Transcript Class Chondrichthyes - Valhalla High School

Class Chondrichthyes
“Cartilage Fish”
Class Chondrichthyes
• Two sub-classes
– Elasmobranchii
• Sharks
• Rays
• Skates
– Holocephali
• Rat fish
• Rabbit fish
• Parrot fish
Class Chondrichthyes
• Most are marine
• Most are active predators
– Few plankton eaters
(whale & basking sharks)
Relationship to Humans
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Used for food
Liver oil
Clothing
Jewelry
Competition
fishing
Characteristics
• Paired Fins
• Tough placoid scales:
“placoderms”
– Provide protection
– Aid in streamlining
– Some species secrete
mucous
Characteristics
• Powerful jaws, multiple rows
of replaceable teeth
– Great white bites with force
greater than a shot from 30-06
rifle
• Mouth is ventral
• Heterocercal tail – unequally
divided
Characteristics
• Skeleton – cartilaginous, with no true
bones
– Notochord present in young
– No ribs – larger species die when taken from
water due to body weight on organs
• 2 chambered heart (atrium & ventricle)
– Closed circulatory
– Heart is ventral, in head region
– Blood pumped through aorta to gills, then to
body tissues, back to heart through veins
Characteristics
• Cold blooded – “poikilothermic” – internal
body temp. can have wide range
– Body temp matches the environment
• Reproduction
– Dioecious, with internal fertilization
– Dogfish & rays are oviparous
– Most species are viviparous
Characteristics
• Wide range of sizes
– Dogfish= 3ft
– Great white= 20 ft
– Basking shark= 40 ft
– Whale shark= 45+ft
(largest fish)
Characteristics
• Nervous system: well
developed brain
– Olfactory – 2 nostrils for
taste/smell
– Optic – well developed
eyesight
– Auditory – Ears inside body,
well developed; works with…
– Lateral line – sensory openings
along length of body, pick up
low frequency vibrations
Characteristics
• Nervous system cont…
– Electromagnetic receptors=
“ampullae of lorenzini”
• Detects electric currents given
off by any living thing
• May help orient animal to
earths electromagnetic field
Characteristics
• Respiration
– 5-7 gill pairs
– Most species have spiracles just behind
eyes
• Provide direct oxygen supply to eyes