Walking while Parasitized: Effects of a Naturally-Occurring Nematode on Locomotor Activity of Horned Passalus Beetles

Davis, Andrew K.; Hurd, Christian; Brandon, C.I.; Vásquez, David

doi:10.1007/s10905-021-09769-x

Cited by 1 publication

(6 citation statements)

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“…parasitized by C. passali, both in terms of prevalence and individual burden [34,44]. Most of the physiological and biological functions evaluated thus far also appear to show that males and females do not differ substantially, especially in terms of energy use; baseline metabolic rate [37] and heart rate [38,45] are both similar between the sexes.…”

Section: Plos Onementioning

confidence: 87%

“…Beetles can have dozens to hundreds of worms [33,44], and so we used a visual scoring system to simplify nematode assessment. Nematode burden was recorded on a 0-3 scale, where 0 = no worms present, 1 = fewer than 10 worms present, 2 = between 10 and 100, and 3 = more than 100 worms [34,36]. This same categorical scale has been used in multiple prior studies from our lab [35][36][37], and although crude, it does allow for a rapid visual assessment.…”

Section: Parasite Assessmentmentioning

confidence: 99%

“…Nematode prevalence Females = males [34] Parasite Biology Host nematode burden Females = males [44] Host Biology Body size Females>males [32,44] Host Biology Walking/exploration behavior Females>males [34] Host Biology Wood breakdown rate Females = males [17] Host Biology Physical lifting/pulling strength Females = males [39,44,46] Host Biology Fighting ability Females = males [36] �…”

Section: Parasite Biologymentioning

confidence: 99%

“…There is no indication that the immune system of males and females differ either, based on hemocyte density [38]. Behaviorally, there are a few sex differences, such as a greater propensity in females to explore than do males [34], and females give more frequent alarm calls than males when attacked. Both of these could be indicators of greater overall boldness in females, though taken with the results from the current study, we now wonder if these prior findings were the result of the parasite, and not the beetle gender per se.…”

Section: Plos Onementioning

confidence: 99%

“…If indeed the parasitized beetles are simply "hungrier", does this mean they would be less motivated to adopt any anti-predator behavior that necessitates inactivity? Another follow-up question would be to evaluate if the impact of nematodes on female behavior differs from males; prior work with this system also indicated that female beetles are inherently more motivated to be active than males [34]. Here, we describe a series of experiments using this beetle-nematode system that were designed to address these questions, with results yielding a surprising answer.…”

Section: Introductionmentioning

confidence: 99%

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Sex-specific effects of a parasite on stress-induced freezing behavior in a natural beetle-nematode system

et al. 2023

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Some animals react to predation threats or other stressors by adopting a freezing posture in an attempt to avoid detection, and the duration of this behavior usually corresponds with individual personality, such that timid individuals freeze longer. Despite decades of research on this or related behaviors (thanatosis), never has the impact of parasitism been considered. Parasites could prolong the duration, if hosts are less motivated to move (i.e. lethargic), or they could reduce it, if hosts are motivated to forage more to compensate for energy drain. We examined this behavior within a natural beetle-nematode system, where hosts (horned passalus beetles, Odontotaenius disjunctus) are parasitized by a nematode, Chondronema passali. We exposed beetles (n = 238) to four stressors in our lab, including noise, vibration, light and inversion, and recorded how long they adopt a frozen stance. Afterward, we determined nematode burdens, which can range from dozens to hundreds of worms. Beetles tended to freeze for 20 seconds on average, with some variation between stressors. We detected no effect of beetle mass on the duration of freezing, and this behavior did not differ in beetles collected during the breeding or non-breeding season. There was a surprising sex-based difference in the impact of nematodes; unparasitized females remained frozen twice as long as unparasitized males, but for beetles with heavy nematode burdens, the opposite was true. From this we infer that heavily parasitized females are more bold, while males with heavy burdens would be more timid. The explanation for this finding remains elusive, though we can rule out many possibilities based on prior work on this host-parasite system.

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