Complexity in Parasite Life Cycles: Population Biology of Cestodes in Fish

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. This paper examines the population biology of two related species of bothriocephalid cestodes, parasites of teleostean fish, which live in sympatry. One species, Bothriocephalus barbatus, needs in its life cycle only one obligatory intermediate host, a copepod. The second species, B. gregarius, needs the same intermediate host first, but also utilizes a non-obligatory paratenic host, which is a gobiid fish. In the case of B. gregarius, definitive hosts can be infested via the intermediate host or the paratenic host. A simple mathematical model was built to investigate the effect of the addition of a paratenic host into the life cycle of a parasite. Results of the simulation clearly demonstrated that the maintenance or absence of infectivity of cestode larvae in the paratenic host could explain the observed levels of infection in both definitive hosts. 3. Acquisition of paratenic hosts has two advantages: the recovery of lost infective stages in a previously non-suitable intermediate host, and an increase in the time of infection during which the definitive host could be infected as the result of eatingcopepods in its planctonophagous juvenile existence and by eating gobies in its predaceous older stages. 4. Using the basic transmission rate as a measure of fitness, we also investigated the possibility of maturation of B. gregarius in the paratenic host, e.g. the acquisition of a new definitive host by the parasite. Basic transmission rates and numerical simulations suggest that there is no benefit for the parasite in evolving towards this strategy.

Asymmetric exploitation of two echinoid host species by a parasitic pea crab and its consequences for the parasitic life cycle

“…This may have consequences for the evolution of parasite life history traits (Gandon 2004). Patterns are not simple, however, and parasite fitness may be increased by the exploitation of 2 or more host species (Morand et al 1995, Choisy et al 2003 but also by the specialisation toward a given host species (Joshi & Thompson 1995, Pedersen et al 2005. The exploitation of different host species may also have consequences for the parasite life cycle.…”

Development of the philometrids Philometra overstreeti and Philometroides paralichthydis in the experimentally infected copepod Oithona colcarva

“…This contention is supported by the occurrence of infection of both species in large piscivorous flounder, which do not feed upon copepods, and the fact that such transport hosts are a wellknown and important component in the life cycle of numerous other piscine parasites (Morand et al 1995).…”

The evolutionary ecology of complex lifecycle parasites: linking phenomena with mechanisms

“…Morand et al (1995) (Robert et al, 1988). Although not strictly necessary for the parasite to complete its lifecycle, gobies likely benefit B. gregarious infectious stages by increasing overall transmission: the total prevalence of B. gregarious is higher than that of B. barbatus (Morand et al, 1995).…”

“…Morand et al (1995) (Robert et al, 1988). Although not strictly necessary for the parasite to complete its lifecycle, gobies likely benefit B. gregarious infectious stages by increasing overall transmission: the total prevalence of B. gregarious is higher than that of B. barbatus (Morand et al, 1995). However, although comparing two closely related parasite species with different levels of complexity is useful, one cannot isolate the effect of differing lifecycle complexity from other unknown phenotypic influences on parasite transmission potential; B. barbatus and B. gregarious are different in many respects in addition to the complexity of their lifecycles, for example, the identity of their definitive hosts.…”

“…As Figure 1 shows, a CLP can undergo growth in intermediate hosts alongside few (if any) other genotypes, and then reproduce in definitive hosts, where there may be many parasite genotypes. Indeed, both the intensity (measured as parasite burden) and genetic diversity of infections tend to be higher in definitive hosts compared with intermediate hosts, because of concentration of parasites up the food chain (Morand et al, 1995;Brown et al, 2001). For example, in the trematode Diplostomum pseudopathaceum, a small number of parasite genotypes (usually just one) establish infections in the first intermediate (snail) host, thus Figure 1 Growth-reproduction trade-off for SLPs and CLPs.…”