Metazoan parasites in an intermediate host population near its southern border: the common cockle (Cerastoderma edule) and its trematodes in a Moroccan coastal lagoon (Merja Zerga)

Abstract

The metazoan parasite community of Cerastoderma edule was studied in the southern geographical range of the host (the coastal lagoon Merja Zerga, Morocco). A total of 11 metazoan species was found in cockles. Nine of these were trematodes using cockles as either first intermediate host (three species) or second intermediate host (six species). In addition, two other endo-metazoan species (Pinnotheres pisum and Paravortex cardii) were recorded from cockles in the studied lagoon. All the observed metazoans in cockles from Merja Zerga have previously been recorded at sites north of Africa.Up to 10% of the cockles in the studied size-groups were first intermediate hosts to castrating parasites (Gymnophallus choledochus, Labratrema minimus and Monorchis parvus). Among trematodes having metacercariae in cockles (second intermediate host) Meiogymnophallus minutus was the most widespread as it was observed in all cockles from all the examined habitats in the lagoon and it occurred in record high intensities. Different sub-communities of the trematode fauna using cockles as second intermediate host could be identified (subtidal vs intertidal associations).The richness and species composition of the macroparasite community in cockles from Morocco are discussed in relation to patterns seen in cockles from other sites along their geographical range. Migratory fish and waterbirds (final hosts) are generally responsible for the large scale spread (latitudinal spread) of trematodes. However, the distributional patterns of involved intermediate hosts in the life-cycles of the different trematode species in cockles are determining the richness and species composition patterns seen in cockles at shallow water sites along the east Atlantic shoreline.

Effect of trematode parasites on cockle Cerastoderma edule growth and condition index: a transplant experiment

“…Conversely, for RO, Meiogymnophallus minimus com pletely disappeared from cockles (−99.9%), precluding the hypothesis that the more infected cockles died. No metacercariae were hyperparasitized, as observed elsewhere (Carballal et al 2005, Gam et al 2008, and environmental conditions at Arguin are potentially suitable for infection to develop, as this parasite is present in the transplant area (de Montaudouin & Lanceleur 2011). Although transplantation can be a general explanation for M. minimus mor tality, this study found that the lifespan of the metacercariae can be shorter than that of their host, and therefore one must be careful in always attributing a decrease in metacercariae in the host to parasitedependent mortality (Anderson & Gordon 1982, Kennedy 1984, Desclaux et al 2004).…”

Influence of disseminated neoplasia, trematode infections and gametogenesis on surfacing and mortality in the cockle Cerastoderma edule

“…Shedding and transmission of trematode larvae is known to be temperature dependent (Jensen et al 1999, Gam et al 2008, Thieltges 2008. In temperate tidal areas the period of infection is spring to autumn (Desclaux et al 2006, Thieltges 2008.…”

“…Fermer et al (2009) found the acquisition of metacercariae was associated with shell length when cockles were smaller, but this was less important in older cockles. However, others have found no relationship between size and intensity (Gam et al 2008). The assumption that larger cockles would have a higher intensity of trematodes is based on larger cockles having larger siphons and in gesting cercariae with greater ease.…”

Marine infectious disease dynamics and outbreak thresholds: contact transmission, pandemic infection, and the potential role of filter feeders

“…For this purpose, the more complex sessile invertebrate disease models, including contact with or filtration of waterborne pathogens and particle diffusion processes, are built up from those simpler contact-based SI models applied to fish and mammal diseases. The models presented here do not cover facultative bacterial parasites (Kazama and Fuller 1977) or complex life cycles of protozoan (Robertson 2007) or metazoan parasites (Gam et al 2008) requiring intermediate hosts.…”