Halopteris australis Galea & Gioia Di Camillo & Maggioni & Montano & Schuchert 2018, sp. nov.
Creators: name: Galea, Horia R.
name: Gioia Di Camillo, Cristina
name: Maggioni, Davide
name: Montano, Simone
name: Schuchert, Peter
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Cnidaria
Hydrozoa
Leptothecata
Halopterididae
Halopteris
Halopteris australis

description: Halopteris australis Galea, sp. nov.
Figs 1E, 2F, 6; Table 5; Appendix 1
Halopteris buskii – Vervoort & Vasseur, 1977: 72, fig. 31 [non Halopteris buskii (Bale, 1884)].
Halopteris polymorpha – Schuchert, 1997 (pro parte): 64, fig. 23 [non Halopteris polymorpha (Billard, 1913)].
Type material: MHNG-INVE-82742; France, New Caledonia, Nouméa, south of N’Géa islet, -22.296° 166.489°, 9 m, coll. E. Tardy; 06.10.2012; fertile (female) colony in alcohol and two microslides (H20/37-38), with stems up to 1.8 cm high, growing on algae.
Diagnosis: Small-sized Halopteris, with cormoids not exceeding 2.5 cm high. Stems monosiphonic, homomerously-segmented, internodes rather long, bearing a hydrotheca in their proximal half, a lateral apophysis, and up to 8 nematothecae (1 mesial, a pair of laterals, a pair of axillar, as well as up to 3 superiors in two parallel rows). Cladia alternate, heteromerouslysegmented; 1st ahydrothecate internode with 1, exceptionally 2, nematothecae in a row; ordinary ahydrothecate internodes with 1 nematotheca; hydrothecate internodes with a hydrotheca and its up to 5 associated nematothecae (1 mesial, a pair of laterals, and 1, or rarely 2, axillar); hydrotheca cup-shaped, deep, adnate for 2/3rd its adaxial wall, swollen basally, rim distinctly sinuated in lateral view, aperture circular, lateral nematothecae long, borne on well-developed apophyses, surpassing hydrothecal rim. Female gonothecae given off from caulus; piriform, borne on quadrangular pedicel, 2 basal nematothecae, aperture large, circular, perpendicular to long axis of theca, rim thickened, a watch-glass-shaped operculum.
Etymology: From the Latin austrālis, meaning “of the south” with reference to its occurrence in the South Pacific.
Description: Colonies composed of a varied number of upright cormoids, up to 2 cm high in present material, arising from creeping, branching, anastomosing hydrorhiza. Stems erect, simple, monosiphonic (Figs 1E, 2F), composed of a basal, ahydrothecate part, irregularly divided into a few segments (up to 5) by means of transverse constrictions of the perisarc, and carrying a varied number of nematothecae arranged in two parallel rows; above, remainder of stem comprising a much longer, hydrothecate part, homomerouslysegmented into regular internodes by means of oblique nodes (Fig. 6A), slightly marked proximally to more conspicuous distally; occasionally, transverse nodes can be inserted towards the distal end of cauli, creating a heteromerous segmentation; a hinge joint between the two parts of the stem. Up to 26 relatively long cauline internodes, almost collinear proximally, gradually becoming geniculate towards distal end; each provided with a hydrotheca in its proximal half, a well-developed, lateral apophysis, as well as up to 8 nematothecae: 1 mesial, a pair of laterals, a pair of axillar (only one of these subsisting distally on stem) (Fig. 6B), as well as 1-3 superior ones in two parallel, closely-set rows (when only two of these are present, they may occur at the same level, or one above the other; they are confined to a separate ahydrothecate segment when transverse nodes intervene towards distal end of caulus). Cladia up to 2.5 mm long, alternate, except in the proximal most cauline internodes, where they are opposite; composed of a short, quadrangular segment proximally, followed by a heteromerous division into alternating ahydrothecate and hydrothecate internodes; the former with proximal node transverse and distal node oblique; the reverse in hydrothecate internodes (Fig. 6D); 1st ahydrothecate internode comparatively longer than subsequent ones, and carrying single nematotheca (exceptionally 2); ordinary ahydrothecate internodes short, and provided with one nematotheca; hydrothecate internodes up to 5 per cladium, comparatively longer than their ahydrothecate counterparts, and carrying a centrally-placed hydrotheca and its up to 5 associated nematothecae: a mesial, a pair of laterals, and generally one axillar, although a pair could be occasionally noted (Fig. 6C). Hydrothecae cup-shaped, rather deep, about 1/3rd adnate; abaxial wall slightly sigmoid, rounded proximally and slightly flaring below the rim; aperture circular in apical view, but distinctly sigmoid when seen laterally, due to broad (though shallow) abaxial emargination, giving the impression that an abaxial cusps occurs (Fig. 6A, D). All nematothecae, including the axillar ones, bithalamic and movable; mesial nematothecae triangular in frontal view, with deep adaxial emargination (Fig. 6E 3); laterals relatively long, surpassing the hydrothecal rim (Fig. 6D), and borne on well-developed apophyses; basal chamber high and narrow, upper chamber shallow, with sigmoid adaxial wall (Fig. 6E 4-7); axillar nematothecae (Fig. 6 E 6, 7) small, with wall of upper chamber lowered on side facing adaxial wall of hydrotheca; both cladial (Fig. 6E 2) and cauline (Fig. 6E 1) nematothecae characteristically turned posteriad, tall, conical, with rim of apical chamber lowered adaxially. Female gonothecae borne on cauli by means of short, lateral apophyses given off from below the hydrothecae, followed by a pedicel composed of a quadrangular segment; large, piriform, with 2 basal nematothecae, and a large, apical aperture with thickened rim, perpendicular to long axis of the theca, and closed by a watch-glass-shaped operculum (Fig. 6F). Male gonothecae elongated-ovoid, curved proximally and provided there with single nematotheca; aperture distal, small, circular. Hydranths badly preserved, tentacle number could not be ascertained. Cnidome (Fig. 6G): only large capsules (ca. 17.5 × 6.3 μm), likely pseudostenoteles, observed in the material in hand. Color in life: milky white (Fig. 1E).
Dimensions: See Table 5.
Remarks: There is little doubt that the present material from New Caledonia is conspecific with the specimens with distinctly sinuated hydrothecal margins from French Polynesia examined by Vervoort & Vasseur (1977, as H. buskii) and, subsequently, by Schuchert (1997, provisionally assigned to H. polymorpha). Their main morphological and morphometrical features are compared in Table 5. Unfortunately, it was not possible to obtain the material of Vervoort & Vassueur for a re-examination, due to ongoing renovation of NBC.
The cauline internodes bear commonly 1 (52%) or 2 (44%) superior nematothecae, although up to 3 may occasionally (4%, n = 75 internodes belonging to 5 different stems) be present in the material in hand. Schuchert (1997), however, reports up to 5 of these. The number of axillar nematothecae was apparently overlooked by Vervoort & Vasseur (1977):
1) Schuchert (1997) stated that, occasionally, these may occur in pairs behind the hydrocladial hydrothecae, a conclusion confirmed by our observations;
2) it was noted that, on cauli, one nematotheca of a pair, namely that bent towards the cladium, is hidden by the apophysis supporting its lateral counterpart, and requires a careful examination to be noticed; alternatively, it should be stated that only one nematotheca of a pair subsists on the distalmost cauline internodes.
Only female gonothecae occur in the present material (Fig. 6F), although those of both sexes were illustrated by Schuchert (1997, fig. 23B, right).
Halopteris australis, through the presence of pairs of axillar nematothecae especially on the stem, and the heteromerous segmentation of its cladia, resembles H. brasiliensis sp. nov., H. liechtensternii, and H. vervoorti. However, any of these is provided with the distinctively sinuated hydrothecal margin displayed by it.
In addition, H. brasiliensis has thicker stems and cladia, its lateral nematothecae are relatively short and conical, and do not surpass the hydrothecal rim. Halopteris liechtensternii is readily distinguished through the shape and size of its gonothecae, the females being long and almost tubular, while the males are dwarfed. Halopteris vervoorti forms comparatively shorter cormoids, with shorter stem internodes (and, consequently, more approximated cladia) provided with 1-2 superior nematothecae characteristically arranged in a row, and its hydrothecae are slightly shorter and narrower. Additional differences to other congeners are summarized in Appendix 1.
Distribution: New Caledonia (present study), French Polynesia (Vervoort & Vasseur, 1977; as H. buskii).
description: Published as part of Galea, Horia R., Gioia Di Camillo, Cristina, Maggioni, Davide, Montano, Simone & Schuchert, Peter, 2018, A reassessment of Halopteris polymorpha (Billard, 1913) (Cnidaria: Hydrozoa), with descriptions of three new species, pp. 21-59 in Revue suisse de Zoologie 125 (1) on pages 36-38, DOI: 10.5281/zenodo.1196007