Parasite Induced Summer Mortality in the Cockle Cerastoderma edule by the Trematode Gymnophallus choledochus

Abstract

In late summer 2004, a conspicuous cockle (Cerastoderma edule) mortality event was observed on a tidal flat in the northern Wadden Sea (North Sea, Germany) with many fresh valves and still living cockles lying on the sediment surface. To investigate whether trematode parasites utilizing the cockle as first or second intermediate host were involved in this mortality, buried and surfaced cockles were sampled and analyzed, and a laboratory experiment conducted. The field survey showed no statistical difference in intensity of parasites encysted in the foot of cockles. Three species of Himasthla utilizing the cockle as second intermediate host and known to impair the cockle's burrowing ability were found in buried cockles with 148.4±111.1 metacercariae/foot and in surfaced cockles with 164.2±84.4. There was also no difference in infection levels of parasites utilizing the cockles as second intermediate host in other cockle tissues between buried and surfaced cockles. In contrast, surfaced cockles showed a ten times higher prevalence (71.0%) than buried cockles (7.4%) of the trematode Gymnophallus choledochus -a parasite utilizing the cockle as first (and second) intermediate host -filling almost the entire body cavity and eliminating gonad structures. In an aquarium experiment of 14 days, all cockles found buried on the tidal flat survived compared to only 23.3% found on the surface. This suggests G. choledochus to be a castrating agent and a serious mortality factor in adult cockle populations.

Untitled

“…Predation and parasitism are the main biotic factors which controlled the population dynamics of cockles (Beukema and Dekker, 2005;Thieltges, 2006). Main predators of adult cockles in Lake Qarun include many fishes e.g., Tilapia zilli, Solea vulgaris, Sparus aurata and 288 Mugil sp..…”

“…Several reports have been made attributing infections in Cardiidae species to trematode infestations throughout their area of distribution (Derbali et al, 2009). Such trematode infections lead to reduced growth (Wegeberg and Jensen 2003), and enhanced mortality (Desclaux et al, 2004, Thieltges, 2006. Derbali, et al (2009) stated that 15% of C. glaucum from the Gulf of Gabes (southern Tunisia) were found infected by digenean trematode species.…”

“…Several records of C. glaucum were also undertaken from other Egyptian waters, e.g. Lake Bardawil (Fishar, 2005), Suez Canal Lakes (Barash and Danin, 1972) and Lake Timsah (Mohammad, 2002;Mohammed et al, 1992;2006). Nevertheless, available information on C. glaucum is scarce in Egypt (Kandeel et al, 2013;Mohammad, 2002;Mohammad et al, 2006).…”

Spatio-temporal variation in the prevalence of trematodes in the bivalve Perumytilus purpuratus

“…2). These results can be explained because the development of sporocysts and cercariae emergence can be triggered by factors associated with the season, such as temperature (Koprivnikar and Poulin 2009;Thieltges 2006) and water salinity (Koprivnikar and Poulin 2009), especially at intertidal rocky pools (Rees 1948). However, each trematode species has its own transmission strategy to infect the host; therefore, there are many other factors that are not associated with the season that affect egg and cercaria development (Koprivnikar and Poulin 2009;Lei and Poulin 2011;Pietrock and Marcogliese 2003;Rees 1948).…”

Trematode parasites of Otago Harbour (New Zealand) soft‐sediment intertidal ecosystems: Life cycles, ecological roles and DNA barcodes

“…1). Because trematodes occur at relatively high abundance in intertidal zones, and because of their well-documented impacts on the growth, survival, reproduction and behaviour of their hosts (e.g., Curtis 1987;Huxham et al 1993;Lafferty 1993;Probst & Kube 1999;Ferreira et al 2005;Thieltges 2006), they can be important drivers of host population dynamics, community structure, and foodweb stability (Sousa 1991;Mouritsen & Poulin 2002; Thompson et al 2005;Lafferty et al 2006;Wood et al 2007). …”