Shark Anatomy

• Skin

  • Covered in dermal denticles, millions of tiny teeth
  • Dermal denticles point backwards, effectively reducing surface drag, making the shark swim faster
  • Shark sheds denticles and replaces them as they grow
  • Denticles vary in shape depending on the species and placement of body
• Teeth


  • Made of enamel
  • Appear in huge numbers in the fossil records
  • Born with teeth, have rows of teeth that are constantly being replaced
  • Replace their teeth approximately every two weeks
  • Some species have been known to lose 30,000 teeth in a lifetime
• Teeth


  • Insights into a shark's diet can be seen through the teeth
  • Flat crushing teeth = shellfish
  • Point teeth = gripping fish
  • Shark serrated teeth = larger prey, seals
  • Teeth may change with age, as the pup's diet changes an adult diet
• Lateral Line


  • Able to pick up vibrations in the water
  • Important determinant of detecting prey, current speed and direction
  • Sensory organ is a hollow tube, with pores connecting to the surrounding skin, and extending along the length of the body and into the tail
  • Responds to hydrodynamic stimuli
  • Alerts sharks to potential prey and predators
  • Their own body movement creates waves which in turn bounce of obstacles allowing them to create a pressure map of their surroundings
• Fins


  • Provide balance, stability
  • Large dorsal fin to provide balance, commonly there is a smaller dorsal fin further back towards their tail
  • Pectoral fins are used to steer and lift themselves in the water
  • Tails are used to propel themselves forward
  • Size and shape of a shark's fin and tail can vary
  • Faster sharks (Shortfin Mako) tend to have shorter crescent shaped tails
  • Slower moving shark (Bluntnose Sixgill Shark) have longer thinner tails
• Ampullae of Lorenzini - Electroreception


  • Complex electro-sensory system enabled by receptors covering the head and snout area
  • Receptors sit in jelly-filled sensory organs known as ampullae of Lorenzini
  • Pores are extremely sensitive and are able to detect even the faintest of electrical fields, e.g those generated by Earth's geomagnetic field or muscle contractions in prey
  • Earth's geomagnetic field is believed to help sharks orientate themselves and navigate
• Gills


  • Used to breathe, in order to breathe most shark species remain in constant forward motion
  • As they swim water is driven through their mouth and out over their gills, process known as 'ram-ventilation'
  • Water passes over the gills, oxygen gets absorbed into tiny blood vessels and transported around the body
  • Nurse and Zebra Sharks are able to suck water into their mouth and squeezing it over their gills, this process is called the Buccal Process
• Smell


  • Up to two thirds of a shark's brain is dedicated to smell
  • Sensitive to smells produced by potential predators, prey or mates
  • Some can detect blood of prey from large distances- one part of blood to one million parts of water. Equivalent to one teaspoon in average sized swimming pool
• Buoyancy


  • Light skeleton
  • Lift effect produced by their fins as they move through the water
  • Large livers storing low-density oils, in some species the liver makes up 25% total body weight in comparison for mammals this is only 5%
• Sight


  • Vision becomes more acute 15m from an object
  • Sharks have a 'tapetum lucidum' a reflective layer of shiny cells which are behind the retina, improves vision in low light conditions, benefiting nocturnal and deep-water species to hunt more successfully
• Muscles


  • 2 types of muscle- red and white
  • Red muscle breaks down the fat in the sharks body, good blood supply and helps the shark swim for long periods of time
  • White muscle works by using energy from the breakdown of glycogen, allowing sharks to make short fast sprint to catch prey or escape danger
  • Long bundles of muscle fibres run from the top of a shark's head to the tip of its tail, following the contraction of the muscles a series of undulations are produced through the body, giving the shark to ability to propel itself through the water with its tail
• Sound


  • Acute sense of hearing and are sensitive to low-frequency signals
  • Able to track sounds, showing interest in sounds made by wounded prey
• Touch


  • Not highly adapted
  • Taste has no impact on hunting
  • Will often 'test bite' potential food to see if its edible, if not they'll spit it out, likely accounts for the high survival rate of shark encounters- where sharks have bitten then left
• General Reproduction


  • All sharks have internal fertilization
  • Very little information about this as very few shark mating encounters are viewed
  • The females tend to be passive
  • The male bites onto the female and holds on using his teeth
  • Gestation varies dramatically with it being about a year of a majority, but with some such as the frilled shark having gestation periods of about 3 years
• Temperature Control


  • Most fish are cold-blooded causing their body temperature to fluctuate with their environment
  • But mackerel sharks can warm their blood, including White Sharks, Porbeagle, Salmon Shark, Shortfin Mako and Longfin Mako
  • Retaining warmth makes for more efficient predators
  • Heat is lost through a shark's gills, where blood vessels get exposed to cooler water
  • In attempt to minimise heat loss mackerel sharks have a network of tiny capillaries which act as a heat exchange system (rete mirabile)
  • Body temperature of mackerel sharks can be 10°C higher than the surrounding water