The Variation in the Occurrence of Diatoms in the External Mucus of Florida Sharks
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Elasmobranch skin has been extensively studied for its drag-reducing hydrodynamic structure and its implications for reduction in ship fuel cost1. Shark mucus and biofilm may also have antifouling properties of interest to ecologists and ship engineers. However, the external mucus and associated biofilm of sharks has not been widely studied. This study examines the mucus/biofilm of 7 shark species for the presence of diatoms, a universal precursor microfouler. Bacteria and diatoms attach to all submerged surfaces and secrete Extracellular Polymeric Substance (EPS). EPS and associated microorganisms constitute a marine biofilm. All submerged surfaces develop biofilms3,8,10, but environmental and substratum characteristics will determine which species of bacteria and diatoms will be present and dominate2,4,5. The properties of this initial biofilm can inhibit or promote macrofoulers from settling and further fouling the surface6. Natural antifouling compounds, such as those potentially present in shark biofilms, are of interest in anti-tumor and anti-fouling research, and a focus of some biochemists and pharmaceutical companies7. In this study, the mucus of seven species of Florida sharks was sampled and tested for diatoms. The presence (or absence) of diatoms in the external mucus of sharks could provide insight into the mechanisms underlying the absence of macrofouling on sharks.