Zygophylax dispersa Peña Cantero 2020, sp. nov.
Creators: name: Peña Cantero, Álvaro L.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Cnidaria
Hydrozoa
Leptothecata
Lafoeidae
Zygophylax
Zygophylax dispersa

description: Zygophylax dispersa sp. nov.
(Figs 1 A–B, 2, 3A–B)
urn:lsid:zoobank.org:act: 37FF8BBE-19DC-4907-AA4A-D88087ADE03A
Material examined. BIOGEOCAL Stn CP 297, 20°38.64’– 20°38.67’S, 167°10.77’– 167°11.07’E (off Lifou, Loyalty Islands, New Caledonian region), 1230–1240 m, 28.04.1987: one stem 45 mm high, with two coppiniae (Holotype, MNHN-IK-2019-2042).
Description. Erect, stiff stem 45 mm high (Fig. 1A), almost completely polysiphonic, slightly geniculate (Fig. 2A), yellowish-coloured. Branching alternate in one plane, though hydrocladia grouped in sub-opposite pairs; two hydrothecae between successive pairs. Branches or lower-order stems formed by much-developed hydrocladia that become strongly polysiphonic and that give rise in turn to new hydrocladia, which may also undergo further development and become lower-order branches (up to third-order branches present). Angle between stem or branches and hydrocladia 60–70° (Fig. 1A). Even though branching is typically alternate, some of the strongly polysiphonic primary branches frontally directed, forming two planes with a very open angle. Polysiphony even present in the hydrocladia, which are monosiphonic only distally.
Hydrocladia straight (Fig. 2B), resting on apophyses, with distinct perisarc constriction between them (Fig. 2A). Corresponding cauline hydrotheca on apophysis resting on hydrocladial apophysis (Fig. 2C). Hydrocladial apophyses with two nematothecae, one on each side, placed beyond hydrothecal apophysis, which is deprived of nematothecae (Figs 2A, C, 3A).
Hydrothecae on short apophyses (Figs 2B, D–E, 3B), with distinct separation between hydrothecal pedicel and apophysis, marked by a node and a distinct reduction in diameter.
Hydrothecae alternately arranged in one plane (Fig. 2B). Relatively large distance between hydrothecae (Figs 1A, 2 A–B). Hydrotheca cylindrical, diameter roughly constant along distal two-thirds, smoothly decreasing towards pedicel (Figs 2 A–E, 3A–B). Abcauline wall roughly straight; adcauline one slightly convex at basal half, but straight at distal half (Figs 2 D–E, 3B). Aperture circular. Rim even, slightly everted, with up to three, relatively long, renovations. Pedicel short, separated from hydrotheca by a distinct annular diaphragm (Figs 2 D–E, 3A–B). Pedicel abcauline side straight or slightly concave, adcauline one slightly convex (Figs 2B, E, 3B). Sometimes, a short ring (likely related to regeneration) between apophysis and hydrothecal pedicel (Fig. 2D), giving the pedicel a ringed appearance.
Two nematothecae on apophyses (Fig. 2A), one on each side, resting on short pedicel (Fig. 2F). Nematothecae low, roughly cylindrical, with a large distal circular aperture (Fig. 2F); sometimes with one distal extra segment.
Coppinia fusiform (Fig. 1 A–B), composed of closely packed gonothecae (Fig. 1B, 2 G–H). Gonotheca bottleshaped, widening from base to top of contiguous portion and proceeding with a slenderer hood-shaped distal part with lateral aperture (Fig. 2H). Without defensive tubes (Fig. 1 A–B).
Measurements (in µm). Hydrothecae: height 250–350, diameter at aperture 85–100, diameter at diaphragm 60– 70, length of pedicel 50–70. Nematothecae: height 45–50, diameter at aperture 25–35, maximum diameter 30–40. Gonothecae: height 550–560 (distal part 150–180), maximum diameter 200–300, aperture 70 x 100.
Remarks. Zygophylax dispersa sp. nov. is morphologically close to Z. crozetensis Millard, 1977 in the general shape of hydrothecae and nematothecae, but Millard’s species has distinctly larger hydrothecae (e.g. 160–200 µm in diameter at hydrothecal aperture) and nematothecae (e.g. height 90–190, diameter at aperture 50–80). They also differ in the structure of the coppinia (that of Z. crozetensis having irregularly branching structures arising among the gonothecae and provided with nematothecae and rarely hydrothecae) and the shape of the gonothecae (those in Millard’s species have a pointed, sometimes curved, horn). In addition, in Z. crozetensis, hydrothecae are more packed together and hydrocladia are divided into internodes, each with one or two hydrothecae. Finally, the hydrothecal diaphragm is oblique in Z. crozetensis, but transverse in our material.
By the shape of the hydrotheca, Z. dispersa sp. nov. is also similar to Z. sagamiensis Hirohito, 1983, but the two species differ is several features. The colony of Z. dispersa sp. nov. is stiff and almost completely polysiphonic, while that of Z. sagamiensis has hydrocladia polysiphonic only on their basal part (occasionally further on their distal part). Whereas Hirohito’s species is characterised by usually having one to five internodes between hydrothecal pedicel and apophysis, in Z. dispersa sp. nov. only a short ring between apophysis and pedicel has been occasionally observed (probably due to regeneration). In addition, the hydrotheca in Z. sagamiensis is much larger (e.g. 450–500 µm in length). Finally, the shape of the gonotheca is completely different, because the gonothecae have a long sharp distal projection in Hirohito’s species.
Etymology. The specific name dispersa refers to the fact that the hydrothecae are separated by a relatively large distance.
description: Published as part of Peña Cantero, Álvaro L., 2020, On six new species of Zygophylax Quelch, 1885 (Cnidaria, Hydrozoa Zygophylacidae) from the New Calendonian region, pp. 389-404 in Zootaxa 4822 (3) on pages 389-390, DOI: 10.11646/zootaxa.4822.3.4, http://zenodo.org/record/4401711