Pygmy carp

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Pygmy carp
Dwarf carrot (female)

Dwarf carrot (female)

Systematics
Subordination : Cyprinodontoidei
Family : Viviparous toothcarps (Poeciliidae)
Subfamily : Live-bearing toothcarps (Poeciliinae)
Tribe : Heterandrini
Genre : Heterandria
Type : Pygmy carp
Scientific name of the  tribe
Heterandrini
Agassiz , 1853
Scientific name of the  genus
Heterandria
Agassiz , 1853
Scientific name of the  species
Heterandria formosa
Girard , 1859

The Heterandria Formosa ( Heterandria formosa ) is a from North America originating fish of the subfamily of livebearing carp . It is the only species in the monotypic genus Heterandria .

features

It is one of the smallest viviparous toothcarps with a size of around 3.6 cm in the female sex, occasionally females from domesticated trunks can reach a body length of more than four centimeters. The males remain significantly smaller at around 2 cm and have a remarkably long gonopodium . The gonopodium only forms during the development of the sexual dimorphism , around the fourth or fifth week of life. From this age on, the sexes can also be distinguished from one another. The pygmy carvings reach sexual maturity between about ten and twelve weeks of age. Young, not yet sexually mature females are usually mated by older males without prior courtship. The not yet sexually mature female stores the sperm and uses them later to fertilize the egg cells.

In contrast to many other poeciliids, the species is characterized by superfetation and a follicular placenta. The ovary usually contains several eggs in different stages of development. The body of the female does not act as a pure shelter for egg development ( ovoviviparous ) - as with other poeciliids - but it also supplies the young with nutrients via the follicular placenta. Pygmy fish are thus matrotrophically viviparous .

Occurrence

The freshwater fish inhabit heavily weed standing ponds and slowly flowing bodies of water like ditches up to the brackish water region. In these waters, he is typically at the edges of the water. Its range extends from the Cape Fear River in North Carolina to the Orange River in Texas .

The water temperatures over the entire distribution area fluctuate in the course of the year with brief frosts from 4 ° C to 39 ° C in the summer months.

behavior

The dwarf carp loves tight structures, be it the gaps between heavily weed plants or crevices between stones - but the former prefers. The occurrence of these structures also determines the water region in which he prefers to stay.

The females move through the available water space, individually or in small groups, in the creeping mode of locomotion inherent in the pygmy carp, keeping to the edges of narrow structures. They are generally peaceful and show no damaging aggressive behavior with one another, apart from a few jostling.

With a “normal” population density of male dwarf fish, the males show the tendency to form small territories that are defended against other males. So they do not move through the available water space like the females, but sit in their small prairies and wait for females to pass by, who are then followed and watched within the area like on a string (Lauerbalz / Überfallbalz). The size of these areas lies in the radius range of a few centimeters, largely determined by the density of weeds and the proximity of other males to the area.

If a male crosses the border into another area - usually while chasing a female in wait - it is immediately driven out of the area by the owner of the area with threatening behavior and shocks. The threatening behavior is characterized by a backbone curved into a clear "hollow back". The little pygmy male is reminiscent of a small boat. This threat is usually associated with a lightening of the body color to yellowish and the fading of the dot and stripe pattern.

The districts are always tied to herbaceous or tightly structured areas. The more weed, the more popular the area is.

The young animals stay, if possible, in the most densely weedy water regions. Like the adults, their movement is creeping, only much more extreme. They usually move so slowly and evenly that it is difficult to see them. The more open the water space around them, the closer they are to solid structures. They only become more relaxed within densely growing herbs or algae pads. There they sometimes - even the smallest - do small skirmishes with other juvenile fish of their kind.

On the run, young and old usually shoot headfirst into the next best herb cushion or the soft mole or substrate.

Reproduction

The dwarf carp belongs to the group of viviparous toothcarps , i. H. the males mate with the females with the help of the anal fin that has been transformed into a mating organ ( gonopodium ). The young hatch in the womb of the female and are born alive.

The dwarf carp has an interesting adaptation to dwarfism : the superfetation . The young grow up in the females in different stages of development, as it were on an assembly line, and are nourished by the female through the follicular placenta in the body. Only a few young animals (1 to 4) are born every day, on some days up to 9 young fish can be born, but this is rather the exception. Overall, depending on size, a female produces around 30 young animals over a period of approx. 4 weeks (depending on the size of the female and the time of year).

The courtship behavior is essentially limited to a lurking pursuit of the females who are currently roaming the male's territory.

Aquarium keeping

Temperatures

Due to its distribution area and its preference for small types of water, the dwarf carp tolerate temperatures of 10 to 30 ° C. This makes these fish suitable for a cold water aquarium with not too large roommates. The normal temperature range should be around 13 to 22 ° C with changing day / night or seasonal rhythms. Constantly high storage temperatures are not beneficial. In addition to low temperatures, shorter lighting times are also appropriate during winter. When it gets warmer again in the spring and the days get longer, a new breeding season begins, because the pygmy carrot follows a seasonal reproduction that has its peak in the months May to July.

nutrition

As with most livebearers, nutrition in the aquarium is quite simple. From live food to flakes of food, everything is taken, but live food is preferred and an at least sporadic administration of live food keeps the fish healthier and is clearly beneficial for permanent reproduction.

As a result of the clearly different sizes of the two sexes, females and males use different food sources. Females are able to feed relatively large animals such as B. to eat mosquito larvae (up to approx. 2 cm). Males, however, only cope with much smaller food animals such as water fleas and hippos.

Multiplication

It is not difficult to reproduce dwarf carp in the aquarium. When the fish feel good, the offspring usually come in on their own. The fry can simply remain in their parents' tank, as they usually do not follow them. At the beginning they will find enough food in a weed-covered tank, but they can also be fed with Artemia nauplii or other small live food.

Individual evidence

  1. ↑ Alfy Morales-Cazan, James S. Albert: Monophyly of Heterandriini (Teleostei: Poeciliidae) revisited: a critical review of the data. In: Neotropical Ichthyology. Volume 10, No. 1, 2012, pp. 19-44.
  2. ↑ M. Kempkes: The Zwergkärpfling. Magdeburg 2014, ISBN 978-3-89432-251-9 .

literature

  • Katrin Plöger-Brembach: Livebearers . Kerner Verlag, 1982, ISBN 3-87401-040-6 .
  • Alexander Dorn: Ethological and morphological investigations into the reproduction of Heterandria formosa. Thesis. 2004
  • Michael Kempkes: The dwarf carp. (= The new Brehm library. Volume 683). Wolf, Magdeburg 2014, ISBN 978-3-89432-251-9 .
  • S. Soucy, J. Travis: Multiple paternity and population genetic structure in natural populations of the poeciliid fish Heterandria formosa. Department of biological science, Florida State university, Tallahassee.

Web links

Commons : Pygmy Carrot ( Heterandria formosa )  - Collection of images, videos and audio files