Solenoscyphus subtilis Galea, 2019

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, European Journal of Taxonomy 562, pp. 1-70 : 10-11

? Solenoscyphus subtilis Galea , sp. nov.

urn:lsid:zoobank.org:act:B6AF627E-5000-401E-A02D-F5301FECB368

Figs 2C , 3 L–M; Table 1

Diagnosis

Colonies flabellate, arising from root-like hydrorhiza. Stems lightly fascicled, irregularly branched several times; division into internodes indistinct. Hydrothecae alternate, rather distant; long, tubular, adnate for ¼ their length, with an apical raised collar of distinctly thickened perisarc. Whole colony covered by finely and densely-striated perisarc. Gonothecae unknown.

Etymology

From the Latin ‘ subtīlis ’, meaning ‘slender’, to describe the shape of its hydrothecae.

Material examined

Holotype PACIFIC OCEAN • a colony without gonothecae, 4.1× 2.3 cm; off New Caledonia, stn DW4759; 23°12′ S, 168°03′ E; 317–343 m; 26 Aug. 2016; KANACONO leg.; a fragment was used for DNA extraction, DNA1360; voucher MHNG-INVE-120794; barcode identifier MK073088; MNHN-IK-2015-382 .

Paratype PACIFIC OCEAN • a colony without gonothecae 3.8 × 0.8 cm; off New Caledonia, stn DW4759; 23°12′ S, 168°03′ E; 317–343 m; 26 Aug. 2016; KANACONO leg.; MNHN-IK-2015-487 .

Additional material

PACIFIC OCEAN • two colonies without gonothecae, 3× 0.5 cm and 3.3 × 0.8 cm, respectively; off New Caledonia, stn DW4759; 23°12′ S, 168°03′ E; 317–343 m; 26 Aug. 2016; KANACONO leg.; MNHN-IK-2015-488 • originally a 2.3 cm high colony without gonothecae; off New Caledonia, stn DW4760; 23°15′ S, 168°03′ E; 319– 304 m; 26 Aug. 2016; KANACONO leg.; a 0.7 cm long distal fragment was cut off for DNA extraction, DNA1361; voucher MHNG-INVE-120795; barcode identifier MK073089; MNHN-IK-2015-383 .

Description

Colonies flabellate, up to 4.1 cm high and 2.3 cm wide, arising from root-like hydrorhiza firmly anchoring the colony to its substrate. Main stem indistinct, except for its basal 1–3 mm above origin from hydrorhiza, then branching irregularly and forming up to 2 nd order branchlets; lightly fascicled basally, grading to monosiphonic distally; division into internodes indistinct; stem and branches with similar structure: each equivalent of internode moderately-long, slightly geniculate, bearing a hydrotheca distally; 1 st internode of a side branch comparatively longer than subsequent ones; branches given off nearly perpendicularly to axis of higher order branches, but rapidly pointing upwards at geniculation introduced by 1 st hydrotheca. Hydrothecae alternate, in two parallel, coplanar rows; exceedingly long, cylindrical, adnate for ca ¼ their length to the corresponding internodes; free adaxial and abaxial walls parallel and straight; adnate adaxial wall curved, ending in basal perisarc plug; there is no complete base for the hydrotheca, but only a short lamellar projection of the perisarc on abaxial side; a conspicuous raised collar of thickened perisarc immediately below the rounded aperture; opercula not observed. Perisarc straw colored to lightly dark in older parts, finely and densely-striated throughout the colony. Gonothecae unknown.

Remarks

The present species comes close to S. striatus through the appearance of its colonies and their hydrothecae with striated walls and thickened apertures. Evidence from molecular data confirms the fact that they are, indeed, congeneric (see ‘Molecular study’ section below). As a specific difference, S. subtilis sp. nov. has comparatively slenderer (hence its specific name) and less adnate hydrothecae (compare Fig. 3M and 3B ).

Distribution

Only known from off New Caledonia (present study).

Figures

Fig. 2. A.? Solenoscyphus striatus Galea, 2015, fertile colony from sample MNHN-IK-2015-364. — B.? S. striatus, morphotype with approximated hydrothecae, sample MNHN-IK-2015-377. — C.? Solenoscyphus subtilis Galea, sp. nov., paratype colony (left), MNHN-IK-2015-487; holotype colony (middle), MNHN-IK-2015-382; one colony from sample MNHN-IK-2015-488 (right). Scale bar: 2 cm.

Fig. 3. A–E.? Solenoscyphus striatus Galea, 2015, branch fragment (A), hydrotheca (B), female gonotheca in lateral (C) and apical (D) views, all from sample MNHN-IK-2015-364; male gonotheca (E) in lateral (left) and frontal (right) aspects, from sample MNHN-IK-2015-368. — F–K.? S. striatus, morphotype with approximated hydrothecae:colony fragments (E–F, from samples MNHN-IK-2015-376 and MNHN-IK-2015-377, respectively), hydrothecae (H–I, from samples MNHN-IK-2015-378 and MNHN-IK-2015-377, respectively), male gonotheca (K, from sample MNHN-IK-2015-377). — L–M.? Solenoscyphus subtilis Galea, sp. nov., colony fragment (L), hydrotheca (M), both from sample MNHN-IK-2015-382. Scale bars: B, H–I, M = 500 µm; A, C–G, J–L = 1 mm.