Mormyridae

Source: Wikipedia, the free encyclopedia.

Freshwater elephantfish
Gnathonemus petersii
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Osteoglossiformes
Family: Mormyridae
Genera

see text

The Mormyridae, sometimes called "elephantfish" (more properly freshwater elephantfish), are a superfamily of weakly electric fish in the order Osteoglossiformes native to Africa.[1] It is by far the largest family in the order, with around 200 species. Members of the family can be popular, if challenging, aquarium species. These fish have a large brain size and unusually high intelligence.

They are not to be confused with the marine and brackish-water

callorhinchid elephantfish
(family Callorhinchidae) of Southern Hemisphere oceans.

Description and biology

The elephantfish are a diverse family, with a wide range of different sizes and shapes. The smallest are just 5 cm (2.0 in) in adult length, while the largest reach up to 1.5 m (4.9 ft). They do, however, have a number of unique features in common. Firstly, their

embryos) of which it has the same histological structure, nor is it therefore related to the pharynx.[5]

Some species possess modifications of their mouthparts to facilitate electrolocating and feeding on small invertebrates buried in muddy substrates. The shape and structure of these leads to the popular name "elephant-nosed fish" for those species with particularly prominent mouth extensions. The extensions to the mouthparts usually consist of a fleshy elongation attached to the lower jaw. They are flexible, and equipped with touch, and possibly taste, sensors. The mouth is not protrusible, and the head (including the eyes), the dorsum, and belly are covered by a thin layer of skin that is perforated with small pores leading to electroreceptors.[citation needed]

The retina is called a "grouped retina", an eye structure seen in mormyrids and a few other fishes.

Gymnarchus are also unique in being the only vertebrates where the male sperm cell does not have a flagellum.[9]

Electric fields

Mormyromast, a type of electroreceptor found only in mormyrid fishes
Further information: Electroreception and electrogenesis

Elephantfish possess

electric organs that generate weak electric fields, and electroreceptors (ampullae of Lorenzini, knollenorgans, and Mormyromasts) that detect small variations in these electric fields caused by the presence of prey or other objects of different conductivities. This allows them to sense their environment in turbid waters where vision is impaired by suspended matter.[10][11]

Electric fish can be classified into two types: pulse fish or wave fish. Pulse-type discharges are characterized by long intervals between electric discharges, whereas wave-type discharges occur when the interval between consecutive pulses is so brief that the discharges fuse together to form a wave.[12] The electric discharge is produced from an electric organ that evolved from muscle, as can also be seen in gymnotiform electric fish, electric rays, and skates. The convergent evolution between the South American gymnotiforms and the African Mormyridae is remarkable, with the electric organ being produced by the substitution of the same amino acid in the same voltage-gated sodium channel despite the two groups of fish being on different continents and the evolution of the electric sense organ being separated in time by around 60 million years.[13] Convergent changes to other key transcription factors and regulatory pathways in both Gymnotiforms and Mormyridae also contributed to the evolution of the electric sense organ.[14]

Classification

Main article:
Mormyridae_(superfamily) § Classification

The roughly 221 species of elephantfish which are sometimes grouped into two subfamilies, the

Petrocephalinae
. The latter has only a single genus:

Phylogeny[15][16]
Mormyridae

Eschmeyer's Catalog of Fishes classifies the family as follows[17] Family Mormyridae

In culture

Bronze figurine of Oxyrhynchus fish, Late Period-Ptolemaic Egypt

The Medjed was a sacred fish in Ancient Egypt. At the city of Per-Medjed, better known as Oxyrhynchus, whose name means "sharp-nosed" after the fish, archaeologists have found fishes depicted as bronze figurines, mural paintings, or wooden coffins in the shape of fishes with downturned snouts, with horned sun-disc crowns like those of the goddess Hathor. The depictions have been described as resembling members of the genus Mormyrus.[19]

References

  1. ^ Froese, Rainer; Pauly, Daniel, eds. (2017). "Family Mormyridae". FishBase.
  2. doi:10.1017/S0952836901000966
    .
  3. ISBN 978-0-08-045046-9
    .
  4. S2CID 12951395
    .
  5. ^ Orts, S. (1967): Contribution to the comparative anatomy and systematics of Mormyroïdes (RAOS Prize 1966) - Ann. Acad. Roy. Sc. d'Outre Mer, Classe des Sc. Nat. et Méd., Bruxelles, XVII, 3, 1-89, 30 figs, 3 tabs, 8 pls, 1967 (in French)
  6. S2CID 39081714
    .
  7. ^ "Elephant-Nosed Fish Has Funky Eyes, Too". livescience.com. 28 June 2012.
  8. ^ Bernd Kramer. P.J.B. Slater; J.S. Rosenblatt; C.T. Snowdon; M. Milinski (eds.). "Communication Behavior and Sensory Mechanisms in Weakly Electric Fishes" (PDF). Advances in the Study of Behaviour. 23: 233–270.
  9. ^ Miller, S.; Sullivan, J. "Mormyridae Bonaparte, 1831". Mormyridae - African weakly electric fishes. Retrieved 20 October 2023.
  10. ^ Bustami, H.P. (2007). Smart elephant fish navigates in darkness with electric fields. life-of-science.net
  11. ^ The generation of these electric fields and their use in providing the fish with additional sensory input from the environment is the subject of considerable scientific research, as is research into communication between and within species
  12. PMID 10210664
    .
  13. PMID 21127261
    .
  14. PMID 24970089
    .
  15. doi:10.1046/j.1095-8312.2003.00170.x
    .
  16. PMID 10648209
    .
  17. Catalog of Fishes. California Academy of Sciences
    . Retrieved 3 November 2024.
  18. PMID 27006619
    .
  19. ISBN 978-3-89646-674-7
    .
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