Elephantnose fish
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Elephant Trunk Fish ( Gnathonemus petersii ) in the aquarium |
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| Gnathonemus petersii | ||||||||||||
| ( Günther , 1862) |
The elephantnose fish ( Gnathonemus petersii ) belongs to the family of the Nile pike (Mormyridae) from the order of the osteoglossiformes, which are only found in Africa , but there are widespread and species-rich .
features
Gnathonemus petersii reaches a total length of an average of 25 centimeters. The German popular names Elefantenrüsselfisch and Tapirfisch refer to the fleshy and trunk-like appendage on the lower jaw of the terminal mouth. The color is dark brown. A narrow, light-colored transverse band runs between the beginning and the middle of the dorsal fin and anal fin . The scales are quite small towards the head and slightly larger towards the caudal fin, the number along the lateral line is 60–69.
The base of the anal fin is slightly longer than the base of the dorsal fin. Fins formula : dorsal 25–31 soft rays, anal 32–36 soft rays.
The sexes differ in the shape of the anal fin. In males it is concave and straight in females.
Gnathonemus petersii is an active, weakly electric bony fish, which generates its own currents with a high expenditure of energy, which are used for orientation in the habitat, for food acquisition and for intra-species communication. Gnathonemus petersii is able to perceive its environment via active electrolocation. With the help of an electrical organ in the tail stalk, it sends out short, weak electrical pulses. These pulses build up a bipolar, three-dimensional field around the fish's body. Changes in this field are perceived by specialized electroreceptor organs, so-called Mormyromasts, which are located on the head, abdomen and back. In addition, these fish have ampullary receptors for passive electrolocation and tuberous organs for intraspecific electrical communication on their skin. The principle of location based on electric fields is simple. Structures and objects in the vicinity of the fish have a different conductivity than the water and change the self-generated electrical field. These changes are perceived by electroreceptors distributed throughout the fish's body. Other living beings are distinguished from inanimate objects by their capacitive properties. The cerebellum of the elephantnose fish is disproportionately large in order to receive and process the electrical signals. The ratio of brain weight to body weight - the so-called allometry factor - is greater in them than in humans. The diverse and species-specific vocabulary of electrical communication is very pronounced, as is the case with all Nilhechten who live in larger social associations.
Occurrence and ecology
The elephantnose fish is widespread and common in all flowing waters of West Africa. The species is nocturnal and feeds mainly on insect larvae, which it searches for and prey on in the benthal of its habitats.
Reproduction
There is no verifiable information about the reproductive behavior of this species. Related Mormyrids, Campylomormyrus cassaicus , Mormyrus rume , Pollimyrus isidori and Petrocephalus bovei have already been bred under laboratory conditions. For this purpose, an artificial rainy season was simulated by increasing the water level and lowering the conductivity and pH value .
Systematics
Günther described the species as Mormyrus petersii in 1862 using a single specimen from Old Calabar , Nigeria . The holotype is in the British Museum of Natural History , London , under catalog number 1863.9.29.141 . Synonyms are Gnathonemus brevicaudatus Pellegrin, 1919 and Gnathonemus histrio Fowler, 1936.
Importance to humans
In their homeland, all the Nile pike, which make up a significant part of the biomass of their living waters, are important food animals that are regularly fished. The elephantnose fish is a popular laboratory animal in science. So CC Bell was able to show the adaptable efficiency copy and thereby explain why the active electrical location does not overload the passive sensors. In 1998 Gerhard von der Emde examined how well distances can be recognized. Frank Kirschbaum achieved all first-time breeding through climate simulation. Gnathonemus petersii is an aquarium fish that is always offered in pet shops.
literature
- Günther Sterba : The world's freshwater fish. 2nd Edition. Urania, Leipzig / Jena / Berlin 1990, ISBN 3-332-00109-4 .
Web links
- Elephant Trunk Fish on Fishbase.org (English)
- Cunning fish with a flashlight in its tail ( Memento from June 1, 2013 in the Internet Archive ) In: Netzeitung from August 21, 2007
- Gnathonemus petersii or the elephantnose fish Accessed January 31, 2008
- Gnathonemus petersii inthe IUCN 2013 Red List of Threatened Species . Posted by: Awaïss, A., Lalèyè, P. & Moelants, T., 2009. Retrieved January 12, 2014.
Individual evidence
- ↑ a b c Morphology Data of Gnathonemus petersii at FishBase Online ( Memento of the original from December 5, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Gunde Rieger, Wilfried Westheide: Special Zoology. Part 2: vertebrates or skulls. Spektrum Akademischer Verlag, 2009, ISBN 978-3-8274-2039-8 , p. 283.
- ^ A b Albert Günther: A new kind of Mormyrus. In: Archive for Natural History , 1862, Volume 28, Volume 1. Online ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. (PDF; 418 kB)
- ↑ Schwarz, S. & von der Emde, G., 2000: Identification and categorization of artificial and natural objects in the weakly electric fish Gnathonemus petersii. In Neuroscience, pp. 202. Brighton: FENS.
- ^ Göran E. Nilsson (1996) Brain and body oxygen requirements of Gnathonemus petersii, a fish with an exceptionally large brain . J Exp Biol. 199 (Pt 3): 603-7
- ↑ Gerhard von der Emde et al. : Electric fish measure distance in the dark. 1998 In: Nature 395, 890-894
- ↑ Kirschbaum, F., Schugardt, C .: Reproductive strategies and developmental aspects in mormyrid and Gymnotiform Fishes. J. Physiol. 96 (5-6), 557-566 (2002)
