Biology subjects

Pull, C. D.

Publications and source records attributed to Pull, C. D..

6 recordsLinked to original sources

bioRxiv2024

Ant queens cannibalise infected brood to contain disease spread and recycle nutrients

Filial cannibalism, where parents eat their own offspring, is a taxonomically widespread behaviour with a multitude of potential adaptive explanations. Of these, the impact of parasites on the expression of filial cannibalism is particularly poorly understood. On one hand, cannibalising young with low survival probability may enable parents to reinvest valuable resources into future reproduction; on the other, cannibalising offspring harbouring parasites that can potentially also infect the parents may select against this behaviour. Although disease-induced cannibalism of eggs has been reported in fish, the benefits of consuming infected brood to contain infections - as an explanation for the evolution of filial cannibalism - remains largely unexplored. Here, we demonstrate that solitarily founding ant queens cannibalise all sick larvae in their nests before they become contagious, showing clearly that filial cannibalism both (i) contains an otherwise lethal infection without any long-term consequences on queen survival and (ii) enables the reinvestment of recouped energy into additional egg production.

evolutionary biology↗

bioRxiv2024

A neural correlate of learning fails to predict foraging efficiency in Bombus terrestris.

The mushroom bodies (MB) are integrative structures in the insect brain that, in social bees, contribute to both visual and olfactory learning. Changes in the density of presynaptic boutons (or microglomeruli) within the calyx region of the MB have been repeatedly linked to various aspects of foraging, including forms of learning that are thought to be key to support foraging efficiency. Here we set out to directly test the relationship between foraging efficiency and microglomerulus density in a bumblebee model, Bombus terrestris. We found no evidence that microglomerulus density predicted real-world foraging performance, nor any relationship with foraging experience. Instead, our data suggest a potential non-linear relationship between individual age, independent of foraging experience, and microglomerulus density in the lip region of the calyx, which is associated with olfactory processing. Our findings suggest that in real-world scenarios there is no simple direct relationship between microglomerular density, learning ability and foraging efficiency in bumblebees, highlighting the gap in knowledge regarding the relationships between learning abilities, neuroanatomy and foraging efficiency.

animal behavior and cognition↗

bioRxiv2023

No evidence of "social immune memory" in Acorn ants (Temnothoax nylanderi)

Social organisms are predicted to experience higher rates of infectious disease, as the likelihood of transmission increases with higher spatial and temporal proximity of potential hosts. In social insects, this risk is counteracted through a social immune system, where altruistic and collective anti-pathogen behaviours reduce or eliminate the impact of disease at the colony, or superorganism, level. Superorganismal immune strategies are often analogous to immune responses in metazoan organisms, suggesting that disease may have played a crucial role in shaping multiple major evolutionary transitions. In this study, we investigated whether acorn ants use prior experience with a pathogen to perform more efficient social immunity behaviours upon pathogen reencounter, a potential parallel to metazoan immune memory that we term social immune memory. Using Temnothorax nylanderi ants, we created experience with the fungal pathogen Metarhizium brunneum both individually and in groups, to investigate the effect of prior experience when presented with the same pathogen. We further examined the effect of prior pathogen experience when groups of ants differ in their pathogen-experience levels. We found no evidence for social immune memory in our experiments, suggesting positive results in previous studies may be due to sublethal infections, rather than cognitive effects. Alternatively, ants may employ different immune defence strategies depending on context or species, with potential differences in immune system flexibility across major evolutionary scales.

evolutionary biology↗

bioRxiv2021

Ecology dictates the value of memory for foraging bees

"Ecological intelligence" hypotheses posit that animal learning and memory evolves to meet the demands posed by foraging, and together with social intelligence and cognitive buffer hypotheses, provide a key framework for understanding cognitive evolution. However, identifying the critical environments where cognitive investment reaps significant benefits has proved challenging. Here, we capitalise upon seasonal variation in forage availability for a social insect model (Bombus terrestris) to establish how the benefits of short-term memory vary with resource availability. Through analysis of over 1700 foraging trips carried out over two years, we show that short-term memory predicts foraging efficiency - a key determinant of colony fitness - in plentiful spring foraging conditions, but that this relationship is reversed during the summer floral dearth. Our results suggest that selection for enhanced cognitive abilities is unlikely to be limited to harsh environments where food is hard to find or extract, highlighting instead that the complexity of rich and plentiful environments could be a broad driver in the evolution of certain cognitive traits.

animal behavior and cognition↗

bioRxiv2017

Ants express risk-adjusted sanitary care

Being cared for when sick is a benefit of sociality that can reduce disease and improve survival of group members. However, individuals providing care risk contracting infectious diseases themselves. If they contract a low pathogen dose, they may develop micro-infections that do not cause disease, but still affect host immunity by either decreasing or increasing the hosts vulnerability to subsequent pathogen infections. Caring for contagious individuals can thus significantly alter the future disease susceptibility of caregivers. Using ants and their fungal pathogens as a model system, we here tested if the altered disease susceptibility of experienced caregivers, in turn, affects their expression of sanitary care behaviour. We found that micro-infections contracted during sanitary care had protective or neutral effects upon secondary exposure to the same (homologous) pathogen, but consistently induced high mortality upon super-infection with a different (heterologous) pathogen. In response to this risk, the ants selectively adjusted the expression of their sanitary care. Specifically, the ants performed less grooming yet more antimicrobial disinfection, when caring for nestmates contaminated with heterologous pathogens as compared to homologous ones. By modulating the components of sanitary care in this way, the ants reduced their probability of contracting super-infections of the harmful heterologous pathogens. The performance of risk-adjusted sanitary care reveals the remarkable capacity of ants to react to changes in their disease susceptibility, according to their own infection history, and to flexibly adjust collective care to individual risk.

evolutionary biology↗

bioRxiv2017

Destructive Disinfection Of Infected Brood Prevents Systemic Disease Spread In Ant Colonies

Social insects protect their colonies from infectious disease through collective defences that result in social immunity. In ants, workers first try to prevent infection of colony members. Here, we show that if this fails and a pathogen establishes an infection, ants employ an efficient multicomponent behaviour - \"destructive disinfection\" - to prevent further spread of disease through the colony. Ants specifically target infected pupae during the pathogens non-contagious incubation period, relying on chemical sickness cues emitted by pupae. They then remove the pupal cocoon, perforate its cuticle and administer antimicrobial poison, which enters the body and prevents pathogen replication from the inside out. Like the immune system of a body that specifically targets and eliminates infected cells, this social immunity measure sacrifices infected brood to stop the pathogen completing its lifecycle, thus protecting the rest of the colony. Hence, the same principles of disease defence apply at different levels of biological organisation.

evolutionary biology↗