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Taxonomic revision leads to description of new moray eel species

Underwater photo of Gymnothorax elaineheemstrae

Gymnothorax elaineheemstrae is a new species of moray eel described by Sithole et al. in a study recently published in the international peer-reviewed journal, Zootaxa. Yonela Sithole, a PhD student registered at Rhodes University and supervised at the South African Institute for Aquatic Biodiversity, and her colleagues, revised the taxonomic status of the diverse and widely distributed undulated moray eels (Gymnothorax undulatus). Gymnothorax is the largest genus of the fish family Muraenidae and G. undulatus is one of the most common tropical reef associated species distributed in the Indo-Pacific region. It was first described in 1803 by the French naturalist Bernard Germain de Lacepède. In describing Gymnothorax undulatus, early researchers noted that: “The colour pattern of the species on the body typically varies from light to dark brown with diffuse vertical bars, with or without irregular brown rectangular spots, separated by a narrow pale reticulum.” Today, the new discovery stems from Sithole’s 2017 MSc project in which she used morphological and genetic data to revise the taxonomic status of Gymnothorax undulatus in the Western Indian Ocean (WIO). Her discovery shows that there was a one genetically and morphologically distinct South African species within the Indo-Pacific undulated moray eel complex.

For morphological data, Sithole looked at morphometrics (measurements), meristics (counts) and colour patterns. She examined 101 specimens preserved at the South African Institute for Aquatic Biodiversity, Museum National d’Histoire Naturelle (National Museum of Natural History, Paris) in France, the Smithsonian Institution (Washington, DC) in the United States and the Bernice Pauahi Bishop Museum in Honolulu, Hawaii. All the specimens were recorded as Gymnothorax undulatus in these museums. However, the morphological results, based on colour pattern and the number of total vertebral count, showed that all the specimens collected from South Africa were morphologically different from those in other geographic areas. DNA sequences were also analysed to ascertain whether the morphological differentiation corresponded with genetic analyses. This analysis revealed that Gymnothorax undulatus is differentiated into at least two lineages. The morphological characteristics and molecular markers provided sufficient evidence that the G. undulatus specimens from South Africa represented an unidentified species for science.

The newly recognised species was found to be a distinct species which was long confused with Gymnothorax undulatus, a species common across the Indo-Pacific Ocean. Sithole et al. explain that “Gymnothorax elaineheemstrae has 134-136 total vertebrae and a mottled and faintly reticulated pattern, whereas Gymnothorax undulatus has different vertebral counts (depending on locality) and irregular rectangular blotches separated by large reticulations.” This new endemic species is found along the east coast of South Africa from northern KwaZulu-Natal to Algoa Bay in the Eastern Cape.

Sithole explains that her naming of the new species, G. elaineheemstrae is in honour of her mentor, SAIAB Research Associate, Elaine Heemstra. Elaine says that she was proud to have this moray named for her, she feels sure that Yonela will discover more undescribed species in the future as this pioneering young taxonomist is already breaking new ground in the field. Although the science of discovering, describing and naming new fish species spans well over a century in South Africa, South African ichthyologists interested in taxonomy are scarce at present and we need more home-grown material.

Yonela Sithole and Elaine Heemstra


Yonela Sithole was born and raised in the village of Qunu, Mthatha in the Eastern Cape. She officially joined NRF-SAIAB in 2013 as an intern in the Marine Systematic Research Division and is currently a PhD student registered at Rhodes University and based at NRF-SAIAB on the NRF-DST Professional Development Programme.

In 2018, she was recognised by the Golden Key International Honour Society based on the exceptional achievement on her MSc thesis project and was fortunate to be one of the only two South African students who attended the 10th International Indo-Pacific Fish Conference (IPFC) in Tahiti, French Polynesia.In 2019, she was one of the five participants selected within the African continent to attend a 3 month Fish taxonomy and FishBase Training in Royal Museum for Central Africa (RMCA), Belgium.