Wild rabbit host and some parasites show trophic-level relationships for delta C-13 and delta N-15: A first report

We report the first isotopic study of an animal host-parasite system. Paras itic, intestinal nematodes, Graphidium strigosum and Passalurus ambiguus, w ere N-15-enriched relative to their host, the European rabbit Oryctolagus c uniculus, while parasitic cestodes, Cittataenia denticulata and Mosgovoyia pectinata, were N-15-depleted, suggesting different trophic relationships. Host embryos were more similar in their delta(13)C and delta(15)N values to maternal muscle than were any of the parasites. Coprophagy, the direct rec ycling of food by the rabbit eating its own faeces, did not lead to isotopi c differences between stomach contents and faeces, suggesting that the majo r point for isotopic discrimination in lagomorph nitrogen metabolism is in the animal rather than in the gut. We conclude that bulk delta(13)C and del ta(15)N can reveal valuable new information about host-parasite relationshi ps, and these could be explored further at the biochemical lever using comp ound-specific isotopic analyses.