Evolutionary Applications (Dec 2021)

Long‐lasting effects of chronic exposure to chemical pollution on the hologenome of the Manila clam

  • Mariangela Iannello,
  • Marica Mezzelani,
  • Giulia Dalla Rovere,
  • Morgan Smits,
  • Tomaso Patarnello,
  • Claudio Ciofi,
  • Lisa Carraro,
  • Luciano Boffo,
  • Serena Ferraresso,
  • Massimiliano Babbucci,
  • Sandro Mazzariol,
  • Cinzia Centelleghe,
  • Barbara Cardazzo,
  • Claudio Carrer,
  • Maurizio Varagnolo,
  • Alessandro Nardi,
  • Lucia Pittura,
  • Maura Benedetti,
  • Daniele Fattorini,
  • Francesco Regoli,
  • Fabrizio Ghiselli,
  • Stefania Gorbi,
  • Luca Bargelloni,
  • Massimo Milan

DOI
https://doi.org/10.1111/eva.13319
Journal volume & issue
Vol. 14, no. 12
pp. 2864 – 2880

Abstract

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Abstract Chronic exposure to pollutants affects natural populations, creating specific molecular and biochemical signatures. In the present study, we tested the hypothesis that chronic exposure to pollutants might have substantial effects on the Manila clam hologenome long after removal from contaminated sites. To reach this goal, a highly integrative approach was implemented, combining transcriptome, genetic and microbiota analyses with the evaluation of biochemical and histological profiles of the edible Manila clam Ruditapes philippinarum, as it was transplanted for 6 months from the polluted area of Porto Marghera (PM) to the clean area of Chioggia (Venice lagoon, Italy). One month post‐transplantation, PM clams showed several modifications to its resident microbiota, including an overrepresentation of the opportunistic pathogen Arcobacter spp. This may be related to the upregulation of several immune genes in the PM clams, potentially representing a host response to the increased abundance of deleterious bacteria. Six months after transplantation, PM clams demonstrated a lower ability to respond to environmental/physiological stressors related to the summer season, and the hepatopancreas‐associated microbiota still showed different compositions among PM and CH clams. This study confirms that different stressors have predictable effects in clams at different biological levels and demonstrates that chronic exposure to pollutants leads to long‐lasting effects on the animal hologenome. In addition, no genetic differentiation between samples from the two areas was detected, confirming that PM and CH clams belong to a single population. Overall, the obtained responses were largely reversible and potentially related to phenotypic plasticity rather than genetic adaptation. The results here presented will be functional for the assessment of the environmental risk imposed by chemicals on an economically important bivalve species.

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