Caledoniana microgona 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 : 4-11

Caledoniana microgona Galea, 2015

Fig. 1C

Caledoniana microgona Galea, 2015a: 6 , figs 1C, 2E–G.

Material examined

PACIFIC OCEAN • a 2.4 cm high colony fragment with 3 male gonothecae in middle part, with only the perisarc left; off New Caledonia, stn DW4672; 22°47′ S, 167°26′ E; 310– 290 m; 13 Aug. 2016; KANACONO leg.; MNHN-IK- 2015 -360 • originally a 1.8 cm high colony fragment bearing a 2.2 cm long side branch, the latter carrying 2 female gonothecae; off New Caledonia, stn DW4670; 22°58′ S, 167°24′ E; 680– 612 m; 12 Aug. 2016; KANACONO leg.; a 0.8 cm long fragment of the main axis was cut off for DNA extraction, DNA 1348; voucher MHNG-INVE- 120782; barcode identifier MK 073080 ; MNHN-IK- 2015 -363 .

Remarks

The hydrothecae are closer to one another in this species than in C. decussata and, as stated by Galea (2015 a), their adaxial wall is comparatively shorter, these two characters readily distinguishing them. Like the previous species, C. microgona also appears sexually dimorphic and forming monoecious colonies. Its specific name is obviously inappropriate, as the hydroid was originally described based on specimens provided with ‘small’, saccular gonothecae that were not recognized then as being male. The female gonothecae are similar to those described in C. decussata (see above), but are of comparatively larger proportions (ca 6890 µm long and 3715 µm wide, when seen laterally; one gonotheca measured).

Distribution

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

? 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 MK 073081 ; 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 MK 073082 ; 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 MK 073083 ; 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 MK 073086 ; 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 MK 073087 ; 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).

? 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 MK 073088 ; 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 MK 073089 ; 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).

? Solenoscyphus decidualis Galea, 2015

Solenoscyphus decidualis Galea, 2015a: 9 , figs 3B, 4C–D.

Material examined

PACIFIC OCEAN • a 5.7 cm high colony and the 1.1 cm long tip of a second colony, both without gonothecae; off New Caledonia, stn DW4715; 22°50′ S, 167°27′ E; 424 m; 18 Aug. 2016; KANACONO leg.; one cladium from the largest colony was used for DNA extraction, DNA1354; voucher MHNG- INVE- 120788; barcode identifier MK 073084 ; MNHN-IK-2015-375 • a colony without gonothecae, 6.8 cm high; off New Caledonia, stn CP4676; 22°51′ S, 167°30′ E, 383 m; 13 Aug. 2016; KANACONO leg.; a basal cladium was cut off and used for DNA extraction, DNA1355; voucher MHNG-INVE- 120789; barcode identifier MK 073085 ; MNHN-IK-2015-376 .

Remarks

The present material, forming pinnate colonies with lightly fascicled stems and long, tubular, weakly adnate hydrothecae, is in full agreement with the holotype described earlier by Galea (2015a). The perisarc of the colony (including that of the hydrothecae) is uniformly smooth, and the hydrothecal rim is thickened distally for only a very short distance (ca 40 µm) just below the aperture.

Despite forming regularly-pinnate colonies provided with tubular hydrothecae possessing rounded, deciduous opercula, the present species and S. candelabrum may prove to not be congeneric. The available 16S sequences place this species clearly outside the clades of Solenoscyphus and Staurothecidae ( Fig. 20 and ‘Molecular study’ section), but without any supported relationships to other taxa. This makes it likely that this species does not belong to the genus Solenoscyphus . However, the available 16S data do not resolve sufficiently well the family relationships, and additional markers are needed for this purpose. Therefore, and also because no diagnostic traits are evident, we decided to leave it in the genus Solenoscyphus until a more detailed study allows firmer conclusions.

Distribution

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

Genus Tasmanaria Watson & Vervoort, 2001

Figures

Fig. 1. A–B. Caledoniana decussata Galea, 2015, female (MNHN-IK-2015-361) and male (MNHN- IK-2015-362), gonothecae. — C. Caledoniana microgona Galea, 2015, female gonotheca arising from below base of hydrotheca (MNHN-IK-2015-363). Scale bar: 1 mm.

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.

Fig. 20 (opposite page). 16S maximum likelihood phylogenetic tree of selected Leptothecata species obtained with PhyML(GTR+G+I model) and based on 622 aligned basepair positions of the mitochondrial 16S gene. Node-support values are bootstrap values of 100 pseudoreplicates (shown only if> 70%). Species treated in this study are in bold. Some family clades with sufficient bootstrap support discussed in the present study are highlighted in blue boxes. N.B.: Two species names were not used as given in GenBank (FJFJ550462 and FN424141), and the reasons are given in the Material and methods section.