Bony Fish (Class Osteichthyes) INTERNAL ANATOMY The largest group of fish are the bony fishes and includes As the name suggests, bony fish have a bony skeleton with a eels, seahorses and pipefish. The total number of species of protective bony plate called the operculum covering the gill bony fish is thought to be more than 15,000. cavity and a single external gill slit. Lateral line Gills Hearing, vision and balance are controlled by the Fish have a simple, single-loop circulatory interaction of the inner ear, lateral line and swim system were blood flows from the heart to bladder. The lateral line is a sensory organ that runs the gills, and then to the rest of the body in along the sides of the fish’s body, under the skin. a continuous loop through a series of veins Vertebral column Neuromast cells are located in the inner ear and in the and arteries. (spine) canals of the lateral line system. These cells translate vibrations in the water into nerve impulses. Nerves Gills consist of gill arches, which are a connect the lateral line to the ears and the brain. supporting structure, gill rakers that remove The swim bladder acts as a transducer to amplify solid material, and gill filaments, across Spinal cord Kidney Muscle sounds as the swim bladder vibrates. which gas exchange occurs. Gas exchange is the diffusion of oxygen from the water Brain into the blood vessels of the filaments, with carbon dioxide diffusing out of these blood vessels into the water passing over them.
Gill raker Gill arch Gill filaments trunk canal system head canal system
lateral-line canal epidermis external opening Water flows in through the mouth
neuromast
Water flows over gills, then out through the operculum lateral-line nerve
Otolith Whilst fish don’t have ears in the Vent human sense, they ‘hear’ sounds well The vent, or anus, is in their own environment and can the external opening tell what direction it is coming from. to the digestive and Fish might not have ‘ear holes’ to let in reproductive systems. sounds, but instead use their whole Stomach bodies to pick up vibrations that Swim bladder sounds make. The stomach is where digestion commences. Most bony fishes (adult The otolith or flounder and some Reproductive organs The main components ‘ear bone’ is the bonito are an exception) The reproductive organs of fish are Heart of the digestive system fish’s inner ear, have a swim bladder, referred to as gonads. These organs are The heart is a muscular include the liver, enabling them Intestine a gas filled sac . The usually paired. Female gonads (ovaries) organ which pumps stomach, intestine and to listen to sound waves that travel The intestine is the swim bladder controls produce eggs and are usually pink, red Feeding blood throughout the pyloric caecae. through the water. main site of digestion the fish’s buoyancy. The or orange in colour and are covered in Like sharks and rays, fish body. Tell me your age Liver and absorption. As a amount of gas contained numerous blood vessels. Male gonads have a one way digestive Similarly to sharks, The liver produces general rule, fish with within the bladder is (testes) produce sperm and are usually system. Food enters Researchers can determine the age of Pyloric caecae bony fish by studying their otoliths. As blood is circulated by a enzymes (chemicals) short intestines are adjusted to allow the fish white (cream) or grey in colour. the mouth and travels 2-chambered heart and to aid in digestion. It is carnivorous (meat- Finger-like pouches to move up and down in via the oesophagus to a fish grows, tiny white and clear bands Reproduction of calcified material are laid down in passes through the gills also a storage area for eating) and those with attached to the intestine the water column while the stomach. From the The majority of bony fish reproduce by the otolith, similar to growth rings in where it loses carbon fats, blood sugars and long, coiled intestines (immediately following conserving energy. In stomach it is passed into external fertilisation of their eggs and a tree. The growth bands are counted dioxide and receives a vitamins and breaks are herbivorous (plant- the stomach), which some species the swim the intestine for further have a pelagic larval stage. Most bony under a microscope to determine the fresh supply of oxygen down toxins and old eating), as fibrous plant are believed to have bladder is also used digestion. Digested wastes fish produce thousands (and in some age of the fish. prior to coursing the blood cells for excretion materials are harder to a digestive and/or in hearing and sound are eliminated from the remainder of the body. or recycling. break down. absorption function. production. fish, millions) of eggs each year. intestine via the anus.
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