Department: Integrative Biology

Advisor: Douglas Fudge; dfudge@uoguelph.ca

Education: B.Sc. Hons. Zoology at the University of Guelph; M.Sc. Candidate Integrative Biology at the University of Guelph

Specimens of Study: Atlantic Hagfish (Myxine glutinosa), Pacific Hagfish (Eptatretus stoutii)

This project focused on the mechanisms by which hagfish slime becomes established when introduced into turbulent mixing seawater. Hagfish slime originates as a two-component glandular exudate comprised of coiled bundles of cytoskeletal intermediate filaments (thread skeins) and glycoprotein containing mucin vesicles. Holocrine secretion of the slime into seawater results in the rapid deployment of both fibrous and mucin components, resulting in about a liter of dilute slime. Deployment of the thread skeins involves their unraveling in a fraction of a second from a 150 mm-long ellipsoid bundle to a thread that is 100X longer. We hypothesized that thread skein deployment requires both vigorous hydrodynamic mixing and the presence of mucin vesicles, both of which are required for whole slime deployment. This project provides evidence that mixing and mucin vesicles are indeed crucial for skein unraveling. Specifically, we show that mucin vesicles mixed into seawater swell and elongate into high-aspect ratio mucin strands that attach to the thread skeins, transmit hydrodynamic forces to them and effect their unraveling by loading them in tension. Our discovery of mucin strands in hagfish slime not only provides a mechanism for the rapid deployment of thread skeins in vivo, it also helps explain how hagfish slime is able to trap such impressive volumes of seawater via viscous entrainment. We believe that the deployment of thread skeins via their interaction with shear-elongated mucins represents a unique mechanism in biology and may lead to novel technologies for transmitting hydrodynamic forces to microscale particles that would typically be immune to such forces.

Our previous work demonstrated that whole slime establishment is critically dependent on the swelling and elongation of the mucin vesicles into strands that adhere to the surface of the thread skeins and transmit the hydrodynamic forces of mixing to unravel the them. The tendency for thread skeins to remain condensed in the absence of physical perturbation by the mucin strands raised a number of questions regarding how the ionic strength and pH of the thread skeins chemical environment might influence their stability. We hypothesized that: (1) Upon release from the slime gland changes in the skein’s chemical environment, such as ionic strength and/or pH, loosen forces of adhesion between loops of thread and thereby allow for the release of strain energy which facilitates unraveling, and (2) The pH and/or ionic strength of the skeins chemical environment can induce structural changes in the slime thread that induce skein level changes that facilitate skein unraveling. Our work provides evidence that the stability of the skeins is critically dependent on their chemical environment and that no preparatory requirements are likely needed to occur prior to skein unraveling. This work also provides insight into the swelling properties of this matrix-free IF bundle.

The Evolutionary and Developmental History of Hagfish Slime Thread Skeins

Hagfish are well known for their remarkable slime-producing abilities. This unique defensive behavior has been highly conserved among all extant species of hagfish and has likely facilitated their survival over the past 300-400 million years. My past research on hagfish slime not only elucidated a tenable mechanism for hagfish slime deployment, but also led to a number of additional insights into the stabilization of hagfish slime thread skeins both within, and following deployment from the slime gland. As a result of this work I have become intensely fascinated with developing a stronger understanding of this remarkable biomaterial. Specifically, I am interested in examining the cellular mechanism by which the fibrous component of hagfish slime is synthesized within the hagfish slime gland by the gland thread cells. As a part of this work I would also like to examine evolutionary developmental history of the skein by comparing the development of the slime thread skein with that of the epithelial thread skein shared by hagfish and lampreys. Furthermore, I am interested in comparing the morphological and biomechanical characteristics of hagfish slime thread skeins between samples from available extant species. The significance of this research would be to develop a means for the in vitro production of hagfish slime threads.

Publications:

Fudge, D. S., Winegard, T., Ewoldt, R.H., Beriault, D., Szewciw, L. and McKinley, G.H. (2009). From ultra-soft slime to hard α-keratins: The many lives of intermediate filaments. Journal of Integrative Comparative Biology. 49, 32-49.

Herr, J.E., Winegard, T.M., O’Donnell, M.J., Yancey, P.H. and Fudge, D.S. (2010). Stabilization and swelling of hagfish slime mucin vesicles. Journal of Experimental Biology. 213, 1092-1099.

Winegard, T.M., and Fudge, D.S. (2010). Deployment of hagfish slime thread skeins requires the transmission of mixing via mucin strands. Journal of Experimental Biology. 213, 1235-1240.

Ewoldt, R.H., Winegard, T.M. and Fudge, D.S. (2010). Non-linear Viscoelasticity of Hagfish Slime. Submitted to the International Journal of Non-linear Mechanics. Accepted August 30, 2010. Submission ID: NLM-D-10-00132.

Fully formed slime network