Halopteris millardae Galea, 2018

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, Revue suisse de Zoologie 125 (1), pp. 21-59 : 38-40

publication ID	https://doi.org/ 10.5281/zenodo.1196007
DOI	https://doi.org/10.5281/zenodo.5590666
persistent identifier	https://treatment.plazi.org/id/03A487AE-FF92-2C08-FF14-8A58FC656959
treatment provided by	Plazi
scientific name	Halopteris millardae Galea
status	sp. nov.

Treatment

Halopteris millardae Galea , sp. nov.

Figs 1F View Fig , 2G View Fig , 7 View Fig ; Table 5 View Table 5 ; Appendix 1

Halopteris polymorpha – Millard & Bouillon, 1973 (pro parte): 83, fig. 10F, G, H, J. – Bouillon et al., 1995: 49. – Schuchert, 1997 (pro parte): 66, 72, fig. 22A-D [non Halopteris polymorpha ( Billard, 1913) ].

non Halopteris polymorpha – Millard & Bouillon, 1973 (pro parte): 83 (= H. platygonotheca Schuchert, 1997 ).

Halopteris buskii – Rees & Vervoort, 1987 (pro parte): 119, fig. 25A-B [non Halopteris buskii ( Bale, 1884) ].

Holotype material: MACT 2700; Seychelles, Mahé I., coll. J. Bouillon ( MRAC Expedition); 1966; numerous cormoids, 1.5-7 cm high, with both female and male gonothecae [material studied by Millard & Bouillon (1973), as H. polymorpha ( Billard, 1913) ; not studied here due to ongoing renovation of MRAC; however, 4 microslides (MHNG-INVE-37494, H12/32-35) prepared from the holotype, were examined for the purpose of the present study; according to Schuchert (1997: 55), cormoids of H. platygonotheca Schuchert, 1997 co-occur in the original sample].

Paratype: MHNG-INVE-98634; Republic of Maldives, Faafu Atoll , 3.06497° 72.9212°, 35 m, coll. D. Maggioni and S. Montano; 14.04.2016; colony composed of 6 sterile stems, 1.7-3.9 cm high; 16S sequence MF773747 View Materials .

Diagnosis: Halopteris with tall cormoids, reportedly reaching 7 cm high; stems homomerously-segmented, each internode moderately-long, carrying a hydrotheca, a lateral apophysis, and up to 7 nematothecae: 1 mesial, a pair of laterals, a scale-shaped axillar one, as well as 2-3 superior ones arranged in two parallel rows; cladia alternate, heteromerously-segmented; ahydrothecate internodes with 2 laterally-displaced nematothecae (distally, only 1 of these subsists); hydrothecate internodes with a hydrotheca and its 4 associated nematothecae: 1 mesial, a pair of laterals, and a small, scale-shaped axillar one. Colonies monoecious. Female gonotheca borne on stems, large, ovoid, laterally flattened, with 2 basal nematothecae, and a distal, transverse aperture closed by glass-watch-shaped operculum. Male gonothecae borne on both stems and cladia, small, fusiform, with narrow distal aperture, and one basal nematotheca.

Etymology: This species honors the late N.A.H. Millard (1914-1997) for her outstanding contribution to the hydrozoan research.

Description: Colonies composed of a varied number of tall stems (reportedly up to 7 cm in height) arising from tortuous, creeping, branching, anastomosing hydrorhiza, devoid of nematothecae. Stems erect, simple, monosiphonic ( Figs 1F View Fig , 2G View Fig ), composed of a basal, ahydrothecate part of varied length, and a much longer, distal part bearing hydrothecae and hydrocladia; basal part arising directly from hydrorhiza without constriction above origin, usually not segmented by transverse nodes, and carrying a varied number of nematothecae in two parallel rows; distalmost node deeply-cut and oblique; remainder of stem homomerously-segmented into regular internodes by means of oblique nodes; each internode moderately long, with a hydrotheca in its basal half, a short lateral apophysis supporting a cladium, and up to 8 nematothecae: 1 mesial, a pair of laterals, a small, scaleshaped axillar one, as well as generally 2, occasionally 3, or exceptionally 4, superior nematothecae arranged in two parallel rows ( Fig. 7A, B View Fig ); proximal most internode carries 2 opposite apophyses supporting a pair of cladia, and usually bears 3-4 superior nematothecae. Cladia borne on corresponding stem apophyses, alternate, composed of a proximal, short, quadrangular segment, followed by a succession of athecate and thecate internodes resulting from a heteromerous segmentation ( Fig. 7A View Fig ); ahydrothecate internodes with straight node proximally and oblique node distally; the reverse in hydrothecate internodes; the latter, up to 5 per cladium in the material in hand, comprising a centrally-placed hydrotheca, and its 4 associated nematothecae: 1 mesial, a pair of laterals, as well as a minute, scale-shaped axillar one ( Fig. 7C, D View Fig ); ahydrothecate internodes shorter than their hydrothecate counterparts, with generally 2 laterally-displaced nematothecae, either opposite or subopposite, more often found in proximal most internodes, whereas only one of these is retained by the distalmost internodes. Hydrothecae cup-shaped, moderately-deep, fused for about 1/3rd their adaxial length; abaxial wall straight for most of its length, slightly everted below aperture; the latter perfectly circular in apical view, slightly flaring and showing a sinuated rim in lateral view, though not producing an abaxial cusp ( Fig. 7D View Fig ). All nematothecae, except the axillar ones, bithalamic and movable; mesial ones triangular in frontal view, with deeply-scooped rim on adaxial side ( Fig. 7 E View Fig 5 View Fig , 6 View Fig ); laterals borne on rather short apophyses, conical, with thickened walls ( Fig. 7E 7 View Fig ), not surpassing the hydrothecal rim ( Fig. 7D View Fig ); cauline ( Fig. 7 E View Fig 1 View Fig , 2 View Fig ) and cladial ( Fig. 7 E View Fig 3 View Fig , 4 View Fig ) nematothecae characteristically turned posteriad ( Fig. 7A, C View Fig ), long, conical, with tall basal chambers and comparatively shallow apical chambers, with adaxiallyscooped rims; axillar nematothecae associated to the hydrothecae of both caulus ( Fig. 7E View Fig 8 View Fig ) and cladia ( Fig. 7E View Fig 9 View Fig 9 ), monothalamic. Stems monoecious. Female gonothecae borne below the stem hydrothecae through short lateral apophyses and a single-segmented, quadrangular pedicel; large, ovoid, laterally-flattened, with two nematothecae on base, and a distal, transverse, conspicuously thickened aperture closed by a glasswatch-shaped operculum. Male gonothecae borne on both stems and cladia, through short, lateral apophyses and a single-segmented, quadrangular pedicel; comparatively smaller than female, fusiform, with distal, narrow, circular aperture, and a basal nematotheca. Color in life: brownish ( Fig. 1F View Fig ). Cnidome ( Fig. 7F View Fig ) composed of 3 types of microbasic mastigophores: large, elongated-ovoid [(19.9-21.3) × (7.3-8.0) μm, in nematophores, as well as scattered in the coenosarc]; small, banana-shaped [(5.8-6.5) × (2.1- 2.3) μm, in tentacles]; small, ovoid capsules [(5.1-5.8) × (2.9-3.1) μm, scattered in the coenosarc].

Dimensions: See Table 5 View Table 5 .

Remarks: Upon comparison of the newly-collected Maldivian specimens with the slide material MHNG-INVE-37494 (H12/32-35) prepared from the holotype designated herein [sample MACT2700 studied by Millard & Bouillon (1973), as H. polymorpha ( Billard, 1913) ], it appears that both are conspecific.

The description of the gonothecae, often distorted in the slide material available (H12/32: ♂; H12/33: ♂ & ♀; H12/35: ♂), was taken after Millard & Bouillon (1973: 84, fig. 10H & J) and Schuchert (1997: 22, fig. 22D, as H. polymorpha ).

The tallest cormoid examined here (3.9 cm high) bears 54 cauline hydrothecate internodes. Not only the proximal most internode gives rise to a pair of cladia, but this situation is also repeated in several subsequent, consecutive, more distal internodes. In one cormoid, a secondary stem arises from one of the paired, basalmost hydrocladia.

The first cladial ahydrothecate internodes do not differ much in length compared to their subsequent counterparts; they generally bear 2 nematothecae, though exceptionally 3 were noted. The remaining internodes equally bear 2 nematothecae (although, exceptionally, two pairs could be found) when they are found in the proximal parts of the cladia, while only one nematotheca occurs in those internodes confined to the distalmost parts of the cladia.

Rees & Vervoort’s (1987) record from Zanzibar (Stn. 112) assigned to H. buskii likely belongs to the present species. Indeed, the occurrence of pairs of suprahydrothecal nematothecae, and of a single axillar nematotheca on the cauline internodes, are distinctive. However, the authors mention only one nematotheca per ahydrothecate cladial internode; as stated above, this situation is, quite often, met with in the distalmost internodes of the material MHNG-INVE-37494. It should also be stressed that only one nematotheca of a couple is visible when the cladia are seen laterally, especially in material mounted between slide and coverslip. Strangely, Rees & Vervoort do not mention a sinuated hydrothecal rim, though it should be underlined that this peculiarity is only noticeable towards the adaxial thecal wall, where the presence of lateral nematothecae could make it less obvious upon a routine examination.

Halopteris millardae comes close to a few congeners with homomerously-segmented cauli and a heteromerous division of their cladia, and whose both cauline and cladial hydrothecae are provided with an axillar nematotheca, namely H. nuttingi ( Billard, 1911) and H. polymorpha . Halopteris nuttingi has proportionally shorter cauline internodes [compare fig. 21B in Schuchert (1997) with Fig. 7A View Fig herein], provided with up to three pairs of superior nematothecae in two parallel rows, and the upper chamber of its lateral nematothecae is globular, with the rim scooped on both ad- and abaxial walls [ Billard (1913), as H. buski (sic!); Schuchert (1997, fig. 21C, H), as H. polymorpha ]. Halopteris polymorpha has comparatively longer stem and cladial ahydrothecate internodes ( Fig. 3A, B View Fig ), its hydrothecae are shallower ( Fig. 3D, F View Fig ) and are provided with an even rim. Additional differences to other congeners are summarized in Appendix 1.

Distribution: Seychelles [ Millard & Bouillon (1973), as H. polymorpha ( Billard, 1913) ], Maldives (present study), Zanzibar [ Rees & Vervoort (1987), as H. buskii ( Bale, 1884) ].