Population biology of Meiogymnophallus minutus (Trematoda: Gymnophallidae) in cockles from the Exe Estuary

Abstract

Spatial, seasonal and age-related differences in infection of the cockle, Cerastoderma edule, with the trematode Meiogymnophallus minutus were studied on the Exe Estuary, England. Prevalence of infection was 100% across all samples with mean abundances between approximately 300 and 1000 larvae per host (maximum=4930 larvae). Aggregration of M. minutus in cockles was extremely high (variancermean ratios >100) and increased linearly as abundance increased. Mean abundance was highest in cockles collected from muddy substrates where the average age of cockles was high. In summer, numbers of larvae fell to less than half of spring levels and then increased after infection by a new wave of cercariae in August. Cockles accumulated larvae for up to 2 y but not thereafter, and levels of aggregation fell in the oldest age class. A peaked pattern of mean abundance and aggregation with age may be a result of parasite-induced death of older hosts or may be due to the inability of cercariae to establish in older hosts.

Intrapopulational distribution of Meiogymnophallus minutus (Digenea, Gymnophallidae) infections in its first and second intermediate host

“…Usually, prevalence of infection approaches such a high value only amongst rather large host individuals in natural environments (Desclaux et al 2006;Nikolaev et al 2006). Bowers and James (1967) occasionally detected M. minutus in cockle spat older than 6 months, whilst Goater (1993) revealed the first metacercariae to occur in 1-year-old cockles. Our results show for the first time that metacercarial infections may appear very early in the cockle life.…”

“…Goater (1993) stated that the close association of all three hosts required in the M. minutus life cycle may best explain such high parasite burdens. The high intensity revealed by the present study far exceeds infection levels reported from the Burry Inlet (Wales), the Ria de Aveiro (Portugal) and the island of Sylt (Germany; Bowers and James 1967;Russell-Pinto 1990;Thieltges et al 2006), but is comparable to those found in the Exe Estuary (England) and Merja Zerga (Morocco; Goater 1993;Gam et al 2008). It may be ascribed to high infection rates and levels in the primary host, the short distance between intermediate host populations as well as favourable conditions for transmission at the sampling site.…”

“…However, this assumption is based on a limited number of studied hostparasite systems. The gymnophallid Meiogymnophallus minutus occurs in sheltered soft sediment habitats across Europe (Bowers and James 1967;Russell-Pinto 1990;Goater 1993;Thieltges et al 2006). Like the majority of digenean trematodes, M. minutus exhibits a three-host life cycle.…”

“…M. minutus displays pronounced host specificity in its intermediate hosts (Lauckner 1983;Bowers et al 1996). Another remarkable aspect is that metacercariae have regularly been reported to be hyperparasitised by the microsporidian Unikaryon legeri (Bowers and James 1967;Canning and Nicholas 1974;Azevedo and Canning 1987;Goater 1993;Gam et al 2008). However, the role of hyperparasitism in the host-parasite relationship has been largely neglected so far.…”

Factors influencing the distribution of trematode larvae in blue mussels Mytilus edulis in the North Atlantic and Arctic Oceans

“…Studies involving bivalve second intermediate hosts are scarcer (e.g. Goater 1993;de Montaudouin et al 1998de Montaudouin et al , 2012de Montaudouin and Lanceleur 2011;Desclaux et al 2004;Thieltges 2007;Thieltges and Reise 2007). In particular, blue mussels Mytilus edulis have received little attention Thieltges 2006;Prinz et al 2011;Wilson et al 2013).…”