Jawless Fish & Cartilaginous Fish
I.
Jawless Fish (Class: Agnatha)
o Lack jaws
o Feed by suction with the aid of a round,
muscular mouth and rows of teeth
o Elongated body
o Lack paired fins and scales
o Evolved from vertebrates
Examples:
- Sea Lampreys & Hagfish
II. Cartilaginous Fish (Class:
Chondrichthyes)
o Skelton made of cartilage – lighter and
more flexible
o Do NOT possess an operculum
o Possess movable jaws
o Rough skin covered by placoid scales
Examples:
- Sharks, Skates, & Rays
A. Sharks
 350 species (50 to be known to be
dangerous to humans)
 most famous of all dangerous marine
organisms
 caudal fin is well developed and
muscular
 upper surface of the body features two
dorsal fins, the 1st which is larger
 paired pectoral fins are large and
pointed
 tiny pores in the snout contain nerve
receptors called Ampullae of Lorenzi
that can pick up electric currents give
off by the muscles of organisms
 5-7 gills slits on each side of the body
(most sharks need to be in constant
motion to breath OR die)
 Counter shadowing – dark dorsally &
light ventrally
 Male sharks have claspers located on
the inner edge of the pelvic fins (this
structure aids in reproduction)
 sharks can detect a drop of blood over
½ mile away
 no eyelids – eyes roll back when they
open their jaws
 no swim bladder – as a result sharks
must continuously swim or sink
 attracted by:
i. low-frequency vibrations
ii. blood
iii. light colored clothing
SHARK FACTS:
- greatest chance of attack - Australia
- Feeding Frenzy – uncontrollable violent
feeding response
- Size Range: 6” (Dwarf Shark) – 60’
(Whale Shark)
- Basking & Whale Sharks feed on
plankton
- attack in spirals or zig-zag patterns
- 50-80% of all shark victims die from
loss of blood and shock
B. Rays & Skates
 approximately 300 species
 flattened bodies
 have their gill slits (5 pairs) on the
underside of the body
 pectoral fins are flat and look like
wings
 eyes on top of their head
 demersal
Stingrays:
- have a whip-like tail usually equipped
with stinging spines
Skates:
- similar to rays but NO whip-like tail or
stinging cells