Koboldkärpfling

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Koboldkärpfling
Leprechaun female, female

Leprechaun female, female

Systematics
Order : Toothpies (Cyprinodontiformes)
Subordination : Cyprinodontoidei
Family : Viviparous toothcarps (Poeciliidae)
Subfamily : Live-bearing toothcarps (Poeciliinae)
Genre : Gambus ( Gambusia )
Type : Koboldkärpfling
Scientific name
Gambusia affinis
( Baird & Girard , 1853)
male
Females with gestation mark

The goblin fish ( Gambusia affinis , from the Spanish gambusino 'a ridiculous nothing' and affinis 'related, bordering on another species'), also known as western mosquito fish , Texas or silver fish , is a fish that is artificially settled in many places to combat mosquito larvae . Since it plays an important role in the containment of malaria , the name mosquitofish established itself in English-speaking countries . Towards the end of the 20th century, however, the negative effects of settlement on the biodiversity of its new habitats were increasingly explored. Due to the enormous adaptability and reproductive capacity of the goblin fish , it is one of the 100 most invasive animal species worldwide .

distribution and habitat

The goblin fish originally comes from the river systems of the southern USA and northern Mexico . The demands on its habitat are extremely low: it mainly lives in bodies of water in a temperature range of 12–29 ° C, but can also survive at temperatures of only 3–4 ° C and up to 42 ° C. Actually a freshwater fish, it also lives in brackish water and generally shows a high tolerance for salinity . The demands on the water quality and the oxygen content of the inhabited waters are similarly low.

As a result of stocking measures to control mosquitoes since the beginning of the 20th century and its high level of invasiveness, the goblin fish is now widespread almost worldwide.

features

The Koboldkärpfling is translucent gray to brown in color, the sides have a slightly bluish tinge. Occasionally there are some black speckles on the body, otherwise there is no body drawing. The coloration varies both between individuals and between different populations. In addition, the goblin fish can adapt its brightness to its surroundings by accumulating or reducing melanin in the chromatophores . This process is reversible .

The head is noticeably flattened, the upper mouth is small and does not reach the relatively large eyes. The skin of the goblin fish is covered with large scales and lacks a visible sideline .

Females can grow up to 7 cm, the males stay smaller with a maximum of 4 cm. As with all viviparous toothcarps , the male's anal fin is transformed into a gonopodium .

  • Fins formula : dorsal 7–9, anal 9, pectoral 13–14, ventral 6.

Way of life

A major reason for the introduction of the goblin carrot in regions not previously populated by it was its eating behavior. By eating mosquito larvae, he was supposed to help fight malaria. In fact, its food spectrum is much broader. It feeds on insects , crustaceans , snails , eggs, larvae and pupae of invertebrates that have fallen into the water , as well as on algae and other vegetable food. The goblin fish also eats tadpoles and amphibian eggs . Smaller fish are also hunted, which can lead to cannibalism . Foraging takes place throughout the day, but morning and dusk are the times of the most intensive food intake. A goblin fish is able to consume half to one and a half times its body mass per day.

Goblin fish are often very aggressive towards both strange fish and their own conspecifics. The intra-species disputes are not limited to threatening gestures, but also include bites, knocks and jostling. As a result, hierarchies emerge in which the big fish dominate. Interestingly enough, goblins can still be seen swimming in groups, with the individual individuals only keeping a minimal distance from one another.

The breeding season lasts from mid-spring to mid-autumn, with reproductive activity peaking in summer. At the beginning of the season, the otherwise mostly separated males and females gather. Usually each female is accompanied by several males. These are particularly aggressive towards each other during this phase; the larger animals usually drive the smaller ones out of the immediate vicinity of the female. During the actual courtship, the male dominating the group woos the female with quite rough advances that are not yet directly aimed at mating. Advertising is successful when the female being courted accepts the male's proximity or approaches himself. The courtship success does not necessarily occur, however, it is also possible that the female simply swims away. If mating occurs, several attempts are usually required before the male gonopodium can be successfully inserted into the female urogenital opening . The actual copulation is then very short with an average of one second. The offspring will be born after 2 to 3 weeks of gestation. The size of the litter varies between 5 and over 100 boys, who, if there is sufficient food, reach sexual maturity after 3 months. Female goblins can give birth approximately every 3 to 4 weeks. Six, more rarely nine, broods per breeding season have already been observed frequently. Since the females store sperm in the oviduct for several months after mating and thus can have several broods with one mating, it is unclear how often goblin pups actually mate.

Role in the ecosystem

The English name mosquitofish , with a positive connotation throughout , was partially replaced by the name plague minnow ('plague minnow') at the end of the 20th century . This was intended to express the effects of the almost worldwide settlement of the goblin fish. The use of goblins against larvae of malaria-transmitting mosquitoes was very successful, not least because of its resistance and its penetration into very shallow water. This resistance to adverse environmental conditions, its extensive food palette and its high reproductive capacity also allow the goblin fish, despite its small size, to displace autochthonous species in the local ecosystems of the settlement areas.

literature

  • Graham H. Pyke: A review of the biology of Gambusia affinis and G. holbrooki , Reviews in Fish Biology and Fisheries (2005) 15: 339-365

Web links

Commons : Koboldkärpfling  - album with pictures, videos and audio files

Individual evidence

  1. ^ S. Lowe, M. Browne, M. De Poorter: 100 of the World's Worst Invasive Alien Species. A Selection from the Global Invasive Species Database. In: Aliens 12, 2000. Updated version from 2004 as PDF online , p. 9.