Consistent isotopic differences between Schistocephalus spp. parasites and their stickleback hosts

Area of Science:

• Ecology
• Parasitology
• Stable Isotope Ecology

Background:

• Parasite-host systems exhibit diverse nitrogen-15 (¹⁵N) and carbon-13 (¹³C) isotopic fractionation patterns.
• Previous research indicates parasites can be depleted or enriched in ¹⁵N and ¹³C relative to their hosts.
• The consistency of these patterns across different ecosystems remains largely unexplored.

Purpose of the Study:

• To investigate whether isotopic fractionation patterns are conserved in comparable parasite-host systems from distinct ecosystems.
• To determine the ¹⁵N and ¹³C fractionation between Schistocephalus spp. endoparasites and their fish hosts (nine-spined and three-spined sticklebacks).

Main Methods:

• Stable isotope analysis (¹⁵N and ¹³C) of Schistocephalus spp. endoparasites and their respective fish hosts (Pungitius pungitius and Gasterosteus aculeatus).
• Comparison of isotopic values (δ¹⁵N and δ¹³C) between parasites and hosts across different geographical locations.

Main Results:

• Schistocephalus spp. endoparasites were consistently depleted in ¹⁵N (average -2.13 to -2.20 ‰) compared to their nine-spined and three-spined stickleback hosts.
• Isotopic differences (δ¹⁵N and δ¹³C) between parasites and hosts were consistent across biogeographically distinct study sites.
• While overall stable isotope values correlated between hosts and parasites, individual Schistocephalus specimens within the same host exhibited notable variation in δ¹³C.

Conclusions:

• Isotopic fractionation patterns between Schistocephalus spp. and their stickleback hosts are consistent across different ecosystems.
• Observed δ¹³C variation in parasites within the same host may indicate selective feeding or differing metabolic rates.
• Further research into parasite feeding, physiology, and metabolism is crucial for understanding their role in aquatic food web dynamics.