External Structures of Dog Fish Shark Ms. Hays – Spring 2014

External Nares (Nostrils) Pair of openings on each side of the head cranial from the eyes Taken up into the smaller of the two openings and expelled through the larger openings Water passes a sensory membrane allowing the shark to detect chemicals in water

Spiracles Small openings caudal behind the eyes Provides oxygenated blood directly to the eye and brain through a separate blood vessel

Spiracles Nostrils

Mouth Location: front of the head Function: to eat; used for the intake of water that passes through the gills

Gill Slits 5 vertical slits Location: in front of the pectoral fin Function: to take the oxygen from the water passing over the gills and discharge carbon dioxide

What is the function of the gill slits in this picture? Gas Exchange!

Lateral Line Location: extends noticeably from the pectoral fin past the pelvic fin. Function: senses tiny pressure disturbances in the water The lateral line is a line of pores that run along each side of the shark that help the shark orient to movement & sound.

Cloaca Location: between the pelvic fins & claspers Function: Opening for the sex organs as well as being used for excretory waste 

Clasper Only present in males! Location: down the middle of each pelvic fin Function: Used to introduce the sperm into the cloaca of the female

What is the name of the structure that is on the side of the pelvic fins that is only present in males? Claspers

Fins 5 fins: 1 st & 2 nd Dorsal Fin – anti-roll stabilizing fins Pectoral Fin – steering fins Pelvic Fin – stabilizing fins Caudal Fin – provides thrust

What are the names of the 5 fins of a shark? 1 st Dorsal Fin 2 nd Dorsal Fin Pectoral Fin Pelvic Fin Caudal Fin

Rostrum Pointed snout located at the front of the head

Dorsal Spines Used defensively by the shark Each has a poison gland associated with it

What is a characteristic of the lateral lines and what is a characteristic of dorsal spines? Lateral Lines: senses tiny pressure disturbances in water Dorsal Spines: used as a defensive mechanism, each has a poison gland associated with it

Denticles Tooth-like scales on the surface of the sharks skin Reduce drag and allow sharks to swim more silently & smoothly.

What is one characteristic of the dermal denticles on the surface of the sharks skin? Tooth-like Used to allow sharks to swim more silently & smoothly

Ampullae of Lorenzini Small vesicles and pores that form part of an extensive sensory network system. Found on the head of the shark Detect weak magnetic fields produced by other fishes This enables the shark to locate prey that are buried in the sand or to orient to nearby movement They may also allow sharks to detect changes in water temperature

Where are the Ampullae of Lorenzini located on the shark? Head

Nictitating Membrane A membrane that is present over the eyes that covers & protects the eyes during feeding.