Zygophylax laertesi Peña Cantero, 2020

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 : 17-20

Zygophylax laertesi Peña Cantero, 2020

( Figs 8–11 , 25 ; Tables 4 , 5 , 8 )

Zygophylax laertesi Peña Cantero, 2020: 394 , figs 1D, 3F–H, 5.

Material examined. MNHN-IK-2015-3024, KANADEEP 2 Stn. PL743-04 : a colony on coral, composed of three stems, 1.5–5 cm high, tallest bearing two coppinia; compact appearance, hydrothecae slightly curved, the two rows coplanar.—MNHN-IK-2019-2104, KANACONO Stn. DW 4744: an originally ca. 5 cm high, sterile colony, now broken into two pieces; compact appearance, hydrothecae slightly curved, the two rows coplanar.—MNHN- IK-2019-2105, KANACONO Stn. DW 4759: two colonies, 6.1 and 5.3 cm high, the latter bearing two coppinia; compact appearance, hydrothecae slightly curved, the two rows coplanar.—MNHN-IK-2019-2106, KANACONO Stn. DW 4743: four colonies, 5.5–10 cm high, tallest bearing a coppinia; compact appearance, hydrothecae slightly curved, the two rows coplanar.—MNHN-IK-2019-2107, KANACONO Stn. DW 4719: five colonies, 4.5–8 cm high, all but one sterile; compact appearance, hydrothecae slightly curved, the two rows coplanar; GenBank: OP724371 .— MNHN-IK-2019-2122, KANACONO Stn. DW 4671: a 5.8 cm high, sterile colony; straggling appearance, cladia separated by 4–7 slightly-curved, coplanar hydrothecae; GenBank: OP724372 .—MNHN-IK-2019-2123, KANACONO Stn. DW 4670: numerous colonies, fertile or infertile, 1.8–7 cm high; straggling appearance, cladia separated by 3–8 hydrothecae (and as much as 20, apically on a stem), the latter slightly curved and coplanar.— MNHN-IK-2019-2124, KANACONO Stn. DW 4698: two sterile colonies, 3.5 and 5 cm high; compact appearance, hydrothecae slightly curved, the two rows coplanar.—MNHN-IK-2019-2125, KANACONO Stn. DW 4747: two colonies, one 5.2 cm high bearing a coppinia, the other 5.6 cm high and sterile; compact appearance, hydrothecae slightly curved, the two rows coplanar.—MNHN-IK-2019-2126, KANACONO Stn. DW 4758: a ca. 5 cm high, sterile colony; compact appearance, hydrothecae slightly curved, the two rows coplanar.—MNHN-IK-2019-2127, KANACONO Stn. DW 4672: five colonies, 3.7–7 cm high, tallest bearing incipient coppinia; straggling appearance, cladia separated by 2–5 cauline hydrothecae, the latter slightly curved and coplanar; GenBank: OP724373 .— MNHN-IK-2019-2128, KANACONO Stn. DW 4681: a 5.5 cm high, fertile colony (1 coppinia); straggling appearance, cladia separated by 4–7 hydrothecae, the latter slightly curved and coplanar.—MNHN-IK-2019-2129, KANACONO Stn. DW 4748: a 8.8 cm high, sterile colony; compact appearance, hydrothecae slightly curved and coplanar.—MNHN-IK-2019-2130, KANACONO Stn. DW 4764: colony on sponge, composed of several stems, 1–4.5 cm high, tallest bearing a coppinia; compact appearance, hydrothecae distinctly curved, the two rows forming an acute angle; GenBank: OP724374 .—MNHN-IK-2019-2131, KANACONO Stn. DW 4777: colony on coral, composed of many stems, 1.3–3.5 cm high, two of them bearing a coppinia each; compact appearance, hydrothecae distinctly curved, the two rows forming an acute angle.—MNHN-IK-2019-2132, KANACONO Stn. DW 4781: colony on worm tube, composed of many stems to 3 cm high, three of them bearing coppiniae; compact appearance, hydrothecae distinctly curved, the two rows forming an acute angle.—MNHN-IK-2019-2133, KANACONO Stn. DW 4780: colony on worm tube, composed of many stems to 3.5 cm high, of which three bear a coppinia each; compact appearance, hydrothecae distinctly curved, the two rows forming an acute angle. —MNHN-IK-2019- 2134, KANACONO Stn. DW 4763: colony composed of three sterile stems, 1.2–3.5 cm high; compact appearance, hydrothecae distinctly curved, the two rows forming an acute angle.—MNHN-IK-2019-2135, KANACONO Stn. DW 4782: colony composed of a few stems, 1.3–3.7 cm high, the tallest one bearing a coppinia; compact appearance, hydrothecae distinctly curved, the two rows forming an acute angle; GenBank: OP724375 .—MNHN-IK-2019- 2141, KANACONO Stn. DW 4764: a 5.5 cm high, sterile colony; compact appearance, hydrothecae slightly curved, the two rows coplanar.—MNHN-IK-2019-2143, KANADEEP Stn. DW 4993: two sterile colonies, 2.8 and 3 cm high; straggling appearance, cladia separated by up to 5 cauline hydrothecae, the latter distinctly curved, the two rows forming an acute angle; GenBank: OP724376 .—MNHN-IK-2019-2144, KANACONO Stn. DW 4696, a 5.9 cm high, sterile colony; compact appearance, hydrothecae slightly curved, the two rows coplanar.—MNHN- IK-2019-2145, KANACONO Stn. DW 4711: colony composed of several sterile stems, 1–4.5 cm high; compact appearance, hydrothecae distinctly curved, the two rows forming an acute angle; GenBank: OP724377 .—MNHN- IK-2019-2149, KANACONO Stn. DW 4749: colony on coral, composed of several stems to 3 cm high, one bearing a coppinia; compact appearance, hydrothecae distinctly curved, the two rows forming an acute angle .

Description. Colonies erect and quite stiff, flabellate, to 10 cm high and 5.5 cm wide, arising from rhizoid stolons firmly attached to various substrates; stem and branches fascicled, the former to 1.5 mm wide above origin from stolon; branching strictly in one plane, up to 4 th order branches. Main cauline tube usually undivided, but occasionally with irregular, transverse constrictions of the perisarc; commonly composed of modules comprising a well-developed, proximal apophysis (together with its axillary hydrotheca mounted on its own apophysis) supporting a cladium, two alternate, comparatively shorter apophyses above, each supporting a hydrotheca, and a second, distal cladial apophysis, together with its axillar hydrotheca; the number of hydrothecae separating two successive “pairs” of (subopposite) cladia could vary in some colonies, giving them a straggling appearance (see Remarks section below); main cauline tube slightly geniculate, notably at the insertions of cladia and, to a lesser extent, at each hydrothecal apophysis. Accessory tubes of stem and branches running parallel to their corresponding main tubes, forming occasional anastomoses and communicating through large, lateral pores in their perisarc; depending on the colony, they bear a varied number (from relatively scarce to dense) of scattered, digitiform, occasionally renovated nematothecae. Cladia unbranched, coplanar, alternate along the stem, grouped in subopposite pairs, proximally fascicled, main tube usually undivided, though occasional transverse constrictions of the perisarc could be noted here and there; equivalents of internodes moderately-long, from collinear to slightly geniculate in appearance, bearing distally a short apophysis supporting a hydrotheca; apophyses alternate, from coplanar to distinctly shifted on to one side of the colony, forming in various colonies differently acute angles between them. Hydrothecae pedicellate; pedicels distinct and of varied length among the colonies, and even withing the same colony, although to a lesser extent; merging smoothly into their corresponding hydrothecae, demarcation through internal diaphragms; hydrothecae tubular, though variably-shaped in lateral view, from slightly to distinctly-curved distally; thin to thick-walled, outer surface of perisarc finely and densely-striated transversely; an invagination (with thickened perisarc) of varied shape and extent above the middle of adaxial wall, lacking either in some colonies or in some hydrothecae belonging to the same colony; diaphragm of uncommon shape, obliquely-set in lateral view, internal edge upraised and of irregular shape, its latero-abaxial walls converging distally and fusing into a common, median, scalloped crest anchored at varied levels on the abaxial wall of hydrotheca; hydropore broadly circular in apical view; hydrothecal aperture slightly everted, circular, often with numerous, closely-set renovations, rim entire; occasional deciduous opercula in some hydrothecae; in the colonies with unilaterally-shifted hydrothecal apophyses (towards the “frontal” aspect), all thecal apertures facing backwards. Nematothecae variably-shaped among various colonies, from short and barrel-shaped, to moderately-long and digitiform; occurring singly or in pairs on both the hydrothecal and cladial apophyses, rarely singly on some hydrothecal pedicels; occasionally renovated once or twice. Gonosome as up to 7 × 3 mm, muff-shaped coppinia, composed of gonothecae borne on the basal parts of nematothecate tubuli arising from the accessory tubes of stem and branches; gonothecae closely-packed, although not fused, urn-shaped, finely and densely striated transversely, with two distal, opposite, short, conical, lateral projections, each bearing apically a large, rounded, transversely-set aperture; tubules unbranched proximally, but frequently divided dichotomously above the gonothecae, branchlets nematothecate, often anastomosing, forming an impenetrable canopy over the gonothecae.

Remarks. Upon the examination of the quite rich material present in the collections, Z. laertesi proves to be a morphologically-varied species. Most colonies (e.g. MNHN-IK-2015-3024) have a rather compact appearance, with cladia close to one another, the (subopposite) “pairs” being constantly separated by two alternate hydrothecae; in contrast, some other colonies are more straggling in appearance, their “pairs” of cladia being separated by 3–8 hydrothecae (e.g. MNHN-IK-2019-2122, -2123, -2127).

The two rows of hydrothecae may be either coplanar (e.g. MNHN-IK-2019-2107), slightly shifted on to the “frontal” aspect of the colony (e.g. MNHN-IK-2015-3024), or decidedly forming a very acute angle between them (e.g. MNHN-IK-2019-2131). In the first case, all apertures of cladial hydrothecae are facing alternately upward and outward and, in the two latter, decidedly backward.

The hydrothecal shape varies between slightly (e.g. MNHN-IK-205-3024) to distinctly curved (e.g. MNHN-IK- 2019-2131). At the curvature of the hydrotheca, on the adaxial side, there is a notch in the wall, corresponding to an internal thickening of the perisarc (e.g. MNHN-IK-2015-3024) but, depending on the colony or portion of colony, it is not always present in all the hydrothecae (e.g. MNHN-IK-2019-2130 and -2131).

Some specimens in sample MNHN-IK-2019-2123, although possessing the distinctive, striated hydrothecae, often provided with a conspicuous adaxial notch, display several differences: 1) the perisarc is thinner and lighter in color, and the thecae are highly movable at their insertion on the corresponding apophyses; 2) their pedicels are often segmented and the nematotheca, originally borne on the apophysis, sometimes migrates on one of those segments; 3) the diaphragm has a variably upturned internal edge, instead of forming an abaxial crest; 4) the gonothecae are more elongated, and occasionally there are up to three, more upwardly-projecting apertures; however, it should be stated that, in order to preserve the integrity of the available material, only a couple of coppinia have been partially dissected, and a limited number of gonothecae examined; consequently, the available data on their morphology and size is not sufficient to be considered representative of the intraspecific variation.

Distribution. Only known from off New Caledonia ( Peña Cantero 2020; present study).

Figures

FIGURE 8. Zygophylax laertesi Peña Cantero, 2020 (part). A–D. Four colonies corresponding to various morphotypes. From samples MNHN-IK-2015-3024 (A, compact colony with slightly curved, coplanar hydrothecae), -2019-2130 (B, compact colony with distinctly curved hydrothecae in two rows forming an acute angle), -2019-2122 (C, straggling colony with slightly curved, coplanar hydrothecae) and -2019-2123 (D, straggling colony with slightly curved, coplanar hydrothecae). Scale bar: 1 mm.

FIGURE 9. Zygophylax laertesi Peña Cantero, 2020 (continued). A, B. Nematothecae from the accessory tubes of the stem. C–R. Cauline (C–G), axillar (H–L) and cladial (M–R) hydrothecae from various colonies; note deciduous operculum in C. From samples MNHN-IK-2015-3024 (A, C, H, M), -2019-2122 (E, J, P), -2019-2130 (D, I, N), -2019-2131 (O), -2019-2144 (B, F, K, Q) and -2019-2123 (G, L, R). Scale bars: A, B = 100 µm; C–R = 300 µm.

FIGURE 10. Zygophylax laertesi Peña Cantero, 2020 (continued). A–D. Nematothecae from the apophyses supporting the hydrothecae. E–O. Details of the hydrothecae, showing notably the basal diaphragm in frontal (F, H, O), lateral (E, I, J, K, N) and apical (M) aspects, as well as the notch in the adaxial wall (G, L). From samples MNHN-IK-2015-3024 (A, E–G, N, O), -2019-2122 (B), -2019-2130 (H–J), -2019-2144 (C, D) and -2019-2123 (K–M). Scale bars: A–M = 100 µm; N, O = 50 µm.

FIGURE 11. Zygophylax laertesi Peña Cantero, 2020 (concluded).A–D. Gonothecae. E–G. Portions of nematophorous tubules. H, I. Nematothecae borne on the tubules. From samples MNHN-IK-2019-2107 (A, E, H), -2130 (B, F, I) and -2146 (C, D, G). Scale bars: A–G = 500 µm; H, I = 100 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.

Tables

TABLE 5. Measurements (in µm) of the gonosome of Z. laertesi Peña Cantero, 2020

Material examined	IK-2019-2107	IK-2019-2130
Tubuli
- diameter	60–70	30–50
Nematothecae
- length	65–85	50–90
- maximum width	ca. 20	ca. 30
- diameter at aperture	ca. 5	ca. 5
Gonothecae
- length	ca. 770	ca. 740
- width (at aperture region)	ca. 540	ca. 560
- width (below aperture region)	ca. 380	ca. 360
- aperture diameter	ca. 90	ca. 85