A cryo-scanning electron microscopic study of the skin surface of the pilot whale Globicephala melas
Summary. Skin surfaces of pilot whales Globicephala melas were studied by scanning electron microscopy with particular emphasis on surface condition and epibiontic marks of biofouling. In order to minimize artificial cross-linking of cell structures, dislocation of epibionts or dilution of salt crystals, untreated fresh skin samples were stored and examined by cryo-scanning electron microscopy at controlled low temperature in the first study of its kind. The samples were compared with aldehyde-fixed skins of pilot whales.The results obtained show that the surfaces of the fresh skin areas are covered with a smooth biofilm of alternating hydrophilic-hydrophobic sectors and exhibit negligibly low concentrations of epibiontic organisms or salt crystals. In contrast to the smooth biofilm observed in cryo-scanned samples, the aldehyde-fixed skin areas were covered with a more spongy layer of irregular structures, supposedly representing denatured remnants of the biofilm. We consider the biofilm to be the structural basis of skin smoothness and the primary site of epibiontic settlement.