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Novel insights on aquatic mammal MHC evolution: Evidence from manatee DQB diversity

Developmental and Comparative Immunology
By: , , , , , , , , , , , and 
https://doi.org/10.1016/j.dci.2022.104398

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Abstract

The low diversity in marine mammal major histocompatibility complex (MHC) appears to support the hypothesis of reduced pathogen selective pressure in aquatic systems compared to terrestrial environments. However, the lack of characterization of the aquatic and evolutionarily distant Sirenia precludes drawing more generalized conclusions. Therefore, we aimed to characterize the MHC DQB diversity of two manatee species and compare it with those reported for marine mammals. Our results identified 12 and 6 alleles in T. inunguis and T. manatus, respectively. Alleles show high rates of nonsynonymous substitutions, suggesting loci are evolving under positive selection. Among aquatic mammals, Pinnipeda DQB had smaller numbers of alleles, higher synonymous substitution rate, and a dN/dS ratio closer to 1, suggesting it may be evolving under more relaxed selection compared to fully aquatic mammals. This contradicts one of the predictions of the hypothesis that aquatic environments impose reduced pathogen pressure to mammalian immune system. These results suggest that the unique evolutionary trajectories of mammalian MHC may impose challenges in drawing ecoevolutionary conclusions from comparisons across distant vertebrate lineages.

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Publication type Article
Publication Subtype Journal Article
Title Novel insights on aquatic mammal MHC evolution: Evidence from manatee DQB diversity
Series title Developmental and Comparative Immunology
DOI 10.1016/j.dci.2022.104398
Volume 132
Year Published 2022
Language English
Publisher Elsevier .
Contributing office(s) Wetland and Aquatic Research Center
Description 104398, 10 p.
Country Belize, Brazil, United States
State Florida
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