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

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.

Sediment reworking of intertidal sediments by the benthic foraminifera Haynesina germanica : the importance of motion behaviour and densities

“…Thus, our findings suggest that Haynesina germanica , which was initially classified as a surficial biodiffusor species, may be redefined as a gallery biodiffusor species. Indeed, surficial biodiffusor species like the cockle Cerastoderma edule [68] do not display a burrow-dwelling behaviour and hence do not generate biogenic sedimentary structures such as burrows and tubes in the sediment [9,69]. Furthermore, this work further contributes to confirm the infaunal microhabitat of H. germanica [44].…”

Himasthla spp. (Trematoda) in the edible cockle Cerastoderma edule: review, long-term monitoring and new molecular insights

“…Indeed, laboratory and field experiments have demonstrated that, under moderate infection and normal environmental conditions, H. continua and H. interrupta do not increase cockle mortality (Jensen et al ., 1999 ; Wegeberg and Jensen, 2003 ). Similarly, H. interrupta and H. quissetensis do not impair C. edule shell growth and production (Wegeberg and Jensen, 2003 ; Gam et al ., 2009 b ), and H. elongata has no significant effect on cockle bioturbation activity (sediment reworking and bioirrigation rates) (Richard et al ., 2021 ). Nevertheless, when cercariae encyst in the cockle foot, they can induce damages such as muscle fibre destruction (Jensen et al ., 1999 ) through mechanical pressure and tissue lysis related to the secretion of enzymes by the cercariae (Lauckner, 1983 ).…”

Parasitism dramatically alters the ecosystem services provided by freshwater mussels

“…This reduction in function will be exacerbated by unionid declines (Lopes‐Lima et al, 2021), especially considering the fact that parasites influencing functionally important hosts are expected to have the greatest impacts (Preston et al, 2016). In general, the effect of parasites on hosts and ecosystems may be wide ranging but also context dependent (Lange et al, 2014; Richard et al, 2021). Different parasites may show variable infection patterns and respond in different ways to environmental factors, emphasising that their life‐history characteristics need to be carefully considered.…”