Gelation kinetics of the gel collected from the corneocytes of the pilot whale, Globicephala melas

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Summary. We have reported on the smooth and clean skin surface of the pilot whale Globicephala melas (Baum et al 2000 Aquatic Mammals 26:7). Smoothness and self-cleaning abilities of the skin surface are based on a gel that filles the nanoscalic inter-cellular space between the corneocytes. This gel is an important factor in the defence against adhesive glycoconjugates and organisms, that may negatively influence health and hydrodynamic demands of the dolphin. It was our aim to measure the rheological properties of the gel in order to confirm its viscoelastic behaviour predicted from our previous findings.Untreated fresh frozen skin samples of the pilot whale and centrifugates of mechani-cally ablated corneocytes were prepared for cryo-scanning electron microscopy (see Baum et al 2000 Aquatic Mammals 26:7). We examined the surface sculptures of the samples and documented different grades of polymerization seen in the centrifugates. Changes in viscoelasticity of the centrifugates were immediately after centrifugation monitored by means of a stress-controlled rheometer (Haake RS 150) with cone-and-plate geometry (35 mm, apex angle 1°) under oszillatory shear conditions.When centrifugates polymerized, their surface morphology appeared similar to the sur-faces of the untreated fresh skin samples. The gelation kinetics measured confirm that the centrifugates underwent polymerization within 2.5 - 3 hours after processing. At the beginning of the experiments, the high fluctuating pattern of the storage modul GŽ showed the presence of performed aggregates, which were destroyed by the oszillating force. After 2.5 - 3 hours new aggregates built up a gel. We found that in vitro the gela-tion terminates in a duroplastic gel, indicating gelation based on covently cross-linked network bridges.We thank Dr. D. Bloch and Dr. H.-P. Joensen, University of the Faroe Islands, for their help in specimen collection from legal harvest. This study was supported by a grant of the Deutsche Forschungsgemeinschaft (ME 1755/ 1-1).

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Baum, C. , Fleischer, L. G. , Meyer, W. , Siebers, D. and Stelzer, R. (2001): Gelation kinetics of the gel collected from the corneocytes of the pilot whale, Globicephala melas , Zoology[Suppl. IV], 104 .

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