Class Osteichthyes

1. Class Osteichthyes aka: Bony Fishes

3. Body Shape Body shape is directly related to the niche of the fish Streamlined fish are fast swimmers Laterally compressed fish are lazy swimmers that are capable of burst of speed Bottom feeding fish are often flat with eyes that point upwards Eel like body shapes allow for the animal to hide in tight spaces Body shape can also aide in camouflage The animal can be adapted to look like the vegetation it is living in

4. General Characteristics Have a skeleton made at least partially of bone Makes up almost half of all vertebrates Skin is composed of cycloid scales Thin, flexible, overlapping tissue Gills are covered by a flat of bony plates and tissue called the operculum Fins are generally composed of thin tissue supported by spines The mouth is located at the tip of the body and is jointed to allow for a wide range of movement Have a swim bladder to control buoyancy

7. Coloration The color for the fish is found in specialized cells called chromatophores Irregular in shape Capable of almost any color in the rainbow Give the fish the ability to change color by contracting and expanding the chromatophores Some fish have iridophores which are cells that reflect a certain wavelength of light Color is used for camouflage, warning coloration or countershading

9. Movement Most fish swim with an S motion A rhythmic side to side moving from the head to the tail Controlled by bands of muscle called myomeres Run parallel along the sides of the fish Visible in fish you eat Makes up 75% of the fishes weight White muscle is used for bursts of speed Red muscle is used for constant locomotion The fins are used like rudders to change direction in the water Some fish move by moving only their fins and not their body

11. Feeding Fish can be either carnivorous or herbivorous (mostly carnivorous) The teeth will tell you what they eat Used for grasping and holding the prey Prey is usually swallowed whole Usually have one preferred food source A type of fish, anemone, urchin etc Fish that feed on algae are called grazers

12. Digestion Very similar to our digestion Food passes through the mouth to the stomach In the stomach food is turned into the basic chemical forms The chemicals are then absorbed in the intestines Accessory organs create digestive juices that aide in digestion

14. Circulatory System All fish have a two chamber heart Simpler than ours with one direction flow

15. Respiratory System Respiration is done through the gills of the fish Water is taken in through the mouth � passed over the gills and into the water Gills are supported by gill arches which hold the gill open The gills contain capillaries Thin walled blood vessels that allow the diffusion of gases O2 is higher in the water so it diffuses into the capillaries CO2 is higher in the fish so it diffuses out of the fish To increase the efficiency of the gill the blood flows in the opposite direction of the water in the gills

17. Osmotic Regulation Marine fish osmoregulate to prevent dehydration Fish replenish lost water by swallowing salt water Some salts pass out of the body Some salts are excreted by the kidney

18. Nervous System Most fish have a complex sense of smell Used to detect prey, mates and predators Smell is detected in the nares (nostrils) Fish also have taste buds Found in the mouth, fins and skin Catfish have taste buds on barbels (whiskers) Rely on vision Eyes focus by moving closer or further from the object they wish to view Covered by a nictitating membrane � clear membrane that allows the fish to see while protecting the eye

20. Nervous System Fish use a lateral line to detect vibrations in the water Lined with clusters of sensory cells Allows fish to detect predators and prey Helps them to orient themselves with the current Helps them school Fish can detect sound using ears like ours

22. Behavior Territoriality An established area that the fish protects against invaders Some are only territorial during mating period others are for life Thought this helps ensure there is enough food for the fish Defended by aggressive behavior like making themselves appear larger or by chasing other fish Fights are rare

23. Behavior Schooling 4000 fish school at some point in their lives Can provide protection against predators Can cause confusion Less likely to be the one eaten if there are thousands of other fish around you Can increase swimming efficiency by reducing the drag of the water Can be advantageous for mating or feeding

25. Reproduction Separate individuals for each sex External fertilization Production of gametes (sperm and eggs) occurs only at specific times of year Ensures that the eggs and sperm will be released together Controlled by length of day, moon light and water temperature Called spawning Some fish have the ability to change sex if needed Young develop in eggs laid outside the mothers body and the care given depends on the species