Miniaturisation of sensory systems in ants

Abstract

The main focus of this thesis is the study of sensory systems in the context of changing body-size. In particular the study of ant sensory systems and how these are shaped by miniaturisation. The study of insect visual ecology and physiology is used as a basis to develop a framework for the study of ant antennal sensilla and chemosensation, to interpret anatomical variation from a functional and organ design perspective. This thesis reviews the anatomy and nomenclature of antennal sensilla through two case studies on an extremely large species Myrmecia pyriformis and a small species Temnothorax rugatulus. These two studies additionally quantify intraspecific variation and discuss the potential functional consequences of this variation for self-organising insect societies and task allocation. A large scale comparative study takes the tools developed in previous chapters to focus in on how chemosensilla vary in their numbers, size and distribution through the Fomicid phylogeny. The gross anatomy of the antenna and changes in shape from club to filiform antennae are described in detail. Anatomical data are analysed to identify scaling trends and potential adaptations driven by miniaturisation. Ecological and phylogenetic considerations are discussed wherever relevant. The wide ranging impacts of body size changes are reviewed, incorporated into the interpretation of results and used to propose promising avenues for future research. Finally, ant body size and some of the different methods used in the literature to measure size and size variability are critically analysed. The functional implications of body size variability within species are discussed using Iridomyrmex purpureus as an example. This thesis makes use of a variety of microscopy techniques. In addition to the methods sections of each chapter a dedicated methods chapter is included. This chapter reviews some of the techniques used in the main data chapters and in the additional publications produced over the course of this thesis.