Chapter 34 - Fish

Ichthyology - the study of fish

Classification

Kingdom Animalia
--Phylum Chordata
----Subphylum Vertebrata

Characteristics of Fish

• Gills
• Backbone (vertebrae)
• Paired fins
• Single loop circulation

Fish Respiration

Water flows over gills as the fish swims - this water is flowing in the opposite of the flow of blood (countercurrent flow). Oxygen diffuses from the water and into the blood

Gills are made of thousands of gill filaments

When a fish opens its mouth, it "swallows" water, water passes over the gills and then out the gill slits, which are covered by the fish's operculum. You can see the operculum opening and closing.

Fish Circulation

The fish heart is a single loop circulation which has 2 chambers. Blood flows into the gills, picks up oxygen goes to the body and then returns to the heart.

Maintaining Water Balance - HOMEOSTASIS

Remember that salt sucks?

Salt water fish have a tendency to lose water
Fresh water fish have a tendency to gain water (the fish is saltier on the inside)

This is why you can't put a saltwater fish in fresh water - it is not adapted to it.

Kidneys maintain homeostasis and water balance

Fish Reproduction

Most fish fertilize their eggs externally

Spawning - the process of fertilizing eggs (fish reproduction)
Fry - baby fish

Salmon have a unique method of spawning.

Salmon Resources

The Salmon Challenge
Life Cycle of a Salmon

Types of Agnathans

Hagfish - ocean scavengers, not much is known of them

Lamprey - fresh and salt water, they are parasitic on other fish. Cartilage skeletons and circular (suckerlike) mouths

Types of Cartilage Fish

Sharks

• adapted for predatory lifestyle
• pectoral fins do not move - increases speed and stability (like an airplane)
• cartilage skeletons
• teeth replaced frequently
• special scales that feel like sandpaper
• no operculum (gill cover), sharks must keep moving to breathe
• most have live births

Manta Rays and Sting Rays

• flexible pectoral fins and wide flat bodies
• most live in shallow water and are fairly docile
• mouth located on the underside, they prey on fish

Types of Bony Fish (Osteichthyes)

Ray-finned - majority of fish are this type, fins are supported by bony structures called rays.

Teleosts -most advanced form of ray finned fish, symmetrical tales, mobile fins

Lobe Finned Fishes

Fins consist of long, fleshy muscular lobe, supported by a central core of bones
Thought to be the ancestors of amphibians

Coelacanth (rare, see pic)
Lungfsh (see pic)

Fish Adaptations

Lateral Line System - Used to detect vibrations, orientate fish in the water. A line of cells running down the side of the fish

Gill Cover (Operculum) - covers gills, movement of operculum allows more water to be drawn in

Swim Bladder - a gas filled sac that helps the fish maintain bouyancy (sharks do not have swim bladders, they sink when they stop swimming

Fins