The Mexican tetra (Astyanax mexicanus) is a blind, freshwater cave fish native to central and eastern parts of Mexico. Growing to a maximum total length of 12 cm (4.7 in), this species is notable for having no eyes or pigment; it has a pinkish-white color to its body (resembling an albino).

The Mexican tetra spends most of its time in midlevel water above the rocky and sandy bottoms of pools and backwaters of creeks and rivers of its native environment. Coming from a subtropical climate, it prefers water with 6.5–8 pH and a temperature range of 20 to 25 °C (68 to 77 °F). In the winter, some populations migrates to warmer waters. Its natural diet consists of crustaceans, insects, and annelids.

Given their peaceful nature, this species is popu ...

Teenagers are known for making impulsive choices and decisions. Studies of the adult brain show that risk-taking among teenagers can be narrowed down to the "feel-good" hormone dopamine. Dopamine is a neurotransmitter that helps control the brain's reward and pleasure centers, as well as helping to regulate movement and emotional responses, see rewards and take action to move toward them.

When it comes to adolescents, neurons sensitive to dopamine are activated less when looking at the prospect of a reward compared to adults. Tests conducted on rats show that adult rats appear to obtain a small dopamine rush from simply anticipating a reward, while adolescent rats do not exhibit the same level of dopamine-based satisfaction. In terms of hum ...