Humboldt-Universität zu Berlin - Behavioural Physiology

Behavioural Physiology










Professor Dr. Rüdiger Krahe


Sensory systems provide a wealth of information about the environment and the body to the animal. From this wealth of information, the brain extracts information that is relevant for making behavioural decisions, e.g., in the context of foraging or communication with conspecifics. The main focus of our lab is on understanding the tasks and constraints encountered by sensory systems under natural conditions. Our goal is to understand the factors that have been shaping these brain mechanisms in the course of evolution.

The active electric sense of weakly electric fish is well suited for this endeavour, even though these fishes live rather cryptic nocturnal lives in often highly turbid tropical freshwaters. They produce so called electric organ discharges (EODs) with a specialized electric organ in their tail to set up electric fields in the surrounding water. By sensing the self-generated current flow through the skin, they can detect both nearby objects, such as prey, and the EODs of other electric fish. This active sense allows the animals to navigate, forage, and communicate in dark and turbid waters. Fortunately for us, we can detect their EODs by placing simple electrodes into the water and thus monitor their electric behaviour and their movements in the lab, but also in their natural tropical rainforest habitats.


Snapshots of the electric fields generated by an electric fish (top) and modulations of the fish's electric organ discharge (EOD) caused by a nearby object (a, electrolocation situation) or the EOD of a conspecific (b, electrocommunication). In "wave-type" species, the EOD is an oscillatory, quasi-sinusoidal signal. Perturbation of the ensuing field by an object (a) leads to modulations of the amplitude (AM) of the oscillatory signal as received by  electroreceptor organs in the skin (green area on the skin). The interaction with the EOD of a conspecific leads to periodic AMs (b). From Krahe and Maler (2014).


Snapshots of reconstructed interactions of weakly electric fish (Apteronotus rostratus) recorded in their natural habitat in the Panamanian rainforest. From Henninger et al. (2018).

Questions we currently pursue:

- How do environmental factors, such as oxygen availability in the
  water and temperature, affect the acquisition of sensory information?
  What are the metabolic costs of sensing?
  How do variations in environmental parameters affect the generation
  of electric signals, the associated sensory processing, as well as
  brain cell proliferation and neurogenesis?

- What are the properties of electrosensory scenes (akin to visual
  scenes) experienced by fish swimming and interacting freely in their
  natural habitat? What challenges and tasks do these natural sensory
  scenes pose for the fish’s neuronal processing of sensory

- What is the role of limbic circuits in the processing of social
  information in South American weakly electric fish?