Zygophylax sagamiensis Hirohito, 1983

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 : 32-34

Zygophylax sagamiensis Hirohito, 1983

( Figs 19 , 25 ; Tables 6 , 8 )

Zygophylax sagamiensis Hirohito, 1983: 30 , fig. 11.— Campos, 2017: 160, fig. 38 (cum syn.).

Material examined. MNHN-IK-2019-2154, KANADEEP Stn. DW 4962: a ca. 13 cm high colony bearing several coppinial masses on the stem and a branch; GenBank: OP724384 .

Description. Colony upright but flaccid when out of liquid, ca. 13 cm high, arising from a stolonal mass embedded in what appears to be a coral; sparingly and irregularly branched; stem (1.5 mm wide above origin from stolon) and main branches fascicled; main cauline tube undivided, composed of successive modules comprising a proximal apophysis (and its axillar hydrotheca mounted on its own apophysis) supporting a cladium, two alternate apophyses above (each supporting a hydrotheca), and a distal apophysis (together with its axillar hydrotheca atop its own apophysis) bearing a cladium given off on opposite side with respect to its proximal counterpart; a slight geniculation in the stem at each origin of a cladium; apophyses rather distant from one another, ending distally in transverse nodes; all hydrothecal apophyses shifted on, to a varied degree, to the “anterior” side of the colony, while the apophyses supporting the cladia are always coplanar; accessory tubes of the stem running parallel to the main tube, often branching and anastomosing, communicating between them through quite large, lateral, ovoid foramina, surface provided with some rare nematothecae; additional cladia are given off abundantly and randomly from the accessory tubes, and point in all directions around the stem. Cladia to 10 mm long, lightly fascicled proximally, especially in the older parts of the colony; beyond that size, gradually-developing cladia adding both length and increasing fasciculation, and giving rise to side branches (of up to the 2 nd order); irregularly divided, here and there, by transverse constrictions of the perisarc; equivalents of internodes long, up to 16 per cladium, imperceptibly geniculate, each with a latero-distal apophysis bearing a hydrotheca; apophyses alternate. Hydrothecae pedicellate; pedicels distinct and of varied length, usually with 1–2 twists proximally, smooth distally, expanding gradually and merging smoothly into the hydrotheca, junction marked internally by an obliquely-set diaphragm with raised internal edge (forming a short, circular funnel for the passage of the hydranth); diaphragm occasionally reduplicated a couple of times; hydrotheca conical and slightly curved away from the internode in lower half, tubular in distal half; aperture distal, set transversely, margin slightly everted, usually with many renovations (reaching as much as 8), rim circular, even. Hydranths strongly contracted within their corresponding gonothecae; tentacle number could not be counted. Nematothecae occur distally, either singly on the apophyses bearing the hydrothecae, and commonly in pairs on the apophyses supporting the cladia; relatively long, tubular, basally rounded, movable, borne on indistinct pedicels, aperture distal, set transversely, margin slightly flaring, rim rounded, even; occasionally renovated, usually once or twice (occasionally up to 5 times). Coppiniae in present specimen borne on both the stem and a branch; long, muff-shaped, given off in adjacent groups, notably on the stem, covering as much as 20 mm of its length; up to 2 mm wide; all gonothecae aggregated, amongst which protrude hollow, simple or rarely ramified tubes (barely surpassing the thecae) bearing a few nematothecae similar to those of the trophosome, occasionally a hydrotheca apically; gonothecae thick-walled, polygonal in apical view, urn-shaped in lateral aspect, some prolonged distally by a free, long, curved, hollow, pointed spine, at the base of which is an ovoid aperture, while some others are devoid of the distal appendage, and are only provided with an almost hooded aperture; lumina of distally-tapered gonothecae filled with ca. 4 large, ovoid oocytes; gonothecae devoid of the apical spine apparently spent.

Remarks. Watson (2003: 161) reported on “small, cylindrical, tightly packed [gonothecae], with low hooded semicircular orifice, a few with an apical peak”, similarly to the situation met with herein. According to Hirohito (1983: 30), the male gonothecae are similar in shape to the female ones described herein. Therefore, it could be assumed that the lack of the apical spine, correlated to the empty condition of the thecae, is possibly due to a mere degenerative process after the spawning.

Campos (2017) mentioned rare situations in which, apparently, gonothecae with more than one apical projection can be found, while specifying that “next to the pointed projection, there is a smaller projection like a nematotheca”. However, nematothecae “on surface of coppinia” (Watson 2003: 161) have already been documented in the present species, but seem to occur in the present New Caledonian material, as well (although, given their small size and the fact that coppinia are covered in adhering particles, they are hardly noticeable).

Distribution. Japan, Macquarie Island, Mid-Atlantic Ridge, Cape Verde Islands ( Vervoort 2006), New Caledonia (present study).

Figures

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.