Differential patterns of definitive host use by two fish acanthocephalans occurring in sympatry: Pomphorhynchus laevis and Pomphorhynchus tereticollis.

Marie-Jeanne Perrot-Minnot,Emilie Guyonnet,Loïc Bollache,Clément Lagrue

doi:10.1016/j.ijppaw.2019.01.007

Abstract

Parasites with complex life-cycles and trophic transmission are expected to show low specificity towards final hosts. However, testing this hypothesis may be hampered by low taxonomic resolution, particularly in helminths. We investigated this issue using two intestinal fish parasites with similar life-cycles and occurring in sympatry, Pomphorhynchus laevis and Pomphorhynchus tereticollis (Acanthocephala). We used species-specific ITS1 length polymorphism to discriminate parasite species from 910 adult acanthocephalans collected in 174 individual hosts from 12 fish species. Both P. laevis and P. tereticollis exhibited restricted host range within the community of available fish host species, and transmission bias compared to their relative abundance in intermediate hosts. The two parasites also exhibited low niche overlap, primarily due to their contrasting use of bentho-pelagic (P. laevis) and benthic (P. tereticollis) fish. Furthermore, parasite prevalence in intermediate hosts appeared to increase with taxonomic specificity in definitive host use. Comparison of P. laevis and P. tereticollis adult size in the two main definitive hosts, barbel and chub, suggested lower compatibility towards the fish species with the lowest parasite abundance, in particular in P. laevis. The determinants of low niche overlap between these two sympatric acanthocephalan species, and the contribution of definitive host range diversity to parasite transmission success, are discussed.

Highlights

Host specificity and infection patterns are fundamental concepts in the ecology and evolution of parasitism (Shaw and Dobson, 1995; Poulin, 2007; Poulin et al, 2011)
To assess relative compatibility towards fish hosts, we focused on the two main hosts of P. laevis and P. tereticollis, based on their use and on their local abundance within the fish community: the barbel Barbus barbus and the European chub Squalius cephalus
We investigated whether variable levels of compatibility towards fish species was involved in niche segregation between P. laevis and P. tereticollis, by quantifying parasite development and reproduction

Summary

Introduction

Host specificity and infection patterns are fundamental concepts in the ecology and evolution of parasitism (Shaw and Dobson, 1995; Poulin, 2007; Poulin et al, 2011). Determinants of specificity and patterns of host use include parasite species-specific features, such as life-cycle (direct or complex) and transmission mode (e.g. passive, active or trophic; Shaw and Dobson, 1995; Wilson et al, 2002; Poulin, 2007). Parasites with complex (i.e. heteroxenous) life-cycles and trophic transmission rely on the consumption of infected intermediate hosts by predators suitable as definitive hosts to complete their life-cycle. They are expected to accumulate in definitive hosts, especially those occupying higher trophic levels as these hosts are likely to consume large numbers of infected intermediate host prey (Pérez-del-Olmo et al, 2011; Lester and McVinish, 2016). Spatial distribution among hosts and variations in the level of host specialization are still poorly documented in heteroxenous parasites capable of host behavioural manipulation (Fredensborg, 2014)

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