Do trematode parasites affect cockle (Cerastoderma edule) secondary production and elimination?

Abstract

Digenean trematodes are omnipresent in the cockle Cerastoderma edule, a common coastal bivalve of (semi-)sheltered northeastern Atlantic coasts. They can use their host as a second intermediate host where they remain in a relatively latent stage as metacercariae. Cockle population dynamics and trematode parasite load were monitored for two years in two sites, Arcachon (France) and Merja Zerga (Morocco) for the cockle cohort of 2005. Individual growth was slightly higher at Arcachon than at Merja Zerga (Von Bertalanffy parameters: K ¼ 1.5 yr 21 in both sites but L 1 ¼ 31.2 mm at Merja Zerga against 38.3 mm at Arcachon). Production during cockle life was twice as high at Merja Zerga (48.5 compared to 22.2 gDW.m 22 at Arcachon). Elimination compensated production at Merja Zerga while elimination was low at Arcachon (8.1 gDW.m 22 ) due to sediment dynamics which concentrated cockles within the sampling area. P/B was similar in both sites (2.4 -2.6 yr 21 ) while E/B was higher at Merja Zerga (2.2 yr 21 versus 1.0 yr 21 ). Trematode communities were similar in both sites in terms of species and abundance. During the cockle cohort lifespan, there were 3 to 5 events in the parasite abundance survey that suggested parasite-dependent mortality. At Merja Zerga, trematodes metacercariae did not affect P/B (2.4 yr 21 ) but increased E/B (þ14%). At Arcachon, they also had no effect on P/B (2.6 yr 21 ) but on the contrary increased E/B (þ20%). The threshold of metacercariae abundance beyond which cockles are affected was lower for Echinostomatid trematodes at Merja Zerga, suggesting an interaction with other factors such as temperature which is higher at the southern limit of cockle distribution.

Review: Bucephalus minimus, a deleterious trematode parasite of cockles Cerastoderma spp.

“…According to Gam et al (2009), this shell length corresponds at Banc d'Arguin to an age of approximately 4 months. Thus, it gives an order of magnitude of the necessary time for sporocysts to become visible (although the date of infection remains unknown).…”

“…In order to detect such seasonal trend, the best way would be to monitor host cohort infection along time as it has been performed with metacercariae in second intermediate host (Desclaux et al 2004;Gam et al 2009). However B. minimus prevalence in cockle is too low to be monthly monitored and, as previously specified, infection time by miracidium remains unknown.…”

“…Typically, as metacercariae, parasite usually displays high prevalence but their pathogenicity is reported as low (little interaction between parasite and host). Occasionally, parasite abundance can reach relatively high values and disrupt basic function like growth or even cause mortality (Desclaux et al 2002(Desclaux et al , 2004Gam et al 2009). As sporocyst (or rediae), effects on host individual are often severe due to strong interaction between parasite and vital host organs like gonads, digestive tract or gill (Dubois et al 2009).…”

Temporal variation ofMeiogymnophallus minutusinfections in the first and second intermediate host

“…The metacercarial stage found in C. edule remains unencysted and occurs beneath the hinge and surrounding extrapallial space, enveloped by host mantle epithelium. A remarkable aspect is that metacercariae of M. minutus have regularly been found to be hyperinfected by the microsporidian Unikaryon legeri (Bowers & James, 1967;Canning & Nicholas, 1974;Azevedo & Canning, 1987;Goater, 1993;Gam et al, 2008Gam et al, , 2009Fermer et al, 2009).…”

How life history contributes to stress response in the Manila clam Ruditapes philippinarum

“…Cercariae, transformed into metacercariae, complete their cycle when their host is eaten by the final host. In the present work, we focused on the metacercarial stage in the second intermediate host, which can be deleterious when metacercariae are numerous (Desclaux et al 2004;Gam et al 2009). In the sympatric bivalve C. edule, a mean prevalence of 90% was found at Arguin ).…”