Zygophylax infundibulum Millard, 1958

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 : 12-14

Zygophylax infundibulum Millard, 1958

( Figs 6 , 7 , 25 ; Tables 3 , 8 )

Zygophylax infundibulum Millard, 1958: 180 , fig. 4B–C.— Millard, 1980: 143, fig. 4D.— Campos et al., 2020: 545 , pl. 4 (cum syn.).

Material examined. MNHN-IK-2015-3064, KANACONO Stn. DW 4737: five colonies, 2.5–6 cm high, largest with a 4 × 3 mm (incipient) coppinia. —MNHN-IK-2019-2150, KANACONO Stn. DW 4780: a colony composed of three densely-branched stems, to 7 × 6 cm (height × width), growing on worm tube; one stem is fertile and bears an originally 10 × 4 mm coppinia (now dissected); GenBank: OP724368 .—MNHN-IK-2019-2151, KANACONO Stn. DW 4749: four badly-preserved, sparingly-branched colony fragments, to 16 cm high; one of them bears a 12 × 5 mm coppinia; GenBank: OP724369 .—MNHN-IK-2019-2152, KANACONO Stn. DW 4781: a 9 × 11 cm colony bearing a 8 × 5 mm coppinia near its base; GenBank: OP724370 .—MNHN-IK-2019-2155, KANACONO Stn. DW 4741: two sterile colonies, 17 × 11 cm and 6.5 × 4.5 cm.—MNHN-IK-2019-2153, KANACONO Stn. DW 4743: two badly-preserved colonies, one 6 × 4.5 cm and sterile, the other 8 × 6.5 cm and bearing three small coppinia.—MNHN-IK-2019-2148, KANACONO Stn. CP 4786: a 11 × 6.5 cm, sparingly-branched, rather badlypreserved colony bearing a 8 × 4 mm coppinia .

Description. Whole, well-preserved colonies flabellate, to 9 × 11 cm, relatively stiff, quite able to support themselves when out of liquid; main stem branched irregularly in a single plane, bearing up to 4 th lower-order branches; stem and branches fascicled, the former up to 2 mm wide above origin from hydrorhiza; the latter composed of dense, branched, anastomosed stolonal fibers spreading over the substrate and firmly attaching the colonies to it. Main tube of the stem usually undivided, though occasional transverse nodes may occur; structurally regular, built up of stacked modules, each comprising a proximal, well-developed apophysis (together with its axillary hydrotheca atop its own apophysis) supporting a cladium, followed above by two short apophyses supporting two alternate hydrothecae, and distally a second cladial apophysis (together with its corresponding axillar hydrotheca borne on its own apophysis) on opposite side with respect to its proximal counterpart; a slight bent is introduced in the structure of the stem at each cladial apophysis, giving it a slightly geniculate appearance, solely noticeable in its distalmost, monosiphonic portion. Auxiliary tubes of the stem running parallel to the main tube, occasionally branching and anastomosing, and devoid of nematothecae. Apophyses supporting the cladia usually bearing a nematotheca (but occasionally up to 4) close to the distal, transverse node that makes the junction with the corresponding cladium; the latter up to 8 mm long, divided by transverse nodes into irregularly-long internodes bearing 1–6 short apophyses, each supporting a hydrotheca; a nematotheca on the abaxial side of each apophysis; up to 20 hydrothecae per cladium; gradually developing cladia increasingly fascicled from base to tip, and ending up forming new branches. Hydrothecae on stem, branches and cladia biseriate, alternate, distinctly shifted on to the “anterior” side of the colony, forming an acute angle between the two rows; borne on distinct, elongated pedicels, usually smooth-walled, occasionally wrinkled to ringed; pedicels indistinctly merging into their corresponding hydrothecae, junction marked internally by an oblique diaphragm whose internal, abaxial edge projects slightly upwards with respect to that of the opposite side; hydropore circular in apical view; hydrothecae long, tubular, distally bent adaxially, apertures facing alternatively upward and inward (the axillar hydrothecae have their apertures facing upward); rim flared, circular; perisarc of hydrotheca finely and densely-striated transversely. Hydranths, although strongly contracted within their respective hydrothecae, provided with ca. 12 filiform tentacles. Nematothecae all alike, short, barrelshaped, occasionally renovated once or twice, aperture distal, small, circular. Coppinia arising irregularly within a colony, generally on a branch; muff-shaped, to 12 mm long and 5 mm wide; composed of numerous, closely-set, dichotomously- and repeatedly-branched distally, nematophorous tubules, arising from the accessory tubes of the stem; gonothecae free from one another, given off, at varied levels, from the long, proximal, unbranched portion of the tubules; broadly urn-shaped, tapering basally, gradually expanding distally, ending in 2–3 short, funnel-shaped, upwardly-facing neck regions, each bearing apically a rounded, non-operculate aperture; walls of gonotheca thick, outer surface finely and densely-striated transversely; lumen occupied by up to 10 large, almost spherical oocytes; gonothecae deeply-immersed in a dense, thick canopy formed by the distal, anastomosed parts of the nematophorous tubules; nematothecae present here and there along the tubules, either long and tubular or renovated and “divided” by 1–2 transverse constrictions; aperture distal, rounded, minute.

Remarks. The hydrothecal pedicels are commonly smooth-walled but, occasionally, can be wrinkled to ringed. The hydrothecae are usually distinctly curved adaxially (e.g. MNHN-IK-2019-2150), though specimens with less curved thecae also occur (e.g. MNHN-IK-2019-2151). The hydro- and gonothecal striations were not reported so far.

This hydroid resembles Z. unilateralis Totton, 1930 , but there are a couple of characters allowing them to be readily separated: 1) “the proportions of the hydrothecae, which are more slender (sic)” in the former ( Millard 1958: 181); 2) the gonothecae of the latter are “sac-shaped, swollen and more or less oval to round in outline” ( Rees & Vervoort 1987: 77).

Distribution. South Africa ( Millard 1975), off northern Madagascar ( Campos et al. 2020), New Caledonia (present study). A record from southern Brazil ( Miranda et al. 2015), cited by Campos et al. (2020), is not supported by a formal assessment of its specific identity.

Figures

FIGURE 6. Zygophylax infundibulum Millard, 1958 (part). A. Apical part of a colony. B–H. Cauline (B, C), axillar (D–F) and cladial (G, H) hydrothecae. From samples MNHN-IK-2015-3064 (B, D, G) and -2019-2150 (A, C, E, F, H). Scale bars: B–H = 300 µm; A = 1 mm.

FIGURE 7. Zygophylax infundibulum Millard, 1958 (continued). A, B. Simple (A) and renovated (B) nematothecae borne on the cladial apophyses supporting the hydrothecae. C, D. Gonothecae arising, at various levels, from the nematothecate tubuli. All from sample MNHN-IK-2019-2150. Scale bars: A, B = 100 µm; C, D = 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.