Differential transport of a guild of mutualistic root aphids by the ant Lasius flavus

Mutually beneficial associations are widespread in ecological networks. They are typically assembled as multispecies guilds of symbionts that compete for one or more host species. The ant Lasius flavus engages in an intriguing and obligate mutualistic association with a community of aphids that are cultivated on plant roots in its nests. The ant displays a repertoire of amicable behaviors toward the aphids, including their transport. I examined whether L. flavus preferentially carried some of the root aphids. Using a no-choice and a choice experiment, I comparatively analyzed the transport rate of 5 obligate and one loosely associated species back to the ant nest and used the transport rate of the ant larvae as a reference. All associated root aphids were carried back to the nest, but in a clear preferential hierarchy. Geoica utricularia, Forda Formicaria, and Trama rara were rapidly transported, but slower than the own larvae. Tetraneura ulmi and Geoica setulosa were collected at a moderate rate and the loosely associated Aploneura lentisci was slowly retrieved. In contrast, different species of unassociated aphids were not transported and even provoked aggressive behavior in L. flavus. This study revealed that co-occurring symbionts may induce different degrees of host attraction, which ultimately may affect the coexistence and assembly of ant-symbiont communities.

"O Sister, Where Art Thou?"-A Review on Rescue of Imperiled Individuals in Ants

Altruism is defined as an action that decreases the lifetime direct fitness of an actor and benefits one or more recipients. This phenomenon, which is generally difficult to understand and explain, requires special research attention. The subject of this review, rescue, is a type of altruistic behavior in which the actor puts itself at risk to save another individual, the recipient, that is in danger. The highest numbers of published empirical works have been devoted to rescue behavior in ants and they have enormous potential for further study. We review studies devoted to the subject and group them into four main areas of research on ant rescue actions: (1) variation in rescue behavior activity on a between-individual scale, (2) factors contributing to the evolution of rescue behavior on a between-species scale, (3) rescue behavior releaser signals and (4) rescue behavior benefits and costs. We highlight the progress in research on rescue behavior in ants, indicate that this behavior is probably much more common than previously thought yet thus far demonstrated in only a few species, and uncover research gaps and open questions that remain unexplored. We additionally point out some gaps in knowledge that become evident when research devoted to rescue behavior in rats, the second most studied group of animals in this context, is briefly overviewed. We hope to help navigate among studies on rescue behavior and provide the most up-to-date summary of the relevant literature. Moreover, we hope to encourage and facilitate researchers in behavioral ecology and other subdisciplines to further experimentally analyze rescue behavior, not only in ants but also in other taxa.

Restoration of prosocial behavior in rats after heroin self-administration via chemogenetic activation of the anterior insular cortex

The anterior insular cortex (AIC) mediates various social, emotional, and interoceptive components of addiction. We recently demonstrated a disruption of prosocial behavior following heroin self-administration in rats, as assessed by examining the animals' propensity to rescue its cagemate from a plastic restrainer while having simultaneous access to heroin. To examine the possibility that heroin-induced deficits in prosocial function are mediated by the AIC, the present study examined the effects of chemogenetic activation or inhibition of excitatory AIC pyramidal neurons on heroin-induced prosocial deficits. After establishment of baseline rescuing behavior, rats received bilateral infusions of viral vectors encoding either a control virus (AAV-CaMKIIα-GFP), stimulatory DREADD (AAV-CaMKIIα-hM3Dq-mCherry) (Experiment 1), or inhibitory DREADD (AAV-CaMKIIα-hM4Di-mCherry) (Experiment 2), into the AIC. Rats were then allowed to self-administer heroin (0.06 mg/kg/infusion) 6 hr/day for 2 weeks. Prior to re-assessment of prosocial behavior, animals were administered clozapine-N-oxide (1.5 mg/kg, i.p.) to assess the effects of chemogenetic activation or inhibition of the AIC. Relative to control animals, chemogenetic activation of the AIC reversed deficits in rescuing behavior induced by heroin, whereas chemogenetic inhibition of the AIC had no effect. We hypothesize that stimulatory neuromodulation of the AIC may be a novel approach for restoring prosociality in opiate abuse.

Saving the injured: Evolution and mechanisms

Rescue behavior focused on injured individuals has rarely been observed in animals. These observations though are from very different taxa's: birds, mammals and social insects. Here we discuss likely antecedents to rescue behaviors in ants, like social carrying and alarm pheromones. We then compare similarities and preconditions necessary for rescue behavior focused on injured individuals to evolve across taxa's: a high value of individuals, a high injury risk and social interaction. Ultimately we argue that a similar problem, how to rescue injured group members, has led to different mechanisms to save injured individuals across different taxa.

Increased Risk Proneness or Social Withdrawal? The Effects of Shortened Life Expectancy on the Expression of Rescue Behavior in Workers of the ant Formica cinerea (Hymenoptera: Formicidae)

In social insects behavioral consequences of shortened life expectancy include, among others, increased risk proneness and social withdrawal. We investigated the impact of experimental shortening of life expectancy of foragers of the ant Formica cinerea achieved by their exposure to carbon dioxide on the expression of rescue behavior, risky pro-social behavior, tested by means of two bioassays during which a single worker (rescuer) was confronted with a nestmate (victim) attacked by a predator (antlion larva capture bioassay) or immobilized by an artificial snare (entrapment bioassay). Efficacy of carbon dioxide poisoning in shortening life expectancy was confirmed by the analysis of ant mortality. Rescue behavior observed during behavioral tests involved digging around the victim, transport of the sand covering the victim, pulling the limbs/antennae/mandibles of the victim, direct attack on the antlion (in antlion larva capture tests), and snare biting (in entrapment tests). The rate of occurrence of rescue behavior was lower in ants with shortened life expectancy, but that effect was significant only in the case of the entrapment bioassay. Similarly, only in the case of the entrapment bioassay ants with shortened life expectancy displayed rescue behavior after a longer latency and devoted less time to that behavior than ants from the control groups. Our results demonstrated that in ant workers shortened life expectancy may lead to reduced propensity for rescue behavior, most probably as an element of the social withdrawal syndrome that had already been described in several studies on behavior of moribund ants and honeybees.

Toward a behavioral ecology of rescue behavior

Although the study of helping behavior has revolutionized the field of behavioral ecology, scientific examination of rescue behavior remains extremely rare, except perhaps in ants, having been described as early as 1874. Nonetheless, recent work in our laboratories has revealed several new patterns of rescue behavior that appear to be much more complex than previously studied forms. This precisely-directed rescue behavior bears a remarkable resemblance to what has been labeled empathy in rats, and thus raises numerous philosophical and theoretical questions: How should rescue behavior (or empathy) be defined? What distinguishes rescue from other forms of altruism? In what ways is rescue behavior in ants different from, and similar to, rescue in other non-human animals? What selection pressures dictate its appearance? In this paper, we review our own experimental studies of rescue in both laboratory and field, which, taken together, begin to reveal some of the behavioral ecological conditions that likely have given rise to rescue behavior in ants. Against this background, we also address important theoretical questions involving rescue, including those outlined above. In this way, we hope not only to encourage further experimental analysis of rescue behavior, but also to highlight important similarities and differences in very distant taxa.

Rescue behavior: Distinguishing between rescue, cooperation and other forms of altruistic behavior

Reports of rescue behavior in non-human animals are exceedingly rare, except in ants where rescue is well known, but has not been explored experimentally until recently. Although we predict that rescue behavior should be limited to circumstances in which the victim and the rescuer are highly related to one another, or in which unrelated individuals must cooperate very closely with one another, we also predict that it is likely to be far more common than the current literature would suggest. To address this oversight, we propose a rigorous definition of rescue behavior, one that helps researchers to focus on its necessary and sufficient components, at the same time that it helps to differentiate rescue behavior from cooperation and other forms of helping behavior. In this way we also hope to expand our understanding of altruism in particular and kin selection in general.