Caledoniana decussata 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 : 3-4

Caledoniana decussata Galea, 2015

Fig. 1 A–B

Caledoniana decussata Galea, 2015a: 4 , figs 1B, 2C–D.

Material examined

PACIFIC OCEAN • originally a 5.8 cm high colony; off New Caledonia, stn DW4744; 22°55′ S, 167°37′ E; 310– 290 m; 23 Aug. 2016; KANACONO leg.; a 3.0 cm long, basal, fascicled portion was cut off for DNA extraction, DNA1342; voucher MHNG-INVE- 120777; MNHN-IK-2015-359 • a 3.8 cm high colony fragment with single, basal, immature gonotheca; off New Caledonia, stn DW4775; 23°03′ S, 168°17′ E; 140–277 m; 28 Aug. 2016; KANACONO leg.; used as a whole for DNA extraction, DNA1343; voucher MHNG-INVE- 120778 • originally a 4.5 cm high colony fragment with a short basal branch, carrying 3 female gonothecae; off New Caledonia, stn DW4697; 22°48′ S, 167°15′ E; 465- 449 m; 16 Aug. 2016; KANACONO leg.; a 1.2 cm long, distal portion was cut off for DNA extraction, DNA1344; voucher MHNG-INVE- 120779; barcode identifier MK 073078 ; MNHN- IK- 2015-36 • a 2.5 cm high, unbranched colony without gonothecae; off New Caledonia, stn DW4726; 22°40′ S, 167°03′ E; 240– 181 m; 20 Aug. 2016; KANACONO leg.; MNHN-IK-2015-362 • a colony without gonothecae, 6.0× 3.5 cm (height ×width; the same applies to all subsequent materials and species), with one side branch; same collecting data as for preceding; MNHN-IK-2015-362 • a colony, 2.3× 3.7 cm, with 2 side branches, carrying an immature female gonotheca; same collecting data as for preceding; MNHN-IK-2015-362 • a ca 9× 7 cm, branched (up to 2 nd order branches), fully fertile male colony; same collecting data as for preceding; a short, distal fragment was cut off for DNA extraction, DNA1345; MNHN-IK-2015-362 • originally a 4.5 cm high colony with one side branch, the latter bearing an immature, likely female, gonotheca; same collecting data as for preceding; a 1 cm long fragment from the branch was cut off for DNA extraction, DNA1346; voucher MHNG-INVE- 120780; MNHN-IK-2015-362 • a ca 11 × 12 cm, fan-shaped, fully fertile male colony; off New Caledonia, stn DW4728; 22°43′ S, 167°02′ E; 150 m; 20 Aug. 2016; KANACONO leg.; a short, distal fragment was cut off for DNA extraction, DNA1347; voucher MHNG-INVE- 120781; barcode identifier MK 073079 ; MNHN-IK-2015-365 .

Remarks

The decussate arrangement of the hydrothecae, although quite irregular within a given colony, occurs in all the material examined, a condition never met within the two other species of the genus, C. alata Galea, 2015 and C. microgona Galea, 2015 . The species is monoecious and sexually dimorphic. The gonothecae arise laterally from below the hydrothecal bases. The male ones are club-shaped, ca 3200 µm long and 1170 µm wide (one gonotheca measured), tapering below into an indistinct pedicel; there is no noticeable aperture distally. The female gonothecae are large, ca 3890 µm high and 2630 µm wide in lateral view (one gonotheca measured), recalling a closed hand wearing a mitten; they are bilaterally symmetrical and contain a large, globular, inner cavity protecting at least a large, ovoid oocyte, the latter ca 925× 590 µm; the aperture is half-moon-shaped, faces downwards, and does not appear to possess an opercular apparatus.

Although the morphology of the fully-formed gonotheca of C. alata , the type species of the genus, is as yet unknown, it is assumed that the specimen depicted by Galea (2015a, Fig. 2A ) is likely to adopt a similar shape to that of its counterparts produced by both C. decussata and C. microgona (see below), thus further justifying their assignment to the same genus.

The three species of Caledoniana Galea, 2015 were included provisionally in the family Sertulariidae Lamouroux, 1812 ( Galea 2015a) , but it is now demonstrated that, at least C. decussata and C. microgona , belong instead to the Staurothecidae Maronna et al., 2016 (see ‘Molecular study’ section).

As noted earlier by Galea (2015a), C. decussata shows affinities with Staurotheca megalotheca Vervoort & Watson, 2003 , especially regarding the size and the decussate arrangement of their hydrothecae. However, the gonothecae of the latter differ much from those of both C. decussata and C. microgona , in having a small, rounded, eccentric, sub-terminal aperture borne on a short neck region, unless it is proved that its gonothecae are sexually dimorphic, thus strongly resembling to the males of “ Solenoscyphus ” striatus Galea, 2015a (see below). Anyway, it could be reasonably assumed that S. megalotheca is a true staurothecid hydroid, although its assignment to a given genus is impossible in the absence of evidence from molecular data.

In addition, Giganthotheca maxima Vervoort & Watson, 2003 ( Vervoort & Watson 2003: fig. 26E– F) has female gonothecae approaching the morphology of those met with in both C. decussata and C. microgona , suggesting not only a reasonable assignment of this species to the Staurothecidae , but also a possible genus transfer to Caledoniana . But, again, only molecular data are expected to solve the intricacies of this species group.

Distribution

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

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.