HAGFISH (Eptatretus
cirrhatus)
Synonymy: Tuere, napia, blind eel
Hagfish
are one of the most primitive living fish, with an ancestry
stretching back over 350 million years. They consequently have
no bones, jaw, scales or paired fins and a simple paddle-like
tail, which proves to be rather an inefficient form of propulsion.
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They also have degenerate eyes, which are completely covered
by skin and a vestigial third eye, which can be marked on
the top of the head by a white patch. |
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They
have a single nostril which draws water in and across the gills
then out through external gill openings. This water current
moves through the same pharangeal cavity as the hagfish’s
food does on its way to being digested. (see below left)
Hagfish can feed on invertebrates such as worms and crabs, in
addition to scavenging on dead and dying fish which they locate
with their six sensory barbels. Their mouthparts take the form
of two horny plates and a protrusible tongue-like structure,
which they use to drag flesh into their mouth. (see above right)
The reproduction of hagfish is still poorly understood but it
is thought that some species may be sequentially hermaphroditic
(change from one sex to another at a particular point in their
life cycle), even though it is almost impossible to differentiate
between the sexes. Other species overseas lay horny capsules,
which have sticky mucoid threads at each end to help them to
adhere to rocks and debris, and from these capsules small fully
formed hagfish hatch.
Hagfish have the ability to exude huge volumes of mucous as
a defensive mechanism. This mucous production is usually just
enough to act as a protective barrier for the skin, but if a
hagfish is disturbed by a potential predator, it will squirt
enormous quantities of it from glands near the stomach outwards
for several feet. This relatively huge volume of (revolting!)
mucous compared with the size of the fish itself is achieved
by the tightly coiled mucous ‘straightening out’
on contact with saltwater.
Did
you know?
New Zealand’s hagfish is one of the largest in the world
and grows up to one metre in length. Consequently scientists
travel from all over the world to study this evolutionarily
fascinating animal.
