Poster Presentation International Conference on River Connectivity (Fish Passage 2018)

A novel mechanical test to better understand the impact of repeated invasive parasite infection (Anguillicoloides crassus) on the critically endangered European eel (Anguilla anguilla) (#218)

Helen A.L. Currie 1 , Frances M. Davis 1 , Nicholas Flores Martin 1 , Gerardo Espindola Garcia 1 , Paul S. Kemp 1
  1. University of Southampton, Southampton, HAMPSHIRE, United Kingdom

European eel (Anguilla anguilla, L.) populations have drastically declined over the last 40 years.  Arguably, the artificial introduction of invasive parasite, Anguillicoloides crassus, now widespread across Europe, may be one of the most detrimental contributing factors to rapid reductions in numbers.  This swimbladder residing nematode causes structural and inflammatory pathological damage within a naïve organism, with immune responses inducing physical changes which include a reduced swimbladder volume and thickened biotissue wall.   Capable of reinfection across a range of life stages and with a relatively short lifecycle in comparison to its host, absence of nematodes does not necessarily provide insight into epidemiological life history. 

Previous studies have utilised gross pathology indices to evaluate impacts of the parasite on eel swimbladder degeneration.  These studies however have their limitations due to degrees of subjectivity, and high reliance on information taken from measurements of infection at a single point in time, rather than assessing an entire infection history.  Literature alludes to mechanical and structural damage, however other than one study to date, mechanical properties of the damaged swimbladder wall have yet to be directly characterised.

This study uses a simple novel interdisciplinary approach to mechanically test European eel swimbladder biomaterial, conducted utilising specialist tensile strength machinery.  Use of thickness and strength measurements are arguably a more robust and direct characterisation of the repeated infection history of an individual. 

Better understanding degenerative impacts on the swimbladder and subsequent completion of reproductive migrations is essential to prevent further reduction in species recruitment and escapement.  Furthermore provisioning of such information could assist in the implementation of better mitigation and monitoring strategies.