Symplectoscyphus tropicus
Creators: name: Galea, Horia R.
name: Schuchert, Peter
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Cnidaria
Hydrozoa
Leptothecata
Sertulariidae
Symplectoscyphus
Symplectoscyphus tropicus

description: Symplectoscyphus cf. tropicus (Hartlaub, 1901)
Figs 16D, 17 N–O; Table 12
Sertularia variabilis Clarke, 1894: 75, pls 4–5 figs 17–22 [non Sertularella variabilis Bale, 1888 = Symplectoscyphus indivisus (Bale, 1882)].
Sertularella tropica – Hartlaub 1901: 41, fig. 19 (new name for S. variabilis Clarke, 1894). — Nutting 1904: 102, pl. 26 figs 3–4. — Clarke 1907: 14, pl. 10 figs 1–3, 3B. — Billard 1925: 165, fig. 26. — Redier 1971: 142.
Material examined
PACIFIC OCEAN • a 6.5 cm high colony, bearing an incompletely-formed gonotheca on the proximal part of a cladium; off New Caledonia, stn DW4672; 22°47′ S, 167°26′ E; 310– 290 m; 13 Aug. 2016; KANACONO leg.; MNHN-IK-2015-394.
Description
Colony arising from a root-like, ramified hydrorhiza firmly anchoring it to its substrate. Stem simple, 6.5 cm high, fascicled over its proximal 2 cm; divided by weakly-indicated transverse nodes, each internode composed of an indistinct apophysis (supporting a cladium) with its associated axillary hydrotheca, and two alternate hydrothecae above. Cladia generally alternate, but there can be exceptions especially when one, three or four hydrothecae (instead of only two) occur above an axillar hydrotheca. Cladia given off slightly laterally from below the bases of stem hydrothecae, and distinctly shifted on to the ‘anterior’ side of the colony; up to 1.8 cm long and carrying up to 15 hydrothecate internodes separated by distinct oblique nodes; generally unbranched, though one cladium bears three short, secondary branchlets of up to six hydrothecate internodes. Hydrothecae alternate, large, tubular, adnate for about 2/7 to the corresponding internodes; free adaxial wall long, convex proximally, concave distally; adnate adaxial wall slightly curved, ending basally in conspicuous perisarc plug; there is no hydrothecal base, the abaxial wall being a continuation of the internode; aperture circular in frontal view, rim everted on adaxial side, provided with three broad, low, triangular cusps separated by shallow embayments; opercular apparatus composed of three triangular flaps meeting centrally to form a pyramidal roof. A single gonotheca arises from below the base of a cladial hydrotheca, but it is incomplete, having only its basal, vasiform part already formed.
Remarks
The present material comes close to that assigned by Billard (1925) to Symplectoscyphus tropicus (Hartlaub, 1901), although it is of slightly bigger proportions, and doesn’t have fully-formed gonothecae so as to facilitate their comparison. In addition, it is not clear whether this record and that of Billard belong to the same species as the material of Clarke (1894), especially since there are no available measurements for the latter. However, the gonothecae illustrated by both Billard and Clarke appear very similar in shape, supporting a possible conspecificity.
Hartlaub (1901) noted the secondary homonymy between Sertularia variabili s (Clarke, 1894) and Sertularella variabilis Bale, 1888, and renamed the former Sertularella tropica. Both Clarke’s and Bale’s hydroids should be correctly assigned to the tricuspidate genus Symplectoscyphus. In addition, the latter is now considered as a junior synonym of Symplectoscyphus indivisus (Bale, 1882) (Vervoort & Watson 2003).
Distribution
Off Panama (Clarke 1894), off Ecuador (Clarke 1907), Indonesia (Billard 1925), French Polynesia (Redier 1971) and New Caledonia (present study).
description: Published as part of Galea, Horia R. & Schuchert, Peter, 2019, Some thecate hydroids (Cnidaria: Hydrozoa) from off New Caledonia collected during KANACONO and KANADEEP expeditions of the French Tropical Deep-Sea Benthos Program, pp. 1-70 in European Journal of Taxonomy 562 on pages 52-53, DOI: 10.5852/ejt.2019.562, http://zenodo.org/record/3474305