Chapter 39Fish

Section 2

Jawless and Cartilaginous Fish

Fish Adaptations• Stream-lined body & muscular tail• Paired-fins allow fish to manuver • Secrete mucus around body to help

move in water and protect against infections

• Store lipids (fat) to help aid in buoyancy • Use gills for gas exchange

Homeostasis• Freshwater fish = hypertonic

(higher concentration of solutes than the surrounding water- gain water)

• Saltwater fish = hypotonic (contain lower concentrations of solutes than their surroundings- lose water)

Sensory Functions• Fish can sense light, chemicals, &

sound

• Some can sense electrical & magnetic fields

• Many fish can see in color, but most cartilaginous fish can not see in color

Sensory Functions• Chemoreception- ability to detect

chemicals in the environment

• Sharks have great sense of smell & taste

• Barbels- whisker-like organs near mouth

Barbels

Sensory Functions• Lateral line- allows fish to sense

vibration in the water

• Cartilagenous fish (sharks & rays)- ampullae of Lorenzini- detect weak electrical fields- help locate prey

Lateral Line

ampullae of Lorenzini

Jawless Fishes• Hagfish & lamprey

• Have an eel-like body, cartilaginous skeleton, and unpaired fins

• Hagfish live in oceans

• Lampreys live in freshwater

Hagfishes• Bottom-dwellers in cold marine water, no

jaws

• Isotonic- same ion concentration as sea water

• Feed on small invertebrates or dead & dying fish

• Burrow in dead fish & consume internal organs

Hagfish

Lampreys• ½ parasites, ½ free-living

• Attaches to host with disk-shaped mouth

• After feeding, lampreys drop off & host may recover, bleed to death, or die from infection

• Fertilization occurs outside body (external fertilization)

Lamprey

Cartilaginous Fish• Class Chondrichthyes

• Sharks, skates, rays, & ratfish

• Cartilage- flexible, lightweight material made of cells surrounded by tough fibers of protein

• Skin is covered with placoid scales- feels like sandpaper

Sharks• Whale shark- largest shark (60

feet)

• Feed on plankton & floating plants & animals

• Filter water using gill rakers

• 6 to 20 rows of teeth that point inward

Whale Shark

Sharks• One shark uses 20,000 teeth in a

lifetime

• Each tooth is shaped based-on diet

Great White Shark

Hammer Head Shark

Black-tip Reef Shark

Bull Shark

Lemon Shark

Tiger Shark

Rays & Skates• Flatten-bodies with wing-like

pectoral fins and whip-like tails

• Rays have diamond or disk-shaped bodies

• Skates have triangular bodies

• Bottom-dwellers

• Feed on crustaceans

Rays

Skates

Ratfishes• Deep-water

• Have gill slits covered by a flap of skin

• Some have a rat-like tail

• Feed on crustaceans or mollusks

Ratfish

Adaptions• Gas exchange in gills

• Some sharks need to constantly move in order for gas exchange to occur

• Rays usually take in water from ventral side, but when on bottom, they use spiracles located behind eye to draw in water

Adaptations• Sharks have an oil in their liver

called squalene oil that contributes to their buoyancy

• Convert ammonia to urea which is a less toxic waste

Reproduction• Internal fertilization- male

transfers sperm to female’s body

• No cartilaginous fish provides parental care once young are born

REVIEW!!!• Identify three characteristics of fish that

makes them well suited to aquatic life.• Contrast the feeding behavior of

hagfish to the feeding behavior of lampreys.

• Identify the advantages of internal fertilization vs. external fertilization.