Molecular revision of Zoantharia (Anthozoa Hexacorallia) on the east coast of South Africa.

Abstract

The order Zoantharia (Cnidaria: Anthozoa) is ubiquitous on the east coast of South Africa, and despite their widespread distribution they are poorly represented in literature. No molecular identification has been carried out on these organisms on the South African shoreline. Zoanthus sansibaricus Carlgren, 1900 has a global distribution and has been reported having numerous morphotypes in terms of polyp shape, size, colour and oral disk colour. The initial aim in this study was to examine the molecular characteristics of three Zoanthus species; Z. sansibaricus, Z. durbanensis Carlgren, 1938 and Z. natalensis Carlgren, 1938, to determine whether they are three separate species or merely morphotypes of one another. Following on from this research, the aim was to conduct a molecular revision of all zoanthids found in the intertidal zone along the east coast of South Africa, and to identify the Symbiodinium spp. within zoanthids for comparisons with conspecifics elsewhere. Samples were collected at sites along the coast from Umgazana (31.7024° S, 29.4175° E) to Sodwana (27.6594° S, 32.6477° E) and at one site in Libanona, Madagascar (25.0421° S, 46.9952° E). Sequences of cytochrome oxidase subunit one (COI), mitochondrial 16S ribosomal DNA (mt 16S rDNA), the nuclear internal transcribed spacer region of ribosomal DNA (ITS rDNA) for zoanthids and ITS-rDNA region for Symbiodinium spp. were used in this study to run phylogenetic analyses and examine the molecular characteristics for comparisons with zoanthids elsewhere using GenBank. Seven species were identified; Isaurus tuberculatus, Palythoa nelliae, Palythoa tuberculosa, Z. durbanensis, Z. gigantus, Z. natalensis and Z. sansibaricus. The COI sequences (for Z. sansibaricus, Z. natalensis and Z. durbanensis) had little variation between species groups, while the mt 16S rDNA tree showed that Z. sansibaricus matched with sequences of previously reported Z. sansibaricus from the Pacific. Zoanthus natalensis was identical to Z. kuroshio Reimer & Ono, 2006 and Z. durbanensis was identical to Z. vietnamensis Pax & Müller, 1957. The ITS rDNA sequences were very similar for these four species; Z. natalensis, Z. kuroshio, Z. durbanensis and Z. vietnamensis. Palythoa nelliae Pax, 1935 appears to match with Pacific species Palythoa mutuki Haddon & Shackleton, 1891, and this is supported by the mt 16S and ITS rDNA markers. Symbiodinium subclade A1 was most often found with Z. natalensis and subclade C15/C91 was most often found with Z. durbanensis. Subclade C1 sensu LaJeunesse (2002) was found with all Isaurus and Palythoa samples, and most of Z. sansibaricus samples. The results of this study indicate that Z. natalensis is likely conspecific to Z. kuroshio, Z. durbanensis is likely conspecific to Z. vietnamensis, and P. nelliae is likely conspecific to P. mutuki, however, this is only a tentative hypothesis as no formal morphological analyses were done on proposed conspecifics.This work highlights the importance for similar studies in the clarification of zoanthid taxonomy