Effect of light on the trematode Himasthla elongata: from cercarial behaviour to infection success

• Published in: Diseases of Aquatic Organisms
• Main Authors: Correia, Simao, Freitas, Rosa, de Montaudouin, Xavier, Magalhaes, Luisa
• Other Authors: Universidade de Aveiro, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: Cerastoderma edule; Dark:light cycle; Oxygen consumption; Parasitism; Photosensitivity; [SDV.MP.PAR]Life Sciences [q-bio]/Microbiology and Parasitology/Parasitology; [SDV.BA.MVSA]Life Sciences [q-bio]/Animal biology/Veterinary medicine and animal Health; Northeast Atlantic
• Online Access: https://hal.science/hal-04187299; https://hal.science/hal-04187299/document; https://hal.science/hal-04187299/file/EPOC_DAO_2021_Correia.pdf; https://doi.org/10.3354/dao03616

International audience The cockle Cerastoderma edule, a socioeconomically important bivalve of the northeast Atlantic, is host to several trematodes, including Himasthla elongata. In the life cycle of this trematode, cercariae (free-living stages) emerge from the first intermediate host, a snail, to infect cockles as second intermediate hosts. During their lifespan (less than 2 d), cercariae must ensure successful host-to-host transmission via the surrounding water and therefore are exposed to and impacted by different environmental conditions, including abiotic factors. Given that the light:dark cycle is one of the major drivers of behaviour in aquatic habitats, we aimed to determine the influence of light on cercariae and host behaviour based on 3 hypotheses. First, by having a benthic second intermediate host, these cercariae will display a photonegative orientation; second, and conversely, host behaviour will not be influenced by light; and third, cercariae infection success will be light-dependent. Results showed that cercariae display a photopositive orientation (first hypothesis rejected), displaying movements towards light. Host activity (evaluated by oxygen consumption) was similar among conditions, i.e. dark vs. light (second hypothesis accepted), but hosts acquired more parasites when experimentally infected in the dark (third hypothesis accepted). This light-dependent infection of the host is explained by a change of cercarial behaviour when exposed to light, decreasing their infection success. This study highlights that trematode responses to external conditions may be linked to successful life cycle completion rather than being altered by the host habitat. Light influence on cercarial behaviour resulted in increased infection success that may affect trematode population dynamics and their distributional range.