Zygophylax encarnae sp. nov.

(Figs 1C, 3 C–E, 4)

urn:lsid:zoobank.org:act: 18C48841-985C-453B-BF3E-1C95A70EFB7E

Material examined. BIOGEOCAL Stn CP 265, 21°04.09’– 21°04.74’S, 167°00.40’– 166°59.71’E (off Lifou, Loyalty Islands, New Caledonian region), 1760–1870 m, 18.04.1987: one stem 40 mm high, with gonothecae (Holotype, MNHN-IK-2019-2043) .

Description. One stem 40 mm high, broken into three fragments. Stem strongly, almost completely, polysiphonic (Fig. 1C). 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. 1C) and with two hydrothecae between successive pairs. All hydrocladia almost completely polysiphonic. A few basal hydrocladia much developed, becoming branches or lower-order stems and giving rise in turn to hydrocladia (Fig. 1C). Angle between stem or branches and hydrocladia 70–80° (Fig. 1C).

Hydrocladia straight, relatively very long, with up to 35 hydrothecae (Fig. 1C), resting on hydrocladial apophyses (Fig. 4A). More or less distinct separation between hydrocladia and apophyses. Hydrocladial apophyses with two nematothecae, one on each side, beyond first hydrothecal apophysis, which is deprived of nematothecae (Figs 3C, 4B).

Hydrothecae almost with unilateral arrangement, alternate, distally directed, but curved outwards (Figs 3D, 4 C–D). Hydrothecae resting on short apophyses alternately arranged in two planes making an acute angle (Figs 3D, 4 C–D). Hydrotheca with a short, cone-shaped pedicel (Figs 3 C–D, 4E–F), distinctly separated from apophysis by a node and a distinct change in diameter (Figs 3 C–D, 4E–F).

Hydrotheca elongate (Figs 3 C–D, 4A, C–E), relatively long and thin, curved outwards, sigmoid.Adcauline wall convex at basal half and concave at distal half; abcauline side convex, sometimes slightly concave basally (Figs 3 C–D, 4A, C–E). Maximum diameter by the middle; diameter decreasing distally and basally (minimum diameter at pedicel origin). Aperture circular, directed outwards and upwards. Rim even, with up to seven short renovations. Hydrothecal diaphragm consisting of a ring of perisarc, slightly oblique; abcauline side somewhat higher (Fig. 4E).

One nematotheca on each hydrothecal apophysis, outside the space delimited by the hydrothecae. Nematotheca elongate (Fig. 4G), club-shaped, maximum diameter at distal third, strongly decreasing to distal end; aperture relatively tiny (Fig. 4G). Sometimes nematotheca consisting of a series of marked segments (up to three), likely due to regeneration. Nematothecae frequently with an extra distal segment.

Small coppinia present, consisting of a few isolated gonothecae originating at basal part of tubes (Fig. 4H). Gonotheca ovoid, but with two very short distal arms, each with one aperture (Figs 3E, 4H).

Measurements (in µm). Hydrothecae: length of abcauline wall 500–700, length of adcauline wall 520–610, diameter at aperture 110–130, diameter at diaphragm 80–90, length of pedicel 100–130, maximum diameter 130–140. Nematothecae: height 150–250, diameter at aperture 8–10, maximum diameter 45–60. Gonothecae: height 1000, maximum diameter 560, diameter at aperture 160.

Remarks. Zygophylax encarnae sp. nov. is easily distinguishable from the remaining species of the genus by the almost completely unilateral arrangement of the hydrothecae and their peculiar shape. With the proper orientation, some hydrothecae somewhat resemble those of Z. adhaerens Fraser, 1938, but they are actually quite different as in Fraser’s species the hydrothecae are regularly curved, not sigmoid as in Z. encarnae sp. nov., and alternately arranged in one plane (hydrothecae are almost unilateral in Z. encarnae sp. nov.). In addition, there is no distinction between hydrothecal apophyses and the hydrothecal pedicel in Z. adhaerens .

Etymology. The species name encarnae is a dedication to my wife Encarna Sancho Aguilar.