Blind Cave Form
A. mexicanus is famous for its blind cave form, which is known by such names as blind cave tetra, blind tetra, and blind cavefish. Some thirty distinct populations of Mexican tetras live in deep caves and have lost the power of sight and even their eyes. These fish can still, however, find their way around by means of their lateral lines, which are highly sensitive to fluctuating water pressure.
The eyed and eyeless forms of A. mexicanus, being members of the same species, are closely related and can interbreed. Astyanax jordani, however, is another blind cave fish, independently and recently evolved from the sighted surface form, which is sometimes confused with the cave form of A. mexicanus. However, when born, the cave dwelling form of A. mexicanus has eyes. As they grow older, skin just grows over them and the eyes degenerate completely, because there is no need for sight in the pitch-black world of a cave.
Read more about this topic: Mexican Tetra
Famous quotes containing the words blind, cave and/or form:
“For as the body grows old, so the wits grow old and become blind towards all things alike.”
—Herodotus (c. 484424 B.C.)
“In such an armor he may rise and raid
The dark cave after midnight, unafraid....”
—Gwendolyn Brooks (b. 1917)
“The Divine Vision still was seen,
Still was the human form divine
Weeping in weak & mortal clay;
O Jesus, still the form was thine!”
—William Blake (17571827)