Mexican tetra

Astyanax mexicanus

Astyanax mexicanus is an originally living in Texas and New Mexico, and in Northern and Central Mexico freshwater fish of the family of the Real tetras ( Characidae ). The shoal fish are about ten to twelve inches tall.

Name

Originally the species was described as Tetragonopterus mexicanus from around Mexico. Later, the fish were only considered as a subspecies Astyanax fasciatus mexicanus, but then again. , Not only as a distinct species, but even as Artkomplex, which seems confirmed by recent genetic studies

Features

It is mainly silvery colored fish of typical Salmlergestalt, only the fat and caudal fins are yellowish in color, the latter centrally interrupted by a black line, which can extend up to the gill cover, very good but can be seen on the caudal fin and the caudal peduncle is. After, breast and pelvic fins may be slightly tinted red. The dorsal fin is colorless transparent.

The tetras are despite their moderate size as aggressive and as they feed also prey on juvenile fish of other species, they are viewed in the U.S. as problematic, especially since they were kidnapped there in different waters ( presumably as a supernumerary bait fish). Meanwhile, they are also native to other states (eg, Arizona, California, Louisiana, Oklahoma and Ohio).

Cave shapes

According to recent studies it seems to be in the so-called cave forms a unique species to act at least as they are genetically different. Although Yamamoto & Jeffery (2000) were able to show that also form at Höhlensalmler embryos initially eyes, but destroyed later in development, because a gene called pax6 is disabled. Was administered to the embryos of living on the surface Astyanax mexicanus a protein called Sonic Hedgehog, they formed from smaller retinas and almost no eye lenses. Conversely, when the embryo of Höhlensalmler ( Astyanax jordani ) were administered a chemical that inhibits the Sonic hedgehog protein, these fish were greater by almost a third lens train as normal. However, no surface fish could be created from a Höhlensalmler by mere transfer protein in the embryonic stage, a further indication that A. mexicanus a different type than the Höhlensalmler (A. jordani ).