Recruitment rate of gymnophallid metacercariae in the New Zealand cockle Austrovenus stutchburyi: an experimental test of the hitch-hiking hypothesis

Abstract

The rate at which host organisms accumulate parasites is affected by a number of intrinsic and extrinsic factors. The New Zealand cockle Austrovenus stutchburyi is frequently parasitised by trematodes comprising of two species of echinostomes and a species of gymnophallid that use it as a second intermediate host for trophic transmission to avian definitive hosts. The echinostomes are capable of manipulating the burrowing behaviour of the cockle to enhance their transmission success, whereas the gymnophallid is not capable of host manipulation. Previous studies have found patterns of positive associations between the echinostomes and the gymnophallid. Thus, it is possible that the latter is a "hitch-hiking" parasite that preferentially infects cockles already heavily infected by echinostome metacercariae to enhance its own transmission rate. A field experiment involving cockles forced to remain either above or below the sediment surface to simulate manipulated and non-manipulated cockles was conducted to test the hitch-hiking hypothesis. The gymnophallid was not found to display any preference for either surfaced or buried cockles; therefore, it cannot be considered as a hitch-hiking parasite. Possible alternative reasons for the pattern of positive association between the gymnophallid and the echinostomes are proposed.

Cooperation and conflict in host manipulation: interactions among macro-parasites and micro-organisms

“…To test this hypothesis, they conducted a field experiment involving cockles forced to remain either above or below the sediment surface to simulate manipulated and non-manipulated hosts. There was however no evidence for a preference of gymnophallids for either surfaced or buried cockles, thus refuting the hitchiking hypothesis (Leung and Poulin, 2007b). …”

“…A similar case of non-random association between a non-manipulative parasite and a manipulative one has been investigated by Leung and Poulin (2007a, 2007b). It consists in a positive association between infection intensity of the metacercariae of foot-encysting echinostomes and that of gymnophallid metacercariae in their common host, the cockle, Austrovenus stutchburyi .…”

Annotated checklist and genetic data for parasitic helminths infecting New Zealand marine invertebrates

“…References . Leung, Donald, et al (2009); Leung and Poulin (2007); Leung et al (2007); Leung, Donald, et al (2009); Poulin et al (2000).…”

Genetics, intensity‐dependence, and host manipulation in the trematodeCurtuteria australis: following the strategies of others?

“…Whereas many cases of density-dependent cooperative behaviour are based upon aggregations composed entirely of kin (Saul-Gershenz and Millar 2006), the apparent cooperation exhibited by C. australis in this study is more likely to rely on other mechanisms. Like other trematode systems in which large numbers of metacercariae accumulate in second intermediate hosts, the metacercariae that infect cockles are accumulated over a relatively long period of time (Leung and Poulin 2007b) from a number of different first intermediate hosts (Rauch et al 2005, Keeney et al 2007, Leung et al 2009). Therefore, the population of conspecifics found within a cockle is likely to consist mostly of different genotypes.…”