A new scleractinian coral species, Cyphastrea kausti sp. n., is described from 13 specimens from the Red Sea. It is characterised by the presence of eight primary septa, unlike the other species of the genus, which have six, ten or 12 primary septa. The new species has morphological affinities with Cyphastrea microphthalma, from which it can be distinguished by the lower number of septa (on average eight instead of ten), and smaller calices and corallites. This species was observed in the northern and central Red Sea and appears to be absent from the southern Red Sea.

Merulinidae, Saudi Arabia, biodiversity, coral reef, taxonomy, KAUST

The genus Cyphastrea Milne Edwards & Haime, 1848 has an Indo-West Pacific distribution range, from the Western Indian Ocean to the Central Pacific, and contains 19 nominal species, nine of which are considered valid (Hoeksema 2014). The genus was previously included in the family Faviidae Gregory, 1900, but recent molecular work has heavily re-organised the classification of the major scleractinian families and Cyphastrea is now placed in the Merulinidae Verrill, 1865 (Fukami et al. 2008, Budd et al. 2012, Huang et al. 2014).

In his revision of the genus, based on macro-morphological characters of the skeleton and the tissue of the coral polyps, Matthai (1914) recognised five species, i.e., C. microphthalma (Lamarck, 1816), C. serailia (Forskål, 1775), C. chalcidicum (Forskål, 1775), C. gardineri (Matthai, 1914), and C. suvadivae (Gardiner, 1904). However, the last three were later declared junior synonyms of C. serailia by Wells (1954) and Chevalier (1975). Veron et al. (1977) then reinstated C. chalcidicum and declared C. gardineri as junior synonym of C. microphthalma rather than C. serailia.

More recent regional work on the taxonomy, biodiversity, and distribution of scleractinian corals in the Red Sea originally recognised two Cyphastrea species in the region, C. microphthalma and C. serailia, synonymising again C. chalcidicum with C. serailia (Scheer and Pillai 1983, Sheppard and Sheppard 1991). However, DeVantier et al. (2000) and Veron (2000, 2002) subsequently reinstated C. chalcidicum and described a new species from the northern Red Sea, C. hexasepta Veron et al. 2000, leading to four valid species of Cyphastrea in the Red Sea: C. microphthalma, C. serailia, C. chalcidicum, and C. hexasepta.

The genus Cyphastrea has recently been formally revised within the Merulinidae, incorporating molecular phylogeny, macromorphology, micromorphology, and microstructure (Huang et al. 2014) but it has yet to be revised at the species level. Indeed, the species boundaries within the genus have not yet been investigated using an integrated systematic approach, such as for example in the genera Plesiastrea (Benzoni et al. 2011), Blastomussa (Benzoni et al. 2014), Australomussa, and Parascolymia (Arrigoni et al. 2014).

The genus Cyphastrea is characterised by its compact coenosteum (Milne Edwards and Haime 1848). The genus is composed of colonial species, with only extracalicular budding. The corallites are monomorphic, monticules are absent, and the coenosteum is generally spinose. Calice width is smaller than 4 mm, septa are in three cycles or less, costosepta are not confluent, and are unequal in relative thickness. The columella is trabecular and compact, and paliform lobes are weak or moderate (Huang et al. 2014). Species in this genus are commonly described based on the septal arrangement (Wijsman-Best 1980, Sheppard and Sheppard 1991, Veron 2000). Among the species currently recognised in the Red Sea, C. chalcidicum and C. serailia both have two cycles of six septa that are identical in C. serailia and alternating in C. chalcidicum, C. hexasepta has six primary septa, and C. microphthalma has ten primary septa (Veron 2000). Here we describe a new species that resembles C. microphthalma in the field but has eight septa: C. kausti, sp. n. first observed in 2011 in Al Fahal Reef, offshore from the King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.

Colonies of Cyphastrea kausti sp. n. (13 in total) were sampled on SCUBA in 2013 during several expeditions along the coast of the Saudi Arabian Red Sea, from Magna in the Gulf of Aqaba in the north to the Farasan Islands in the south (Fig. 1). Digital images of living corals were taken in the field with a Sony DSC-W80 camera and Sony MPK-WB underwater housing and the depth recorded with a dive computer, when possible. Coral specimens were collected with hammer and chisel and tagged. From each colony, a small fragment was subsampled and preserved in absolute ethanol for molecular analysis. The remaining corallum was placed for 24 hours in sodium hypochlorite to remove all coral tissue, rinsed in fresh water, and dried for microscopic observation. The cleaned skeletons were then photographed with a Canon G9 digital camera. Macro and micromorphological characters were examined using light microscopy (Zeiss Stemi 2000 dissecting microscope) and scanning electron microscopy (SEM), respectively. For SEM, a small fragment of clean skeleton was ground at the base with sandpaper, mounted on a stub using double-sided carbon tape, sputter-coated with a 3 nm layer of conductive gold-palladium (AuPd) film, and examined using a Quanta 200 FEG SEM at the KAUST Imaging & Characterization Core Lab. Samples of C. kausti sp. n. were compared to samples of the other species present in the Red Sea, which were located at the KAUST Biodiversity collection. Specimens of C. kausti sp. n. were morphologically compared with those of C. microphthalma, morphologically the most closely resembling species based on in situ observations and skeletal examination. The morphometric characters (Table 1) were determined post-imaging with a digital measurement analysis tool calibrated on the image scale bar in Adobe Photoshop CS3. The holotype and a paratype of Cyphastrea kausti sp. n. were deposited at the National Museum of Natural History (MNHN), Paris, France. All other material is located at the King Abdullah University of Science and Technology (KAUST), as part of its Red Sea Biodiversity collection. The holotype of C. microphthalma was examined from images taken by A.F. Budd, available online at http://www.corallosphere.org.

Figure 1. 

Map of the Red Sea showing the sampling sites of Cyphastrea kausti sp. n. The red dot indicates the locality of the holotype, the dark red dot indicates the locality of the paratype, and the green dots indicate the localities of the remaining sampled material.

Cyphastrea kausti sp. n. is morphologically closest to C. microphthalma based on the presence of a primary and a secondary septa cycle, a missing third septa cycle, a crown of paliform lobes surrounding the columella (although generally more distinct in C. kausti sp. n.), the growth form, the densely ornamented coenosteum, and the density of corallites. The two species can, however, be distinguished by the average number of septa (8.0 ± 0.4 for C. kausti sp. n. and 9.8 ± 0.5 for C. microphthalma) and by the average calice and corallite size (Figure 3a–f). The calice and corallite diameter are on average smaller in C. kausti sp. n. (1.01 ± 0.13 mm and 1.62 ± 0.19 mm) than in C. microphthalma (1.27 ± 0.11 mm and 2.01 ± 0.18). In their description of C. microphthalma Sheppard and Sheppard (1991) report that Red Sea specimens have a tendency to contain mostly eight primary septa and that this form could be established as a new species in further work, which is done here. Field observations and sampling performed throughout the entire Saudi Arabian coast of the Red Sea between 2013 and 2014 provide evidence that both C. kausti sp. n. and C. microphthalma are present in the Red Sea and co-occurring in some regions, often in similar habitats. However, C. kausti sp. n. appears to be restricted to the central and northern Red Sea and is not found in the southern half of the Red Sea, while C. microphthalma extends out of the Red Sea and is distributed throughout the Indo-Pacific Ocean with an eastern range limit in Tahiti, French Polynesia, in the Central-Pacific Ocean (Sheppard and Sheppard 1991).

The simultaneous presence of both male and female gametes in colonies of C. kausti sp. n. during reproductive surveys shows that it is hermaphroditic and likely to spawn in June in the central Red Sea, along with numerous other species including the congeneric C. serailia, and C. chalcidium, while C. microphthalma was observed to spawn in May (Bouwmeester et al. 2015). Further reproductive surveys are, however, necessary to establish if indeed a reproductive barrier is present between C. kausti sp. n. and C. microphthalma with each species spawning in a different month, or whether one or both of the two species spawn over two consecutive months, as observed in the region for Acropora humilis, Goniastrea edwardsi, and Echinopora hirsutissima, which released gametes during consecutive months in a given year (Bouwmeester et al. 2015).

A molecular phylogeny of all Cyphastrea species remains necessary to test and establish species boundaries within the genus. The phylogenetic position of C. kausti sp. n. will be investigated in further work, integrating a molecular as well as a macromorphological and a micromorphological approach.

Cyphastrea kausti sp. n. is described from the Saudi Arabian Red Sea based on morphological analyses. The eight-septa arrangement in the first septa cycle distinguishes it from other described species in the genus. Cyphastrea kausti sp. n. is further recognized by a crown of paliform lobes around the columella and corallite and calice sizes smaller than in C. microphthalma, to which it is morphologically closely related.

We would like to thank Joey DiBattista, Tane Sinclair-Taylor, Mark Priest, the KAUST Coastal & Marine Resource Core Lab for logistic assistance; the skippers and crews of the MV Dream-Master, MV Dream-Island, MV Deep-Sea, and RV KAUST Explorer for technical support, as well as members of the KAUST Reef Ecology Lab and the BBs for assistance in the field and Danwei Huang for collecting additional specimens. We are grateful to Ali Behzad for his help and training with SEM imaging. Funding was provided by KAUST baseline research funding to MLB and award CRG-1-BER-002 to MLB & AHB. We also would like to thank two anonymous reviewers for their comments and suggestions, which helped improve the manuscript.