Oncorhynchus mykiss Rainbow trout Family: Salmonidae (Salmonids) Order: Salmoniformes (salmons) Class: Actinopterygii (ray-finned fishes) Oncorhynchus mykiss     Rainbow trout    

External Anatomy Head Trunk Tail

External Anatomy Dorsal Fin Adipose Fin Caudal or Tail Fin Pectoral Fins Anal or Ventral Fin Pelvic Fins Pectoral fins: The pectoral fins act as brakes and help the fish turn left and right. Caudal fin: The caudal fin or tail fin is the biggest fin. It provides the “push” for the trout to start moving and also acts as a rudder for steering through the water. Pelvic fins: The pelvic fins help the fish move up and down. Anal, adipose and dorsal fins: These fins are used for swimming and balance.

External Anatomy Operculum Eye Scales Mouth Lateral Line Dar Lateral Line Eye Operculum Mouth Scales Lateral line: Runs from the head of the fish to the tail. It detects vibrations or waves in the water. This helps keep the trout from bumping into things and helps the fish sense danger. Eyes: The pupils have a slight triangle shape which helps the trout see above, in front and below its body. Scales: Protect the fish. They grow as the fish grows. Mouth: Trout use their mouths to grab food and feel things. Operculum: This is a hard plate that covers the delicate gills

Eye Dar Trout can see things both near and far away. The large pupils let as much light as possible enter the eye.

Lens Dar The lens in the eye moves around and allows fish to focus on objects.

External Anatomy Nostril or Nare Teeth Dar Nostril or Nare Teeth The nare is a closed sac. It helps the fish to smell odors. Teeth are found along the upper and lower jaws. They grasp and hold onto prey.

Mouth Food passes through the esophagus to the stomach. Dar Food passes through the esophagus to the stomach. Gill rakers strain particles out of the water to keep the gills from getting clogged and injured. The tongue has teeth which help to hold onto prey.

Expose Gill Tissue Dar Cut off operculum to show the gill.

Gills Gill arch Gill filaments Dar Gill filaments Gill arch Water is taken in through the mouth and passes over the gills. The gills take in oxygen and release carbon dioxide.

Carefully cut a flap to expose the internal organs. Dar Carefully cut a flap to expose the internal organs.

Internal Anatomy Spleen Gall bladder Liver Heart Kidney Pyloric caeca Dar Spleen Gall bladder Liver Heart Kidney Pyloric caeca Stomach Swim bladder Vent: is the opening through which eggs or sperm (milt) pass during spawning.

Kidney Dar Kidney The kidney filters waste from the blood stream and also makes blood. Two canals carry waste from the kidneys to the bladder. From the bladder, the waste passes to the outside through a hole called the vent.

Swim Bladder This is an inflated swim bladder . Dar This is an inflated swim bladder . The swim bladder is like a balloon. It allows the trout to float and move up and down in the water. To fill the swim bladder, fish gulp and swallow air. Fish “burp” to get air out of the swim bladder.

Stomach: This is where food is mixed with hydrochloric acid and mucous and then passes to the intestines. Digestion Dar Stomach Fat Intestine

Path of Digestion Mouth Esophagus Cardiac stomach Vent Pyloric stomach Intestines When a trout eats, both food and water enter the mouth. Water is directed to the gills, and food goes to the esophagus which leads to the stomach. Food moves through the stomachs into the intestines and is eliminated out the vent.

Cardiac Stomach Dar Digestion of food starts in the cardiac stomach. Acid secreted by glands activate enzymes that digest protein.

Pyloric Stomach Dar The pyloric caeca act like a small intestine. They release digestive juices needed to break down food and absorb nutrients into the blood stream . Pyloric caeca

Liver Dar The liver produces bile which is stored in the gall bladder. Bile breaks down fat.

Gall Bladder Dar The gall bladder is connected to the liver and stores bile made by the liver.

Spleen Dar The spleen makes and stores blood.

Heart and Gills Compare the location of the heart to the gills. Dar Compare the location of the heart to the gills. Why is this important? Gills Heart

Close up of Heart Dar Ventricle Atrium Bulbus arteriosus

Heart The heart consists of two chambers, the atrium that receives the blood and the ventricle that pumps the blood to the body. The blood first passes through the gills where it picks up oxygen, then circulates through the body to the organs where nutrients, gases and wastes are exchanged. Dar Ventricle Atrium Bulbus arteriosus

Brain Cerebellum Medulla oblongata Optic lobes Dar Medulla oblongata Cerebellum Optic lobes The brain is the control center of the fish. All sensory information is processed by the brain. Automatic functions (such as breathing) and higher behaviors ("Should I eat that critter ?") happen in the brain.