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

A mechanical approach to understanding the impact of the nematode Anguillicoloides crassus on the European eel swimbladder
A mechanical approach to understanding the impact of the nematode Anguillicoloides crassus on the European eel swimbladder
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 Anguillicoides crassus. Infection primarily impacts 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 to 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, impacting the successful completion of their oceanic migration.
European eel, mechanical damage, parasite, swimbladder
0022-0949
Currie, Helen A.L.
d7b6bb3f-3d2f-44eb-81f2-c19c3d0f7c16
Flores Martin, Nicholas
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Espindola Garcia, Gerardo
0848daa3-9c8c-4054-b790-6f7b633b05c3
Davis, Frances M.
20f89066-bbac-42dc-908d-d89a747dc399
Kemp, Paul
9e33fba6-cccf-4eb5-965b-b70e72b11cd7
Currie, Helen A.L.
d7b6bb3f-3d2f-44eb-81f2-c19c3d0f7c16
Flores Martin, Nicholas
9f9f0ddd-bb25-4d45-ae04-7989f32704f7
Espindola Garcia, Gerardo
0848daa3-9c8c-4054-b790-6f7b633b05c3
Davis, Frances M.
20f89066-bbac-42dc-908d-d89a747dc399
Kemp, Paul
9e33fba6-cccf-4eb5-965b-b70e72b11cd7

Currie, Helen A.L., Flores Martin, Nicholas, Espindola Garcia, Gerardo, Davis, Frances M. and Kemp, Paul (2020) A mechanical approach to understanding the impact of the nematode Anguillicoloides crassus on the European eel swimbladder. Journal of Experimental Biology, 223, [jeb219808]. (doi:10.1242/jeb.219808).

Record type: Article

Abstract

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 Anguillicoides crassus. Infection primarily impacts 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 to 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, impacting the successful completion of their oceanic migration.

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Accepted/In Press date: 30 June 2020
e-pub ahead of print date: 6 July 2020
Published date: 1 September 2020
Keywords: European eel, mechanical damage, parasite, swimbladder

Identifiers

Local EPrints ID: 442265
URI: http://eprints.soton.ac.uk/id/eprint/442265
ISSN: 0022-0949
PURE UUID: 11e9f857-8de8-45a5-8995-3263202376d0
ORCID for Helen A.L. Currie: ORCID iD orcid.org/0000-0001-5792-3488
ORCID for Nicholas Flores Martin: ORCID iD orcid.org/0000-0003-1131-2934
ORCID for Paul Kemp: ORCID iD orcid.org/0000-0003-4470-0589

Catalogue record

Date deposited: 10 Jul 2020 16:31
Last modified: 26 Nov 2021 06:16

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Contributors

Author: Gerardo Espindola Garcia
Author: Frances M. Davis
Author: Paul Kemp ORCID iD

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