Two new genera and nine new species of hydroids (Cnidaria: Hydrozoa) from off New Caledonia

Two new genera and nine new species of hydroids are described based on deep-water material collected from off New Caledonia during various expeditions of the French Tropical Deep-Sea Benthos program. Caledoniana gen. nov., provisionally included in the family Sertulariidae Lamouroux, 1812, presently comprises three new species, viz. C. alata sp. nov., C. decussata sp. nov., and C. microgona sp. nov., while an additional group of three new species, is accommodated in the new sertulariid genus Solenoscyphus gen. nov.: S. candelabrum sp. nov., S. decidualis sp. nov., and S. striatus sp. nov. Furthermore, three new species of Hincksella Billard, 1918 (family Syntheciidae MarktannerTurneretscher, 1890) are described, namely H. cornuta sp. nov., H. neocaledonica sp. nov., and H. similis sp. nov.


Introduction
Large collections of hydroids were gathered during numerous French expeditions, conducted conjointly by the Institut de Recherche pour le Développement (IRD, formerly ORSTOM) and the Muséum national d'Histoire naturelle (MNHN) of Paris, in the tropical southwestern Pacifi c. Launched early in the 1980's as the MUSORSTOM campaigns and continuing until today under the name Tropical Deep-Sea Benthos, these expeditions aimed at exploring the deep-sea fauna (down to 1500 m) of a vast geographical area extending from Taiwan to the Marquesas, and encompassing the Philippines, the Banda Sea, the Solomon Islands, New Caledonia, Vanuatu, Wallis and Futuna, Fiji, Tonga, and the Austral Islands (Bouchet et al. 2008).
A collection of specimens not studied by Vervoort (1993) or collected after the publication of his monograph, comprising species belonging to various genera of Sertulariidae, Syntheciidae, Thyroscyphidae, Campanulariidae, and Haleciidae, was entrusted to me for study.The present report is the fi rst account, based on a fraction of the material in this collection, and deals particularly with nine new species of hydroids, of which six are accommodated in two new genera of sertulariids, while the remaining three belong to the syntheciid genus Hincksella Billard, 1918.

Material and methods
The methods of study were described in detail by Galea (2007Galea ( , 2008)).Station numbers, as indicated in the text, are preceded by a two-letter prefi x referring to the sampling gear used to secure the material, either a Warén dredge (DW) or a beam trawl (CP).The material is deposited in the collections of MNHN.

Diagnosis
Erect, loosely-branched, fan-shaped, weakly-fascicled colonies; branching pattern sparing and irregular; division into internodes indistinct; hydrothecae given off in opposite, though not contiguous pairs, except for the fi rst hydrothecae of the side branches which are unpaired; successive pairs of hydrothecae either coplanar or, occasionally, adopting a decussate arrangement; hydrothecae very large, tubular, free for at least half their length, closed by rounded, deciduous opercula; gonothecae club-shaped to piriform, inserted slightly laterally, below the hydrothecal bases.

Etymology
Named after the area of occurrence of its species, New Caledonia.The genus name is a feminine noun.

Remarks
The new genus is provisionally placed within the family Sertulariidae owing to the presence of hydrothecal opercula, though molecular analyses, based on freshly-collected samples, are needed to confi rm this.
Together with Gigantotheca Vervoort & Watson, 2003, Caledoniana gen. nov. is distinguished from other genera through the presence of huge, tubular hydrothecae, both genera forming a clearly distinct group within the family.Unlike Gigantotheca, in which the hydrothecae are alternate, those of Caledoniana gen.nov.are grouped in opposite pairs, analogous to the generic separation of Hincksella Billard, 1918 and Synthecium Allman, 1872, respectively, in the family Syntheciidae.
The hydrothecae of Caledoniana gen.nov.superfi cially resemble those of Staurotheca Allman, 1888, especially through the presence of deciduous opercula with no defi nite points of attachment (see Peña Cantero et al. 1997: 336).However, the hydrothecae of the latter are arranged in two or multiple longitudinal rows, they are generally deeply immersed in both stems and branches, and their size is much smaller in all species described so far (Peña Cantero et al. 1997, 1999;Peña Cantero & Vervoort 2003a, 2003b).Vervoort & Watson, 2003, a species of so far uncertain generic position, possesses huge hydrothecae arranged in either opposite pairs or decussate groups of three (Vervoort & Watson 2003)

Etymology
From the Latin ālātus, meaning "winged", making reference to the shape of the hydrothecae, recalling the wings of a gliding bird.

Description
Two stem fragments, 3.6 and 4.6 cm high, with no hydrorhizae, possibly detached at base from same colony; lightly fascicled proximally, with a few accessory tubes creeping over main tube bearing hydrothecae.No evident division into internodes, even in monosiphonic parts.Each equivalent of internode short, accommodating pair of opposite, though not contiguous, hydrothecae.Single side branches, given off laterally from below a stem hydrotheca, occur in both specimens; structure similar to that of stem, except for fi rst hydrotheca, which is unpaired.Hydrothecae large, tubular, immersed for about half their length into their corresponding internodes; free parts bent at nearly right angles to internodes, then curving upwards toward their middle; diameter nearly constant for most of length, slightly expanding toward aperture; rim with thickened perisarc; in frontal view, aperture semi-circular on adaxial side and somewhat fl attened on abaxial side; a fi lmy, rounded operculum observed in one hydrotheca, but opercula likely deciduous.Gonothecae large and pyriform, with no distinct aperture; at least three large, globular structures (oocytes or young embryos) present in one of them.Numerous, large foramina (obliterated by thin pellicle of perisarc) below each hydrotheca suggest that gonothecae may occur in pairs in fully fertile specimens.Coenosarc badly preserved, not suitable for tentacle counting or cnidome studies.

Remarks
The hydrothecae are so large that sand grains partially or totally fi ll their lumina.In this case, the fi nding of an operculum closing the aperture of a hydrotheca is truly fortunate.

Etymology
From the Latin dĕcusso, meaning "to form or create a cross in the form of an X", to characterize the arrangement of the hydrothecal pairs in this species.

Description
Colony erect, 5.5 cm high, arising from rhizoid stolon fi rmly attached to substrate.Basal part of stem fascicled, with several accessory tubes creeping over main tube; in monosiphonic parts, division into internodes indistinct; each equivalent of internode relatively short, bearing a pair of opposite, though not contiguous, hydrothecae.Branching sparse and irregular, up to 2 nd order; side branches given off singly or in pairs from below a stem hydrotheca; stem and side branches coplanar; structure of latter similar to that of stem, except for fi rst hydrotheca, which is usually unpaired, though a pair of hydrothecae also occurs within colony.Basal parts of stem and side branches with successive pairs of hydrothecae in coplanar series; more distally, pairs become decussate.Hydrothecae large, tubular, adnate for about half of length, or less, to corresponding internodes; free part bent at about 45°; diameter nearly constant throughout, slightly expanding at rim; rim conspicuously thickened; aperture circular in frontal view; opercula not seen.Gonothecae absent, though basal remains at insertion of one of these (below a hydrotheca) present; numerous, large foramina (obliterated by thin pellicle of perisarc) below most hydrothecae, making the possibly future insertion points for them.Coenosarc badly preserved, not suitable for tentacle counting or cnidome studies.

Etymology
From the Greek μικρός, meaning "small", and γόνος, meaning "seed", to characterize the size of its gonothecae.

Paratypes
NEW CALEDONIA: data as for holotype; numerous fragmented stems up to 6.3 cm high, some sterile, as well as several detached gonothecae (IK-2012-10291).

Description
Colonies erect, up to 7 cm high, fan-shaped, loosely fascicled on basal portions of stems and some lower side branches.Main tube indistinctly divided into moderately long internodes, each of them bearing a distal pair of opposite, though not contiguous, hydrothecae.Side branches sparse, given off irregularly and laterally from below a hydrotheca; up to 2 nd order branching.First hydrotheca of side branch commonly unpaired, although one colony with paired hydrothecae.Hydrothecae large and tubular, immersed for about one-third of adaxial length into internode; free part of nearly constant diameter, projecting outward at wide angle; abaxial wall slightly tumid at infl exion point, then straight distally; free adaxial side slightly convex basally, then parallel to abaxial counterpart; rim thickened; aperture borne on slight terminal constriction of hydrothecal wall; in frontal view rounded on adaxial side and fl attened abaxially; opercula not seen.Gonothecae given off slightly laterally from below bases of hydrothecae; small and club-shaped, with thick perisarc.Coenosarc badly preserved, not suitable for tentacle counting or cnidome studies.

Remarks
Like in C. decussata gen.et sp.nov., the free parts of the hydrothecae of this species are almost straight, thus differing from the sigmoid shape met with in C. alata gen.et sp.nov.However, in C. decussata gen.et sp.nov. the hydrothecal pairs may exhibit a decussate arrangement; their free part is comparatively shorter, while the adnate one is longer.

Diagnosis
Colonies of various sizes and shapes, from irregularly branched to pinnate, with either mono-or polysiphonic stems; cladia always monosiphonic.Hydrothecae long, tubular, with either straight or curved axes, adnate for less than half their length to the internodes; bases as complete septa; opercula fi lmy and rounded in shape, with indistinct points of attachment, clearly deciduous.Perisarc either smooth or fi nely and densely striated.Gonothecae unknown.

Etymology
From the Greek σωληνοειδής, meaning "tubular", and σκύφος, meaning "cup", to characterize the shape of the hydrothecae.It is a masculine noun.
In this respect, it shows similarities with both Caledoniana gen.nov.and Staurotheca Allman, 1888, and this may prove to be equally true for Gigantotheca Vervoort & Watson, 2003 as well.As shown above, Caledoniana gen.nov. is characterized by the presence of huge hydrothecae, a situation not met with in any of the three species described below.On the other hand, Staurotheca comprises a majority of species exhibiting a characteristic arrangement of the hydrothecae in decussate groups, although in a few cases they are either subopposite (S. amphorophora Naumov & Stepanjants, 1962, S. australis Peña Cantero et al., 1997, andS. vervoorti El Beshbeeshy, 2011) or decidedly alternate (S. abyssalis Peña Cantero &Vervoort, 2003 andS. profunda Peña Cantero &Vervoort, 2003).In addition, the hydrothecae of most species of Staurotheca are deeply immersed in both the stem and side branches; they characteristically curve outwards and their bases are often incomplete septa.Moreover, the colony shape in that genus is radically different, ranging from bush-like (with no distinct stems) to fan-shaped or tree-like (Peña Cantero & Vervoort 2003a).Unlike the tropical Solenoscyphus gen.nov., Allman's (1888) genus is essentially Antarctic, with a few species also occurring in the sub-Antarctic and some localities in South America (Peña Cantero & Vervoort 2003a).

Etymology
From the Latin candēlābrum, meaning "candlestick", with reference to the shape of the hydrothecae, the whole colony resembling a phantasmagoric candelabrum with an infi nity of arms.Used as a noun in apposition.

Description
Stems up to 12 cm high, arising from disc-shaped hydrorhizae fi rmly attached to substrate; strongly polysiphonic basally, uniformly grading to monosiphonic towards apices; auxiliary tubes running up, nearly parallel to main tube and establishing occasional anastomoses with each other.Nodes generally poorly indicated, though division into internodes with apparently unusual repetitive sequence: proximal node, short lateral apophysis (supporting a cladium), axillary hydrotheca, two alternate hydrothecae above, second cladial apophysis on opposite side to former, axillar hydrotheca, and distal node.Cladia pinnately arranged, given off at about 70° to stem, up to 3 cm long; straight, unbranched, exclusively monosiphonic; inserting on corresponding stem apophyses by means of short, rectangular, ahydrothecate internodes; nodes indistinct.Hydrothecae of both stem and cladia biseriate, alternate, and coplanar; tubular, S-shaped, facing out-and upward; a prominent internal perisarc thickening occurring along median line of lower half of abaxial wall, together with a transverse ridge arising from middle part of perisarcal thickening, and extending over both "frontal" and "dorsal" sides of theca; elsewhere perisarc relatively thin; in frontal view, aperture of hydrotheca rounded adaxially and slightly fl attened abaxially; deciduous opercula rarely seen at apertures of some hydrothecae.Gonotheca unknown.

Etymology
From the Latin dēcĭdŭus, meaning "deciduous", with reference to the condition of the hydrothecal operculum.

Description
Essential part of hydrorhiza missing, but remains of what appears to be a rhizoid stolon, fi rmly attached to substrate, could be seen.Colony erect and pinnate, ca. 4 cm high.Stem lightly fascicled basally, grading to monosiphonic distally; auxiliary tubes fused to one another, forming outer layer of perisarc enveloping main tube; monosiphonic part of stem with indistinct nodes; equivalents of internodes composed of proximal "node", two alternate hydrothecae, short lateral apophysis (supporting cladium) on side opposite to second hydrotheca, axillary hydrotheca, and distal "node".Cladia up to 1.2 cm long, inserted on corresponding stem apophyses, occurring at an angle of about 70° with stem; nodes indistinct; equivalents of internodes relatively short, each carrying a hydrotheca on its distal half.Hydrothecae of both stem and cladia biseriate, alternate, given off at 70-75° to "internodes"; tubular, adnate for onefourth of adaxial length; both free adaxial and abaxial walls parallel, imperceptibly convex to almost straight; rim even, aperture circular, placed at right angle to axis of theca; rare, rounded opercula close apertures of some hydrothecae.Gonotheca unknown.Solenoscyphus striatus sp.nov.urn:lsid:zoobank.org:act:6ED544D2-AD80-469D-AF97-DFE1062D6E0DFigs 3C, 4E-G; Table 2 Diagnosis Colonies lightly fascicled basally; branching irregular, in one plane; nodes indistinct; each internode relatively short, bearing a hydrotheca; the latter long, tubular, facing outward and upward, apically swollen; operculum deciduous; perisarc of colonies densely and fi nely striated.

Etymology
From the Latin strĭātus, meaning "marked with striae", to characterize the external condition of the perisarc.

Description
Smaller specimen (paratype) 3.1 cm high, comprising a branched fragment of either a stem or a side branch; larger specimen (Fig. 3C, holotype) 5.2 cm high, possibly a branched stem missing hydrorhiza; both possibly originally parts of a single colony with multiple stems.This colony obviously fascicled to an unknown extent, as largest available fragment comprises an accessory tube running up both main stem and basal part of lowest side branch.Division into internodes indistinct; each equivalent of internode relatively short, carrying a single hydrotheca on distal half.Branching pattern irregular and sparing, with up to second order side branches given off laterally from below bases of hydrothecae; side branches with same structure as stem; proximal-most internode comparatively longer than following ones.Hydrothecae biseriate and alternate; tubular in shape, adnate for slightly more than one-third of adaxial length, facing up-and outward; abaxial wall almost straight, except for proximal part, which is convex at point where hydrotheca becomes free on opposite side; free adaxial side straight and parallel to adaxial counterpart.Apical part of hydrotheca distinctly swollen and there perisarc much thinner than elsewhere; rim indistinctly tilted adaxially; rounded, thin operculum present in some hydrothecae; point of attachment indeterminable; deciduous.External perisarc fi nely and densely striated over entire colony.Gonothecae unknown; scar below one hydrotheca suggests at least one gonotheca was present and subsequently lost; numerous large foramina (obliterated by thin pellicle of perisarc) indicate that colony was about to become fertile.

Remarks
Although not resembling either S. candelabrum gen.et sp.nov.or S. decidualis gen.et sp.nov. in colony shape, the present species nevertheless possesses a deciduous operculum, which is one of the main features of the newly described genus.
Unlike S. candelabrum gen.et sp.nov., both S. decidualis gen.et sp.nov.and the present species possess long, tubular hydrothecae with straight axes.However, their adnate parts are longer and their apertures are wider in S. striatus gen.et sp.nov.Additionally, the entire perisarc of the latter is fi nely and densely striated.Family Syntheciidae Marktanner-Turneretscher, 1890 Genus Hincksella Billard, 1918

Etymology
From the Latin, cornūtus, meaning "horned", making reference to the prominent horns of the gonotheca.

Paratypes
NEW CALEDONIA: data as for holotype, four specimens (3.1 cm high fragment with no basal part, bearing two gonothecae; 3.3 cm high fragment devoid of its basal part; entire, 4.0 cm high stem with one gonotheca; entire, sterile stem 3.8 cm high) (IK-2012-10298).

Description
Stems erect, up to 3.8 cm high, unbranched and monosiphonic, arising from tubular hydrorhizae; basal constriction at origin from stolon; lower parts ahydrothecate and quite long (1.0-1.2 cm), occasionally with signs of breakage and subsequent regeneration; perisarc smooth.Division by nodes indistinct, but equivalents of internodes rather short, slightly geniculate, bearing single hydrothecae on distal halves.Hydrothecae alternate, although the two proximal-most ones may be given off on same side of stem; tubular, adnate for less than half of length; free part facing out-and upward; free adcauline wall slightly convex to almost straight; abcauline wall convex in middle and straight elsewhere; basal foramina with multiple renovations of perisarc (Fig. 5C); rim of hydrotheca often renovated; aperture circular, imperceptibly tilted adaxially.Hydranths enveloped by inner, thin, collapsible periderm, distinct from hydrothecal wall; tentacle number could not be counted.Gonothecae given off from within hydrothecae; broadly ovoid, with wrinkled perisarc, distally with two prominent horns; no signs of aperture; gonophore apparently single, large ovoid mass (oocyte?) occupying nearly entire lumen of gonotheca.Large macrobasic heteronemes (none seen discharged), with parallel walls and rounded ends, and with straight or slightly curved longitudinal axes, occur abundantly in coenosarc.
The remaining congeners with unknown gonothecae differ from H. cornuta sp.nov. in the following respects: 1) H. corrugata Millard, 1958 has comparatively shorter hydrothecae, adnate for as much as half their length, and their surface is transversely wrinkled (Millard 1958); 2) H. indiana Millard, 1967 is a much larger species, with fascicled stems, shorter hydrothecae, conspicuously tilted adaxially (Millard 1967); 3) the poorly described H. projecta (Fraser, 1938) appears to be different due to the lower length/width ratio of its hydrothecae, as well as on biogeographical grounds (Fraser 1938); 4) the hydrothecae of H. rigida (Fraser, 1938) are nearly as broad as deep and, according to Fraser (1938), they are comparatively shorter.

Etymology
Named for its area of occurrence, New Caledonia.

Description
The 2.5 cm high stem fragment is devoid of its hydrorhiza and seems to have been broken off just above its origin from it.Monosiphonic throughout and unbranched; very basal part (ca.2.5 mm long) ahydrothecate; remainder of stem divided into 21 moderately long, slender and geniculate internodes, by means of transverse nodes; perisarc of internodes smooth; a distally-placed hydrotheca per internode.
Hydrothecae alternate, tubular, adnate for one-third of adcauline length, facing up-and outward, and oriented at an angle of c. 45° with internode; free adcauline wall nearly straight to imperceptibly convex; abcauline wall convex at infl exion point, then straight and parallel to its free adcauline counterpart; perisarc of hydrotheca fi nely and densely striated throughout; rim often renovated; aperture circular, perpendicular to long axis of hydrotheca.Gonotheca unknown.Large, parallel-walled macrobasic heteronemes (none seen discharged), with either straight or slightly curved axes and rounded ends, common in coenosarc.

Etymology
From the Latin similis, meaning "similar", on account of its resemblance to H. pusilla Ritchie, 1910.

Description
Colony erect, 2.2 cm high, arising from creeping, tortuous, branching stolon.Stem monosiphonic, unbranched; basal part 9 mm long, ahydrothecate; remainder of stem divided by means of indistinct nodes; each equivalent of internode rather short, slightly geniculate to almost collinear, each bearing a hydrotheca distally.Hydrothecae tubular, given off at an angle of c. 65-70° with internode, long axis slightly sigmoid; abcauline wall markedly curved where hydrotheca becomes free; aperture rounded, rim even, slightly fl ared; renovations occasional; perisarc of hydrotheca fi nely and densely striated, especially on free adcauline side and proximal part of abcauline wall.Gonotheca unknown.Large macrobasic heteronemes (none seen discharged), with parallel walls and rounded ends, and with straight or slightly curved longitudinal axes, occur abundantly in coenosarc.

Remarks
The alternate, long, tubular, non-operculate hydrothecae and the large nematocysts scattered in the coenosarc place this species, with little doubt, in the genus Hincksella Billard, 1918.This species resembles both H. pusilla Ritchie, 1910, through the shape of its hydrothecae, and H. neocaledonica sp.nov.through their striations.However, the former is a much smaller species (see dimensions in Galea 2010: table 3), while the latter has comparatively longer and more geniculate internodes, its hydrothecae are given off at more acute angles, their free part is shorter, and the striations extend over the whole perisarc of the colony.