Atypical behavior of a black fly species connects cavity-nesting birds with generalist blood parasites in an arid area of Spain

Nayden Chakarov,Jesús Veiga,Francisco Valera,Ignacio Ruiz-Arrondo

doi:10.1186/s13071-021-04798-z

Abstract

BackgroundThe feeding behavior of bloodsucking insects determines the transmission, distribution, host spectrum and evolution of blood parasites in the wild. Conventional wisdom suggests that some vector groups (e.g. black flies, family Simuliidae) are consistently exophagous daytime biters. We aimed to understand more about the exceptions to this pattern by combining targeted trapping and molecular identification of parasites in vectors.MethodsIn this study, we collected black flies in nest boxes used by European rollers Coracias garrulus in southeastern Spain. We molecularly analyzed 434 individual insects, identifying the black fly species caught in the nest boxes, their potential vertebrate blood meals, and the haemosporidian parasite lineages that they carried.ResultsOnly one black fly species, Simulium rubzovianum, appeared to enter the nest boxes of rollers. Among the trapped specimens, 15% contained vertebrate DNA, which always belonged to rollers, even though only half of those specimens were visibly engorged. Furthermore, 15% of all black flies contained Leucocytozoon lineages, indicating previous feeding on avian hosts but probably not on infected adult rollers. The known vertebrate hosts of the recorded Leucocytozoon lineages suggested that large and/or abundant birds are their hosts. Particularly represented were cavity-nesting species breeding in the vicinity, such as pigeons, corvids and owls. Open-nesting species such as thrushes and birds of prey were also represented.ConclusionsOur data strongly suggest that S. rubzovianum bites uninfected roller nestlings and infected individuals of other species, potentially incubating adults, inside nest boxes and natural cavities. This simuliid does not appear to have a strong preference for specific host clades. Contrary to the general pattern for the group, and possibly enhanced by the harsh environmental conditions in the study area, this black fly appeared to intensively use and may even have a preference for confined spaces such as cavities for feeding and resting. Preferences of vectors for atypical microhabitat niches where hosts are less mobile may enable social and within-family transmission and parasite speciation in the long term. At the same time, a lack of host preference in concentrated multispecies communities can lead to host switches. Both processes may be underappreciated driving forces in the evolution of avian blood parasites.Graphical abstract

Highlights

The feeding behavior of bloodsucking insects determines the transmission, distribution, host spectrum and evolution of blood parasites in the wild
The feeding ecology of black flies is not well understood because colonies of very few species have been established in laboratories and feeding behavior is almost never performed in captivity
Habitat and nest height explain the prevalence of black fly-transmitted Leucocytozoon lineages observed in host bird assemblages, while cavity nesting increases the probability of high Leucocytozoon prevalence in bird hosts [19]

Summary

Introduction

The feeding behavior of bloodsucking insects determines the transmission, distribution, host spectrum and evolution of blood parasites in the wild. Black flies (Diptera, Simuliidae) are one of the main groups of bloodsucking dipteran vectors, with members of the family transmitting haemosporidian parasites, trypanosomes and filarial nematodes [7]. Valuable information complementary to that obtained with classic methods can be gathered by investigating the wide spectrum of habitat niches and hosts that attract different black fly species. Black fly species are distinguishable as either mammalophilic or ornithophilic, but blood meals of engorged black flies in Scandinavia suggest species-specific preferences for different bird host groups [17]. The host species composition and parasite loads of black flies in central Europe suggest lack of host specificity for some ornithophilic black fly species but a preference for specific habitat niches, e.g. the upper forest canopy [14, 18]. Habitat and nest height explain the prevalence of black fly-transmitted Leucocytozoon lineages observed in host bird assemblages, while cavity nesting increases the probability of high Leucocytozoon prevalence in bird hosts [19]

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