Biology of Fish

Fish belong to the group Chordata Includes around 52,000 species including fish, mammals, reptiles, etc.

Characteristics of Chordates Chordates: named for the notochord structure found in all chordate embryos. Chordate embryos also share: Hollow, dorsal nerve cord (becomes brain and spinal cord) Have slits in the pharynx (behind the mouth) Tail that extends beyond the anus (possesses a notochord) Notochord: flexible rod that extends through the length of the body

Chordates - Fish What is this diagram called? What are the traits that separate the different groups?

Diversity of Fish Fish were the 1st jawed vertebrates Make up 30,000 of the +52,000 species of vertebrates Two main groups of fish: Cartilaginous fish: skeleton made of cartilage Ex. sharks and rays One class Chondrichthyes Bony fish: skeletons contain bone hardened by calcium compounds Ex. ray finned fish, coelacanths, a lungfish, tilapia, salmon Class: Osteichthyes Three subclasses: Actinopterygii, Actinistia, Dipnoi

Sharks vs. Fish Attributes Sharks Fish Skeleton Cartilage only Bones and cartilage Swimming Can only swim forward Swim forwards and backwards Buoyancy Large oily liver Gas-filled swim bladder Skin Rough, sandpaper-like scales Slippery, overlapping scales Gills Gill slits, but no gill cover Covered gill slits

Chondricthyes (Sharks, rays, and ratfishes) 850 species Bony skeleton replaced with flexible cartilage for buoyancy no swim bladder exposed gill slits have well developed sensory organs

Osteichthyans (bony fish)

Actinopterigii (ray-finned fish) Flexible rays support fins Operculum flap protects and ventilates gills Air-filled swim bladder regulates buoyancy Skin contains bony scales and lateral line pits Most are oviparous (lay eggs) with external fertilization, but many reproductive strategies can be found in this group including hermaphrodites capable of cloning themselves and species who give birth to live young operculum swim bladder lateral line gills

Actinistia (lobe-finned fish) Includes the coelacanth and tetrapod lineages Thick muscles of pectoral and pelvic fins surround rod-shaped bones (have paddle like fins with fleshy bases) Coelacanths were thought to be extinct until 1938 when they were discovered of the coast of east Africa. Since then a second population has been found in Indonesia

Dipnoi (Lungfish) Found only in Southern Hemisphere Adaptation to Air Sac that can function as lungs during periods of drought. Also have gills to obtain oxygen from water. They burrow into the mud and cover themselves in mucus to stay moist until the pond refills. In the dry season, when the water evaporates and little but wet mud is left, the fish burrows down into this substrate (see drawing at right) where it forms a cocoon of mucus and mud. Its metabolic rate greatly decreases; it requires only an occasional breath of air via a small opening in the top of its burrow, and can survive in this state of aestivation despite the mud around it completely drying out. Months later, when the rains return, the lungfish re-emerges into the water and resumes living like a fish.

What do fish need? Clean Water: Good pH, low ammonia, no harmful chemicals Oxygen: Take in oxygen dissolved in water Food: Need high amount of protein Proper Temperature: Fish are cold-blooded, so metabolism slows in cold temps Proper Salinity: Depends on freshwater or saltwater

Fish Anatomy Lateral line: sensory organs running along the body help sense changes in water pressure (feel other animals) Gills: extract oxygen from the surrounding water Swim Bladder: aids in “hearing” for many fish and transmits vibrations to sensory organs (sharks use electromagnetic fields), the lungfish use these as a respiratory organ to breath air Fins: swimming and defense Gills are large sheets of thin frilly tissues filled with capillaries that take in oxygen dissolved in water.

Fish External Anatomy - Fins

Fish External Anatomy - Fins Caudal fin - used for forward propulsion of the fish. Soft dorsal fin - may be used for forward propulsion and as a rutter to change direction. Spiny dorsal fin - used as a keel to maintain fish balance. Can be lowered to increase streamlining of fish (increase swimming speed) Pectoral fin - used for braking and turning while swimming and may be used for forward propulsion. Pelvic fin - prevents fish from floating upward when fish brakes (with pectoral fins) Anal fin - acts as a rudder for turning, may be used for forward propulsion.

Fish Internal Anatomy

The digestive system is similar to other animals. What are the parts of the fish digestive system? The digestive system is similar to other animals. Size and shape of each component of the system will vary with the type of fish and its diet. Carnivores Fish that eats meat. Have a large stomach and short intestines.

Parts include: What are the parts of the fish digestive system? Mouth Teeth Tongue Branchiospines Esophagus Stomach Intestines Anus

Mouth Carnivores mouth Other fish What are the parts of the fish digestive system? Mouth Entry point of system. Carnivores mouth Have many teeth that point inwards. Not used for chewing. Used to capture and hold prey. Other fish Few or no teeth.

What are the parts of the fish digestive system? Tongue Helps move food around in the mouth. Branchiospines Act as filters to capture small food from water as the fish swims. Part of the gill structure that helps fish swim. Esophagus Short tube that connects mouth to stomach.

What are the parts of the fish digestive system? Stomach Organ where digestion begins. Some stomachs will expand greatly. Allows them to eat large quantities of food. Other stomachs are small that will accommodate small amounts of food. Some fish have almost no stomach. Esophagus connects directly to intestines.

What are the parts of the fish digestive system? Intestines Site of food digestion and nutrient absorption. Herbivorous have longer intestines than that of carnivorous animals. This is because their diet is made up of fiber and cellulose that is hard to digest. This means that the herbivorous need a longer digestive track to digest their foods completely. Anus Exterior opening of system. Unused food and wasted material is exited.

Nervous/Muscular System Nervous System Relatively simple system Central Nervous System Brain and Spinal Cord Peripheral Nervous System Cranial Nerves and Spinal Nerves Muscular System Muscle segments in the shape of “W” Muscle is the edible part of the fish

Circulatory/Respiratory System Heart and Blood Vessels 2 chambered heart: distributes O2 in the body Atria-collects blood from body Ventricle-sends blood to the gills Humans have a 4 chambered heart – fish need less 02 Arteries: carry blood away from the heart Veins carry blood back to the heart Gills Blood-filled membranes that exchange oxygen and carbon dioxide Like the lungs in a human

EXIT SLIP-January 29, 2014 1. What is one difference between Cartilaginous Fish and Bony Fish? 2. What are the three groups of Bony Fish? 3. How does a fish’s heart differ from humans? 4. What type of Bony fish is a Tilapia? 5. What organ allows a fish to stay motionless in the water without sinking?