Chondricthyes (sharks) Flashcards
1
Q
Chondrictheyes
A
-
2
Q
Shark anatomy
A
- Nostrils
- Teeth
- Eye
- Spiracle
- Gill slits
- Pectoral fins
- Fin spine
- Dorsal fin
- Lateral line
- Pelvic Fins
- Claspers
- Anal fin
- Second dorsal fin
- Caudal fin
3
Q
Sensory receptors in sharks
A
Lateral line organ
- fluid filled channels running length of body
- receptors present called neuromasts; a cluster of tiny, hair cells that respond to vibrations, pressure changes, water movement, contained within a jelly filled cupula to pick up vibrations over long distances (up to a mile)
Nostrils
- heightened sense of smell
- large olfactory lobe of brain
- odor goes into olfactory pits (nostrils)
- scent sensitive membranes (lamellae) line the nostrils
- zig zag swim motion so water alternates going into each nostril; hones in on strongest smell so if left nostril is plugged, shark will swim in clockwise circle, always turning right
- detect 1 part blood in a million parts water
Ampullae of Lorenzini
- small pores on snout
detect electric fields generated by living organisms
- detect earth’s magnetic fields which some sharks may use in navigation
Eyes
- good eyesight, see colors
mirror-like layer in the back of the eye, the tapetum lucidum; enhances light sensitivity.
- more rods (light intensity sensors) than cones (color sensors), so sharks are very sensitive to small differences in light intensity (dark versus light) or the contrast.
- nictitating membrane; thin membrane that covers shark’s eyes for protection while feeding (not in Great Whites)
4
Q
Shark’s body structure
A
- streamlined, torpedo shaped strong caudal fin for: fast speed and quick acceleration - max speed 30 mph (Mako shark) - body muscles are arranged bilaterally in segments called myometers
2 kinds of tail:
- Heterocercal tail; upper lobe is larger than lower lobe, slower sharks, may be used to stun fish (Thresher shark)
- Homocercal tail; lobes are equal, provides greater speed and acceleration
5
Q
Reproduction in sharks
A
- observed by Aristotle; two claspers along underside of male shark move into cloaca of female
Oviparous
- young develop in eggs laid externally
- survive on yolk
- “mermaid’s purse”; egg capsule made of keratin (protein)
- Four corners have long tendrils that coil around rocks or algae
- e.g cat sharks, horn sharks
Ovoviviparous
- most common form in sharks
- develop internally in yolk sac, live birth
- no placenta like in mammals
- in some species, fetuses feed on each other inside uterus; oophagy, uterine cannibalism
- e.g makos, tiger
Viviparous
- connection of yolk sac to uterus = placenta
- most advanced
- e.g great whites, hammerheads
6
Q
Countershading
A
- distinctive color shading of dorsal and ventral surface
- dorsal surface is darker, so that when viewed from above, the shark blends in with dark ocean bottom
- ventral surface is lighter, so that when viewed from below, the shark blends in with bright light coming from the surface
7
Q
Teeth
A
- about 1000 razor sharp teeth in 5 rows
- when a tooth breaks off, another tooth moves forward and replaces it
- 30,000 teeth shed in a shark’s lifetime
8
Q
Spiracle
A
- holes behind eye
- helps bottom-dwelling sharks breathe
- may aid in aerating oxygen to eyes/brain
9
Q
Shark attacks
A
- Only 25 species have attacked humans
- 90% cannot or have not been recorded as hurting people
- most dangerous: great white, tiger, and bull
- 53 unprovoked attacks in 2016; 4 fatal, 58% in the US, Florida (23/36)
- inflict massive wound on prey, then release
wait for bleeding prey to be weak and defenseless
no determined way to repel sharks:
- copper acetate was used in WWII, but found to be ineffective
- poison from Moses Sole flatfish is latest idea
- shocking them with electricity has also been experimented with
10
Q
Buoyancy
A
-
11
Q
Fins
A
-
12
Q
Skin
A
-
13
Q
Commercial uses
A
-
14
Q
Whale Shark
A
- Rhincodon typus
- ebisuzame (Japanese for good luck symbol)
- 60 feet long
- Tropical and warm waters around world (atlantic, pacific, Indian)
- largest fish in the sea
- Identified in 1828
- feeds on crustaceans and tiny fish; sucks in fish with suction, 15,000 tiny teeth to hold onto food drawn in, water flows into mouth, and past gill rakers which catch the food and pass it down the throat
- Collisions with ships; recognized maritime hazard by US Navy
- Docile, can climb on and ride
- Little known about breeding; ovoviviparous (live young birth)
15
Q
Thresher Shark
A
- Alopias vulpinus
- 20 feet long max
- Aka: fox shark, sea fox
- uses long tail to stun fish, birds, prey
- weak jaws, so tails must be used for something
- Ovoviviparous
- splashes water with tail
- drives fish into a tight pack, then drives thru them eating as much as possible
- squid, octopus, sea birds
