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The
Diversity of The World of Life
Chordates
(Chordata)
Hagfish
(Hyperotreti)
Representative
Hagfish
Biology
ENVIRONMENTS
Hagfish
are marine species, living in cold seawater.
DESCRIPTION
The streamlined, eel-like body of hagfish bears slimy,
scale-less, typically pinkish skin; no paired side fins; many gill slits; and
a jawless
mouth surrounded by four small tentacles and enclosing a tongue-like organ
with two pairs of rasping, pinching teeth. The body has a
"notochord" (a spine of rubbery cartilage, not bone) with a
partial "cranium" (skull, although with no true brain inside)
but no vertebrae: Hagfish are, thus, "craniate chordates"
but not true vertebrates (Compare lampreys,
with which they were previously grouped).
FEEDING HABITS
Hagfish typically
prey on live invertebrates, particularly segmented
worms; but they may scavenge on dead or dying fish. With their
slow metabolism, hagfish may not feed for many months at a time.
CIRCULATION
Hagfish
have three "accessory hearts".
COORDINATION
Hagfish
have no true brain. Their sense of sight is very poor; their senses
of touch (as via the oral tentacles) and smell, very good.
REPRODUCTION
The
egg of a hagfish is large (up to an inch long) and within a tough
shell. The female lays relatively few of these eggs. Unlike
most fish, hagfish have no "larvae": The hatchlings look
like small adults. Young hagfish are "hermaphrodites"
(with both male and female sex organs); older hagfish are either male or
female, although they may change from one sex to the other!
Chordates
(Chordata)
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