Phylum Chordata
4/12/07
HW: Study These Notes.
General characteristics
1. bilaterally
symmetrical,
deutersostomate
animals
– an
animal whose mouth
develops from cells
other than those at
the opening of the
gastrula.
 deuterostome
General characteristics, cont’d
 4 unique characteristics present at
some stage in development:
 Notochord
 Pharyngeal
Slits
 Dorsal Tubular Nerve Cord
 Postanal Tail
Notochord
 The notochord is:
a
supportive rod that extends most of the
length of the animal dorsal to the body
cavity and into the tail
Notochord on
developing
zebrafish.
Pharyngeal Slits
 Pharyngeal Slits:
a
series of openings in the pharyngeal
region between the digestive tract and the
outside of the body
Dorsal Tubular Nerve Cord
 Dorsal Tubular
Nerve Cord:

runs along the
longitudinal axis of
the body, just dorsal
to the notochord, and
usually extends
anteriorly as a brain
Postanal Tail
 The postanal tail:
 extends
opening
posteriorly beyond the anal
Examples of Chordates
1. sea squints (or tunicates)
2. amphioxus
3. lampreys
4. hagfish
5. sharks, rays, skates
6. bony fishes
7. frogs, toads, salamanders
8. alligators, snakes, lizards
9. birds
10. mammals
Dogfish Shark
 The representative member of the phylum
Chordata we will begin with is the spiny dogfish
shark, Squalus acanthias.
phylum Chordata (having general characteristics
listed above)
 subphylum Vertebrata (having backbone)
 class Chondrichthyes (skeleton made of
cartilage)
 subclass Elasmobranchii
The spiny dogfish shark, Squalus
acanthias.
a.k.a piked dogfish, skittledog, spotted dogfish,
white-spotted dogfish, codshark, and thorndog
Dogfish Anatomy
Habitat
 Worldwide distribution, from the
temperate to the subpolar regions, from
the shallow waters of the seashore to
depths of 100 fathoms (600 feet)
Niche
 They are voracious eaters, feeding on:
 fish
 Crustaceans
 Squid
 Gastropods
 jelly fish
 even red and brown algae.
 omnivorous – devouring both plant and
animal matter
Life Span
 Typically from 25-30 years.
Reproduction
 Internal fertilization; most shark “pups”
hatch internally, and continue their
development within the uterus of the
mother
 Ovoviviparous – born alive as much
smaller versions of the adult
 Gestation period up to 2 years (the
longest of any vertebrate)
Adaptations
 Sharks do not drink water?! The
regulate their osmotic pressure by
retaining a high concentration of urea
and other solutes in their body fluids.
Water enters their cells by osmosis.
Adaptations, Cont’d
 The lack a swim bladder as seen in most
bony fish.


The above 2 facts are responsible for the following
interesting fact. Sharks must keep moving in
order to survive. If they stop moving they sink
because they are somewhat heavier than the
water they displace. If stopped, they sink, and will
be crushed by the water pressure of the deep
ocean. Sharks of the deeper ocean must continue
to move from the moment of birth to the moment
of death!
That’s why they eat so much!!