1. Section 30.1 Summary – pages 793-802
Fishes breathe using gills
As a fish takes water in through its mouth, water passes over the gills and then out through slits at the side of the fish.
Gill Filaments
Capillary networks
in filament
Water
Gill
filaments
Artery
Vein
Water
Section 30.1 Summary – pages

2. Section 30.1 Summary – pages 793-802
Fishes breathe using gills
Oxygen and carbon dioxide are exchanged through the capillaries in the gill filaments.
Gill Filaments
Capillary networks
in filament
Water
Gill
filaments
Artery
Vein
Water
Section 30.1 Summary – pages

3. Section 30.1 Summary – pages 793-802
Fishes have two-chambered hearts
Aorta
Capillary
network
Gills
Heart
Section 30.1 Summary – pages

4. Section 30.1 Summary – pages 793-802
Fishes reproduce sexually
Although the method may vary, all fishes reproduce sexually.
Fertilization and development is external in most fishes.
Eggs and sperm can be released directly into the water, or deposited in more protected areas, such as on floating aquatic plants.
Section 30.1 Summary – pages

5. Section 30.1 Summary – pages 793-802
Most fishes have paired fins
Fishes in the classes Chondrichthyes and Osteichthyes have paired fins.
Fins are fan-shaped membranes that are used for balance, swimming, and steering.
Section 30.1 Summary – pages

6. Section 30.1 Summary – pages 793-802
Most fishes have paired fins
The paired fins of fishes foreshadowed the development of limbs for movement on land and ultimately of wings for flying.
Dorsal
fins
Pectoral
fin
Anal
fin
Caudal
fin
Pelvic
fins
Section 30.1 Summary – pages

7. Section 30.1 Summary – pages 793-802
Fishes have developed sensory systems
The lateral line system is a line of fluid-filled canals running along the sides of a fish that enable it to detect movement and vibrations in the water.
Lateral line
Gelatin-like fluid
Receptor cells
Nerve
Section 30.1 Summary – pages

8. Section 30.1 Summary – pages 793-802
Most fishes have scales
Scales are thin bony plates formed from the skin.
Scales can be toothlike, diamond-shaped, cone-shaped, or round. Shark scales are similar to teeth found in other vertebrates.
Section 30.1 Summary – pages

9. Types of Scales
Cycloid Scales: have a smooth outer edge, and are most common on fish with soft fin rays, such as salmon
Ctenoid Scales: have a toothed outer edge, and are usually found on fish with spiny fin rays, such as bass and crappie
Placoid Scales: are found on cartilaginous fish including sharks.
Ganoid Scales: can be found on Gars. They have a diamond-shaped, shiny, and hard scale.

10. Section 30.1 Summary – pages 793-802
A Bony Fish
Lateral line system
Swim bladder
Kidney
Scales
Urinary bladder
Reproductive organ
Fins
Stomach
Intestine
Liver
Heart
Gills
Section 30.1 Summary – pages

11. Jawless Fish The only existing Jawless fish are hagfishes and lamprey
Jawless fish’s skin has neither plates nor scales
The bodies of hagfish and lamprey are eel-like, have a cartilaginous skeleton, unpaired fins, and the notochord remains throughout their lifetime

12. Key Features - Paired fins are generally absent.
- No jaws. Instead they have two pairs of rasps on top of a tongue. They pull meat into their mouths with the tongue, then tear it off the prey with the rasps.
- Paired fins are generally absent.
- Early species had heavy bony scales and plates in their skin

13. Key features con’t
In most cases the skeleton is cartilaginous. The embryonic notochord persists in the adult.
Seven or more paired gill pouches are present.
Hagfish sheds slime layer

14. Key features con’t A light-sensitive pineal eye is present.
The digestive system lacks a stomach.
External fertilization; both ovaries and testes present in individual but gonads of only one sex functional in hagfishes, no larval stage; separate sexes and a long larval stage in lampreys.

15. Lampreys
About half of adult lampreys are non-parasitic, and the other half are parasites that feed on the blood and body fluids of other fish
Lampreys use their disk-shaped mouths to attach to its host
It then scrapes a hole in the host’s body with its rough tongue and secretes a chemical that keeps the host’s blood from clotting
Once it is done feeding it drops off the host and the host may recover, bleed to death, or die from infection
Lampreys can live in salt and fresh water, but all lampreys breed in fresh water
Reproduction takes place in the form of external fertilization

18. Hagfishes
They are bottom dwellers that live only in cold marine waters
Hagfish do not have vertebrae
Hagfish are isotonic
This means their body fluids have the same ion concentration as sea water
Hagfish feed on small invertebrates and dead and dying fish
Within its mouth are two moveable plates and a rough tonguelike structure it uses to pinch off chunks of flesh
Since they lack fins they often borrow into the body of a dead fish and once inside they will eat their internal organs

19. Hagfish Hagfish can be found in chilly waters
They tend to live on and in muddy sea floors in very dense groups (up to 15,000 in an area).
Because females tend to produce large eggs in small numbers, their population sizes suggest a low death rate.

20. Hagfish Diet is made up of marine worms and other invertebrates
They have a ring of short sensitive tentacles around their mouths.
Large slime glands line their sides along the length of their bodies.
Can sneeze to clear slime from nostrils

21. Hagfish have a very low metabolism
Hagfish have a very low metabolism. Once they eat, they may not have to again for up to seven months.
Although hagfish have a partial skull, they have no back bone, so are not true vertebrates. What skeleton they do have is made of cartilage.

22. Cartilaginous Fishes Made up of sharks, skates, and rays
The fish in this class have skeleton composed of cartilage, which is a flexible lightweight material made of cells surrounded by tough fibers of protein
Unlike jawless fish, they have movable jaws, skeletons, and paired fins
Most live in saltwater and are carnivores
Some cartilaginous fishes are also scavengers
The skin of cartilaginous fishes is covered in placoid scales
They are small toothlike spines that feel like sand paper
They are thought to reduce turbulence of the water flow and thus increase swimming efficiency

23. Sharks The mouth of a typical shark has 6 to 20 rows of teeth
When a tooth breaks or wears down a replacement tooth moves forward to take its place
Sharks may use up to 20,000 teeth over its lifetime
The structure of each species’ teeth has been adapted to that species’ feeding habits
Example: Sharks that eat large fish or mammals have big, triangular teeth with sawlike edges that hook and tear flesh

24. Adaptations of Cartilaginous Fishes
Gas exchange: occurs in the gills, which lie behind the head
Fast-swimming sharks push water through their mouths, over their gills, and out their gill slits by swimming
Most cartilaginous fish pump water out of their gills by expanding and contracting their mouth cavity and pharynx
Rays and skates draw water through their spiracles, which are two large openings on the top of their head behind their eyes

25. Adaptations of Cartilaginous Fishes
Elimination of Waste: Instead of releasing ammonia cartilaginous fishes use energy to convert ammonia into a compound called urea
Sharks retains large amounts of urea in their blood and tissues, which raises the concentration of solutes in their body to the same level of that found in water
The concentration of sodium and chloride in a shark’s body is less than the concentration found in sea water, therefore these ions diffuse into the body across the gills and are absorbed with food
The rectal gland removes excess sodium and chloride ions from the blood and releases them to the rectum for elimination

26. Adaptations of Cartilaginous Fishes
Cartilaginous fishes maintain their position in the water in two ways:
1. The caudal and pectoral fins generate lift as the fish swims and it can remain at the same level in the water as long as it keeps moving
2. The storing of large amounts of low-density lipids in their livers. The lipids give sharks buoyancy by reducing the overall density of the body

27. Chondrichthyes Reproduction
oviparous (laying eggs that hatch outside the mother's body)
ovoviviparous (brooding eggs that hatch within the mother's body, and then releasing the young)
viviparous (young develop within a uterus inside the mother's body, and are nourished prior to birth via a connection with the mother's bloodstream (placenta).

28. Reproduction in Cartilaginous Fishes
Fertilization occurs inside the female’s body (Internal Fertilization)
Internal Fertilization occurs when the male transfers sperms into the female using modified pelvic fins called claspers
Young are born in three ways
1. After fertilization the female lays large yolky eggs
2. The eggs develop inside the females body and the young are born alive
3. The mother nourishes the developing sharks while they are in her body
No cartilaginous fish provide parental care for their young after they are born or hatched

29. Mermaid Purses?
Shark egg sacs