Sienna Navarro 9B
 Meaning
• It comes from the Greek words
chondr and ichthyes = cartilaginous fish
cartilage
fish
 First
Fossil
• Comes from the early Devonian age
• 416 million years ago
 Elasmobranches: Cladoselache
 Number
of Species
• 934 species:
 383 species of sharks
 516 species of rays
• 35 species of chimaeras
 Characteristics
• Endoskeleton entirely cartilaginous
• Tough skin covered in dermal denticles
• No Swim Bladder
• Two chambered heart
• Acute senses
• Sharks shed and replace teeth
 Life
Cycle & Expectancy
• Average life expectancy: 20-50 years
• Longest living species: whale shark 100-150 years
• 3 types of embryonic development:
 Oviparous: “egg birth”
 Ovoviviparous: “live egg birth”
 Viviparous: “live birth”
 Oviparous-
“egg birth”
• Female shark deposits eggs cases in sea
• Developing embryo receives nutrients from a yolk
formed prior to fertilization
 Ovoviparous-
“live egg birth”
• Female retains membrane covered eggs
• Embryo sheds membrane  develops in uterus
 Some species receive nutrients from direct lining
 Other species the embryo obtains nutrients by
swallowing eggs / other embryos
 Viviparous-
“live birth”
• Embryo and attached yolk grow in uterus
• Outside layer of yolk contacts mother’s uterus
• Receives nutrients
 Digestive
System
• Swallow food whole or in large pieces
• Strong acids and enzymes used to dissolve food
 Creates liquid mush
 Nutrients absorbed in intestine
• Indigestible things are vomited
 Respiratory
System
• Species breathe through 5-7 gills
• Pelagic fish must continue swimming to keep
oxygenated water moving though their gills
• Demersal fish pump water in through spiracles; out
through gills
 Circulatory
System
• Closed circulatory system
• Two chambered heart:
 Atrium
 Ventricle
• Atrium pumps blood to ventricle
• Venticle pumps blood to conus
• Blood travels from conus to gills
• Oxygenated blood flows through
body
• Blood returns to atrium

Sensory System
• One inner ear
 Detects sound, acceleration, gravity
• Lateral line
• Eye sight
 Sensitive to light and moving objects
• Smell
 Very acute
 Not connected with the mouth
 Barbels: responsive to chemical movement

Meaning:
 It translates to “no jaws”

Number of Species
• 84 species
• Lampreys
• Hagfish

First Fossil
• Appeared during Cambrian period:
• 524 million years ago
• Myllokunmingia
 Characteristics
• Jaws are absent
• No appendages
• 7+ “gill” pouches
• The digestive system lacks a stomach
• Cartilaginous skeleton
• Two chambered hearts
• Slender, eel-shaped body
• Notochord persists in adults
 Provides support
 Lamprey:
Life Cycle & Expectancy
 Eggs hatch - become larvae
 Larvae live in river mud from 3-10+ years
 Feed off of decaying organisms and fecal matter
 Metamorphic Phase(3-4m) / Migrate to sea (12-20m)
 Develop teeth on sucking disks
 Spawning Phase (3m) / Death
 Lay eggs
 Die within the month spawning
 Lamprey:
Digestive System
• Attack prey
• Attach mouth to prey’s body
• Cut through the skin and scales
• Food = fish blood
• Mouth  Pharynx  Esophagus
• Esophagus directly to intestine (nutrients absorbed)
• Waste released through anus
• Dual immune defense system
 Hagfish: Life Cycle & Expectancy
 Little is knows of hagfish life span
• Born fully developed
• Hermaphroditic
• Choose sex during mating season (can alternate)
• Females lay small number of eggs for their size
• Live in numbers as large as 15,000
 Hagfish:
Diet & Digestive System
• Scavenger
• Eats dead animals
 Devours from inside out
 Absorb nutrients through their skin and gills
 Mouth is designed to tear flesh
• Slow metabolism
• Can survive months between feedings
• Food is enclosed in permeable membrane
• Waste is excreted
 Respiratory
System

Cutaneous Respiration

Diffusion
• Dissolved oxygen diffuses into blood
• Carbon dioxide diffuses out
 Sensory
System
• 10 cranial nerves
• No external ears
• No eyelids
• Hagfish:
 Poor vision
 Releases slimy mucus when in danger
 Lateral line system (sense water currents/vibrations)
• Lamprey:
 Lateral line system
 Medial nostril (“smell” perceiving chemicals in water)
 Pineal organ (perceives light/dark)