Sep 01

A mechanical approach to understanding the impact of the nematode Anguillicoloides crassus on the European eel swimbladder

Research Article

Each CDT SIS cohort undertake a group project with researchers from different disciplines working together to understand and research a complex real world problem sustainable engineering problems. The focus is on defining, managing and implementing an open-ended group research project. The students apply the knowledge they have gained during the first year of the PhD, to a real engineering problem thereby integrating research and engineering science. They gain experience of working as part of a project team with different experiences and skills; tackle a real need/problem with industrial or commercial links; learn to meet both personal and group objectives; work and deal with people inside and outside the university; handle the administration, organisation and finances of a project and develop a range of communication and presentation skills.

From the group project this paper was written and published in the Journal of Experimental Biology

A mechanical approach to understanding the impact of the nematode Anguillicoloides crassus on the European eel swimbladder

Helen A. L. Currie, Nicholas Flores Martin, Gerardo Espindola Garcia, Frances M. Davis, Paul S. Kemp

Journal of Experimental Biology  2020  223: jeb219808 doi: 10.1242/jeb.219808 Article

Published 1 September 2020

Nematode Anguillicoloides crassus


One of the most detrimental factors in the drastic decline of the critically endangered European eel (Anguilla anguilla) was the inadvertent introduction of the invasive nematode Anguillicoloides crassus. Infection primarily affects the swimbladder, a gas-filled organ that enables the eel to control its depth in the water. A reduction in swimbladder function may be fatal for eel undergoing their spawning migration to the Sargasso Sea, a journey of over 5000 km. Although the physiological damage caused by this invasive parasite is well studied through the use of quantifiable gross pathological indices, providing a good measure of the swimbladder health status, they cannot separate the role of mechanical and morphological damage. Our study examined the appropriateness of three commonly used indices as a measure of mechanical damage by performing uniaxial tensile tests on swimbladder specimens obtained from an infected eel population. When the test results were compared with the gross pathological indices it was found that thickness correlated most strongly with mechanical damage, both confirming and, more importantly, explaining the counterintuitive findings of earlier work. In a damaged swimbladder, the immune response leads to a trade-off; increasing wall thickness raises the pressure required for organ rupture but decreases strength. The results indicate that for moderate infection the mechanical integrity of the swimbladder can be maintained. For severe infection, however, a reduction in mechanical integrity may reach a tipping point, thereby affecting the successful completion of their oceanic migration.


  • Competing interests

The authors declare no competing or financial interests.

  • Author contributions

Conceptualization: P.S.K.; Methodology: H.A.L.C., N.F.M., G.E.G., F.M.D.; Formal analysis: H.A.L.C., F.M.D.; Investigation: H.A.L.C., N.F.M., G.E.G., F.M.D.; Writing – original draft: H.A.L.C., N.F.M., F.M.D.; Writing – review & editing: H.A.L.C., N.F.M., G.E.G., F.M.D., P.S.K.; Visualization: H.A.L.C., G.E.G., F.M.D.; Supervision: F.M.D., P.S.K.; Funding acquisition: F.M.D., P.S.K.

  • Funding

H.A.L.C., G.E.G. and N.F.M. were funded by the Training Grant for the EPSRC Centre for Doctoral Training in Sustainable Infrastructure Systems. F.M.D. was supported by a Leverhulme Trust Early Career Fellowship.

  • Data availability

All data accompanying this paper can be downloaded from the University of Southampton repository at: https://doi.org/10.5258/SOTON/D1184

  • Supplementary information

Supplementary information available online at https://jeb.biologists.org/lookup/doi/10.1242/jeb.219808.supplemental