Effects of the Naturally Occurring Parasitic Nematode<i>Chondronema passali</i>Leidy on Lifting Strength and Captivity-Related Body Mass Patterns in the Horned Passalus Beetle,<i>Odontotaenius disjunctus</i>(Illiger) (Coleoptera: Passalidae)

Coogler

Johnson

2017

Insects

There are many events in the lives of insects where rapid, effective stress reactions are needed, including fighting conspecifics to defend territories, evading predators, and responding to wounds. A key element of the stress reaction is elevation of heartrate (HR), for enhancing distribution of blood (hemolymph) to body compartments. We conducted two experiments designed to improve understanding of the insect stress reaction and how it is influenced by parasitism in a common beetle species (Odontotaenius disjunctus). By non-destructively observing heartbeat frequency before, during and after applying a stressor (physical restraint) for 10 min, we sought to determine: (1) the exact timing of the cardiac stress reaction; (2) the magnitude of heartrate elevation during stress; and (3) if the physiological response is affected by a naturally-occurring nematode parasite, Chondronema passali. Restraint caused a dramatic increase in heartrate, though not immediately; maximum HR was reached after approximately 8 min. Average heartrate went from 65.5 beats/min to a maximum of 81.5 (24.5% increase) in adults raised in the lab (n = 19). Using wild-caught adults (n = 77), average heartrates went from 54.9 beats/min to 74.2 (35.5% increase). When restraint was removed, HR declined after ~5 min, and reached baseline 50 min later. The nematode parasite did not affect baseline heartrates in either experiment, but in one, it retarded the heartrate elevation during stress, and in the other, it reduced the overall magnitude of the elevation. While we acknowledge that our results are based on comparisons of beetles with naturally-occurring parasite infections, these results indicate this parasite causes a modest reduction in host cardiac output during acute stress conditions.

Section: Discussionsupporting

confidence: 74%

Section: Discussionmentioning

confidence: 58%

Section: Introductionmentioning

confidence: 99%

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The Heartrate Reaction to Acute Stress in Horned Passalus Beetles (Odontotaenius disjunctus) is Negatively Affected by a Naturally-Occurring Nematode Parasite

Coogler

Johnson

2017

Insects

“…Of the 113 beetles in this experiment, 79 (69.9%) were parasitized with C. passali nematodes, which is typical in terms of prevalence [11,12]. Parasitized beetles weighed 1.7 g (0.24 s.d.)…”

Section: Resultsmentioning

confidence: 96%

The sicker the better: nematode-infected passalus beetles provide enhanced ecosystem services

Prouty

2019

Biol. Lett.

Self Cite

There is growing appreciation for the role that parasites have in ecosystems and food webs, though the possibility that they could improve an ecosystem service has never been considered. In forest ecosystems, fallen trees naturally decay over time and slowly return their nutrients to the soil. Beetles in the family Passalidae play a key role by excavating tunnels and consuming wood from these logs, thereby breaking down the wood into smaller debris. In the eastern United States, the horned passalus (Odontotaenius disjunctus) is host to a naturally occurring nematode, Chondronema passali, which appears to cause little harm to the beetles. We suspected this was due to compensatory food consumption by parasitized individuals, which we tested here. We collected and housed 113 adult beetles in individual containers with wood for three months, then determined the amount of wood each beetle had processed into fine debris and frass. We then assessed beetles for C. passali and compared wood processing rates between parasitized and non-parasitized groups. Results showed the average daily processing rate of parasitized beetles ( x ¼ 0.77 g d 21 ) was 15% greater than that of unparasitized ones ( x ¼ 0.67 g d 21 ). Parasitized beetles were 6% larger, and this may explain some of this pattern, though the effect of parasitism was still significant in our analysis. By extrapolating the daily rates, we estimate that 10 adult beetles without nematodes would break down approximately 2.4 kg of wood in a single year, while a group of 10 parasitized beetles would break down 2.8 kg. While our data are consistent with the idea of compensatory feeding, because these results are based on natural infections, we cannot rule out the possibility that beetles with heightened wood consumption are simply more likely to acquire the parasite. At an ecosystem level, it may not matter which is the case; parasitized beetles provide a more effective ecosystem service.

“…Moreover, individual beetles can harbour thousands of nematode worms (Pearse et al ., ; Cox & Davis, ). The high prevalence and within‐individual abundance should be significant to the biology of this host, and recent work in our laboratory has aimed to determine the many sublethal impacts of this parasite (Cox & Davis, ; LeFeuvre & Davis, ; Vasquez Jr. et al ., ; Davis et al ., ; Ebot‐Ojong et al ., ). For example, beetles with C. passali nematodes appear to have a diminished physiological stress reaction when faced with stressors, including a dampened heart rate elevation (Davis et al ., ) and, importantly, a dampened elevation of immune cells during the stress reaction (Davis et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Healing while parasitized: impact of a naturally‐occurring nematode during energy‐intensive wound‐healing in a beetle

Calderon

Lefeuvre³

et al. 2019

Physiol. Entomol.

Self Cite

The rigours of the daily lives of insects sometimes lead to minor injuries and wounds, which must be healed to avoid entry of pathogens and to resume normal function. Such healing requires energy, which must be diverted from other bodily reserves. What happens if energy reserves are already low, as would occur in individuals coping with internal parasites? This question is addressed in the presemt study, using horned passalus beetles (Odontotaenius disjunctus) and their naturally-occurring nematode Chondronema passali. Oxygen consumption rates are tested at rest, as well as after an experimental wound is applied, to evaluate energy requirements of wound-healing in parasitized and nonparasitized hosts. Furthermore, wound-healing rates are visually tracked with a numerical scoring system to directly measure the cost of parasitism on healing. At rest, parasitized beetles show no elevation in respiration (oxygen consumption). After wounding, the oxygen consumption of parasitized beetles is 10% higher than that in nonparasitized beetles. Beetles with moderate-to heavy worm burdens have slower healing than those with few or no nematodes. These results show that this parasite carries little cost to the host during day-to-day activities, whereas, during times of immediate energy demand, there is a cost; hosts require more energy to repair wounds, and the wounds take longer to close. This conclusion leads to the question of whether this parasite is truly benign, and how many other apparently benign parasites, in insects or other animals, have similar 'hidden' effects.