Abstract
Reproduction and parasites have significant impacts on marine animal populations globally. This study aimed to investigate the associative effects of host reproduction and a host–parasite interplay on a marine bivalve, along a geographic gradient of latitude. Cockles Cerastoderma edule were sampled from five European sites (54°N to 40°N), between April 2018 and October 2019. A histological survey provided data on trematode (metacercaria and sporocyst life stages), prevalence, and cockle stage of gametogenesis to assess the influence of a latitudinal gradient on both interplays. Sex ratios at the northernmost sites were skewed toward females, and spawning size was reduced at the lower latitudes. Trematode infection did not follow a latitudinal gradient. Localized site‐related drivers, namely seawater temperature, varied spatially, having an impact on cockle–trematode interactions. Spawning was related to elevated temperatures at all sites. Prolonged spawning occurred at southern latitudes, where seawater temperatures were warmer. Trematode prevalence and the impact of trematodes on gametogenesis were found to be spatially variable, but not latitudinally. Therefore, it is not possible to determine the likelihood of boom and bust events in cockles, based on the latitudinal location of a population. In terms of sublethal impacts, it appeared that energy was allocated to reproduction rather than somatic growth in southern populations, with less energy allocated to reproduction in the larger, northern cockles. The demonstrated spatial trend of energy allocation indicates the potential of a temporal trend of reduced cockle growth at northern sites, as a result of warming sea temperatures. This awareness of the spatially varying drivers of populations is crucial considering the potential for these drivers/inhibitors to be exacerbated in a changing marine environment.
Highlights
Boom and bust cycles with a pattern of population growth and decline are a commonly reported phenomenon, in species exploited for fisheries and aquaculture (e.g., Hofmann & Powell, 1998; Korman et al, 2017; You & Hedgecock, 2019)
Examining the reproduction of cockles is vital for assessing populations, allowing for appropriate adjustments to be made to the minimum landing size and harvest quota, to provide protection for fisheries and ecosystems into the future
This study highlighted the biogeographical differences in cockle populations, showing that there is an associative influence of trematode infection, temperature, and latitude on population dynamics and reproduction development
Summary
Boom and bust cycles with a pattern of population growth and decline are a commonly reported phenomenon, in species exploited for fisheries and aquaculture (e.g., Hofmann & Powell, 1998; Korman et al, 2017; You & Hedgecock, 2019). Host populations experiencing high rates of castration may exhibit altered life histories, with expedited maturity (Lafferty & Kuris, 2009) This 19-month study aimed to examine the influence of latitude, as well as the associative influence of trematode infection and site- specific drivers (environmental and fishing type), on cockle reproductive health and population characteristics across a large proportion of its range. These findings will be vital for understanding this host– parasite system, under the context of climate change
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
