A new species of Lucanicum (Cyclophorales, Bacillariophyta) associated with loggerhead sea turtles from South Africa

ABSTRACT

A new Lucanicum species, L. ashworthianum Majewska, K.Robert & Van de Vijver sp. nov., was found in multiple samples of biofilm growing on loggerhead sea turtles Caretta caretta and their symbiotic barnacles Chelonibia testudinaria collected on the beaches of Kosi Bay, eastern coast of South Africa, during the two nesting seasons (the austral summers of 2017/2018 and 2018/2019). The new species possesses several features typical of the genus Lucanicum, including the uniseriate striae composed of one large macroareola, the presence of large apical slit fields and transapically elongated rimoportulae at both poles, and a cingulum composed of numerous open, doubly perforated copulae. It differs from the only other Lucanicum species known to date, the coral-associated L. concatenatum, in having considerably smaller cells with clearly rostrate or sub-capitate apices and internal rimoportula opening composed of a C-shaped inner lip and an oval, flap-like outer lip – a feature not observed previously in Lucanicum. Based on these new observations, an amendment of the genus description is proposed.

KEYWORDS:

• Barnacle
• biofilm
• epibiosis
• epizoic diatom
• Indian Ocean
• loggerhead
• marine
• South Africa

Acknowledgments

All sampling activities were carried out under research permits issued by the South African Department of Environmental Affairs (RES2016/67, RES2017/73, RES 2018/68, and RES 2019/05). The authors are grateful to Diane ZM Le Gouvello du Timat, Anthony Evlambiou, and Wynand van Losenoord (Nelson Mandela University, South Africa) for their invaluable help during the material collection. Franco De Ridder (North-West University, South Africa) and Christopher R. Nolte (Nelson Mandela University, South Africa) collected some of the samples containing the new taxon, Danay Stoppel and Carla Swanepoel (North-West University, South Africa) performed some of the laboratory procedures, and William Goosen (Nelson Mandela University, South Africa) assisted during the scanning electron microscopy observations. The authors further thank Prof. Jan Neethling and the team from the Centre for High Resolution Electron Microscopy (Nelson Mandela University, Port Elizabeth, South Arica) for their generous support of this project and the possibility to use the scanning electron microscope. Luc Ector and one anonymous reviewer are thanked for their useful comments on the previous version of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was done with partial financial support from The Systematics Association (UK) through the Systematics Research Fund Award granted to R. Majewska (2017).

Notes on contributors

Roksana Majewska

Roksana Majewska is a post-doctoral research fellow at North-West University, South Africa. Her studies focus mainly on the ecology and taxonomy of marine and brackish diatoms. She has collaborated on various multidisciplinary projects in subjects including biotechnology, geology, biophysics, nanostructures, pharmacology and medicine. Nevertheless, her primary interests remain in microbial biology and biodiversity. One of her current research projects deals with the phenomenon of diatom epibiosis and surface associations in marine communities. Author's contribution: original concept and supervision of the sea turtle diatom project in South Africa, material collection and processing, microscopic analyses, writing the manuscript.

Käthe Robert

Käthe Robert graduated in biology (MSc), with a specialization in biodiversity, conservation and restoration, at the University of Antwerp in Belgium. Her master thesis focusses on the diversity of epibiotic diatom communities associated with loggerhead sea turtles from four geographically different populations. She likes to practice nature photography and scuba diving, especially in a scientific context. As a volunteer, she participated in a coral reef monitoring project in Egypt with the Red Sea Environmental Center, where she obtained a Reef Check Ecodiver certificate. She plans to follow an educational master program while staying involved in the epibiotic diatom research as a volunteer at the Meise Botanic Garden. Author's contribution: material processing, microscopic analyses, editing the manuscript.

Bart Van de Vijver

Bart Van de Vijver is a full-time researcher at the Meise Botanic Garden, Belgium, and a part-time professor at the University of Antwerp, Belgium. His research focuses mainly on the taxonomy, morphology and biogeography of Antarctic freshwater and terrestrial diatoms. He has been studying diatoms in various parts of the Antarctic region for more than 20 years. His second research topic concentrates epizoic diatoms living on marine vertebrates. He has described almost 400 new taxa and revised an additional 250 taxa. Author's contribution: microscopic analyses, discussing the results, editing the manuscript.

Ronel Nel

Ronel Nel is an academic and marine ecologist at Nelson Mandela University, South Africa with specializations in sandy beach ecology, coastal conservation and management and sea turtle biology and conservation. She has more than 40 publications that investigate aspects of ecosystems function and match conservation policy with sound science. Author's contribution: providing access to the research station and equipment, organizing fieldwork, editing the manuscript.