We favor the comparative approach towards neuroethology,
and ants are particularly well suited for this approach. Although most ants
look just like ants (or like little specks to the naked eye), the behavior of
different species or castes may be very different. All ants rely on olfaction
for their communication (pheromones), and many species predominantly use odor
cues for orientation. However, some ants are expressively visual animals that
catch prey using their keen sight, or they navigate by visual landmarks or analyze
the polarization pattern of the skylight. In a current project we try to find
out how the brains differ in ants that show such obviously different behaviors.
Visual ants have larger eyes and their brains comprise larger optic lobes, but
this increased amount of sensory information needs to be further processed to
give rise to the appropriate behavior. The mushroom bodies are central brain
structures that process multimodal information and are supposedly involved in
orientation, movement control and learning and memory in different insects.
Mushroom bodies are also a major olfactory processing center, and they are very
large in ants.
To learn more about the function of the mushroom bodies and their involvement in learning or orientation, we employ
- morphometric analysis of the brains of many different ant species to quantitatively describe the differences in brain design;
- neuroanatomical analysis of visual and olfactory input using classical neuroanatomical methods and fluorescent tracer techniques as well as immunocytochemistry;
- quantitative assessment of behavior (walking, learning, orientation) involving video observations, arena and maze tests;
- lesioning techniques to determine behavioral deficits corresponding to mushroom body lesions
- electro-physio-logical analysis of the response characteristics of neurons that can be identified and compared in many different species;
The mushroom bodies are also involved in behavioral changes, such as the transition from nurse to forager. Mushroom body changes associated with such transitions are examined in deprivation experiments in which the importance of sensory experience for the development of the brain and of normal behavior is accessed. After the mating flight when young, winged queens are mated, they shed their wings and start a new, subterranean life in the dark. After rearing their first young workers their activities are mainly reduced to egg-laying. This transition from virgin to mature queen goes along with a substantial reduction of overall brain volume and of the optic lobes in particular.
Organization of direct visual afferents to the mushroom bodies in the honey bee
Organization of direct visual afferents to the mushroom bodies in the carpenter ant
Brain plasticity and behavioral plasticity in ant queens
Organization of mushroom bodies in ants