The dark markings in the shark embryo pictured above indicate gene expression in the electro-sensory organs in the animal's head. University of Florida researchers traced the origin of a shark's electro-sensory powers to the same type of embryonic cell that gives rise to many head and facial features in humans. Photograph © 2006 Renata Freitas/University of Florida
Nares Nostril-like structures Nostril-like structures Detect scents Detect scents Pheromones for mating Pheromones for mating Can smell one drop of blood up to a quarter of a mile away! Can smell one drop of blood up to a quarter of a mile away!
Lateral Line Series of fluid filled canals that contain little sensory hairs called neuromasts Series of fluid filled canals that contain little sensory hairs called neuromasts These hairs detect vibrations of swimming creatures or change in water movement These hairs detect vibrations of swimming creatures or change in water movement
Ampullae of Lorenzini Large pores on snout filled with gelatinous substance. Large pores on snout filled with gelatinous substance. Detect changes in electric field Detect changes in electric field Living things emit electricity due to muscular activity Living things emit electricity due to muscular activity
They have a tapetum, a part of the eye that They have a tapetum, a part of the eye that helps sharks to see better in the dark Can see 50 feet in clear water Can see 50 feet in clear water (Still not as well as humans with a mask) (Still not as well as humans with a mask)
Other Shark adaptations
Nictitating membrane Protective covering that protects sharks Protective covering that protects sharks During feeding
Having mostly rods (a few cones), sharks Having mostly rods (a few cones), sharks see mostly shades of grey and shadows Can detect fast-irregular movements and Can detect fast-irregular movements and interpret them as prey Could be part of the cause for mistaken Could be part of the cause for mistaken attacks on humans
Ram ventilation VS. Buccal Breathing Ram Ventilation: Sharks must swim in order to move water over gills for respiration. Buccal Pumping: Sharks can use cheek muscles to suck water into gills without swimming.
Ram Ventilators Pelagic sharks such that do not live on the bottom must stay on the move for life Swim with mouths open “Sleep”: a changed state of metabolism (lowered) Basking Shark
Buccal Pumping Sharks that sit on the bottom Port Jackson sharks, Angel Sharks, Nurse Sharks
Shark Reproduction
Male sharks have a pair of organs called claspers between their pelvic fins, which transfer sperm into the female.
Some sharks have internal development and bear live young. Other sharks ( and skates ) have external development where embryos develop within a black, leathery egg casing called a mermaid ’ s purse.
These embryos take more than a year to develop and can be found washed up on the beach.
Unlike bony fish, fertilization in cartilaginous fish is INTERNAL!
Once fertilization is complete, development may occur in one of three ways: Viviparous (live) Ovoviviparous (egg/live) Oviparous (egg)
Some sharks have internal development and bear live young, this is known as Viviparous development. The young is nourished by a placenta like structure.
Viviparous sharks include Hammerheads
In some sharks, the young are nourished by a yolk sac within the female followed by live birth. This is called Ovoviviparous development.
Ovoviviparous sharks include Tiger sharks Dogfish sharks Whale sharks
Many sharks and skates lay eggs this is called Oviparous development