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Böni, Lukas Johannes
Windhab, Erich Josef
- Other Conference Item
When hagfish (Myxinidae) are attacked they immediately secrete an elastic, dilute, and cohesive slime made of mucins and long protein threads (≈ 15 cm) [1, 2, 3]. The long protein threads are initially coiled up within the fish but unravel within seconds once in contact with seawater, forming a fibrous network for the water-binding mucin. The slime exerts its defensive mechanism by clogging the gills of predators. The threads as well as the mucins are hardening in extension, which was suggested to support the defense against suction feeding predators [2,4]. Despite the importance of the ionic strength on the properties of marine biopolymer systems, little is known about the influence on the flow properties of hagfish mucins and on the functionality of hagfish slime. Using capillary breakup extensional rheology (CaBER) we found that seawater showed faster capillary breakup, less pronounced strain hardening, a lower extensional viscosity, and shorter Zimm relaxation times than milliQ water (Fig. 1a). The observed effects were found to strongly depend on and scale with the ionic strength of the water (Fig. 1b and c). However, despite a markedly increased drag of a higher viscosity at low ionic strength, the unraveling of the thread required for slime formation was found to be much faster in milliQ than in seawater (Fig. 1d). The lower the ionic strength, the faster and more uncontrolled the slime formed, eventually leading to a dysfunctional slime. We propose that the slime formation faces a trade-off between two distinct purposes: efficient gill-clogging and proper network formation. Although gill-clogging would be more efficient at higher viscosities, a proper network formation is likely to be more important for the defensive properties. A functional network thus likely compensates for the lower mucin viscosity by providing an optimal mesh spacing, leading to an impressive water entrapment despite the lower mucin viscosity Show more
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Subjecthagfish; slime; Rheology; Hydrogel; capillary breakup extensional rheology (CaBER); longest protein fibers on earth
Organisational unit03345 - Windhab, Erich Josef
03831 - Studart, André R.
08821 - Fischer, Peter (Tit.-Prof.)
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