engleski

The epibiotic diatoms associated with loggerhead sea turtles in the Adriatic Sea

In recent years, there is a growing scientific interest in epibiotic communities on sea turtles. A broad array of animals such as crustaceans, annelids, molluscs and macroalgae are known to thrive successfully as macro- epibionts on the sea turtle body surfaces. Together with these macroscopic organisms, sea turtles also host unique and diverse micro- epibiotic diatom communities composed of a large number of genera, several of which that have been described as new to science in the past five years. Typical examples include the genera Chelonicola, Medlinella and Poulinea, known exclusively from the carapaces and skin of different marine turtle species (Majewska et al. 2015, Frankovich et al. 2016). During a survey of the diatom flora associated with the carapaces of loggerhead sea turtles (Caretta caretta) from the Adriatic Sea, a fairly diverse diatom assemblage was observed composed of several Diploneis, Fallacia and Amphora taxa together with three unknown diatom taxa that initially could not be identified even on genus level. For at least two of them, further analysis revealed that they most likely represent new genera whereas a third one could be assigned to the genus Catenula. A first unknown taxon belongs to the monoraphid diatoms based on the presence of both a raphe and rapheless valve. The rapheless valve is characterized by the presence of a large silica crest surrounding the entire valve and covering part of the valve margin. The striae consist of two large areolae, separated by a broad hyaline plate and covered externally by porous hymenes. The raphe is rather simple with bent terminal fissures and straight, simple central endings. Comparison with achnanthoid genera such as Scalariella, Kolbesia and Madinithidium yielded both clear similarities but also distinct differences (Desrosiers et al. 2014, Riaux- Gobin et al.2012). The second unknown taxon shows similarities to the members of the genera Nitzschia, Rhopalodia and Psammodictyon based on the presence of an eccentric raphe, distinct fibulae and a dorsiventral valve outline. Finally, the third taxon is most likely a new Catenula species, a small amphoroid genus with only marginal striae, a very simple raphe structure and non-perforated, narrow girdle bands. These observations show the special nature of the epibiotic flora found on loggerheads and confirm our lack of taxonomic knowledge increasing the importance of the currently ongoing research investigating microepibiotic assemblages associated with sea turtles.

epizoic diatoms ; loggerhead sea turtles ; taxonomy ; new species

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