The Fishes

Vertebrate Success In Water

Cool Facts About Fish First animal to have a skull to

protect their brain. 41% of all fishes are freshwater

even though only less than 0.01% of the earth’s water is freshwater.

It is estimated that there may still be over 15,000 fish species that have not yet been identified.

The largest fish is the great whale shark which can reach fifty feet in length.

The smallest fish is the Philippine goby that is less than 1/3 of an inch when fully grown.

Fish have excellent senses of sight, touch, taste and many possess a good sense of smell and 'hearing'.

Fish feel pain and suffer stress just like mammals and birds.

Approximatelyhow long agodid the firsttrue vertebrateappear?

About 510 million years ago, during the Cambrian Period.

The 3 Classes

1. Agnatha- lack jaws and paired appendages; ex. lampreys & hagfish

2. Chondrichthyes – cartilaginous fish; ex. sharks

3. Osteichthyes – bony fish; beta fish, salmon, trout, tuna, bass, goldfish, guppies, etc.

Class Agnatha Lack jaws. Lack paired appendages. Have a cartilaginous skeleton. Have a notochord that

persists into adulthood. Ostracoderms are extinct

agnathans that had bony armor for protection. They were bottom dwelling, filter feeders, about 1 foot long.

Today’s agnathans are hagfish and lampreys.

Class Agnatha: Hagfish Most primitive of all fish. Hagfish are almost blind, but have well

developed senses of touch and smell. Hagfish live buried in the sand and mud of

marine environments. They feed on soft-bodied invertebrates and

scavenge dead and dying fish. When the hagfish finds a suitable fish, they enter through the mouth and eat the contents of the body, leaving only a sack of skin and bones.

Their metabolism is so slow that they can go up to 7 months without food.

Have 3 hearts. Secrete a thick, slimy mucous, and will even

sneeze when the mucous clogs their nostrils.

http://www.metacafe.com/watch/1597296/hagfish_and_the_disgusting_slime/

Class Agnatha: Lamprey Common in both marine and

freshwater environments. An adult lamprey has a circular

mouth, called an oral disc, that exerts strong suction. Teeth are located on the oral disc and also on the tongue.

Adult lampreys prey on the blood of other fish, while lamprey larvae are filter feeders.

Lamprey larvae are toothless and blind. They burrow into sediment at the bottom of a stream where they feed on tiny organisms that they filter out of the water. After some three to eight years, the larvae change into adults. The adults die soon after spawning (laying their eggs).

http://www.geobeats.com/videoclips/finland/pori/lamprey

Class Chondrichthyes Sharks, skates, & rays. (Rays

have live births, skates lay eggs.)

Paired appendages for precise steering an maneuverability.

Have jaws. Cartilaginous body. Carnivores and scavengers. Most are marine. Have scales that reduce friction

while swimming. In fact, a shark’s teeth are just modified scales that are continually replaced throughout its lifetime.

http://videos.howstuffworks.com/discovery/30421-perfect-predators-tiger-shark-teeth-video.htm

Shark Teeth

Myths About Sharks

1. Sharks can’t hear because they don’t have ears. Wrong! Sharks’ ears are on

the inside of their head and they can hear very well!

2. Sharks have poor eyesight. Wrong! Sharks can see as

well, if not better, than we can. 3. Sharks have to swim

continuously in order to breathe. Wrong! Sharks have spiracles

that force water over the gills even when the shark is at rest.

More about sharks! Currently, there are about 400 different

species of known sharks! Sharks are one of the most formidable

predators of the oceans. Like humans, sharks make use of sight,

sound, smell, touch and taste--and they also have an "electrosense" that gives them an extra advantage underwater.

A shark's snout is dotted with jelly-filled, sensory pores called ampullae of Lorenzini that pick up faint electrical signals emitted by even the quietest, best camouflaged prey.

http://www.sharkwater.com/new_videos/US%20Trailer%20Web%20Finals/US%20Trailer%20w%20Blood-US%20Trailer%20HD%20Blood%20WEb%20TEXT-MPEG-4%20800Kb.mp4

WHY DO WE NEED SHARKS?

They are at the top of the food chain. Sharks feed on the sick and weak, thereby keeping the schools of fish on which they feed healthy. Lions and tigers serve the same role in their respective ecosystems, removing the weaker animals from the herds, and keeping the gene pool strong.

Also, if the populations of these primary & secondary consumers were to explode, they would consume all the oceans’ algae. Humans and other animals need this algae for the production of oxygen through photosynthesis. Sharks keep these populations in check, thus allowing us to breathe.

Skates & Rays Rays are usually larger than skates. Rays give birth to live young while skates lay eggs. Some rays (like the sting ray) contain venomous tails. Skates have

NO venom. Rays usually have thinner tails, while skates’ tails are fleshier.

Class Osteichthyes: The Bony Fish

Have a skeleton made of bone.

Have an operculum – gill cover.

Most have a swim bladder to control their depth in the water.

Two major types: Coelacanths (lobe-finned fish) and modern bony fish (pretty much all the fish we’re familiar with).

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The Coelacanth It has paired lobe fins that

extend away from its body like legs and move in an alternating pattern, like a trotting horse.

Coelacanths are elusive, deep-sea creatures, living in depths up to 2,300 feet (700 meters) below the surface. They can be huge, reaching 6.5 feet (2 meters) or more and weighing 198 pounds (90 kilograms). Scientists estimate they can live up to 60 years or more.

studies in the Comoros suggest only about 1,000 remain there. They are considered an endangered species.

Modern Bony Fish Streamlined to reduce friction

while swimming. Secrete a mucous that further

reduces friction while swimming.

Most are predators that spend the majority of their day searching for food. Some have teeth, others do not have teeth.

If it is a filter feeder, it will have gill rakers that trap plankton while the fish is swimming.

Have a complete digestive system that begins with a jawed mouth, then lead to a stomach, small intestines, and ends at the anus.

Circulation & Gas Exchange

Fish have a complete, closed circulatory system that works with the gills to obtain oxygen and deliver it to the body.

Sensory Functions

Fish have all the same senses we do, plus an extra one- their lateral line.

The lateral lines are used to sense changing water currents, indicating that a predator or prey species is nearby.

Some even have a seventh sense- electroreception. This means that the fish can sense the tiny amount of electricity that all living things produce. This can help them locate prey and avoid being prey for another fish.

Lateral Lines

External Anatomy of a Bony fish

Fin Identification and Purpose

Caudal fin – propulsion Dorsal fin – stability Pectoral fin – controls direction and

movement Anal fin – stability Pelvic fin – assists in moving up & down in

the water column

Internal Anatomy of a Bony Fish:

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Lung Fish Breathe air when lake

or river dries up Have both gills and

one primitive lung Fins are clumsy Somewhat adapted

for life on land – but not very well.

BCRThere are many important distinguishing characteristics between

the different classifications of fish. Explain the characteristics used to group fish into different Classes. In your response, be sure to:

Identify and compare several criteria use by taxonomists to classify fish.

Describe the composition and function of scales in both Chondrichthyes and Osteichthyes.

Give an example of how each type of scale is advantageous in its own environment (niche).

Use appropriate scientific vocabulary.

Identify and compare several criteria use by taxonomists to classify fish.

Some of the characteristics that are used to classify fish include:Number of gillsLocation of gillsType of snout/bill/mouth/chinLocation of eyesLocation of finsTypes of fins

Compare: Venn Diagram

Describe the composition and function of scales in both Chondrichthyes and Osteichthyes. Osteichthyes – most have

ctenoid scales. These overlapping scales grow larger as the fish grows. The overlapping gives the fish a large range of movement as it swims.

Chondrichthyes – have placoid scales also known as dermal denticles. These scales do not overlap nor do they grow with the fish. Instead, as the fish grows, more placoid scales are added.

Give an example of how each type of scale is advantageous in its own environment (niche). Placoid scale advantages

Counter shading of scales color Well-developed sensory system embedded in scales. Allow for deep dives and movement in shallow water Reduces drag or friction in water

Ctenoid advantages Scales hold lateral line that allows for tubular canal bearing sensory

organs-they are sensitive to pressure and temp changes in water currents.

Mucus on scales also makes capture more difficult Light, thin and flexible, which increase mobility and speed. Help to increase feeding efficiency or predatory avoidance