A pinboard by
Susie Hewlett

PhD student, Macquarie University


Comparing and contrasting the proximate mechanisms of insect sociality with vertebrate findings.

Today we can see many examples of group living in the animal kingdom, each varying in size and degree of cohesion, which is thought to correlate with the level of cognitive complexity required. Honey bees (Apis mellifera) live in large societies and continuously interact with thousands of nestmates to maintain the functioning of the colony via coordinated and altruistic actions, making them an excellent species to study the neurobiology of social behaviour.

My research focuses on uncovering the neural chemicals driving this gregarious instinct that leads to the formation and maintenance of their cooperative groups. I designed a new behavioural assay that assesses honey bee sociability and nestmate affiliation and used this to describe how they develop. We found that both honey bee sociability and nestmate affiliation depends on the social environment experienced as an adult, much like vertebrate species.

Currently I am combining this new assay with neuropharmacological treatments, to determine the role of various neurochemical systems in these behaviours. As more than thirty years of study has uncovered the dominant roles of oxytocin and dopamine in mammalian pair bond formation, and octopamine is implicated in the neuromodulation of insect aggression and social recognition, I will activate and inhibit these neural systems via agonist and antagonist injection into the bee brain.

Furthering our understanding of insect brain chemistry in relation to the formation and maintenance of their societies is important for developing strategies to improve the success and survival of this dominant pollinator species. For example, chemical stressors such as pesticides can be designed so as not to effect the neural systems involved in honey bee sociability. Moreover, these studies will provide new evidence for the debate around the social brain hypothesis that correlates brain size with social group size and individual cognitive ability. The development of this invertebrate sociability bioassay, that allows direct comparison with vertebrate studies, has major implications for uncovering the evolution of sociality.


The social brain hypothesis and its implications for social evolution.

Abstract: The social brain hypothesis was proposed as an explanation for the fact that primates have unusually large brains for body size compared to all other vertebrates: Primates evolved large brains to manage their unusually complex social systems. Although this proposal has been generalized to all vertebrate taxa as an explanation for brain evolution, recent analyses suggest that the social brain hypothesis takes a very different form in other mammals and birds than it does in anthropoid primates. In primates, there is a quantitative relationship between brain size and social group size (group size is a monotonic function of brain size), presumably because the cognitive demands of sociality place a constraint on the number of individuals that can be maintained in a coherent group. In other mammals and birds, the relationship is a qualitative one: Large brains are associated with categorical differences in mating system, with species that have pairbonded mating systems having the largest brains. It seems that anthropoid primates may have generalized the bonding processes that characterize monogamous pairbonds to other non-reproductive relationships ('friendships'), thereby giving rise to the quantitative relationship between group size and brain size that we find in this taxon. This raises issues about why bonded relationships are cognitively so demanding (and, indeed, raises questions about what a bonded relationship actually is), and when and why primates undertook this change in social style.

Pub.: 04 Jul '09, Pinned: 30 Sep '17

Sociability and preference for social novelty in five inbred strains: an approach to assess autistic-like behavior in mice.

Abstract: Deficits in social interaction are important early markers for autism and related neurodevelopmental disorders with strong genetic components. Standardized behavioral assays that measure the preference of mice for initiating social interactions with novel conspecifics would be of great value for mutant mouse models of autism. We developed a new procedure to assess sociability and the preference for social novelty in mice. To quantitate sociability, each mouse was scored on measures of exploration in a central habituated area, a side chamber containing an unfamiliar conspecific (stranger 1) in a wire cage, or an empty side chamber. In a secondary test, preference for social novelty was quantitated by presenting the test mouse with a choice between the first, now-familiar, conspecific (stranger 1) in one side chamber, and a second unfamiliar mouse (stranger 2) in the other side chamber. Parameters scored included time spent in each chamber and number of entries into the chambers. Five inbred strains of mice were tested, C57BL/6J, DBA/2J, FVB/NJ, A/J and B6129PF2/J hybrids. Four strains showed significant levels of sociability (spend- ing more time in the chamber containing stranger 1 than in the empty chamber) and a preference for social novelty (spending more time in the chamber containing stranger 2 than in the chamber containing the now-familiar stranger 1). These social preferences were observed in both male and female mice, and in juveniles and adults. The exception was A/J, a strain that demonstrated a preference for the central chamber. Results are discussed in terms of potential applications of the new methods, and the proper controls for the interpretation of social behavior data, including assays for health, relevant sensory abilities and motor functions. This new standardized procedure to quantitate sociability and preference for social novelty in mice provides a method to assess tendencies for social avoidance in mouse models of autism.

Pub.: 04 Sep '04, Pinned: 30 Sep '17