functional morphology and anatomy of fishes

Question 1

sight and hearing

Answer 1

eyes : similar to other vertebrates
hearing : good in chondrichthyans and actinopterygians
- sound transmits well in water
- detection in inner ear
- detection based on density differences among tissues :
* Otoliths (in actinopterygians)
* gas bladder

Question 2

Mechanoreception

Answer 2

• gelatinous cupula displaced by water motion
• cupula moves cilia of hair cells
• hair cells initiates a change in signals to brain
  able to filter out background “noise”

Question 3

chemoreception

Answer 3

olfaction :
- olfactory chambers

Gustation
receptors on:
- mouth , lips, barbels
- … also fins and trunk
- often clustered into taste buds

Question 4

maintaining water / salt balance

Answer 4

hagfish : isosmotic, simple kidneys
Lamprey : similarities with teleosts
Sarcopterygians : similarities with sharks and rays
sharks and rays :
- slightly hyperosmotic to seawater
- excrete salt using rectal gland
- concentrate urea and TMAO to maintain high osmolarity
- excrete dilute urea

Question 5

marine teleost : maintaining water/salt balance

Answer 5

• hypo-osmotic
• problem : water loss and salt gain
• drink water
• excrete salt (gills and gut)
• excrete scant urine

Question 6

freshwater teleost : maintaining water/salt balance

Answer 6

• hyperosmotic
• problem : water gain and salt loss
• avoid drinking
• uptake salt (gills)
• excrete copious urine

Question 7

the buccal pump : chondrichthyes

Answer 7

• expand volume of the mouth (buccal) cavity
  
  • lower floor of mouth
  • expand pharynx
• sucks water in through the spiracle and mouth
• close mouth and force buccal cavity smaller (contract pharynx and raise floor of mouth)
• water forced over gills, out through gill slits
• water flow is unidirectional and pulsatile
• also RAM ventilation

Question 8

Circulation : Myxinomorphi

Answer 8

• partially open circulatory system
  
  • arteries -> sinuses -> veins
• 4 rudimentary hearts
  primary 3-chambered heart
  1. near gills : branchial heart
  auxiliary 1-chambered heart
  2. behind mouth : paired cardinal heart (re-establish flow)
  3. mid-body : portal heart (cardinal vein + intestine -> liver)
  4. end of tail : paired caudal heart (re-establish flow)
• branchial & portal powered by intrinsic muscle
• paired heart powered by extrinsic, skeletal muscle

Question 9

circulation : Petromyzontomorphi

Answer 9

• partially open circulation, more closed than hagfish
• main sinus un branchial region : for blood-gas exchange
• 1 heart, posterior to gills
• cutaneous respiration

Question 10

Circulation: Chondrichthyes & Actinopterygii

Answer 10

Positioned behind gills
4 chambers in series
1. Sinus venosus
* a reservoir to collect blood
* assures easy filling
2. Atrium
3. Ventricle (pump)
4. Conus / bulbus arteriosus
* Conus, muscular in sharks
* Bulbus, elastic in bony fish
Sinoatrial and atrioventricular valves maintain unidirectional flow