Mormyridae

From Wikipedia, the free encyclopedia

iElephant fish

Blunt-jawed elephantnose (Gnathonemus tamandua)

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Osteoglossiformes
Family:	Mormyridae

Subfamilies

Mormyrinae
Petrocephalinae

The family Mormyridae, sometimes called elephantfish, are freshwater fishes native to Africa in the order Osteoglossiformes. It is by far the largest family in the order with around 200 species.

Members of the family are popular, if challenging, aquarium species, notable for their ability to generate weak electric fields that allow the fishes to sense their environment in turbid waters where vision is impaired by suspended matter. The generation of these electric fields and their use in providing the fishes with additional sensory input from the environment is the subject of considerable scientific research, as is research into communication between and within species.

Electric discharges are most often pulsitile discharges, with Gymnarchus niloticus being an exception to this rule, discharging its electric organ near approximately 500 Hz, giving it a near-sinusoidal like discharge. The electric organ is a structure that is well established in the scientific literature to be developmentally related to muscle, as in Gymnotiform electric fish, as well as in electric rays and skates. There is a surprising degree of convergent evolution between the South American Gymnotiforms and the African Mormyridae, particularly in the sensory apparatus for detecting and processing electrical signals involved in electrolocation and electrocommunication.

Some species possess modifications of the mouthparts to facilitate feeding upon small invertebrates buried in muddy substrates, the shape and structure of these leading to the popular name of "elephant nosed fish" for those species with particularly prominent mouth extensions. The extensions to the mouthparts (usually consisting of a fleshy elongation attached to the lower jaw) are flexible, and equipped with touch (and possibly taste) sensors.

Among those members of the family lacking extended mouthparts, the body shape and general morphology of the fishes has led to some being known among aquarists by the name of "baby whale", despite the fact that true whales are mammals. Other "mormyrid mammalian misnomers" include the term "dolphin fishes", in reference to certain members of the Genus Mormyrops.

[edit] Classification

Subfamily Mormyrinae
Subfamily Petrocephalinae

[edit] Genera and Species

The family Mormyridae contains the following Genera:

Boulengeromyrus
Brienomyrus
Campylomormyrus
Genyomyrus
Gnathonemus
Heteromormyrus
Hippopotamyrus
Hyperopisius
Isichthys
Ivindomyrus
Marcunesias
Mormyrops
Mormyrus
Oxymormyrus
Paramormyrops
Petrocephalus
Pollimyrus
Stomatorhinus

Among the species that belong to this family are:

Gnathonemus petersi, Peters' elephantnose fish;
Gnathonemus tamandua, the Blunt-jawed elephantnose;
Gnathonemus elephas;
Marcunesias macrolepidotus;
Marcunesias senegalensis;
Pollimyrus castelnaui, known among aquarists as the "baby whale"', along with other relatives in the genus Pollimyrus;
Pollimyrus isidori;
Brienomyrus niger, the "black baby whale";
Campylomormyrus rhynchophorus;
Hippopotamyrus discorhynchus;
Mormyrops deliciosus, a large member of the family utilised as a food fish by humans;
Petrocephalus catostomus, the smallest member of the family (7 cm SL);
Mormyrus lapinus, sometimes called the "dolphin fish" or "freshwater dolphin" by aquarists;
Brienomyrus brachyistius, the "brown baby whale"