Host‐parasite life‐histories of the diurnal vs . nocturnal chronotypes of Schistosoma mansoni : adaptive significance

• Published in: Tropical Medicine & International Health
• Main Authors: Mouahid, Gabriel, Mintsa Nguema, Rodrigue, Al Mashikhi, Khalid, Al Yafae, Salem, Idris, Mohamed, Moné, Hélène
• Other Authors: Interactions Hôtes-Pathogènes-Environnements (IHPE), Université de Perpignan Via Domitia (UPVD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM), Institut de Recherche en Ecologie Tropicale Libreville, Directorate General of Health Services, Department of Microbiology and Immunology, College of Medicine and Health Sciences, Sultan Qaboos University (SQU)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: Schistosoma mansoni; nocturnal chronotype; cercarial emergence pattern; circadian rhythm; sympatric speciation; [SDV.MP.PAR]Life Sciences [q-bio]/Microbiology and Parasitology/Parasitology; Rattus rattus
• Online Access: https://hal.archives-ouvertes.fr/hal-02169763; https://hal.archives-ouvertes.fr/hal-02169763/document; https://hal.archives-ouvertes.fr/hal-02169763/file/Mouahid-2019-TMIH-Host-PREPRINT%20%281%29.pdf; https://doi.org/10.1111/tmi.13227

International audience Objectives: To optimise host-to-host transmission, digenean trematodes (parasites) synchronise their cercarial emission patterns with the aquatic activities of their vertebrate hosts. Schistosoma mansoni has two different circadian chronotypes: a diurnal shedding pattern with a mean peak occurring at 11:00 h, and a nocturnal shedding pattern with a mean peak occurring at 20:00 h. We analysed the life-history variations between these two chronotypes at the levels of the parasite and its hosts.MMethods For each chronotype, we quantified three life-history traits related to the parasite (prepatent period, infection rate and cercarial production) and analysed the morphometry and the morphology of the parasite eggs; we also quantified three life-history traits related to the snail intermediate host (shell diameter, fecundity and survival rate) and one life-history trait related to the experimental definitive host (survival rate). A phylogeny based on the mitochondrial cytochromeoxidase gene was made on samples of both chronotypes. results Life-history analysis revealed significant variations between the two chronotypes. Lifehistory traits were optimal for both the parasite and the snail host for the diurnal chronotype compared to the nocturnal one. The new chronotype behaved like an allopatric population towards its snail host. Phylogenetic analysis supports the hypothesis of a lateral transfer of S. mansoni from humans to Rattus rattus. These results were interpreted in terms of an ongoing sympatric speciation.Conclusion The nocturnal chronotype of S. mansoni showed non-adapted life-history traits in its relation with the snail intermediate host Biomphalaria pfeifferi. The emergence of this new phenotype is probably linked to divergent natural selection.