Acta Parasitologica, Vol. 52, No. 2, 2007, 171–175. DOI: 10.2478/s11686-007-0013-4 François Lefebvre, Pascal Contournet and Alain J. Crivelli* –
Interaction between the severity of the infection by the nematode Anguillicola crassus and the tolerance to hypoxia in the European eel Anguilla anguilla
Station Biologique de la Tour du Valat, Le Sambuc, 13200 Arles, France
*Corresponding author: a.crivelli@tourduvalat.org
ABSTRACT
An experiment was conducted to test the effect of the infection by the swimbladder nematode Anguillicola crassus on the survival
of the European eel Anguilla anguilla when exposed to hypoxic conditions. Forty-four wild caught and naturally infected
eels were placed in an aquarium filled with water from the fishing site (Vaccarès Lagoon, French Mediterranean coast). In
this confined environment (27 l), under decreasing oxygen resources, the first eel death occurred after 45 h (O2 = 0.98 mg l-1)
and the last one after 96 h (O2 = 0.48 mg l-1). After dissection and parasite examination, analyses revealed significant negative
correlations between the time to death and various parameters of parasite pressure (e.g., number of lumen worms, parasite
mass, health state of the infected organ). It was shown that the severity of damage to the swimbladder rather than the count
of living parasites was the major contributing factor in explaining the variation in time to death. These semi-experimental data
demonstrating an increased eel mortality rate under severe oxygen stress are discussed for their relevance under field conditions,
especially during hot summer months.
KEY WORDS: Nematoda, anguillicolosis, fish pathology, swimbladder, oxygen stress, mortality