Atlantic salmon infected with salmon lice are more susceptible to new lice infections

• Published in: Journal of Fish Diseases
• Main Authors: Ugelvik, M. S., Mo, T., Mennerat, Adèle, Skorping, A.
• Other Authors: Ecologie et Dynamique des Systèmes Anthropisés - UMR CNRS 7058 (EDYSAN), Université de Picardie Jules Verne (UPJV)-Centre National de la Recherche Scientifique (CNRS), Department of Biological Sciences Bergen (BIO / UiB), University of Bergen (UiB)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: [SDV]Life Sciences [q-bio]; Atlantic salmon; Salmo salar
• Online Access: https://u-picardie.hal.science/hal-03616644; https://doi.org/10.1111/jfd.12514

International audience Aggregation is commonly observed for macroparasites, but its adaptive value remains unclear. Heavy infestations intensities may lead to a decrease in some fitness-related traits of parasites (e.g. parasite fecundity or survival). However, to a dioecious parasite, increased aggregation could also increase the chance of finding individuals of the opposite sex. In a laboratory experiment, we tested if previous experience with salmon lice (Lepeophtheirus salmonis) affected susceptibility of Atlantic salmon (Salmo salar) to later exposure to the same parasite species. We found that currently infected fish got higher intensities of new lice than naive fish. This suggests that hosts already carrying parasites are more susceptible to new lice infections. For this dioecious parasite, such positive density dependence might be adaptive, ensuring successful reproduction under conditions of low lice densities by increasing the probability of both sexes infecting the same host.