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Chin aids in hunting: elephantnose fish

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Chin used to hunt: elephantnose fish / Joachim S. M.. / LicenseCC-by-nc-sa - Attribution Non-commercial Share Alike

The long chin of the elephantnose fish navigates and detects prey using sensors that pick up distortions in the fish’s electric field.

BIOMIMICRY TAXONOMY
Summary
For fish living in murky or dark waters, like the elephantnose fish, seeing their surroundings is virtually impossible. This makes avoiding predators and finding prey very difficult. Luckily, elephantnose fish have a very special elongated chin, which gives them their name. This chin, called a Schnauzenorgan, isn’t just for looks, and actually acts as a specialized electric organ that emits electric signals and generates electric fields.

By generating electric fields, the Schnauzenorgan is able to map out the fish’s surroundings in a process called electrolocation (similar to how a bat uses sound to detect objects and prey). The electric field created by the Schauzenorgan interacts with the surrounding environment, relaying information back to the fish’s skin, which “reads” the map made by the electric field. When the electric field comes into contact with an object, it is warped, and the electrical signals change their charge and are sent back to the fish. The charges are then interpreted by the many receptors within the fish’s skin, and an image of the environment is formed in the fish’s brain.

Due to the vast number of receptors, the fish is able to determine not only the shape of an object, but also its volume, size, material, and maybe even what direction it is facing. The elephantnose fish is then able to use the images formed through electrolocation to navigate around its environment. In this way, the fish is able to avoid hitting objects as it swims. It's also able to hunt for smaller prey.

Unlike eyesight, however, these images aren’t perfect, but blurry, since the receptors can only collect, and not focus, the signals. Think of it as how someone with glasses sees the world when they don’t have their glasses on. This doesn’t affect the fish too much, however, as basic shapes and patterns are all that the fish needs to deteremine what is around it.

This summary was contributed by Thomas McAuley-Biasi.
Excerpt

 


“Weakly electric fishes generate electrical fields around their bodies by emitting electric signals (electric organ discharges, EODs) with a specialized electric organ.” (von der Emde and Fetz, 2007: 3082)


“In addition, we studied the receptor mosaic of the sensory epithelium, which in the case of G. petersii constitutes almost the entire body surface…”(von der Emde et al., 2008: 280)


“If an object is present near the fish, it causes distortions of the electrical field lines, which change the voltage patterns on the skin of the animal opposite the object. The changed pattern is detected by electroreceptors located all over the fish’s skin.” (von der Emde and Fetz, 2007: 3082)


“Because there is no focusing mechanism, electrical images are always blurred, or “out of focus” and, in this respect, are fundamentally different optical images that are projected onto the retina of a vertebrate eye.” (von der Emde and Fetz, 2007: 3082-3083)


“Prereceptor mechanisms also ensure that the moveable skin appendix of G. petersii, the ‘Schnauzenorgan’, receives an optimal sensory signal during all stages of its movement.” (von der Emde et al., 2008:279)


“Our experiments showed that during active electrolocation, weakly electric fish can do much more than just detect objects and determine their electrical resistance (Lissmann and Machin, 1958). Instead, even in complete darkness, they can perceive parameters such as the volume, size, 3-D shape, contour, material and possibly the orientation of an object.” (von der Emde and Fetz, 2007: 3090)

 
About the inspiring organism
Med_elephantnosefish Elephant fish
Gnathonemus petersii (Günther, 1862)
Common names: Elephant nose, Elephantnose fish, Long-nosed Elephant Fish, Peter's elephantnose, Ubangi mormyrid

Learn more at EOL.org
Some organism data provided by: FishBase
Organism/taxonomy data provided by:
Species 2000 & ITIS Catalogue of Life: 2008 Annual Checklist


Bioinspired products and application ideas

Application Ideas: Tools for aquatic search-and-rescue, less invasive techniques for marine exploration.

Industrial Sector(s) interested in this strategy: Safety, deep-sea exploration

Experts
Neuroethology--Sensory Ecology
Gerhard von der Emde
Institut für Zoologie, Universität Bonn
References
Mary Muers. 2007. 'Seeing' through the chin. news@nature.com [Internet], Accessed August 28, 2007.
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von der Emde, Gerhard; Steffen Fetz. 2007. Distance, shape and more: recognition of object features during active electrolocation in a weakly electric fish. Journal of Experimental Biology. 210(17): 3082-3095.
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von der Emde G.; Amey M.; Engelmann J.; Fetz S.; Folde C.; Hollmann M.; Metzen M.; Pusch R. 2008. Active Electrolocation in Gnathonemus petersii: Behaviour, Sensory Performance, and Receptor Systems. Journal of Physiology-Paris. 102(4-6): 279-290.
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