Transcript I Agnatha PPT

Vertebrate Zoology
Agnatha
Hagfish
& Lamprey
Key Features
o
Jaws are absent.
o
Paired fins are generally absent.
o
Early species had heavy bony scales
and plates in their skin
Key features con’t

In most cases the skeleton is cartilaginous. The
embryonic notochord persists in the adult.

Seven or more paired gill pouches are present.

Hagfish sheds slime layer
Key features con’t



A light-sensitive pineal eye is
present.
The digestive system lacks a
stomach.
External fertilization; both ovaries and
testes present in individual but gonads of
only one sex functional in hagfishes, no
larval stage; separate sexes and a long
larval stage in lampreys.
Jawless, bony plated
Ostracoderm fish
Ordovocian Period
505 mya Paleozoic
Scavengers/
filter feeders
Lamprey Classification
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Cephalaspidomorphi
Order Petromyzontiformes
Family Petromyzontidae
Lamprey Structure
Structure
Round,
suckerlike
jawless mouth filled
with rows of hornlike teeth.
Internal ring of
cartilage supports
rim of mouth.
Single nostril on
dorsal side of the
head.
Skeleton doesn’t
exist, only cartilage.
Lamprey Digestion
Digestion
Pierces
flesh of
prey with numerous
small horn-like
teeth.
Tongue creates
suction and tongue
draws back body
fluids.
Rasp into the flesh
and feed on body
fluids.
Lampreys
mouth
I luv you
External
Fertilization
Hagfish Classification
•
•
•
•
•
•
•
Kingdom Animalia
Phylum Chordata
Class Pteraspidomorphi
Order Myxiniformes
Family Myxinidae
Genus Myxine
Species glutinosa
Slime Glands
Hagfish secrete
slime when disturbed
Hagfish Structure
Structure
Body
supported by
heavy cartilage.
91 cm. Long
Continuous fin
extending upper and
lower body.
No bone structure
Mucous producing
pores along body
length.
Hagfish



Hagfish can be found in chilly waters
They tend to live on and in muddy sea floors in
very dense groups (up to 15,000 in an area).
Because females tend to produce large eggs in
small numbers, their population sizes suggest a low
death rate.
Hagfish
•
Diet is made up of marine worms and other
invertebrates; dead and dying sea life (eats them
from the inside out).
•
They have a ring of short sensitive tentacles around
their mouths.
•
Large slime glands line their sides along the length
of their bodies.
•
Can sneeze to clear slime from nostrils
No jaws. Instead they have two pairs of
rasps on top of a tongue. They pull meat
into their mouths with the tongue, then
tear it off the prey with the rasps.
Hagfish
have a very low metabolism. Once
they eat, they may not have to again for up
to seven months.
Although
hagfish have a partial skull, they
have no back bone, so are not true
vertebrates. What skeleton they do have is
made of cartilage.
Hagfish Anatomy