Non-random patterns of host use by the different parasite species exploiting a cockle population

Abstract

Different parasite species sharing the same intermediate host species may have similar or conflicting interests, depending on whether they are at the same stage in their life-cycle or whether they share the same definitive host. In the New Zealand cockle, Austrovenus stutchburyi, metacercariae of the digenean Meiogymnophallus sp. are positively associated with metacercariae of Curtuteria australis. This relationship is found in different cockle samples, and is independent of cockle shell size, which suggests that it is not merely the product of metacercariae accumulation over time. Both digenean species have the same definitive host, oystercatchers. Metacercariae of C. australis manipulate the phenotype of cockles, impairing the cockle's ability to burrow in the sediments. This makes the host more susceptible to oystercatcher predation. Thus Meiogymnophallus sp. can benefit by associating with C. australis and may hitch a ride with the manipulator parasite. This is supported by the finding that cockles impaired by C. australis and lying at the sediment surface harbour greater numbers of Meiogymnophallus than buried cockles. A third digenean species, whose sporocysts are found in cockles and which is not transmitted by predation, occurred only in surface cockles. Finally, a parasitic copepod with a direct life-cycle was found evenly distributed among buried and surface cockles, independently of their metacercarial loads. These results show that different parasite species do not use cockles in a random fashion, and that not all patterns of host use are consistent with shared or conflicting interests among parasites.

Spatial heterogeneity in parasite loads in the New Zealand cockle: the importance of host condition and density

“…The signi¢cant spatial heterogeneity in infection intensity by Curtuteria australis in cockles, with the highest level of parasitism on the upper part of the intertidal, is in accordance with ¢ndings from other intertidal £ats in the Otago Harbour (Poulin et al, 2000;K. Mouritsen & R. Poulin, unpublished data).…”

“…Curtuteria australis is very abundant in the Otago Harbour (South Island), and its prevalence in mature cockles usually approaches 100%. However, there is still substantial variation in parasite loads among individuals within sites as well as in mean intensities of infection between sites on a larger scale, both vertical and horizontal (Thomas & Poulin, 1998;Poulin et al, 2000). The present study addresses this hitherto unexplained spatial heterogeneity by testing two hypotheses: (i) the intensity of C. australis infection (no.…”

Use of the introduced bivalve,Musculista senhousia, by generalist parasites of native New Zealand bivalves

“…pulex or M. senhousia have been published before and this is the first time this relationship has been reported from these hosts in New Zealand. The copepods found here were not identified to species level, but were assigned to the family Myicolidae, the same family as the copepod Pseudomyicola spinosus, which has been reported from other bivalves in New Zealand (Poulin et al 2000). Copepods have previously been reported from P. canaliculus (Jones 1976;Jeffs et al 1999;hine & Diggles 2002).…”

“…Copepods have previously been reported from P. canaliculus (Jones 1976;Jeffs et al 1999;hine & Diggles 2002). Although copepods are often assumed to feed on host tissue (Poulin et al 2000), no reduction in tissue dry weight was evident in infected hosts. No difference in shell depth or width was observed, suggesting infection with copepods does not alter host tissue or shell growth.…”

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

“…It has been reported from Otago Harbour since its original description (e.g., Poulin et al 2000), but always at very low (<1%) prevalence. The final species, also undescribed and of unknown taxonomic position, occurs at low prevalence in the pulmonate snail Amphib ola crenata.…”