Fish host–cestode parasite stable isotope enrichment patterns in marine, estuarine and freshwater fishes from Northern Canada

Abstract

Cestode parasites from freshwater (threespine stickleback, Gasterosteus aculeatus), estuarine (brook charr, Salvelinus fontinalis) and marine (Greenland cod, Gadus ogac) fish from northern Quebec, Canada, were used to investigate the hypotheses that cestode parasites are (13)C and (15)N enriched relative to host food sources, but (15)N depleted with respect to host muscle tissue as a result of differential enrichment during the assimilation of common nutrient sources. Cestode parasites and fish were generally similarly enriched in (13)C with respect to common food sources and, in the case of Greenland cod, cestode parasites were (13)C enriched relative to host tissue. Cestode parasites were also generally (15)N enriched with respect to mean host dietary signatures, but depleted with respect to host muscle tissue. In the case of Greenland cod cestode parasites, no significant (15)N enrichment relative to host dietary signature was observed. Cestode parasites appear generally to experience smaller (15)N enrichment than hosts as a result of trophic transfer of common dietary sources. Differential (15)N enrichment patterns in parasites and fish may be attributed to differences in parasite and host metabolism, particularly the anaerobic and aerobic natures of their respective metabolisms. Results imply that isotope enrichment paradigms developed for the study of aquatic foodwebs cannot be routinely applied to quantitatively assess the role of parasites in aquatic foodwebs and that reference to host muscle tissue measures will not allow accurate characterization of parasite foodweb position. Appropriate reference to assimilated food sources is required to accurately estimate parasite isotopic enrichment patterns and to determine parasite trophic position relative to the host.

Trophic Relationship between the Parasitic IsopodIchthyoxenus japonensisand the FishCarassius auratus auratusAs Revealed by Stable Isotopes

“…However, our results agree with previous findings that in fish host-parasite systems parasite isotopic signatures referenced to host muscle tissue do not exhibit the conventional pattern of "N and I3C enrichment during the trophic transfer along the food chains ( Fig. I; Pinnegar et al 2001, Deudero et al 2002, Power and Klein 2004. The majority of parasitic cestodes, nematodes, copepods, and isopods showed depleted I' N and 13c with respect to their host fishes.…”

Digenean trematodes–marine mollusc relationships: a stable isotope study

“…Focken & Becker 1998, Yokoyama et al 2005. Although similar enrichment values have been reported (Table 3), much higher enrichment and depletion values have been previously reported between parasite and host for both ectoparasite-and endoparasite-host systems (Iken et al 2001, Pinnegar et al 2001, Deudero et al 2002, Parmentier & Das 2004, Power & Klein 2004, Persson et al 2007). Accordingly, δ 15 N P -δ 15 N H (P: parasite, H: host) ranged from -4.2 to 2.8 ‰ and δ 13 C P -δ 13 C H from -4.1 to -0.1 ‰ for ectoparasites.…”

“…They have reported that the 'regular' isotopic enrichment of 1 ‰ for δ 13 C and 3 to 4 ‰ for δ 15 N is not the rule (Iken et al 2001, Pinnegar et al 2001, Deudero et al 2002, Parmentier & Das 2004, Power & Klein 2004. However, these studies have examined parasite-host systems with physiological links much weaker than in digenean trematode-mollusc systems and have involved species in other phylogenetic groups than trematodes.…”

“…Thus, sporocysts seem to use abbreviated metabolic pathways for energy production. It is likely that this is the case for energy catabolisation (Power & Klein 2004); production of energy for the multiplication of sporocysts and the build-up of cercariae appear to be the main metabolic priority for the sporocyst stage. If most of the material ingested by digenean trematodes were used for Table 3.…”

Aphids alter host-plant nitrogen isotope fractionation

“…However, important exceptions exist. Fluidfeeders, a group that includes blood-feeding parasites and hempiteran insects (2), frequently have been found to deviate from these typical patterns such that fluid-feeders are usually reported as showing no enrichment or even depletion in 15 N relative to their diet (2,(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). Although it is now commonly accepted that fluid-feeders deviate from typical patterns of enrichment, these observations have stimulated considerable speculation (2,14,18) but little, if any, research targeted at explaining the mechanistic basis of such atypical patterns of nitrogen enrichment.…”