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

description: ? Symplectoscyphus acutustriatus Galea, sp. nov.
urn:lsid:zoobank.org:act: DDBE1A82-BE69-405E-A1AD-E5093423E389
Figs 16A, 17 A–E; Tables 8–10
Diagnosis
Colonies erect, with up to 2.5 cm high, monosiphonic, sparingly-branched stems, divided into moderatelylong, geniculate, regular internodes by oblique nodes slanting in alternate directions. Branches with similar structure to that of the stems. Hydrothecae biseriate, alternate, coplanar, conical, adnate for ⅓ or less to the internode, surface distinctly ridged; ridges projecting apically as almost free frills; 7–8 ridges on free axadial wall, 8–10 on abaxial wall; up to seven submarginal, internal projections of the perisarc, present in basalmost hydrothecae, but missing elsewhere and, sometimes, in a whole colony. Gonothecae borne laterally on the stem internodes; elongated-ovoid, transversely ringed, aperture on top of short neck region.
Etymology
The specific name combines two Latin words ‘ ăcūtus, -a, -um ’, meaning ‘sharp’, and ‘ strĭātus, -a, -um ’, meaning ‘provided with striae’, to describe the particulars of the transverse ridges of the outer hydrothecal wall.
Material examined
Holotype PACIFIC OCEAN • a small, fertile colony on limestone, composed of five stems up to 2 cm high, four of which bear one gonotheca each; off New Caledonia, stn DW4977; 19°46′ S, 158°30′ E; 280–304 m; 9 Sep. 2017; KANADEEP leg.; MNHN-IK-2015-460.
Paratype PACIFIC OCEAN • a rather profuse, colony on dead gorgonian with stems up to 2.5 cm high, without gonothecae; off New Caledonia, stn DW4945; 25°22′S, 159°43′E; 130– 108 m; 4 Sep. 2017; KANADEEP leg.; two small stems were used for DNA extraction, DNA1388; voucher MHNG-INVE-120849; barcode identifier MK073102; MNHN-IK-2015-461.
Additional material
PACIFIC OCEAN • a colony composed of several stems, up to 2 cm high, without gonothecae; off New Caledonia, stn DW5026; 20°22′ S, 158°40′ E; 360–410 m; 21 Sep. 2016; KANADEEP leg.; MNHN-IK-2015-446.
Description
Colonies arising from creeping, branching, anastomosing hydrorhiza. Stems erect, monosiphonic, up to 2.5 cm high, composed of a basal, smooth, ahydrothecate part, 3–7 mm long above origin from stolon, and a much longer, distal, hydrothecate part above; the latter divided into regular internodes by means of almost indistinct oblique nodes slanting in alternate directions; branching sparse, with up to three coplanar side branches given off laterally and irregularly from below the bases of some stem hydrothecae, on one or both sides of the stem; branches with similar structure to that of the stem. Internodes relatively short, distinctly geniculate, each bearing distally a hydrotheca; the latter alternate in position, the two rows being coplanar. Hydrothecae moderately-long, conical, adnate for ⅓ or less to the corresponding internodes; surface conspicuously ridged; ridges well-developed, projecting apically almost as free frills; there are 7–8 complete ridges encircling the hydrotheca distally, and up to 8-10 on the abaxial wall, the basalmost ones incomplete; there are seven intrathecal, submarginal projections of the perisarc, visible in the lower stem hydrothecae, but disappearing towards distal parts of the colony: two latero-adaxial, one abaxial, and two latero-abaxial. Gonotheca borne on stems and/or branches, given off laterally in middle of internode on side opposite to hydrotheca; large, piriform, transversely-ridged (12–14 ridges), tapering abruptly basally into indistinct pedicel, distally walls merging progressively; aperture apical, small, rounded, on short neck region with broadly polygonal perimeter, occasionally forming 3 indistinct projections of perisarc.
Remarks
The prominent ridges on the outer walls of the hydrothecae are distinctive. Only a few congeners are provided with transverse undulations or ridges (see Table 9 for comparison), but in none their development reaches the extent met with in S. acutustriatus sp. nov.
The internal, submarginal cusps are variably present among the hydrothecae belonging to the same stem (e.g., MNHN-IK-2015-460), and are even absent in stems of some colonies (e.g., MNHN-IK-2015-446). Only a few congeners have been shown to possess such structures, and their main distinguishing features are summarized in Table 10.
The systematic position of this species is discussed in the ‘Molecular study’ section.
Distribution
Only known from off 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 43-46, DOI: 10.5852/ejt.2019.562, http://zenodo.org/record/3474305