March 27, 2012
Chapter 39: Fishes Section 1 Introduction to Vertebrates Section 2 Jawless and Cartilaginous Fishes Section 3 Bony Fishes
39-1 Introduction to Vertebrates
Objectives:
Identify the distinguishing characteristics of vertebrates.
List an example for each of the nine classes of vertebrates.
Describe the characteristics of the early vertebrates.
Explain the importance of jaws and paired fins for fishes.
Characteristics
Vertebrates are members of the subphylum Vertebrata, within the phylum Chordata.
All Chordates share the following characteristics.
· Notochord · Dorsal hollow nerve cord · Pharyngeal gill slits · Post-anal tail March 27, 2012
Characteristics of Vertebrates
Vertebrates are distinguished from chordates by:
Vertebrae - bones or cartilage that surround the dorsal nerve cord and form the spine.
A cranium - a skull that protects the brain
An endoskeleton - an internal skeleton made of bone or cartilage
Types of Vertebrates
Vertebrates are divided into nine classes: (know these! Common names are fine) (45,000 species total) Class-example · Myxini - hagfishes · Cephalaspidomorphi - lampreys · Chondrichthyes - sharks, rays, skates, and ratfishes · Actinopterygii - ray-finned fishes · Sarcopterygii - lobe-finned fishes (2 groups) · Amphibia - frogs, toads, salamanders, and caecilians (4880 sp) · Reptilia - lizards, snakes, and turtles (8000 species) · Aves - birds (10,000 species) · Mammalia - mammals (4400 species) Ichthyology? March 27, 2012
Vertebrate Evolution
Most biologists think that vertebrates originated about 560 million years ago.
The first fish were jawless.
About 450 million years ago, the first fishes with jaws and paired fins appeared.
Jaws are thought to have evolved from the first pair of gill arches, the skeletal elements that support the pharynx.
The advantages to jaws and paired fins:
· Paired fins increased fishes’ stability and maneuverability in water
· Jaws allowed fishes to seize and manipulate prey
Advantages of Paired Fins Origin of Jaws March 27, 2012
39-2
Objectives Identify three characteristics that make fishes well suited to aquatic life.
Describe three sensory systems in fish.
Evaluate the similarities between jawless fishes and early vertebrates.
Identify two characteristics of cartilaginous fishes.
Contrast reproduction in lampreys with reproduction in cartilaginous fishes.
Fish Adaptations
Fish have several adaptations that make them well suited to life in water:
· Streamlined body plan - allows fish to move rapidly in water
· Adaptations for buoyancy - stored gases or lipids help maintain vertical position in water
· Efficient respiration - internal gills exchange gases efficiently
Fish Characteristics
Fish Adaptations, continued
Adaptations for salt and water homeostasis -
· The concentration of solutes in a fish’s body usually differs from the concentration of solutes in the water.
· Fish have adaptations to maintain ion and water homeostasis. March 27, 2012
Fish Adaptations, Continued Sensory adaptations - Fish have a variety of organs that allow them to sense their environment.
Sight: fish eyes are similar to eyes of land vertebrates
Sound: fish have internal ears sensitive to sound
Chemoreception: the ability to detect chemicals in the environment includes the senses of smell and taste. Fish have nostrils and tastebuds. Tastebuds may be located in their mouths, on their lips, fins, and skin, and on whisker-like organs called barbels.
Fish Adaptations, Continued
Unique senses:
Lateral line: the lateral line is a system of canals in the skin that allow fish to sense vibration in the water
Ampulae of Lorenzini: cartilaginous fishes have sense organs called ampulae of Lorenzini that can detect weak electrical fields
Electroreception and Magnetoreception: some fish have the ability to detect electrical and magnetic fields
Lateral Line System
Lateral Line in Fishes March 27, 2012
Jawless Fishes
Only two classes of jawless fishes are alive today:
Hagfishes Lampreys
Hagfishes (class Myxini) · Hagfishes are bottom-dwellers that feed on dead and dying fish.
Hagfish Slime
Lampreys (class Cephalaspidomorphi) · Lampreys can be free-living or parasitic. · Parasitic lampreys attach themselves to their host with disc- shaped mouths and feed on the blood and body fluids of other fishes. · All lampreys breed in fresh water. · Fertilization occurs outside the body - external fertilization.
Lamprey PSA
Cartilaginous Fishes
All cartilaginous fishes:
belong to the class Chondrichthyes.
have skeletons made of cartilage - a flexible lightweight material made of cells surrounded by tough fibers of protein.
have skin covered with placoid scales - small, toothlike spines that feel like sandpaper. Placoid scales probably reduce turbulence and increase swimming efficiency. page 784 March 27, 2012
Cartilaginous Fishes, Continued Sharks:
Sharks have torpedo shaped bodies that reduce turbulence when swimming, called a fusiform body shape.
Some sharks are filter feeders, and have slender projections on the inner surface of their gills, called gill rakers, that filter the water.
The mouth of a typical shark has 6 to 20 rows of teeth. When a tooth breaks or wears down, a replacement moves forward. One shark may use more than 20,000 teeth over its lifetime.
Shark Senses
Cartilaginous Fishes, Continued Rays and Skates:
Rays and skates have flattened bodies with paired wing-like pectoral fins and, in some species, whip-like tails.
Rays have diamond- or disk-shaped bodies. Most skates have triangular bodies.
Rays and skates are primarily bottom dwellers, and most feed on mollusks and crustaceans.
Cartilaginous Fishes, Continued Ratfishes:
Ratfishes are a small group of strange looking fish that have a flap of skin covering their gill slits.
Ratfishes have long, rat-like tails and feed on crustaceans and mollusks. March 27, 2012
Cartilaginous Fishes, Continued
Adaptations in Cartilaginous Fishes:
Some sharks push water through their mouth and over their gills by swimming.
Most cartilaginous fish pump water over their gills by expanding and contracting their mouth cavity and pharynx.
When lying on the bottom, rays and skates draw water in to their gills through spiracles, two large openings on the top of the head, behind the eyes.
Cartilaginous Fishes, Continued
Adaptations in Cartilaginous Fishes:
Sharks convert ammonia to urea in their bodies.
Sharks retain large amounts of urea in their bodies to raise the concentration of solutes in their bodies to the same level as that found in sea water.
Sharks still tend to take up sodium and chloride ions.
The rectal gland removes excess sodium and chloride ions from the body.
Anatomy of a Shark
Cartilaginous Fishes, Continued
Adaptations in Cartilaginous Fishes:
Cartilaginous fishes maintain their position in the water in two ways:
· The caudal and pectoral fins generate lift, or upward force, as the fish swims.
· Many cartilaginous fish store large amounts of lipids, usually in the liver. Lipids are less dense than water. March 27, 2012
Cartilaginous Fishes, Continued
Reproduction in Cartilaginous Fishes:
Fertilization occurs inside the body of the female, called internal fertilization.
Some cartilaginous fish lay eggs.
The eggs of many species develop within the female’s body.
In some species, the mother nourishes the developing young while they are in her body.
39-3 Bony Fishes Objectives:
List three characteristics of bony fishes.
Distinguish between lobe- finned fishes and ray-finned fishes.
Describe three key features of bony fishes’ external anatomy.
Summarize the major body systems in bony fishes.
Describe the function of the swim bladder.
Discuss reproduction in bony fishes.
Characteristics of Bony Fishes
Bony fishes have three key features:
Bone - the skeletons of most bony fishes contain bone.
Lungs or swim bladder - early bony fishes had lungs, organs which exchange gas between the air and blood. Most bony fishes today have a swim bladder, a gas- filed sac that is used to control buoyancy.
Scales - scales protect the body of a bony fish and reduce friction when swimming. March 27, 2012
Swimbladder in Bony Fishes
Primitive Bony Fishes Swim Bladder is connected directly to the Pharynx.
Swim bladders in more recently evolved fishes is controlled by diffusion of gasses through a capillary bed.
Advantage: Control of bouyancy without having to surface. Allows exploitation of deeper niches.
Compare Pectoral Fin Locations
Characteristics of Bony Fishes, continued
There are two main groups of bony fishes:
· Lobe-finned fishes - have fleshy fins supported by a series of bone.
· Ray-finned fishes - have fins that are supported by long, segmented, flexible bony elements called rays. March 27, 2012
External Anatomy
Operculum Most bony fish have an operculum, a hard plate that opens at the rear and covers and protects the gills.
Fins The fins of most fish are supported by rays or spines. · Rays are flexible, spines are rigid.
Skin The skin of most bony fish are covered with scales. · Scales are thin, round disks of a bonelike material that grow from pockets in the skin and overlap like shingles.
urogenital
Internal Anatomy
Digestive system
Food passes from the mouth into the pharynx, through the esophagus, to the stomach.
From the stomach food passes into the intestine, where nutrients are absorbed.
Undigested material is eliminated through the anus. March 27, 2012
Yellow Perch Internal Anatomy
Internal Anatomy, Continued Circulatory system
The circulatory system of a fish delivers oxygen and nutrients to the cells of the body.
The circulatory system consists of a heart, blood vessels, and blood.
The heart pumps blood through arteries to small, thin-walled vessels called capillaries, in the gills.
From the gills, the blood travels to the body tissues, where nutrients and wastes are exchanged.
The blood returns to the heart through veins.
Heart version 2.0
Internal Anatomy, Continued
Circulatory system
The heart of a bony fish has two chambers in a row, as shown below.
Blood from the body enters the sinus venosus, moves into the atrium, then into the ventricle.
From the ventricle it enters the conus arteriosus, and then goes to the gills. The Heart, version 2.0 March 27, 2012
Fish Heart Structure
Internal Anatomy, Continued
Respiratory system
Fish use gills for gas exchange.
Water flows across the gill filaments in a direction opposite to blood flow, called countercurrent flow.
Countercurrent flow allows more oxygen to diffuse into the blood than would be possible if blood and water flowed in the same direction.
Respiration in Fishes March 27, 2012
Internal Anatomy, Continued
Excretory system
The kidneys filter chemical wastes from the blood to form urine, a solution containing ammonia, ions such as salts, and water.
The kidneys help regulate the ion and water balance in fish.
The gills also allow wastes to diffuse from the blood into the water and help regulate ion and water balance in fish.
Internal Anatomy, Continued
Swim bladder
The swim bladder is a thin-walled sac in the abdominal cavity that contains a mixture of oxygen, carbon dioxide, and nitrogen obtained from the bloodstream.
Swim bladders evolved from balloonlike lungs, which ancestral bony fishes may have used to supplement the oxygen absorbed by the gills.
In some fish the swim bladder is known to amplify sound by vibrating and transmitting sound to the inner ear.
Internal Anatomy, Continued Nervous system
The nervous system of a bony fish includes the brain, spinal cord, nerves, and various sensory organs.
The fish brain consists of several parts:
· Olfactory bulb - processes information about smell · Cerebrum - integrates information from other parts of the brain · Optic tectum - processes information about sight and from the lateral line system · Cerebellum - coordinates muscle movement and balance · Medulla oblongata - controls the function of some organs and relays information from the spinal cord March 27, 2012
Internal Anatomy, Continued Nervous system - The fish brain has a well-developed medulla to coordinate muscle control.
Internal Anatomy, Continued
Spawning
Reproductive behavior in bony fishes is called spawning.
Fertilization in most fish takes place outside the body.
Many species of fishes lay large numbers of eggs. Why?
Some species of fish carry the eggs within their bodies until the eggs hatch.
Egg - Fry - Fingerling - Smolt - Adult
Pacific Salmon (5) Atlantic Salmon (1)
Silver or Coho Atlantic Salmon King or Chinook Chum or Calico (dog) Pink or Humpy Red or Sockeye Salmon have varying life spans depending on the species, but adults return from the ocean to the freshwater stream they were born in to spawn, then die. River ecology has changed greatly over the past 200 years, changing the distribution of salmon species. Alaska and Eastern Siberia have the only remaining populations of wild salmon as they once were.
What are some reasons for changes in stream ecology on such great salmon rivers as the Columbia? March 27, 2012
Sockeye (or Red Salmon) are the most economically important Salmon
Bristol Bay enjoys the largest salmon run in the world.
The proposed Pebble Mine (a copper and Gold mine) west of Lake Iliamna may threaten this great recreational and commercial resource. Sockeye salmon are the only salmon that must have a lake between the stream where they spawn and the ocean. The Smolt live in the lake for one year before returning to the ocean for four more years. The ecology of the entire ecosystem revolves upon the success of the salmon.
Bears, Birds, other fish, marine mammals, marine predators, humans all exist in these regions because the salmon exist