Cockle as Second Intermediate Host of Trematode Parasites: Consequences for Sediment Bioturbation and Nutrient Fluxes across the Benthic Interface

Anaïs Richard,Auriane Rubiello,Olivier Maire,Xavier De Montaudouin

doi:10.3390/jmse9070749

Abstract

Trematode parasites are distributed worldwide and can severely impact host populations. However, their influence on ecosystem functioning through the alteration of host engineering behaviours remains largely unexplored. This study focuses on a common host parasite system in marine coastal environments, i.e., the trematode Himasthla elongata, infecting the edible cockle Cerastoderma edule as second intermediate host. A laboratory experiment was conducted to investigate the indirect effects of metacercarial infection on sediment bioturbation and biogeochemical fluxes at the sediment water interface. Our results revealed that, despite high parasite intensity, the sediment reworking and bioirrigation rates, as well as nutrient fluxes, were not impacted. This finding was unexpected since previous studies showed that metacercarial infection impairs the physiological condition of cockles and induces a mechanical obstruction of their feet, thus altering their burrowing capacity. There are several explanations for such contrasting results. Firstly, the alteration of cockle behavior could arise over a longer time period following parasite infection. Secondly, the modulation of cockle bioturbation by parasites could be more pronounced in older specimens burying deeper. Thirdly, the intensity of the deleterious impacts of metacercariae could strongly vary across parasite species. Lastly, metacercarial infection alters cockle fitness through an interaction with other biotic and abiotic environmental stressors.

Highlights

Parasites represent 40% of the total known animal species, infecting autotrophic and heterotrophic hosts in all terrestrial and aquatic environments [1,2]
The present study aimed to investigate whether infection with Himasthla elongata affects the bioturbation activity of their second intermediate host, the cockle C. edule, and, through cascading effects, oxygen and inorganic nutrient exchanges across the sediment–water interface
Nonparasitized cockles were slightly naturally infected with 4.5 ± 0.4 metacercariae per individual

Summary

Introduction

Parasites represent 40% of the total known animal species, infecting autotrophic and heterotrophic hosts in all terrestrial and aquatic environments [1,2]. These ubiquitous organisms can profoundly impact ecosystem functioning, both directly by affecting ecosystem properties and indirectly by changing the functional role of their hosts [3]. A common marine parasite–host system, Himasthla elongata– Cerastoderma edule, was used in controlled laboratory experiments to investigate the potential indirect effects of parasite infection on second intermediate host engineering behaviors and, through cascade pathways, on benthic ecosystem processes. The common cockle Cerastoderma edule is an infaunal bivalve widespread in shallow coastal waters along the north-east

Methods

Results

Discussion

Conclusion