Molecular examination of rocky shore brachycnemic zoantharians (Anthozoa: Hexacorallia) and their Symbiodinium symbionts (Dinophyceae) in the southwest Indian Ocean

Abstract

The order Zoantharia is ubiquitous on the east coast of South Africa, but despite its widespread distribution its species are poorly represented in recent literature from the region. A previous study in this region has shown that Zoanthus natalensis Carlgren, 1938 and Z. durbanensis Carlgren, 1938 are most likely conspecific to the Pacific Z. kuroshio Reimer & Ono, 2006 and Z. vietnamensis Pax & Muller, 1957, respectively. The aims of the present study were to expand on the previous one by conducting a molecular examination of zoantharians found in the intertidal zone along the east coast of South Africa as well as to identify their Symbiodinium symbionts for comparison with conspecifics elsewhere. Symbiodinium identification can be a useful tool when dealing with species that are synonymous as they are likely to share Symbiodinium spp. from the same subclade. The molecular markers mitochondrial 16S ribosomal DNA (mt 16S rDNA), the nuclear internal transcribed spacer region of ribosomal DNA (ITS rDNA), and for the first time on South African zoantharians, the ITS rDNA region for Symbiodinium spp. were used. Seven species were identified. They were Isaurus tuberculatus, Palythoa nelliae, P. tuberculosa, Z. durbanensis, Z. gigantus, Z. natalensis, and Z. sansibaricus. A possible synonymy was found as Palythoa nelliae Pax, 1935 appears to match with the Pacific P. mutuki (Haddon & Shackleton, 1891). Symbiodinium subclade A1 was most often found with Z. natalensis and subclade C15/C91 was most frequently observed in Z. durbanensis. Subclade C1 was found with all Isaurus and Palythoa samples, and with most of Z. sansibaricus samples. Symbiodinium subclades in this study were generally the same as those reported from Indo-Pacific conspecifics.