Straight-line orientation in the brain of a ball-rolling dung beetle: an interdisciplinary investigation

Popular Abstract

Travelling in a straight line, answers in a beetle brain

If you find yourself outdoors in South Africa you might stumble upon a ball-rolling dung beetle determinately rolling a dung ball. if you then follow the direction of the beetle from where it was rolling along a straight line, you will find yourself at a dung pat. The dung beetle is capable of rolling a dung ball in a straight line. It assigns a certain direction as a goal direction and rolls its ball ensuring that its current direction is pointed towards its goal direction. The answer to how this dung beetle is capable of rolling a dung ball in a straight lies inside its brain.

A specific region of the brain in insects is known as the navigational hub. This specific region is found in the fruit fly but also in the dung beetle. Both these insects can travel along a straight path, but the fruit fly brain has been extremely well studied and provides a good baseline from which to compare the dung beetle brain.

First, we conducted behavioural experiments to see how long a dung beetle could remember its goal direction. we saw that in the dung beetle, like in the fruit fly, the dung beetle remembers its direction for at least 2 hours. This highlighted that the brain stores a goal direction memory similarly between the fruit fly and the dung beetle.

Second, we did scans of brain and saw that within the region of the insect brain the neurons that build up circuits for tracking the beetle current direction are present in the dung beetle and look very similar to the fruit fly. The goal direction circuit is not yet described in the fruit fly, but neurons that are likely part of the goal direction circuit had a similar number to the fruit fly. This highlights the likely similarity of the navigational brain region between the dung beetle and fruit fly.

Thirdly, a genome was acquired for the dung beetle. In the fruit fly, experiments mutating certain genes, rendered them useless, have caused the function or development of this navigational brain region in the fruit fly to be affected. We found sister genes in the dung beetle which again points to the similarity between the two insect’s navigational brain region.

These three very different means of looking at the brain all point to a very similar navigational brain region in both these insects from which we can build a model for straight line orientation in the dung beetle. In our model we propose: 1) The identified neurons of the head direction circuit form a compass like representation of the dung beetle’s orientation in its environment. 2) A random direction from the head direction circuit sent to the goal direction circuit is set as a goal direction. This goal direction, we now know, can be followed for at least two hours. 3) The found neuron of the goal direction circuit could communicate to downstream neurons to correct the path of the dung beetle if the current heading and goal direction are mismatched and steer the beetle back on course.

Studying the brain of the dung beetle has started to help us understand how a dung beetle walks along a straight path away from a dung pat and further studies will hopefully strengthen this understanding.

Masters’s Degree Project in Bioinformatics 60 credits 2023
Department of Biology, Lund University

Advisor: Marie Dacke, Dag Ahren & Elin Dirlik
Department of Biology, Lund University

• author: de Pennart, Auguste
• supervisor: Marie Dacke; Dag Ahrén
• organization: Degree Projects in Bioinformatics
• course: BINP52 20222
• year: 2023
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9140738
• date added to LUP: 2023-11-01 15:47:34
• date last changed: 2023-11-01 15:47:34