Octocorals (Cnidaria, Anthozoa) from Reunion, with a description of two new species of the genus Sinularia May, 1898 and notes on the occurrence of other species

ABSTRACT This article is based on a recent octocoral survey conducted on the reefs of Reunion Island and on re-examination of part of an older collection (early 1970s) from there. It provides a systematic list of the octocorals and evaluates their abundance. The study describes two new species of the genus Sinularia May, 1898. Sinularia shlagmani n. sp. is characterised by relatively small clubs with a central wart and a colony with densely placed crest-like lobes. It was compared to other species of its clade featuring polyps without sclerites and clubs with distinct central wart, and found to differ from all of them in the shape of the lobes. Sinularia tessieri n. sp. belongs to a clade with collaret, points and tentacle-rods, and clubs with an indistinct central wart, and features an encrusting growth form. It differs from the previously described species featuring similar growth form in having distinctly longer clubs on the surface of the lobules. Based on the description of Sarcophyton subviride Tixier-Durivault, 1958, a discussion is provided on this species. The survey yielded in total 34 species of the families Alcyoniidae Lamouroux, 1812, Subergorgiidae Gray, 1859 and Xeniidae Ehrenberg, 1828, among which 28 are new zoogeographical records for Reunion.


INTRODUCTION
The Island of Reunion is located in the southwest of the Indian Ocean, 21°06'S and 55°32'E, north of the tropic of Capricorn, 700 km from Madagascar to the west and 180 km from Mauritius to the northeast (Fig. 1). Reunion is the southernmost of the Mascarene Islands and has fringing reefs, covering part of its leeward western littoral side (Spalding et al. 2001). The 1998 coral bleaching event had some impact on these reefs, but the recovery was good in almost all areas, reaching a stony coral cover of 30-50% after the bleaching (Goreau et al. 2000). The coral reefs there are impacted by both direct and indirect influences of the increasing human population, and are formally protected within a marine park that is routinely monitored (Tessier et al. 2008).
The present article is based on both an octocoral survey carried out in Reunion during 2006-2008, and on the re-examination of part of the original old collection from there (see Tixier-Durivault 1972). It presents a systematic list of octocorals for Reunion with reference to their abundance and distribution at the different sites. Underwater photographs are presented for most of the species. The study includes a discussion of Sarcophyton subviride Tixier-Durivault, 1958 as well as a description of two new Sinularia species, S. shlagmani n. sp. and S. tessieri n. sp.

MATERIAL AND METHODS
Material was collected, using SCUBA, by YB on a field trip conducted in April 2008 (seven days). It yielded a total of c. 140 specimens of octocorals, encompassing the variety of taxa occurring at the 11 explored sites (Fig. 1). All samples were preserved in 70% alcohol and sub-samples were removed and
Re-examination of MNHN specimens revealed that six had been erroneously identified by Tixier-Durivault (1972

description
Co 34408 is an encrusting colony, exhibiting a rather soft texture. Polyparium with a maximum cross-section of 8.5 × 4.5 cm and a height of up to 4 cm (Fig. 2). Polyparium folded, directed towards colony base. All polyps retracted. Tentacles with scale-and rod-sclerites, up to 0.14 mm long (Fig. 3A). Point sclerites with slight indentation at their ends, up to 0.19 mm long (Fig. 3B). An inquiry to the MNHN yielded eight specimens, out of the 18 listed by Tixier-Durivault (1972) for Reunion. They were re-examined and are included in the current study. In order to identify all the material, sclerites from different parts of the colony were obtained by dissolving the tissues in 10% sodium hypochlorite, followed by rinsing in fresh water. When appropriate, they were 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 6480LV electron microscope, operated at 10 kV. Identification of species was facilitated by comparisons with permanent sclerite preparations of type material kept in the ZMTAU and the RMNH. The material is deposited at ZMTAU, RMNH and MNHN as indicated below. A few members of the family Nephtheidae as well as of the genus Metalcyonuim Pfeffer, 1889 and Carijoa Müller, 1867 were also collected and are still being examined. are shorter compared to the type (up to 0.41 vs 0.6 mm, respectively). We consider these differences as reflecting intra-specific variation within S. subviride. Notably, our material constitutes the second finding of S. subviride since the collection of the type in Aldabra Island (north of Madagascar); and with its current finding in Reunion, it seems to have a bi-equatorial Indian Ocean distribution. Surface of polyparium with clubs, smallest 0.09 mm long and longest up to 0.30 mm (Fig. 3C). Clubs featuring ill-defined head and tubercular prominences, also along handles. Interior polyparium with slender tubercular spindles, some slightly curved, up to 0.58 mm long (Fig. 3D).

Colour
In alcohol, preserved specimen beige with light brown stalk.
reMArks Verseveldt (1982) redescribed the type of S. subviride. The colony shape of the type therein (pl. 22, fig. 2) resembles the currently examined colonies, although many of the polyps are not retracted. The redescription referred to flat tentacle rods and additional rods, arranged en chevron, corresponding to the polyp points (p. 78), but neither type of sclerites was depicted by Verseveldt (1982). We examined polyp mounts of the types deposited at RMNH and confirmed that the polyp sclerites there correspond to those depicted in the current description (Fig. 3A,  B). Unfortunately, most taxonomists examining Sarcophyton species have overlooked the polyp sclerites and therefore excluded them from the original descriptions. This also applies to Verseveldt's 1982 revision of the genus, with the exception of S. pulchellum (Tixier-Durivault, 1957   etyMology. -The species is named after Alex Shlagman, collection manager, Zoological Museum, Tel Aviv University, in appreciation of his dedication and professional curatorial work, particularly in the octocoral collection. description Holotype: an encrusting colony, split into two parts, with a maximum cross-section 12 × 9 cm and height up to 4 cm (Fig. 5). Polyparium consisting of rather short, laterally flattened and closely-set crest-like lobes. All polyps retracted. Colony with a hard texture.
Surface layer of the lobes containing sclerites with tubercles, up to 0.06 mm long (Fig. 6A) Tixier-Durivault, 1969, S. pavida, Tixier-Durivault, 1970, S. scabra, Tixier-Durivault, 1970 (for the last three species see Verseveldt 1980) and they also differ from S. shlagmani n. sp. Similarly, S. siaesensis Van Ofwegen, 2008 andS. microclavata Tixier-Durivault, 1969 (for the latter see Verseveldt 1980) feature compound lobes that also differ from the newly-described species. Sinularia compressa Tixier-Durivault, 1945 andS. inflata Tixier-Durivault, 1970 have small lobules, either finger-like or knob-shaped (see Verseveldt 1980). Sinularia conferta has long branched lobes (see Verseveldt 1980: pl. 6), but unfortunately the type has not been found, leading to various misleading conclusions in this species' diagnosis (see Verseveldt 1980: 31-35). Until Dana's type will be appropriately described, its taxonomic position, including its clade allocation, remains in doubt. Nonetheless, the clear difference between the lobes of S. conferta and S. shlagmani n. sp. (long branched lobes vs densely placed crests) leads to the conclusion that the two are separate species. It is thus evident that S. shlagmani n. sp. differs from all previously described Sinularia species of clade 4C and 4D in the shape of the lobes.

S. deformis
We have re-examined the two specimens from Tanzania identified as S. "conferta" by Van Ofwegen & Benayahu (1992). They show polyp sclerites and belong to clade 5B of McFadden et al. (2009): polyps with collaret and point sclerites, tentacles with rods, clubs with central wart distinct. In this clade we could not find a species with the characteristics of the Tanzanian specimens and we now regard these specimens as belonging to a yet undescribed species.
Surface layer of base of colony containing clubs, mostly with central wart, similar to those of lobes, but wider, some with tubercles on handle, 0.07-0.10 mm long (Fig. 7A), also with spindles, up to 0.21 mm long (Fig. 7B).
Interior of the base with spindles, the small ones branched, up to 2.2 mm long (Fig. 7C), with large tubercles (Fig. 7D), or smaller ones (Fig. 7E).

Living features
The colony is beige in colour (Fig. 16F).
Surface layer of the lobules containing clubs with warty heads and tubercles on handle, 0.07-0.16 mm long (Fig. 9D) and with a few crosses (Fig. 9E). In addition with spindles, up to 0.26 mm long, mostly with simple or, less commonly, complex tubercles (Fig. 9F).
Surface layer of base of colony containing clubs, similar to those of lobules, but wider, 0.10-0.20 mm long (Fig. 10A). Also spindles, up to 0.26 mm long (Fig. 10B).
Interior of the lobules with branched stout spindles, up to 2.70 mm long (Fig. 11A), with complex tubercles (Fig. 11B), or with simple ones (Fig. 11C). Interior of base with slightly longer spindles, distribution. -So far known only from the type locality.
etyMology. -The species is named after Dr Emmanuel Tessier, Manager, Association Parc marin de La Réunion, in appreciation of his initiative to conduct the octocoral survey in Reunion and his support during the field work and afterwards.
description Holotype: an encrusting colony, with maximum cross-section of 7 × 4 cm and height up to 4 cm (Fig. 8A). Polyparium consisting of short lobes and a few longer ones that may branch off once. Lobes and lobules mostly flattened, or occasionally knob-shaped, and in part tending to bend down towards each other. Colony with a hard texture.

Colour
Preserved holotype dark brown, almost black.

Living features
The colony is light-grey in colour, expanded polyps are light-beige. features clubs up to 0.25 mm long. Moreover, the stalked species of that clade differ from S. tessieri n. sp. Sinularia grandilobata Verseveldt, 1980 has clubs up to 0.10 mm long compared to up to 0.17 mm in the newly-described species. The clubs of S. capricornis Dautova, Van Ofwegen & Savinkin, 2010 are up to 0.18 mm long and the species features un-branched spindles in the interior of the lobes, as opposed to the stout and heavily branched ones of S. tessieri n. sp. (Fig. 11A). Notably, the latter stout spindles of S. tessieri n. sp. are not found in any of the species of clade 2. It is thus concluded that S. tessieri n. sp. differs from all previously-described species of clade 2.

FURTHER NOTES
The taxonomic results (given below) enabled analysis of octocoral abundance and distribution on the Reunion reefs.  . 1) varied in respect to their number of octocoral species (Table 2). Although these collections were qualitative, it was anticipated that they would encompass all the taxa encountered during the dives, thus allowing us to identify sites with a relatively high octocoral diversity. Each of the following sites featured at least 10 species: Saint-Leu, Pointe des Châteaux (19 species), Saint-Leu, Récif Pointe au Sel (Cimetière) (15), Saint-Paul, Planch' Alizés (12) and Saint-Paul, Pain de Sucre (Maharani) (11).

DISCUSSION
Based on both the recent (2006)(2007)(2008) and the old (Tixier-Durivault 1972) collections, the current study provides for the first time a comprehensive account of the octocorals of Reunion. It yielded two new species, S. shlagmani n. sp. and S. tessieri n. sp. Prior to the current survey, the list provided by Tixier-Durivault (1972) offered the only report on the octocoral fauna there; a report that, unfortunately was found to be erroneous. The revised identification of the MNHN material comprised five species (L. depressum, L. crassum, S. erecta, S. hirta and S. shlagmani n. sp.), all also found in the recent collections (Table 1), thus bringing to 28 the total number of new zoogeographical records from Reunion. The findings revealed Sinularia as the most speciose genus on the Reunion reefs (Table 1: 14 species), albeit fewer than in the Red Sea (38), East Africa (33) and Madagascar (23) (Van Ofwegen 2002). The remote geographical position of Reunion, in the southwest Indian Ocean, 700 km from Madagascar to the west and 180 km from Mauritius to the northeast, could be the reason for the relatively low Sinularia diversity found there. At present there is no information on the octocoral fauna of Mauritius or Rodrigues, the adjacent islands at the southern end of the Mascarene Ridge, and therefore it is still too speculative to posit the zoogeographical patterns of octocorals