of 3.7 μm.
Three different forms were observed in the longitudinal sections of stolons and haptera (Figs 9–11). The section of the node (stolon) connecting the upper axis and the lower hapteron (the main hapteron) resembled a reverse bouquet in appearance with the initial coalesced rhizoidal filaments corticated and then separated into several non-corticated bundles (Fig. 9). Many floridean starch grains were observed in the medullary cells of the stolon (Fig. 9). Another section showed a cylinder-type attachment with rhizoidal filaments coalesced and non-corticated (Fig. 10). Many floridean starch grains were also observed in the medullary cells of the stolon (Fig. 10). The third form was a peg-like attachment with rhizoidal filaments coalesced and corticated in a usual way, although the distal end was non-corticated (Fig. 11). Rhizoidal filaments were grouped in the inner cortex of the stolon and floridean starch grains were also observed in the medullary cells (Fig. 11). Rhizoidal filaments of the hapteron issued from inner cortical cells and were arranged longitudinally (Fig. 11).
A tetrasporangial sorus was borne on the terminal end of each branchlet or axis (Figs 12, 13), irregularly arranged and cruciately divided on surface view (Figs 13, 14). Tetrasporangia developed from the inner cortical cells, surrounded by abnormal cells (Fig. 15). A spermatangial sorus was also borne on the terminal part of each branchlet (Fig. 16), forming a pale patch with a sterile margin (Figs 17, 18). The spermatangia were cut off from surface cortical cells (Fig. 19). Female thalli were not observed.
Morphological comparisons with other Aphanta species are provided in Table 2.
Distribution and Habitat:— Aphanta asiatica is currently known from Hainan Island, China and Shirahama, Wakayama City, Japan. It grows on lower subtidal rocks or rocks at a depth of ~ 3 m (Fig. 20), usually forming turfs (Fig. 21). Thalli growing on higher rocks usually become pale and dead when exposed to the sun (Fig. 22). The tetrasporophytes and male plants were collected during late August and early October.
Etymology:—The specific epithet refers to its current geographical distributions, namely Asian waters.
Molecular analyses of COI-5P and plastid rbc L sequences:—Nine COI-5P and nine rbc L sequences were generated from nine A. asiatica specimens in the present study. Eight COI-5P sequences were identical and only one sequence differed from the other sequences by only one base pair (bp). Interspecific divergences between A. asiatica and A. pachyrrhiza ranged from 10.4% to 10.6% (57–58 bp), and divergences between A. asiatica and A. ligulata ranged from 20.6% to 21.3% (112–116 bp). In rbc L, intraspecific divergences of A. asiatica varied from 0 to 1.4% (0–17 bp). Interspecific divergences between A. asiatica and the other two Aphanta species ranged from 3.0% to 3.3% (A. pachyrrhiza), and 9.8% to 10.1% (A. ligulata). In both the COI-5P and rbc L trees, A. asiatica formed a clade and clustered with A. pachyrrhiza with full support (1.0 BI/100% ML for COI-5P, 1.0 BI /100% ML for rbc L) (Figs 23, 24).
description: Published as part of Wang, Xulei, Sun, Zhongmin, Xia, Bangmei & Wang, Guangce, 2020, Aphanta asiatica sp. nov. (Orthogonacladiaceae, Rhodophyta), a new species from the Asia-Pacific region with the first description of reproductive structures in this genus, pp. 159-170 in Phytotaxa 440 (2) on pages 162-166, DOI: 10.11646/phytotaxa.440.2.5, http://zenodo.org/record/13872269