sharks in action

Question 1

how have Chondrichthyes fins evolved?

Answer 1

tribasal pectoral and pelvic fins

triangular basal cartilage
and parallel radial cartilage to margin
to
the stalk of three basal cartilages
segmented, shorter cartilages in blade

Question 2

what is the purpose of tri-basal structures?

Answer 2

increase mobility and flexibility

collagenous fibres “ceratotrichia” extend to fin margin
muscles within fin

Question 3

why is ceratotrichia desirable?

Answer 3

ceratotichia is a delicacy in Asia called fish fin soup

Question 4

what is the purpose of pectoral fins?

Answer 4

to swim horizontally

to rise

to sink

Question 5

what is the specific movement of the pectoral wings in shakes and rays

Answer 5

dorsoventral flattening of body

lateral extension of pectoral fins

wave-like motion

outer half of wing oscillates most

Question 6

what’s the purpose of shark caudal fin

Answer 6

heterocercal

generates lift

Question 7

how do sharks swim?

Answer 7

musculature extends into dorsal lobe in caudal fin

sharks swim using wave-like body undulations

muscles act as caudal fin changes shape

Question 8

what is the shark bottom fin?

Answer 8

the anal fin is one of the median fins

medians fins like dorsal and anal fins balance roll and yaw in locomotions

may generate thrust

Question 9

how do sharks hunt?

Answer 9

hunting senses:

vision - spherical lens focuses by position not shape
retina rods and cones vary in proportion with haitat

olfactory - can detect 1ppm of blood
nostrils divided externally by flap of skin - incurrent and excurrent nostrils
enable turn to higher concentration

hearing- low frequencies attract sharks

lateral line - detects water displacement through pores by neuromasts also in canals below the skin

electroreception - sense weak electric fields generated by animals e.g. blood electrolytes