Astyanax jordani

Astyanax jordani the blind Höhlensalmler

Astyanax jordani is a blind Höhlensalmler from the family of the Real tetras ( Characidae ). He is one of possibly only two eyeless species of Astyanax fasciatus - group. He is a freshwater fish of up to 10 cm in length.

Name and identity

Originally the species was described as Anoptichthys Jordanian, for a time but then regarded only as a blind cave form of aboveground occurring type Astyanax mexicanus, which in turn was partly considered as subspecies of A. fasciatus mexicanus. Sometimes the status of the blind cave form was also accepted as a subspecies (A. mexicanus jordani ). Even in today's times with genetic testing options, there are several views, according to Ornelas - García et al. (2008), the predominantly mitochondrial DNA, but also a single nuclear gene have analyzed, we have to deal with the blind Höhlensalmlern with two types. The Panuco Tuxpan forms are assigned by the authors A. jordani ( this includes also the taxon Anoptichthys antrobius Álvarez, 1946 from the cave El Pachon ) and the second type, which summarizes the Sabinos - Aguanaval - Mezquital forms, they expect A. hubbsi to. Strecker et al. (2011 ) analyzed in addition to mitochondrial DNA and microsatellite loci and came to the conclusion that the Mexican cave forms represent only one type that needs to A. jordani hot. In contrast, also found Dowling et al. (2002 ) found that the formation of cave forms must be repeatedly done independently.

Dissemination

The species is known from subterranean waters of forested mountainous areas in southeastern San Luis Potosi in Mexico, such as the Chica Cave, Cave Molino and Pachon Cave. Adding to the area of ​​distribution of the taxon A. hubbsi added, the distribution extended to the area of ​​the caves Sabinos, Aguanaval and Mezquital.

Features

Typical Salmlergestalt. As with most cave fish, the pigments can be almost completely formed at A. jordani, making the animals appear white. By living in the lightless waters, the eyes have completely receded in these tetras. However, not all completely lightless caves, so there is gradual increments in the expression of pigment and eye reduction. Tetra from the caves Sabinos, Tinaja Pachón and Yerbaniz are entirely white and have greatly atrophied eyes. Fish from Caballo Moro, the caves Chica and Micos show a variable reduction of pigments and eyes.