Advancing our knowledge of Actinostella: a new species from Yucatan, Mexico, and comprehensive redescription of A. flosculifera (Le Sueur, 1817) (Cnidaria, Actiniaria)

Abstract

Actinostella flosculifera (Le Sueur, 1817) is a common species of sea anemone in the tropical Atlantic’s coastal and reef ecosystems, with records ranging from Bermuda Islands to Brazil, and from some areas of the Eastern Atlantic. Actinostella flosculifera exhibits wide morphological variability, mainly in terms of coloration patterns and a range of different sizes. We conducted a morphological and genetic study of this species using specimens collected from several localities in the Caribbean Sea, the Gulf of Mexico, and Brazil. We also examined specimens previously deposited in the National Museum of Natural History at the Smithsonian Institution, and compared our data with previous studies on A. flosculifera , as well as with other species of Actinostella , such as A. bradleyi and A. californica from the Eastern Pacific. The results of phylogenetic analyses, based on molecular data from two nuclear and three mitochondrial markers, revealed the existence of two subclades of Actinostella in the western Atlantic. Based on combined molecular and morphological evidence, one of these subclades is herein recognized as a distinct species and described as Actinostella yucatanensis sp. nov., found on Chabihau beach, Yucatán Peninsula, Mexico. We provide a detailed description of A. yucatanensis sp. nov., including images of its external and internal anatomy, cnidome and capsule size ranges and distribution, and a molecular diagnosis. In addition, we present an updated description of A. flosculifera and document for the first time the presence of small pore-shaped apertures (similar to cinclides) on the marginal ruff.

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