Zygophylax sp.

Galea, Horia R., Maggioni, Davide & Galli, Paolo, 2022, On some species of Zygophylax Quelch, 1885 (Cnidaria: Hydrozoa: Zygophylacidae) from off New Caledonia, Zootaxa 5214 (1), pp. 1-46 : 39-40

Zygophylax sp.

( Figs 24 , 25 ; Tables 7 , 8 )

Material examined. MNHN-IK-2019-2156, KANACONO Stn. CP 4786: four sterile colonies, 19 × 11 cm, 12 × 11.5 cm, 12 × 8.5 cm and 12 × 3 cm; GenBank: OP724386 .

Description. Colonies erect, stiff, sparingly branched, reaching 19 cm high and 11 cm wide, arising from dense, branching and anastomosing stolonal fibers firmly adhering to corals. Stems and branches strongly fascicled for nearly their whole length; stems up to ca. 2 mm wide above origin from stolons; accessory tubes running parallel to one another, frequently branching and anastomosing, bearing rare, almost globular nematothecae. Branching of stem irregular, but in one plane, above a proximal portion of varied length (up to 6 cm long) devoid of both branches and cladia (the latter are represented by mere stumps, either partly or totally obscured by the auxiliary tubes); distal to this portion, there are a few, usually long, lower-order branches that rebranch again here and there, producing up to 3 rd order branchlets. Stems and branches with similar structure; main tube undivided, composed of successive modules comprising a proximal apophysis (together with its axillar hydrotheca atop its own apophysis) supporting a cladium, two alternate hydrothecae (borne on their corresponding apophyses) above, and a second cladial apophysis (and its axillar hydrotheca mounted on its apophysis) distally, but on opposite side of the stem compared to its proximal counterpart; all apophyses well- and equally developed, each bearing subterminally either a single or a pair of nematothecae (a theca per side), although the apophyses for the axillar hydrothecae do not seem to carry them; distally, a subterminal bulge and a transverse node, the latter making the junction with either a cladium or a hydrotheca. Cladia alternate, in two coplanar rows along the stem and branches; up to 13 mm long, lightly fascicled proximally, grading to monosiphonic distally; undivided, but equivalents of internodes moderately long, each with a distal, lateral apophysis supporting a hydrotheca; apophyses alternate, coplanar, comparatively shorter than their cauline counterparts. Hydrothecae pedicellate; pedicels usually with 1–2 (occasionally 3, exceptionally 4) twists proximally, smooth-walled distally; pedicels widening progressively and merging imperceptibly with their corresponding hydrothecae (internally, the delimitation site is marked by a transverse diaphragm whose abaxial edge is slightly raised). Hydrothecae long, tubular, slightly sigmoid in lateral view (proximal half curved abaxially, distal half curved adaxially); smooth-walled, aperture slightly tilted adaxially, margin slightly everted, rim circular even; polyps not sufficiently well-preserved to allow a reliable count of their tentacle number. Nematothecae all alike in the colony, globular, with minute apical, rounded aperture. Gonosome absent.

Remarks. Since the nematothecae have weak insertions and are easily lost, their number per apophysis could not be stated with certainty; indeed, there are rare apophyses still possessing a pair of thecae; in some others, either one theca is still present and a scar is noticeable on the opposite side, or two scars can be observed on both sides; finally, there are apophyses in which one theca or a scar are present, but neither a paired theca or a scar can be noted on the opposite side.

Given the absence of its gonosome, the present hydroid cannot be identified to species level.

Distribution. New Caledonia (present study).

Figures

FIGURE 24. Zygophylax sp. A. Apical part of a colony. B–D. Cauline (B), axillar (C) and cladial (D) hydrothecae. E, F. Apophyses supporting cladial hydrothecae with either single (E) or a pair (F) of nematothecae. All from sample MNHN-IK- 2019-2156. Scale bars: E, F = 100 µm; B–D = 300 µm; A = 500 µm.

FIGURE 25. Phylogenetic hypothesis for the Zygophylaciidae based on the 16S rRNA gene. Numbers at nodes refer to support values of the maximum likelihood, Bayesian inference and maximum parsimony analyses, respectively, and are shown only when> 70 and 0.7. Sequences generated in this study are followed by voucher numbers.