Who is Oxyrrhis marina? Morphological and phylogenetic studies on an unusual dinoflagellate
Abstract
Oxyrrhis marina is a well studied and common protist, used model to a range of ecological processes. Further, as a result of unusual cytological and genetic features, Oxyrrhis is increasingly a target for the study of evolutionary development within the Alveolata. However, morphological and phylogenetic data suggest that O. marina represents multiple species. As different research groups employ different O. marina isolates, the context in which comparisons between isolates can be made is difficult to assess. Here, we explore the literature that has contributed to the definition of O. marina, highlighting the unusual characteristics that have motivated much of the study on this organism and informed its key phylogenetic position. In addition, we assess historical and contemporary evidence for multiple Oxyrrhis species. Based, in particular on recent molecular genetic data, we assert that O. marina, represents two species: O. marina and O. maritima. Based on historical observations we also indicate that a third species (O. tenticulifera) may occur, though there are no contemporary data to support or refute this designation. Extensive cryptic diversity has important implications for researchers studying Oxyrrhis: caution must be exercised in characterising Oxyrrhis isolates for experimental study (i.e. it is inappropriate to report assessments concerning poorly characterised isolates), and comparative studies of multiple isolates are required to assess individual, population, and species level variation in the genus. Finally, in a broader context, evolutionary processes driving diversity in free-living protists remains poorly understood. Highly diverse model protists such as O. marina and O. maritima, present ideal opportunities to unravel these fundamental processes.
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