Zygophylax pseudafricana Vervoort & Watson, 2003

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 : 28

Zygophylax pseudafricana Vervoort & Watson, 2003

( Figs 15 , 16 , 25 ; Tables 6 , 8 )

Zygophylax pseudafricanus Vervoort & Watson, 2003: 78 , fig. 13A–F (incorrect original spelling).

Zygophylax pseudafricana – Campos, 2017: 146, fig. 33.

Zygophylax dispersa Peña Cantero, 2020: 389 , figs. 1A–B, 2, 3A–B (syn. nov.).

Material examined. MNHN-IK-2015-2760, KANADEEP 2 Stn. DW 5107: a ca. 11 cm high sterile colony (colony A) and a ca. 4 cm high colony fragment bearing a coppinia (colony B); GenBank: OP724381 (A) and OP724382 (B).

Description. Entire colony erect, ca. 11 cm high, arising from dense hydrorhiza firmly attached to a stone, bunching above into a 2 mm thick hydrocaulus giving rise irregularly to many side branches, the proximal most given off in all directions around the stem, while the distalmost tend to be alternate; both stem and branches strongly fascicled, with woody appearance. Main cauline tube undivided, imperceptibly geniculate, composed of a succession of modules, each comprising a proximal apophysis (together with associated axillar hydrotheca atop its own apophysis) supporting a cladium, two alternate apophyses above (each bearing a hydrotheca), and a second apophysis (and its axillar hydrotheca mounted on its apophysis) arising on side opposite to its proximal counterpart; apophyses distant from one another, prominent, ending distally in transverse nodes; a pair of nematothecae on each side of an apophysis; apophyses of axillar hydrothecae usually devoid of nematothecae, exceptionally provided with an unpaired one. Auxiliary tubes of the stem running parallel to the main tube, branching, anastomosing, communicating with one another through large, ovoid pores in the perisarc; provided with scattered nematothecae. Cladia 8.5 mm long, monosiphonic, not divided by nodes, but composed of up to 16 long, collinear equivalents of internodes, each giving rise distally to a short, lateral apophysis supporting a hydrotheca; apophyses alternate, ending distally in transverse node, and bearing a pair of nematothecae, one on each side; longer cladia gain fasciculation and gradually transform into side branches, themselves branching again to form up to 4 th order branchlets; monosiphonic parts of some cladia provided with occasional nematothecae on the “internodes”. Hydrothecae all alike on stem, branches and cladia; alternate, the two rows coplanar; relatively short-pedicellate, pedicels either smooth-walled or with a proximal wrinkle, widening distally and merging imperceptibly into their corresponding hydrothecae; demarcation internal, as an obliquely-set diaphragm with central, rounded hydropore with upturned, internal edges; hydrothecae curved away from the internodes, especially noticeable in the lower third of their adaxial walls; abaxial walls almost straight; most of the distal parts of hydrothecae tubular, aperture slightly everted, rim even, circular, usually with many renovations. Hydranths badly-preserved, their tentacle number could not be counted. Nematothecae broadly tubular, somehow slightly swollen in middle, aperture distal, set transversely, very slightly everted, rim even, circular. A coppinia present on the colony fragment, encircling 3/4 of the outer surface of a stem (or well-developed branch); 5 mm long and 2.5 mm wide, composed of numerous, laterally-fused (for most of their length) gonothecae, polygonal in apical view, thick-walled, broadly vasiform in lateral aspect; distally, a short, free neck region with hood-like appearance, curved away at right angle and opening up into an ovoid aperture; flimsy nematophorous tubules arise between the gonothecae, their length barely surpassing that of the gonothecae; nematothecae similar to those of the trophosome; gonothecal content unassignable to a given sex.

Remarks. The trophosome of Z. pseudafricana is indistinguishable from that of Z. sagamiensis Hirohito, 1983 (compare Fig. 15A and 19A ), but their respective gonothecae are distinct (compare Fig. 16E and 19F ).

The New Caledonian Z. dispersa Peña Cantero, 2020 displays the same morphological features as the present species, with which it was not compared in the original account. Its hydrothecae (250–350 µm long and 85–100 µm wide at aperture) are only slightly larger compared to the measurements given by Vervoort & Watson (2003: 78) for the holotype slide #2882 of their nominal species (250–275 µm long and 62–75 µm wide at aperture). Similarly, its gonothecae (550–560 µm long and 200–300 µm wide) exceed the size of those measured in Z. pseudafricana (440– 450 µm long and 125–150 µm wide). Nevertheless, it should be acknowledged that a certain degree of shrinkage, notably depending on the perisarc thickness, occurs when preparing permanent mounts, hence explaining their comparatively reduced dimensions.

Campos (2017: 147) reported on 350 µm long and 80 µm wide (at aperture) hydrothecae in a liquid-preserved specimen, while the present New Caledonian material has the largest thecae documented so far (see Table 6 ).

Distribution. Between Auckland Islands and the South Island, New Zealand ( Vervoort & Watson 2003), New Caledonia ( Peña Cantero 2020, as Z. dispersa ; present study).

Figures

FIGURE 15. Zygophylax pseudafricana Vervoort & Watson, 2003 (part). A. Apical part of a colony. B–G. Cauline (B, C), axillar (D) and cladial (E–G) hydrothecae. All from sample MNHN-IK-2015-2760. Scale bars: B–G = 300 µm; A = 1 mm.

FIGURE 16. Zygophylax pseudafricana Vervoort & Watson, 2003 (continued). A–C. Nematothecae associated to the axillar (A) and cladial (B, C) hydrothecae, occurring either singly (A, B) or in pairs (C). D, E. Portion of coppinia seen apically (D) and in cross-section (E), showing fused gonothecae. Scale bars: A–C = 100 µm; D, E = 500 µm.

FIGURE 19. Zygophylax sagamiensis Hirohito, 1983. A. Apical part of a colony. B–D. Cauline (B), axillar (C) and cladial (D) hydrothecae. E. Nematotheca. F, G. Gonotheca in frontal (F) and lateral (G) views; note nematothecate tubuli in G. All from sample MNHN-IK-2019-2154. Scale bars: E = 100 µm; B–D = 300 µm; F, G = 500 µm; A = 1 mm.

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.