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:
“O never give the heart outright,
For they, for all smooth lips can say,
Have given their hearts up to the play.
And who could play it well enough
If deaf and dumb and blind with love?”
—William Butler Yeats (1865–1939)
“If the sea were ink
For the words of my Lord,
the sea would be spent before the Words of my Lord are spent.”
—Qur’An. The Cave 18:109, ed. Arthur J. Arberry (1955)
“and so this tree—
Oh, that such our death may be!—
Died in sleep, and felt no pain,
To live in happier form again:
From which, beneath Heaven’s fairest star,
The artist wrought this loved guitar;”
—Percy Bysshe Shelley (1792–1822)