Astyanax mexicanus

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Astyanax mexicanus
Astyanax mexicanus

Astyanax mexicanus

Systematics
Sub-cohort : Ostariophysi
Otophysa
Order : Tetras (Characiformes)
Family : True tetras (Characidae)
Genre : Astyanax
Type : Astyanax mexicanus
Scientific name
Astyanax mexicanus
( De Filippi , 1853)

Astyanax mexicanus is afreshwater fish from the family of the true tetras (Characidae) thatoriginallylivesin Texas and New Mexico , as well as in northern and central Mexico . The schooling fish are about ten to twelve centimeters in size.

Names

The species was originally described as Tetragonopterus mexicanus from near Mexico. Later the fish were only considered as a subspecies Astyanax fasciatus mexicanus , but then again not only as an independent species, but even as a species complex, which seems to be confirmed by recent genetic studies.

features

These are mostly silvery colored fish of the typical tetra shape, only the adipose and caudal fins are tinged yellow, the latter interrupted in the middle by a black line that can extend to the gill cover, but is particularly easy to recognize on the caudal and the caudal peduncle . Anal, pectoral and pelvic fins can be slightly reddish in color. The dorsal fin is colorless and transparent.

The tetras are considered to be aggressive despite their moderate size and since they also feed predatory on juvenile fish of other species, they are viewed as problematic in the USA, especially since they were transported into different waters there (presumably as surplus bait fish). They are now also native to other states (e.g. Arizona, California, Louisiana, Oklahoma, and Ohio).

Cave shapes

The blind cave tetra is a unique species of Astyanax jordani .

According to more recent studies, the so-called cave forms seem to be at least one species in their own right, as they are genetically different. Yamamoto & Jeffery (2000) were able to prove that eyes also initially develop in cave tetra embryos, but are destroyed later in development because a gene called pax6 is deactivated. When a protein called sonic hedgehog was administered to the embryos of surface Astyanax mexicanus , they formed smaller retinas and almost no lenses. Conversely, if the embryos of the cave tetra ( Astyanax jordani ) were given a chemical that inhibits the sonic hedgehog protein, these fish too could develop a lens that was almost a third larger than normal. Nevertheless, no surface fish could be created from a cave tetra by simply adding protein in the embryonic stage, a further indication that A. mexicanus is a different species from the cave tetra ( A. jordani ).

literature

De Filippi, F. (1853): Nouvelles espèces de poissons. Revue et Magasin de Zoologie , (2) 5: 164-171. (PDF; 19.19 MB)

Individual evidence

  1. ^ Lee, DS, CR Gilbert, CH Hocutt, RE Jenkins, DE McAllister & JR Stauffer, Jr. (1980): Atlas of North American freshwater fishes. North Carolina State Museum of Natural History, Raleigh, NC. 1-854.
  2. ↑ Mayden, RL (ed.) (1992): Systematics, historical ecology, and North American freshwater fishes. Stanford University Press, Stanford, CA.
  3. ↑ a b Ornelas-García, CP, Domínguez-Domínguez, O. & Doadrio, I. (2008): Evolutionary history of the fish genus Astyanax Baird Girard (1854) (Actinopterygii, Characidae) in Mesoamerica reveals multiple morphological homoplasies. BMC Evol. Biol. , 8 (2008): 340
  4. ^ Strecker, U., B. Hausdorf & H. Wilkens (2011): Parallel speciation in Astyanax cave fish (Teleostei) in Northern Mexico. Molecular phylogenetics and evolution , doi : 10.1016 / j.ympev.2011.09.005 .
  5. ↑ Yamamoto, Y. & WR Jeffery (2000): Central Role for the Lens in Cave Fish Eye Degeneration. Science , 289 (5479): 631-633. doi : 10.1126 / science.289.5479.631 .

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