Cyphastrea salae, Baird, Andrew H., Hoogenboom, Mia O. & Huang, Danwei, 2017

Baird, Andrew H., Hoogenboom, Mia O. & Huang, Danwei, 2017, Cyphastreasalae, a new species of hard coral from Lord Howe Island, Australia (Scleractinia, Merulinidae), ZooKeys 662, pp. 49-66 : 51-54

Cyphastrea salae sp. n.

Material examined.

Holotype: Australian Museum AM 81_1530 South Flat, Lord Howe Island (LHI), Australia (-31.5611; 159.0741) 1 m depth. Paratypes: AM 81_1822 Malabar, LHI (-31.5115; 159.0575); AM 81_4749 Malabar West, LHI (-31.5118; 159.0508) and see Appendix 2.

Diagnosis.

Cyphastrea salae is found on Lord Howe Island and in the Solitary Islands, where it is the only Cyphastrae species with 12 primary septa.

Skeletal characteristics of the holotype.

The holotype is part of a hillocky colony approximately 50 cm width by 50 cm deep by 50 cm height of a tan colour (Fig. 1A). The most prominent feature of the species in the field are the exsert corallites (Figure 1B). The fragment of the holotype is 10 cm long by 5 cm wide and 4 cm thick (Fig. 1C). Most measured features were uniform: the maximum diameter of the corallites ranged from 2.5 to 2.8 mm, the maximum calyx diameter ranged from 2.0 to 2.4 mm and the maximum diameter of the columella ranged from 0.7 to 0.8 mm. All corallites had two septal cycles and 12 primary septa. In contrast, corallite height was more variable, ranging from 0.4 to 3.3 mm as was the density of corallites which ranged from 5 to 9 cm-2. The holotype has regular free septa and a compact columella (Figure 1D). Septal teeth with multiaxial tips are low (~0.2 mm in height) and narrowly spaced (0.1-0.2 mm), with 7-9 teeth per septum (Figure 1E). Strong pointed or club-shaped granules are scattered on the septal face (Figure 1E). The inter-area on the septa is smooth. Corallite walls are formed by dominant septotheca (Figure 1F). Thickening deposits are fibrous (Figure 1F). Costa and septum centre clusters are weak with approximately 0.3 mm between clusters in the costa and <0.2 mm in the septum. Medial lines are also weak (Figure 1F). Perpendicular crosses absent (Figure 1F). Columella centres are clustered (Figure 1F).

Instraspecific variation.

The most common morphology of colonies in the lagoon at Lord Howe Island is hillocky like the holotype, however, some coralla are massive (e.g. 81_1414; Figure 2A, B) or submassive (e.g. 81_3953; Figure 2C, D); and at depth the corolla can be encrusting (e.g. 81_1822; Fig. 2E, F and 79_4749; Figure 4G, H). The colour of the colony ranges from tan to green to blue. Corallite diameter ranges from 1.7 to 3.2 mm; calyx diameter ranges from 1.4 to 2.7 mm; columella diameter ranges from 0.6 to 1.0 mm; corallite height ranges from 0.4 to 3.5 mm; number of corallites per cm ranges from 5.0 to 14.0 cm-2; and the number of primary septa ranges from 10 in very small corallites to 17 in the largest (Table 1). Corallite density was noticeably reduced in specimens from greater depths on Lord Howe Island (Appendix 2; Figure 2E, F).

Comparison with C. micropthalma .

In general, there were few differences in the measured features of the corallites of C. salae and C. microphthalma . In particular, corallite and calyx diameter were remarkably similar between the two species (Table 1). Corallites were significantly taller (t = 3.43, p = 0.001) and the columella was larger (t = 7.12, p <0.001) in C. salae (Table 1). In addition, corallites were significantly more crowded in C. microphthalma which had 11.4 corallites per cm2 compared with 9.6 per cm2, on average, for C. salae (t = -3.86, p <0.001; Table 1).

The two species are difficult to distinguish in the field based on gross morphology. Cyphastrea microphthalma most frequently forms hillocky colonies (Figure 3 A, B), however, it can also occasionally form massive colonies (Figure 3C). Nonetheless, the species can readily be distinguished in the field and the lab on the basis of the number of primary septa which is generally 12 in C. salae (Figure 1C, D) vs. 10 in C. microphthalama (Figure 3 D–F). Nonetheless, the modal number of septa in the five corallites counted correctly identified the molecular clade identity in 100% of colonies (Appendix 2).

Phylogenetic analysis.

Molecular analyses revealed a monophyletic Cyphastrea with two major clades (Figure 4). One clade contained new sequences from all the C. microphthalma specimens collected from Lord Howe Island, nested within GenBank sequences of C. microphthalma from Singapore and the C. chalcidicium / serailia complex. The second clade comprised all of the sequences from C. salae from Lord Howe Island and the Solitary Islands, as well as C. cf. decadia from Fiji. The first clade was generally unsupported under all optimality criteria for 28S rDNA, but descendent nodes grouping C. microphthalma from Lord Howe Island with other C. chalcidicum / serailia and C. microphthalma sequences had moderate to high supports. The second clade containing C. salae was well-supported under all analyses, and is, although the sister relationship to the branching C. cf. decadia is only strongly supported by IGR (Figure 4).

Cyphastrea salae and C. microphthalma originated from two distinct lineages. Cyphastrea salae formed a well-supported monophyletic group under all analyses, and is sister group to the branching C. cf. decadia (Figure 4). All the IGR sequences of C. microphthalma clustered strongly as a clade, including the representative from Singapore, but the group is split weakly into two with the 28S rDNA marker. The relationships between C. microphthalma and its closely related congeners remained unresolved due to low support by the less variable 28S rDNA (Figure 4).

Etymology.

The species is named after Dr Sally Keith and Ms Sallyann Gudge, who have both made significant contributions to understanding and protecting the coral reefs of Lord Howe Island.

Distribution and frequency.

Cyphastrea salae is common in the lagoon at Lord Howe Island where it commonly co-occurs with C. microphthalma . It has been recorded to 18 m depth outside the lagoon. One colony has been positively identified using the molecular markers from Solitary Islands, where it is sympatric with C. microphthalma . Cyphastrea salae has yet to be recorded in extensive sampling on the Great Barrier Reef and no sequences are present in GenBank.