Zygophylax laertesi sp. nov.

(Figs 1D, 3 F–H, 5)

urn:lsid:zoobank.org:act: F12154FC-7F72-4255-B8C4-0202B01B6413

Material examined. MUSORSTOM 4 Stn CP 216, 22°59.5’S– 167°22.0’E (off Koutoumo Island, New Caledonia region), 490–515 m, 29.09.1985: one stem 40 mm high, with coppinia (Holotype, MNHN-IK-2019-2044) .

Description. Stem 40 mm high (Fig. 1D), stiff, strongly and almost completely polysiphonic. Stem with alternately arranged apophyses giving rise to hydrothecae and hydrocladia. Branching alternate, in one plane, but with hydrocladia grouped in sub-opposite pairs (Fig. 1D, 3F, 5A) and with two hydrothecae between successive pairs. A basal pair of hydrocladia (and another higher) much developed (Fig. 1D), becoming second-order stems or branches and giving rise in turn to hydrocladia. Hydrocladia polysiphonic for most of their extension, except for the youngest ones. Faint separation between hydrocladial apophyses and hydrocladia (Fig. 3F). Angle between stem or branches and hydrocladia 70° (Fig. 1D). Hydrocladia roughly straight (Fig. 1D).

Hydrothecae alternately arranged in one plane (Figs 3G, 5C), resting on short apophyses (Figs 3G, 5C). Separation between apophysis and hydrothecal pedicel usually marked only by a strong constriction of perisarc (Figs 3 F–G, 5A–D, F–G), very sharp on adcauline side (occasionally a node present).

Hydrotheca tubiform (Figs 3 F–G, 5), curved, sigmoid, tapering at base. Hydrotheca bent outwards first, then inwards (Figs 3G, 5 C–D). Adcauline wall convex at basal half and concave at distal half; conversely, abcauline wall convex at distal half and slightly concave at basal half. Aperture circular, rim even but flared, with up to five renovations. Diameter of hydrothecae roughly constant at distal half, but hydrotheca slightly swollen at basal half. Hydrothecal wall with faint transverse wrinkles. A marked internal adcauline cusp present (Figs 3G, 5 C–D, F). Hydrothecal diaphragm marked by a strong, oblique ring of perisarc; diaphragm higher at abcauline side (Figs 3G, 5D, F–G). An internal vertical keel present on abcauline hydrothecal wall above diaphragm (Figs 3G, 5 C–D, F–G). A dish-shaped operculum present in some hydrothecae (Fig. 3D, F).

Two nematothecae resting on hydrothecal and hydrocladial apophyses, one on each side (Fig. 3G). Nematothecae on hydrocladial apophyses beyond first hydrothecal apophysis, which is provided with nematothecae (Fig. 3F, 5B). Striking abundance of nematothecae on accessory tubes (Fig. 5 A–B, H), longer and thinner than those on hydrothecal apophyses. Nematothecae elongate, frequently with extra segments (up to five observed) (Fig. 3F).

Coppinia rounded (Fig. 1D), with an envelope of forked tubes (Fig. 1D) covering independent gonothecae. Gonotheca with inverted pear-shaped outline, with a narrow basal part and a much wider distal one, which form two very short arms with a distal aperture (Fig. 3H).

Measurements (in µm). Hydrothecae: length of abcauline wall 430–460, length of adcauline wall 380–390, diameter at aperture 75–80, diameter at diaphragm 50–60, length of pedicel 80–100. Nematothecae on apophyses: height 90–100, diameter at aperture 15, maximum diameter 25–30. Nematothecae on accessory tubes: height 170– 250, diameter at aperture 8–15, maximum diameter 20. Gonothecae: height 500–550, diameter at aperture 80–100, maximum diameter 400–500.

Remarks. Zygophylax laertesi sp. nov. is easily recognizable amongst the known species of the genus by the shape of the hydrotheca, the internal adcauline cusp and the abcauline vertical keel above the diaphragm. Zygophylax laertesi sp. nov. resembles no other described species.

Etymology. The specific name laertesi is a dedication to my son Laertes Peña Sancho.