Digenean trematode species in the cockle Cerastoderma edule: identification key and distribution along the north-eastern Atlantic shoreline

Abstract

We describe the digenean fauna of one of the dominant intertidal hosts, the common cockle Cerastoderma edule, in terms of biomass, off north-eastern Atlantic shores. Using published and unpublished literature we have prepared an identification key and provide an up-date of the large-scale distributional patterns of digenean species of the common cockle. At least sixteen digenean species, belonging to seven families, use cockles as intermediate host. Among these species two utilize cockles as first intermediate host only, whereas two species utilize cockles as both first and second intermediate host. The remaining eleven species have cockles as their second intermediate host. Water birds and fish are the definitive hosts to twelve and four species, respectively.Cockles are infected with digeneans along the latitudinal gradient from southern Morocco to the western region of the Barents Sea often with high infection levels. Whereas some of these digenean species occur along most of the latitudinal gradient others show a more restricted northern or southern distribution mostly caused by an underlying latitudinal gradient of host species.Knowledge of digenean species and their large-scale distribution pattern may serve as a baseline for future studies dealing with the effects of climate change on parasite-host systems. For such studies the cockle and its digenean community could be an ideal model system.

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

“…In addition to trematode infections, cockle populations that experienced mortalities in Galicia also experienced disseminated neoplasia, which was considered to be another significant factor in contributing to the mortalities (Carballal et al 2001, Villalba et al 2001, da Silva et al 2005. Although mass mortalities were described as having occurred, these losses were not quantified, as enumerating mass mortalities in burrowing animals in their natural habitat is difficult.Of the various diseases and parasites that affect cockles, disseminated neoplasia and metazoan parasites have been reported most frequently in studies of Cerastoderma edule (Carballal et al 2001, Villalba et al 2001, Thieltges 2008, de Montaudouin et al 2009). Neoplasms in C. edule were initially recorded in 1982 in Cork Harbour, Ireland, and in that same year they were also reported in Brittany, France (Twomey & Mulcahy 1988, Twomey 1994, Villalba et al 2001, Romalde et al 2007, Le Grand et al 2010.…”

“…Neoplasms in C. edule were initially recorded in 1982 in Cork Harbour, Ireland, and in that same year they were also reported in Brittany, France (Twomey & Mulcahy 1988, Twomey 1994, Villalba et al 2001, Romalde et al 2007, Le Grand et al 2010. Disseminated neoplasia is a proliferative disorder of the haemocytes and is of unknown origin; it is characterised by very large, mitotically active, pleomorphic and highly invasive cells (Twomey 1994, Krishnakumar et al 1999, Collins & Mulcahy 2003, Barber 2004, Ciocan et al 2006, Le Grand et al 2010, Díaz et al 2011.Throughout their range Cerastoderma edule are known to act as the first or second intermediate host for at least 16 digenean parasites from 7 different families, of which the family Echinostomatidae is the most dominant (de Montaudouin et al 2009). A recent study along the southwest coast of Ireland found 8 species of digenean parasites in C. edule, and Meiogymnophallus minutus (synonym Parvatrema minutus, Scholz 2002) was the most common in terms of prevalence and intensity of infection (Fermer et al 2009).…”

“…A recent study along the southwest coast of Ireland found 8 species of digenean parasites in C. edule, and Meiogymnophallus minutus (synonym Parvatrema minutus, Scholz 2002) was the most common in terms of prevalence and intensity of infection (Fermer et al 2009). Of particular interest is the fact that trematode species contained within the cockle are restricted to certain tissues, so that a microhabitat is created within the cockle (de Montaudouin et al 2009). Of those identified to date in Ireland, M. minutus is confined to the hinge region within the cockle, whereas Gymnophallus choledochus and Bucephalus minimus are located in the gonads.…”

“…Of those identified to date in Ireland, M. minutus is confined to the hinge region within the cockle, whereas Gymnophallus choledochus and Bucephalus minimus are located in the gonads. Others, such as Psilostomum brevicolle, are confined to the visceral mass only, while Renicola roscovita establishes itself in the palps, and Himasthla elongata and H. interrupta are located in the foot, although the latter trematode is also found in the mantle (de Montaudouin et al 2009). C. edule may host such a range of parasites because its geographic range is extensive, the cockles may exist in close proximity to other intermediate hosts and the definitive hosts of these parasites also span a large area (Thieltges & Reise 2006, de Montaudouin & Lanceleur 2011.…”

Parasites, pathological conditions and resistance to Marteilia cochillia in lagoon cockle Cerastoderma glaucum from Galicia (NW Spain)

“…Regarding encysted metacercariae, the wide range of cyst diameter and the variety of microhabitats within the host suggested the occurrence of larvae of the families Echinostomatidae, Renicolidae and Psilostomatidae in the Galician lagoon cockles (Lauckner 1983, de Montaudouin et al 2009, Longshaw & Malham 2013. Regarding unencysted metacercariae, both host species (C. glaucum) and anatomical location (extra-pallial space beside the mantle margin) suggested that the Gymnophallidaelike metacercariae observed in Galician lagoon cockles corresponded to Meiogymnophallus fossarum (Lauckner 1983, de Montaudouin et al 2009). High loads of metacercariae have been reported to cause damage to bivalve molluscs, including impaired growth rate, reduced capacity to burrow and increased mortality (Lauckner 1983).…”