Tomeurus gracilis

Tomeurus gracilis
	Tomeurus gracilis , a male above, a female below, illustration from The freshwater fishes of British Guiana by Carl H. Eigenmann
Systematics
Order :	Toothpies (Cyprinodontiformes)
Subordination :	Cyprinodontoidei
Family :	Viviparous toothcarps (Poeciliidae)
Subfamily :	Tomeurinae
Genre :	Tomeurus
Type :	Tomeurus gracilis
Scientific name of the subfamily
	Tomeurinae
	Eigenmann , 1912
Scientific name of the genus
	Tomeurus
	Eigenmann, 1909
Scientific name of the species
	Tomeurus gracilis
	Eigenmann, 1909

Tomeurus gracilis is a freshwater fish from the viviparous toothcarp family . As the only representative of the subfamily, it does not give birth to live young, but lays well-developed eggs that are fertilized in the female's body.

features

The fish reach a length of 3.5 cm, according to other information, males are up to 7 cm, the females even 8 cm. The body of the Kärpfling is elongated with a small head and relatively large eyes. The dorsal fin is located far back compared to other live-bearing toothcarps. The males' anal fin, which has been transformed into a gonopodium , is long, has an antler-like structure and is located in a hollow on the underside of the abdomen. The anal fin of the females is large, the first rays of the fin are elongated. Both sexes have a shed Kiel in the rear half of the body, the more apparent than in Messerschwanzkärpfling is formed. The basic body color is brown-yellow, the abdominal region remains a little lighter. Especially in the back half of the body, the Kärpfling appears transparent. The fins are colorless, tinged slightly yellow in some populations. A thin black line runs along the horizontal middle of the body.

Occurrence and way of life

Tomeurus gracilis mainly inhabits the tidal zone of coastal rivers in eastern Venezuela , Guyana and Suriname up to the catchment area of the Rio Tocantins in the Brazilian state of Pará . The Kärpflinge prefer to stay on the surface of the water. There are no aquatic plants, only at high tide are grasses from the bank edge under water. It is believed that the fish lay their eggs on these blades of grass, which then regularly dry out at low tide.

Tomeurus females usually only carry a single egg, which, after the internal fertilization typical of viviparous toothcarps, develops in the mother's body for around two weeks before it is deposited and then develops for around two more weeks before the young hatch.

Systematics

Within the viviparous toothcarps, Tomeurus gracilis occupies a special position due to the way it reproduces. The kind is led in its own subfamily Tomeurinae and is considered a basal kind of the family.

Individual evidence

↑ Harro Hieronimus : The egg-laying livebearer: Tomeurus gracilis . In: DGLZ Rundschau 34, 2007, No. 3, pp. 75–80.

literature

Manfred K. Meyer, Lothar Wischnath, Wolfgang Foerster: Livebearers ornamental fish: Species of the world. Mergus Verlag für Natur- und Heimtierkunde Baensch, Melle 1985, ISBN 3-88244-006-6

Web links

Tomeurus gracilis on Fishbase.org (English)

[1] Harro Hieronimus : The egg-laying livebearer: Tomeurus gracilis . In: DGLZ Rundschau 34, 2007, No. 3, pp. 75–80.