Zygophylax pseudoabietinella Peña Cantero 2020, sp. nov.

Zygophylax pseudoabietinella sp. nov.

(Figs 1 G–H, 7D–E, 9)

urn:lsid:zoobank.org:act: 93001359-55B9-4478-8297-A435BE8AA730

Material examined. MUSORSTOM 4 Stn CP 155, 18°52.8’S– 163°19.5’E (N of New Calendonia), 500–570 m, 15.09.1985: seven stems up to 25 mm high, one with coppinia (25-mm-high stem with coppinia holotype, MNHN-IK-2019-2048; remaining material paratype, MNHN-IK-2019-2049).

Description. Stems up to 25 mm high (Fig. 1G), polysiphonic for most of their extension. Stem giving rise to hydrocladia alternately in one plane, but with hydrocladia grouped in sub-opposite pairs (Fig. 1G) and with two hydrothecae between successive pairs. Hydrocladia basally polysiphonic, except those from distal monosiphonic part of stems. Some basal hydrocladia much developed (Fig. 1G), becoming polysiphonic branches or lower-order stems and giving rise in turn to hydrocladia (up to fourth-order hydrocladia present).Angle between hydrocladia and branches or stems 70°. Branches and hydrocladia in a slight zigzag pattern.

Stems, branches and hydrocladia giving rise to hydrothecae alternately arranged almost in one plane (Figs 1G, 7 D–E, 9A–B).

Hydrotheca roughly cylindrical (Figs 7 D–E), diameter more or less constant, sigmoid. Hydrotheca bent outwards and then inwards at distal part. Adcauline wall convex for its basal two thirds and concave at its distal third. Abcauline wall slightly concave at basal half and slightly convex at distal half. Walls faintly striated transversally. Hydrothecal aperture circular, slightly oblique to hydrothecal long axis. Some hydrothecae with a closing apparatus consisting of a circular flap (Figs 7E, 9 D–E). Hydrothecal diaphragm consisting of a strongly developed ring of perisarc, slightly oblique (abcauline side somewhat higher); diaphragm sometimes duplicated or even triplicated (Fig. 9F) Hydrothecal pedicel indistinguishable from apophysis (Figs 7 D–E, 9A–G).

Typically two nematothecae on hydrothecal apophyses, one on each side (Fig. 9G). Sometimes only one present and occasionally both absent, particularly in the youngest distal hydrothecae (Fig. 7E). For hydrocladial apophyses, pair of nematothecae placed beyond first hydrothecal apophysis, which is deprived of nematothecae (Figs 7D, 9A). Nematothecae also present on accessory tubes, though not very abundant. Nematotheca cylindrical, short, with a wide distal aperture (Fig. 9G).

One coppinia, 3 mm in diameter, present on one stem, on one side (Fig. 1 G–H). With a few branched tubes arising between gonothecae (Fig. 1H). Abietinella -like gonotheca, distal part forming a hood-like structure, provided with a lateral aperture (Figs 1H, 9H).

Measurements (in µm). Hydrothecae: length of abcauline wall 420–460, length of adcauline wall 400–420, diameter at aperture 130–140, diameter at diaphragm 80–100, maximum diameter 120, length of pedicel 140–200. Nematothecae: height 60–75, diameter at aperture 25–30, maximum diameter 30–35. Gonothecae: height of distal hooded part 300, aperture 150.

Remarks. The circular flap found at the distal part of several hydrothecae seems to have no fixed insertion (it was observed on the adcauline side in some hydrothecae, but on the abcauline side in others).

Among the known species of Zygophylax, the present species is morphologically similar to Z. kakaiba Campos, Marques, Puce & Pérez, 2016 in colony structure, but their trophosomes differ in the shape of the hydrothecae. In Z. kakaiba the hydrotheca is swollen with the adcauline wall convex except for the most distal part, whereas in Z. pseudoabietinella sp. nov. the diameter of the hydrotheca is more or less constant and the adcauline wall is slightly convex for its basal two thirds and slightly concave at its distal third. Furthermore, whereas the aperture is parallel to the longitudinal axis of the hydrotheca in Z. kakaiba, it is almost perpendicular to that axis in Z. pseudoabietinella sp. nov. The hydrotheca of Z. kakaiba is also smaller (e.g. 290–330 µm in length of adcauline wall). The reproductive structure is unknown for Z. kakaiba.

Zygophylax pseudoabietinella sp. nov. is also morphologically similar to Abietinella operculata (Jäderholm, 1903), but Jäderholm’s species has distinctly larger and more robust hydrothecae (e.g. 715–748 µm in height and 215–241 µm in diameter at aperture in Peña Cantero et al. 2004) and nematothecae (e.g. 163–280 µm in height and 52–65 µm in diameter at aperture in Peña Cantero et al. 2004). Furthermore, the hydrotheca is swollen in A. operculata. Both species also share the presence of a circular flap as a closing apparatus in some hydrothecae, but whereas it is inserted on the adcauline side of the hydrothecal aperture in A. operculata, it has no fixed insertion in Z. pseudoabietinella sp. nov.

Etymology. The specific name pseudoabietinella refers to the fact that in this species the shape of the hydrotheca resembles that of Abietinella operculata (Jäderholm, 1903).