The Effect of a Nematode Parasite on Feeding and Dung-Burying Behavior of an Ecosystem Engineer

Abstract

Dung beetles (genus Phanaeus) consume feces in both their larval and adults forms and because of their unique dietary niche, and behaviors associated with the burial of feces, are considered ecosystem engineers. In addition, because these insects subsist on a diet composed exclusively of feces, it is likely they encounter parasitic propagules more frequently than other animals do. Parasites often alter their host's behavior, so we set out to test whether Physocephalus sexalatus (a cosmopolitan nematode parasite of ungulates) does so in ways that affect the dung beetle's role as an ecosystem engineer and/or its predator-prey relationships (transmission of the parasite). Classic tests of anti-predator behavior did not reveal behavioral differences based on the beetles' infection status. However, this parasite did alter the beetles' behaviors in ways that could be critical for its role in fecal processing and therefore ecosystem engineering. Infected beetles exhibited anorexic behavior and consumed only half the amount of feces ingested by similar uninfected beetles. Infected beetles also buried less feces and did so in tunnels that were significantly shorter than those created by uninfected beetles. Fecal burial is naturally beneficial because it aerates the soil, incorporates nitrogenous compounds, and increases the flow of water thereby making soil and pastureland more productive. We showed that the nematode parasite P. sexalatus itself becomes an ecosystem engineer as it modifies the behavior of its already influential intermediate host.

Magnitude and direction of parasite‐induced phenotypic alterations: a meta‐analysis in acanthocephalans

“…The interest in manipulative parasites is however not limited to their value as a supposedly perfect example of an extended phenotype. Growing attention has been given to the role that such parasites play in ecosystems through their influence on the behaviour and trophic niches of their hosts and, ultimately, on trophic cascades (Thomas et al ., , ; Lefèvre et al ., ; Lafferty & Kuris, ; Sato et al ., ; Boze & Moore, ; Britton & Andreou, ; Reisinger & Lodge, ). Still, the precise impact of manipulative parasites on ecosystem dynamics remains unclear, partly because the relationship between the magnitude of phenotypic alterations and their ecological consequences is difficult to assess.…”

Increased temperature has no consequence for behavioral manipulation despite effects on both partners in the interaction between a crustacean host and a manipulative parasite

“…This is all the more relevant in the case of parasite species that infest and modify the phenotype of host species known as ‘ecosystem engineers’, i.e. species that can affect the physical properties of ecosystems 18 – 20 .…”

A meta‐analysis of how parasites affect host consumption rates

“…For example, dung beetles which consume and burrow faeces contribute to suppression of various pathogens, facilitate soil aeration and fertilization, and increase the rate of nutrient cycling (Nichols et al 2008). Their infection with nematodes considerably decreases the amount of consumed faeces and reduces the burial of faeces below the surface soil (Boze et al 2012, Boze and Moore 2014). In contrast, nematode infection of horned passalus beetles resulted in an increase of their wood consumption by 15% (Davis and Prouty 2019).…”