Solenoscyphus striatus Galea, 2015

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 : 5-9

? Solenoscyphus striatus Galea, 2015

Figs 2 A–B, 3A–K; Table 1

Solenoscyphus striatus Galea, 2015a: 10 , figs 3C, 4E–G.

Material examined

PACIFIC OCEAN • two colonies, one of which is 10 × 8 cm and has a few female gonothecae, the other is 5.5× 4.5 cm and devoid of gonothecae, as well as a number of fragments resulting from the breakage of both; off New Caledonia, stn DW4700; 22°43′ S, 167°16′ E; 245–295 m; 16 Aug. 2016; KANACONO leg.; three fragments from the largest colony were cut off for DNA extraction, DNA 1349; voucher MHNG-INVE-120783; barcode identifier MK073081; MNHN-IK-2015-364 • two colonies without gonothecae, 6.5 × 6.5 cm and 6.5 × 2.5 cm, respectively; off New Caledonia, stn DW4758; 23°12′ S, 168°04′ E; 330 m; 26 Aug. 2016; KANACONO leg.; two small fragments from the largest colony were removed for DNA extraction, DNA 1350; voucher MHNG-INVE-120784; barcode identifier MK073082; MNHN-IK-2015-366 • a colony without gonothecae, 5 × 5.5 cm; off New Caledonia, stn DW4697; 22°48′ S, 167°15′ E; 465– 449 m; 16 Aug. 2016; KANACONO leg.; MNHN-IK-2015-367 • a 6.5 × 2.7 cm colony with several male gonothecae; off New Caledonia, stn DW4705; 22°46′ S, 167°19′ E; 290–317 m; 17 Aug. 2016; KANACONO leg.; two small fragments were cut off for DNA extraction, DNA 1351; voucher MHNG-INVE-120785; MNHN-IK-2015-368 • two colonies, 8× 3.5 cm and 3.5× 3.5 cm, respectively, as well as a colony fragment 4.5× 4.5 cm, all without gonothecae; off New Caledonia, stn CP4658; 22°42′ S, 167°13′ E; 303–315 m; 10 Aug. 2016; KANACONO leg.; MNHN-IK-2015-369 • a 6 cm high colony with two short basal side branches, without gonothecae; off New Caledonia, stn DW4762; 23°16′ S, 168°06′ E; 810– 805 m; 26 Aug. 2016; KANACONO leg.; MNHN-IK-2015-370 • a colony without gonothecae, 3 × 3 cm; off New Caledonia, stn DW4737; 22°45′ S, 167°42′ E; 387–456 m; 22 Aug. 2016; KANACONO leg.; used as a whole for DNA extraction, DNA 1352; voucher MHNG-INVE-120786; MNHN-IK-2015-371 • three colonies without gonothecae, 4× 1 cm, 2.2 × 1.8 cm, and 3× 2 cm; same collecting data as for preceding; MNHN-IK-2015-371 • a colony without gonothecae, 3.2× 0.8 cm, with two short side branches; off New Caledonia, stn DR4773; 23°02′ S, 168°20′ E; 400– 230 m; 28 Aug. 2016; KANACONO leg.; MNHN-IK-2015-372 • a colony without gonothecae, 5.5× 4 cm, with only the perisarc left; off New Caledonia, stn DW4770; 22°58′ S, 168°21′ E; 455–470 m; 28 Aug. 2016; KANACONO leg.; MNHN-IK-2015-373 • two colonies without gonothecae, 9.5× 8 cm and 9.5× 6 cm, respectively, as well as a few smaller fragments resulting from their breakage; off New Caledonia, stn DW4768; 23°25′ S, 168°01′ E; 180–210 m; 27 Aug. 2016; KANACONO leg.; a fragment from the smallest colony used for DNA extraction, DNA 1353; voucher MHNG-INVE-120787; barcode identifier MK073083; MNHN-IK-2015-374 • a colony without gonothecae, 5× 1.8 cm; off New Caledonia, stn DW4678; 22°51′ S, 167°34′ E; 308– 303 m; 13 Aug. 2016; KANACONO leg.; MNHN-IK-2015-465 • a 4.7× 4.5 cm colony (distinct morphotype) with a couple of fully formed female gonothecae, and a few others immature; off New Caledonia, stn DW4682; 22°22′ S, 167°24′ E; 465–495 m; 14 Aug. 2016; KANACONO leg.; a fragment was used for DNA extraction, DNA1359; voucher MHNG-INVE-120793; MNHN-IK-2015-380 • a 7.3 × 9.2 cm colony (distinct morphotype) with numerous male gonothecae, of which only a few are fully formed; off New Caledonia, stn DW4681; 22°23′ S, 167°23′ E; 490– 480 m; 14 Aug. 2016; KANACONO leg.; a fragment was used for DNA extraction, DNA1356; voucher MHNG-INVE-120790; MNHN-IK-2015-377 • a colony, 6.2 × 5.5 cm, with distinct morphotype; off New Caledonia, stn DW4741; 22°52′ S, 167°41′ E; 210 m; 23 Aug. 2016; KANACONO leg.; a fragment was used for DNA extraction, DNA1357; voucher MHNG-INVE-120791; barcode identifier MK073086 ; MNHN-IK-2015-378 • two colonies without gonothecae, 5.5× 3 cm and 4.5× 3.4 cm, respectively; same collecting data as for preceding; MNHN-IK-2015-378 • a 3.8× 5.5 cm colony (distinct morphotype) with a few immature male gonothecae; off New Caledonia, stn DW4679; 22°49′ S, 167°33′ E; 245–249 m; 13 Aug. 2016; KANACONO leg.; a fragment was used for DNA extraction, DNA1358; voucher MHNG-INVE-120792; barcode identifier MK073087; MNHN-IK-2015-379 • a colony without gonothecae, 2.4 × 1.9 cm (distinct morphotype); off New Caledonia, stn DW4685; 22°28′ S, 167°29′ E; 405– 404 m; 14 Aug. 2016; KANACONO leg.; MNHN-IK-2015-381 .

Remarks

Colonies larger (up to 10 cm high and 8 cm wide) than those described originally by Galea (2015a) occur in the present collection, as exemplified by material MNHN-IK-2015-364. The hydrorhiza is a rooted mass of stolonal fibers firmly anchoring the colonies to their substrates. The colonies are flaccid, unable to support themselves when out of liquid; flabellate, with indistinct main stems, except for a short, proximal portion (ca 1 cm long) above the origin from hydrorhiza, then irregularly branching, forming up to 5 th order branchlets. Stem and main branches are strongly fascicled. The branches are almost straight, except proximally, where they curve upwards immediately after their origin. The largest colony is fertile and carries female gonothecae; they originate laterally from below the hydrothecal bases at sites conspicuously marked by comparatively thinner perisarc than in the rest of the colony, forming rounded, filmy patches. The gonotheca is bilaterally symmetrical; broadly piriform, gradually tapering in its lower half into an indistinct pedicel; upper half globular, provided with a number of hollow spines arranged into two whorls (4–5 in the upper one, 8–9 in the lower one); one side of the gonotheca (that facing its corresponding hydrotheca) is provided with a pair of quadrangular crests forming two closelyset ‘lips’, leaving a slit-like passage for a few, large oocytes (badly preserved in present material); the spines, occasionally with truncated tips, have their bases prolonged downwards over the gonothecal wall as broad, prominent, rounded ridges, those from the lower whorl reaching almost the gonothecal base.

The colonies are monoecious and there is a notable sexual dimorphism of the gonothecae. Indeed, material MNHN-IK-2015-368 bears male gonothecae. Similarly to the females, they arise laterally from below the hydrothecal bases, and are bilaterally symmetrical; broadly amphora-shaped, base appressed to its corresponding hydrotheca and tapering abruptly into indistinct pedicel, perisarc finely and denselystriated basally; slightly flattened laterally, distally a short neck region bearing apically a small, rounded aperture; neck inclined to one side.

Opercula are well discernible in many hydrothecae from sample MNHN-IK-2015-370. Terminal stolonization may occasionally occur, as exemplified by samples MNHN-IK-2015-371 and -374; in addition, a tendril may be continued distally by a short sequence of thecate internodes. Multiple, closelyset renovations of the hydrothecal margin occur in MNHN-IK-2015-372.

A peculiar morphotype of this species ( Figs 2B , 32F–K) occurs in several samples, viz. MNHN-IK-2015-377 to MNHN-IK-2015-381. Its main distinguishing features rely in its more compact appearance of the colonies (compare Fig. 2B and 2A , respectively), the hydrothecae closer to one another (compare Fig. 3F and 3A ), adnate for about half their length to their corresponding internodes. In material MNHN-IK-2015-380, the female gonothecae are provided with a number of hollow, distally truncated, occasionally twin spines arranged into two whorls.

As stated earlier by Galea (2015a), this species does not resemble either S. candelabrum Galea, 2015 (type species of the genus) or S. decidualis Galea, 2015 , especially in colony form, although all possess rounded, filmy, deciduous hydrothecal opercula. Unlike S. striatus , the last two species form regularlypinnate colonies, their perisarc is entirely smooth, and there is no conspicuous raised collar of thickened perisarc just below their hydrothecal aperture. In addition, the cladia of S. candelabrum are spirally twisted proximally, and its hydrothecae possess a conspicuous pattern of internal perisarcal thickenings. Gonothecae are only known in S. striatus , and the females – notably – resemble those of some species of Staurotheca , e.g., S. echinocarpa (Allman, 1888) ( Peña Cantero & Vervoort 2003) , suggesting that the present species belongs to the family Staurothecidae .

Similar female gonothecae were also described in Giganthotheca raukumarai Vervoort & Watson, 2003 ( Vervoort & Watson 2003: figs 27B–C, 28B), suggesting that this species could be confidently removed from the Sertulariidae and reasonably assigned to the Staurothecidae , as noted above for G. maxima . In addition, the gonothecae illustrated by these authors ( Vervoort & Watson 2003: fig. 29B, D) are undoubtedly male, and come morphologically close to those of S. striatus . However, the relationships between G. raukumarai and S. striatus are far from fully understood, and only a molecular evidence is expected to clarify the case.

As it will be shown in the ‘Molecular study’ section at the end of this report, S. decidualis does not cluster with either S. striatus or S. subtilis sp. nov. (for description, see below), suggesting that they are not congeneric. Given the morphological peculiarities of S. candelabrum , it could be justifiably assumed that it forms a so-far monotypic genus, while S. decidualis , on one hand, and both S. striatus and S. subtilis sp. nov., on the other hand, could well belong to two undescribed genera. For this reason, when combining the genus Solenoscyphus to one of these three species, it is preceded by a question mark, pending additional data to clarify their taxonomic statuses. For additional comments, see the ‘Molecular study’ section.

Distribution

Only known from off New Caledonia ( Galea 2015a; 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.