A new genus of soft coral of the family Alcyoniidae (Cnidaria, Octocorallia) with re-description of a new combination and description of a new species

Abstract A new genus, Aldersladum (family Alcyoniidae), is established to accommodate a previously described species, Efflatounaria sodwanae Benayahu, 1993 (family Xeniidae) from Sodwana Bay, South Africa that was wrongly assigned to the latter genus. This species is redescribed and a second new species, Aldersladum jengi from Penghu Is., Taiwan, is described. The diagnostic features of the new genus include the presence of only figure-eight shaped platelets in all parts of the colony, thus differentiating it from all known genera of the Alcyoniidae. Based on examination of additional material from other localities, the zoogeographical distribution of the genus is confirmed to include the coral reefs of South Africa, Kenya, Gulf of Oman, Taiwan and Japan. Phylogenetic analyses of two mitochondrial genes strongly support its placement in the family Alcyoniidae.


Introduction
In a study of Alcyonacea from Sodwana Bay, South Africa, the new species, Effl atounaria sodwanae Benayahu, 1993, (family Xeniidae) was described. Th is species features a low crust and has platelet-like sclerites with a distinct waist and either single or double pits on their fl at surface, thus resembling a fi gure-eight. During an octocoral survey conducted in 2006 on the reefs of Penghu Is., Taiwan, a colony with fi ngerlike, fl abby lobes was collected and found to have a similar type of sclerite to those of E. sodwanae. While comparing the colonies of South Africa and Taiwan, we were intrigued by their fi gure-eight sclerites, which resembled those found in polyps of the genera Cladiella Gray, 1869, Klyxum Alderslade, 2000 andRhytisma Alderslade, 2000 of the family Alcyoniidae (see Fabricius and Alderslade 2001), yet had never been recorded among genera of the family Xeniidae (e.g., Alderslade 2001;Benayahu in press). Th ese fi ndings led us to thoroughly re-examine the type material of E. sodwanae, also in relation to the colony from Penghu Is. and other related material kept at the Zoological Museum of Tel Aviv University (ZMTAU) and at the Netherlands Center for Biodiversity, Naturalis, formerly Rijksmuseum van Natuurlijke Historie, Leiden (RMNH). Th e fi ndings resulted in establishing Aldersladum gen. n. (family Alcyoniidae) for placement of the above-mentioned material, which includes A. sodwanum comb. n., which is also re-described; and A. jengi sp. n. which is depicted and described. Based also on molecular analyses, the phylogenetic position of the new genus is discussed.

Materials and methods
Th e material examined in this study was obtained during several octocoral surveys conducted in north-east Taiwan (1998); Yoron Is. and Okinoerbu Is., Ryukyu Archipelago, Japan (2000); Kenya (2001Kenya ( , 2002Kenya ( and 2003Penghu Is., Taiwan (2006) and the Gulf of Oman (2009). Th e 1998 and 2000 material was initially fi xed in 4% formalin in seawater, rinsed in fresh water after 24 hours, and then stored in 70% alcohol. Th e later collections, from 2001 onwards, were fi xed in 70% alcohol and subsamples were removed and preserved in absolute alcohol or DMSO for molecular studies. Sclerites from diff erent parts of the colony (polyps, polypary, base-surface and interior) were obtained by dissolving the tissues in 10% sodium hypochlorite, followed by careful rinsing in fresh water. Th ey were then prepared for scanning electron microscopy as follows: the sclerites were carefully rinsed with double-distilled water, dried at room temperature, coated with gold and examined with a Jeol 840A electron microscope, operated at 15 kV. Th e identifi ed specimens are deposited at ZMTAU and at RMNH as indicated below.
Diagnosis and description. Colonies have a low encrusting base, holdfast-like, from which lobes arise. Th e lobes vary in size from short, knob-like to longer, fi ngerlike. Th e non-retractile monomorphic polyps are densely arranged on the lobes. Th e same type of sclerite is found in all parts of the colony, as confi rmed by both light microscopy and SEM examination. It comprises platelets that are narrower across their mid-lateral line. A longitudinal slit, sometimes narrower in its middle part, is commonly found on the platelet's fl at surface, located at the center and occupying about half its length, thus giving the sclerite a typical fi gure-eight form. Th e surface of the platelets is characterized by the appearance of an uneven crystal deposition that gives it a porous texture. Colonies are zooxanthellate.
Diagnosis and description. For the sake of convenience the revised description also contains the relevant information that appeared in the original description of E. sodwanae. Th e holotype has a fi rm, low, crust-like base, 3-5 mm high, attached to a calcareous fragment. Th e maximum cross-section of the colony is 6 × 3 cm, and its total height (base and polypary) is up to 8 mm (Fig. 1a). Th e polypary consists of numerous knob-like lobes, some of which bud off into one to three smaller side lobules. Obscure material, composed of slime and debris, is found between adjacent lobes. Th e polyps are confi ned only to the lobes and are absent from their basal part. Th e anthocodial wall of some polyps is partially contracted and, very rarely, the tentacles are withdrawn into the mouth.
Th e sclerites are platelets of porous texture, narrower across the lateral middle-line, 0.032-0.048 mm long (Fig. 2). Th ey are found in the polyps and in all parts of the colony. A longitudinal median slit on the fl at surface of the sclerite occupies about half of its length. Th e slit can be narrower in its middle and occasionally widens at its ends, forming aperture-like structures (Fig. 2a). Some of the sclerites have a poorly developed slit (Fig. 2b) while in others this is wider (Fig. 2c), but both possess similar common features. Th e architectural features of the sclerites confer upon them a fi gureeight shape. Under a light microscope the slit and apertures are observed on the surface of the sclerite as bright median areas. Although some sclerites appear as cigar-shaped, these are actually platelets viewed from their narrow lateral surface, as also confi rmed by scanning electron microscopy (Fig. 2d). Th e alcohol preserved colony is creambeige. Th e preserved paratypes diff er in size (e.g., Fig. 1b).
When alive the polyps are light brown and the base of the colony is brighter (Fig.  6a). Th e colonies are quite small, commonly no larger than 30-40 mm in diameter.    Diagnosis and description. Th e holotype is a fl abby colony with a maximum cross-section of 6 × 5 cm (Fig. 3a). It has a low base, holdfast-like, 3-5 mm high, attached to a fragment of calcareous substrate. Th e base gives rise to primary fi nger-like lobes that occasionally branch once or twice into short lobules. Th e polyps feature densely on the lobes, with their density markedly decreasing on the basal part. Th e polyps are expanded and in only a few of them the anthocodial wall is partially contracted. Very rarely, the tentacles are withdrawn into the mouth.

Aldersladum jengi
Th e sclerites are platelets, mostly narrower across their lateral middle-line, 0.023-0.042 mm long (Fig. 4). Th ese sclerites are found in all parts of the colony, including the polyps. Th e vast majority of sclerites have a longitudinal median slit on their fl at surface. Th e slit is often calcifi ed along most of its length, thus leaving two, or rarely one, aperture-like structures at its ends. Th e base of the colony has fewer sclerites compared to the lobes; these reach up to 0.060 mm long, mostly with no median slit (Fig.  5). Th ese latter sclerites may have a circumferential waist, rather than being narrow across their lateral middle-line. Th e architectural features of these sclerites give them the appearance of rods with a median constriction (Fig. 5), which is more pronounced compared to the sclerites of the lobes (Fig. 4). All sclerites feature a "spongy" texture that seems to result from the uneven alignment of the crystal-nodules that construct them. Th e colony is zooxanthellate. Th e alcohol-preserved colony is cream-beige.
Th e preserved paratypes diff er in size (Fig. 3b, c) and are more rigid than the holotype. Th e few sclerites in the base of both paratypes are up to 0.080 mm long, and thus larger compared to those found in the holotype. When alive the polyps of the holotype were dark brown and the surface of the lobes was brighter (Fig. 6b). Th e fl abby lobes tend to undulate with the water surge and in this sense resemble certain Klyxum colonies (pers. obs.)

Discussion
Th e generic diagnosis of Effl atounaria is based on E. tottoni Gohar, 1939, a species that lacks sclerites and is characterized by retractile polyps. Fabricius and Alderslade (2001: 144-145) noted that in this genus "Th ey [polyps] are so highly contractile that they can defl ate until fl ush with the colony surface and appear to be retracted". To the best of our knowledge, except for the original description, the literature has since only once mentioned the occurrence of E. tottoni (Okinawa: Benayahu 1995: 108, 124). Th e latter colony has the suite of diagnostic features noted by Gohar (1939), including the typical colony shape, retractile polyps and absence of sclerites. Interestingly, Gohar (1939) assigned Cespitularia mantoni Hickson, 1931 to Effl atounaria and as a result included a species with sclerites in this genus. Th e lack of sclerites is therefore not an obligate feature of the genus. Both genera feature the corpuscle-like platelets or spheroids that are typical of other members of the Xeniidae. It should also be noted that at present there is some ambiguity concerning the morphological distinction between the two xeniid genera, Effl atounaria and Cespitularia Milne-Edwards & Haime, 1850 (see Fabricius and Alderslade 2001), which further complicates the placement of species in these two genera.
Re-examination of the holotype of E. sodwanae (see also below) revealed no real sign of either contractile or retractile polyps. Indeed, in some of the polyps the anthocodial wall is contracted (Benayahu 1993: 11) to a limited degree. Th e sclerite-architecture of E. sodwanae (Benayahu 1993: 13) markedly diff ers from the corpuscle-like platelets or spheroids attributed to xeniids (see Fabricius and Alderslade 2001). Based on these features it is evident that E. sodwanae can not retain its original generic placement.
Th e following genera of the family Alcyoniidae -Cladiella Gray, 1869; Klyxum Alderslade, 2000 and Rhytisma Alderslade, 2000 -have fi gure-eight sclerites resembling those of Aldersladum gen. n. However, in these genera they are confi ned only to the polyps, while other parts of the colony feature diff erent diagnostic sclerites (Cladiella: dumbbells, Klyxum: spindles and granular rods, Rhytisma: spindles; i.e., Fabricius and Alderslade 2001). We suggest, therefore, that the presence of fi gure-eight sclerites in all parts of the colony justifi es the establishment of Aldersladum gen. n. for placement of E. sodwanae. Since this type of sclerite occurs only in the family Alcyoniidae, the new genus is assigned to that family. Preliminary molecular data based on mitochondrial msh1 and COI gene sequences strongly support the placement of Aldersladum in a clade with the alcyoniid genera Klyxum and Cladiella (McFadden unpub. data).
Th e current study expands the zoogeographical distribution of A. sodwanum from the type locality (Sodwana Bay, South Africa) to several sites along the Kenyan coast, from Likoni, off Mombassa in the north, to Wasini Is. in the south. Th is species has also been recorded from the Gulf of Oman and north-east Taiwan (see above). It is therefore evident that A. sodwanum features a wide zoogeographical distribution ranging from the East-African coast to the Pacifi c reefs. We suggest that the infrequent appearance of the species on the reefs may have hindered its record in reef surveys.
A. jengi fi ts the diagnosis of Aldersladum gen. n. by having lobes arising from a narrow base, non-retractile polyps and fi gure-eight sclerites found in all parts of the colony. Its lobes are much longer compared to A. sodwanum. Th e porous sclerite texture of A. jengi is coarser compared to that of its congener (Fig. 2 vs. Fig. 4, 5). Th e sclerites of the colony base are longer, with some featuring a circumferential waist. We consider these diff erences suffi cient to justify the separation between the two species and to establish A. jengi as a second species within the genus. Analysis of molecular data (mitochondrial msh1 and COI genes) also supports the genetic distinction between these two species; the pair-wise genetic distance (uncorrected p) between A. sodwanum and A. jengi is 0.4%, comparable to or greater than that observed among some morphospecies in the closely related genera Klyxum and Cladiella (McFadden et al. 2011;unpub. data).

Conclusions
Among the genera of the family Alcyoniidae the genus Aldersladum seems to be the only one to possess fi gure-eight sclerites in all parts of the colony. In the alcyoniids Cladiella, Klyxum and Rhytisma this type of sclerite is found only in the polyps, and diff erent, diagnostic sclerite-forms characterize other parts of the colony. Indeed, no other genus of Alcyoniidae has only a single sclerite form in all regions of the colony; for example, Sinularia May, 1898 has clubs on the surface of the lobes and base but spindles in its interior (see Fabricius and Alderslade, 2001). Although some species of the genera Xenia and Ovabunda (family Xeniidae) also have uniform sclerites in all parts of the colony (Benayahu, in press), they are not fi gure-eights. Th e xeniid genera Ingotia, Ixion and Bayerxenia have platelet-like sclerites that are narrow across the lateral middle-line like those of Aldersladum, but they lack the median slit that gives the fi gure-eight appearance; moreover, they are not the only sclerite-form found throughout the colony (Alderslade 2001). Sclerites of Moolabalia (family Clavulariidae) also lack the median slit, and the stoloniferous growth form of this genus is distinctive (Alderslade 2001). Placement of the newly-assigned genus Aldersladum in the family Alcyoniidae on the basis of sclerite-form is supported by molecular results that clearly show that Aldersladum is a close relative of Cladiella and Klyxum.
In the original description of E. sodwanae the resemblance between the fi ne structure of its sclerites and those of Cladiella daphnae Ofwegen & Benayahu, 1992 was noted, indications that its signifi cance in the systematics of Alcyoniidae needed to be studied (Benayahu 1993). Th ere is a certain similarity between A. jengi and C. daphnae as refl ected in their fl abby lobes, fi gure-eight sclerites and the resemblance between the base sclerites of the former (Fig. 5) and the surface stalk sclerites of the latter (Ofwe-gen and Benayahu 1992: Fig. 2 i-n). Despite this similarity, it should be noted that C. daphnae features diff erent sclerites in the lobes to those in the base (Ofwegen and Benayahu 1992: Figs 2, 3: fi gure-eights vs. dumbbells) and hence it diff ers from both A. sodwanae and A. jengi.