Introduction of Electric Fish

This blog post is going to give you a foundation on what an electric fish is and how their special sensory organs works to allow these organisms to thrive in their environment.

There are two different types of electric fish: Weak and strong electric fish with over 340 species encompassing the two groups(Pitchers et al. 2016). The main difference between the two is almost obvious strong electric fish can generate an electric field that is strong enough to stun an organism for predation tactics or for defense (Nelson, 2006). An example of a strong electric fish is an electric eel or an electric ray.  A weakly electric fish produces a very small electric field that is too weak to harm another organism (Nelson, 2006). Electric fish use the electric field to communicate with conspecifics; a conspecific is any animal that belongs to the same species. Electric fish also use their electric field to forge for prey. This can be done because other prey organisms have electricity running through their body due to the electrical impulses from the nervous system and muscle contractions. Lastly, electric fish use their electric field for navigation.

Electrical communication in many species is imperative for their survival.  Many of the species that have an Electric Organ Discharge (EOD) live in areas where there is not a lot of light which makes photoreception (using light to see) very difficult and ineffective.

The brain of electric fish sends signals to the electric organ which is located usually near the caudal end of electric fish (Figure 1).  The electric organ is filled with cells called electrocytes. Electrocytes maintain a negative charge on the inside and a positive charge on the outside however, when the electrocytes receives the signal from the brain to Voltage-gated sodium channels.  The signal then makes this channel open (Kramer 1996). This makes one side of the electrocyte negatively charged and the other side positively charged on both sides of the cell (Figure 2). This kind of charge pattern is seen in a typical battery in series.  The charges from the “batteries” can create an electric field for the benefit of the electric fish.

Electroreceptors can interpret the electric field making them able to locate organisms and navigate in murky water.  As previously stated, strongly electric fish can produce very strong electric fields that immobilize their prey. What happens is the electric fish locates its prey with the electroreceptor and sends a strong electric wave that causes muscle contractions that stuns the prey (Kramer 1996).  The prey is then an easy target for the electric fish to capture.

Electric fish can communicate with electrical fields which can be difficult to wrap our heads around since it is something that we can’t do as humans.  In most communication systems there is an individual that puts out a signal and an individual that receives the signal. In electric fish, the signaler sends out an electric field and the receiver can receive this information with its electroreceptor.  Interpretation of the electric field is based on several variables such as frequency, form, and delay of the wave (Kramer 1996). Electric fish are known to perform jamming avoidance behaviors which means the electric field of one fish won’t affect the electrical field of another (Worm et al. 2018). The main reason electric fish communicate is to identify conspecifics, courtship, environmental conditions, and dangers such as predators.

The next blog post is going to address the effects of Global Climate Change and how extreme environmental changes can affect the survival of electric fish.

Figure 1: Location of the Kidney-shaped Electric Organ in Electric Rays are located more anterior in these species. 
Alexander Graetz, Elektroplax RochenCC BY-SA 3.0
Figure 2: Electrocyte diagram which illustrates the charges during inactive and active periods.
No machine-readable author provided. Tar-Minyatur~commonswiki assumed (based on copyright claims)., ElectroplaxCC BY-SA 3.0

Literature Cited:

  1. Worm M, Landgraf T, Prume J, Nguyen H, Kirschbaum F, Emde G von der. Evidence for mutual allocation of social attention through interactive signaling in a mormyrid weakly electric fish. Proceedings of the National Academy of Sciences. 2018;115(26):6852–6857. doi:10.1073/pnas.1801283115
  2. Pitchers WR, Constantinou SJ, Losilla M, Gallant JR. Electric fish genomics: Progress, prospects, and new tools for neuroethology. Journal of Physiology-Paris. 2016;110(3, Part B):259–272. (Electric Fish Meeting 2016: Electrosensory and Electromotor Systems). doi:10.1016/j.jphysparis.2016.10.003
  3. Nelson,Mark. Electric Fish. 2006 [accessed 2019 Mar 27].
  4. Kramer B. Electroreception and Communication in Fishes. 1996:131.

Leave a Reply

Your email address will not be published. Required fields are marked *