B6 vertebrates, morphology

Question 1

Hearing in fish

Answer 1

Good in Chondrichthyes and Actinopterygians.
Transmits well in water. Detection in inner ear is based on density differences among tissues.

Question 2

Gas bladder

Answer 2

Close to ear. Used as an amplifying device to make the signal larger, so they hear louder.

Question 3

Otoliths

Answer 3

Bones in ear which receive vibrations which convert to sound.

Question 4

Stereocilia

Answer 4

Propagate sound, only work in one direction. When they bend the sound is registered.

Question 5

Mechanoreception

Answer 5

Gelatinous cupula displaced by water motion -> cupula moves cilia of hair cells -> hair cell initiates a change in signals to brain.

Can filter out background noise, located on outside of fish so there’s noise from water movements/other fish.

Question 6

Electroreception (ampullae of lorenzini)

Answer 6

Ampillary receptors (ampulla derived from hair cells), recesses in skin which are connected to outside of the fish with a conductive gel, sensitive to low frequency electrical fields produced by environment/bodies.

Question 7

Electroreception (tuberous organ)

Answer 7

Detect a higher frequency (animals with own electric fields).

Lampreys, sharks, actinopterygians, sturgeons, bony-tongued fish, knife fish, cat fish.

Question 8

Chemoreception (olfaction)

Answer 8

Olfactory chamber to smell on surface of fish. Sensitive to hormones and honing (smelling rivers).

Question 9

Chemoreception (gustation)

Answer 9

Taste receptors on mouth/lips/barbels/fins/trunk (often clustered into taste buds).

Question 10

Digestive system

Answer 10

Herbivorous fish = very long digestive system, good microbiota to digest plant material. Long intestine + smaller stomach

Carnivorous fish = larger stomach, a lot of muscle + smaller digestive tract.

All do absorption digestion too.

Question 11

Water/Salt balance (sharks/rays)

Answer 11

Slightly hyperosmotic to seawater, excrete salt using rectal gland, concentrate urea and TMAO to keep high osmolarity, excrete dilute urea. Match the minerals + osmolarity of the seawater (solutes with very small effects on metabolism).

If salinity drops, they just produce less urea, or excrete it). Shark gills are impermeable to urea.

Sacropterygiians are similar (convergent evo)

Question 12

Water/Salt balance (hagfish/lampreys)

Answer 12

Hagfish = isosmotic, simple kidneys.

Lamprey = sim to teleosts.

Question 13

Salt/Water balance (marine teleosts)

Answer 13

Hypo-osmotic. Problem = water loss, salt gain, drink water, excrete salt (gills and gut), excrete scant urine.

Question 14

Salt/Water balance (freshwater teleosts)

Answer 14

Hyperosmotic- Problem = water gain, salt loss, avoid drinking, uptake salt (gills), excrete copious urine.

Question 15

Respiration in Hagfish

Answer 15

Hagfish = very primitive respiratory systems. Water comes through nostrils, pass over gill sacks and capillaries, then passes back out.

Question 16

Buccal pump (Chondrichthyes)

Answer 16

Expand vol of mouth (buccal cavity) using lower floor of mouth and expand the pharynx. Sucks water in through spiracles + mouth. Close mouth to force the cavity to get smaller (contract pharynx + raise mouth floor). Water forced over gills and out through gill slits, water flow is unidirectional and pulsatile. RAN ventilation.

Water is pumped over the gill, flows in between the filaments, flows along the septum, and back out again. Lamellae are on the gill filaments to increase surface area and thus air absorbed.

Question 17

Buccal and opercular pump (Teleosts)

Answer 17

They can expand opercular pump, so they use both pumps, water enters, pressure drops, pumped through and back out again. They also have to seal water off once inside.

Question 18

Teleost gills

Answer 18

Have separated filaments which fan out so water goes in between gill arches. Very efficient since water doesn’t have to change direction.

Question 19

Brachiostegal rays/membrane

Answer 19

How they open + close the membrane surrounding the gills. It also creates negative pressure so water flows through.

Question 20

Countercurrent exchange

Answer 20

Blood along capillary is always in contact with water that has a higher PO2. Diffusion gradient maintained across whole respiratory surface, so all oxygen can be stripped out of water.

Question 21

Circulation (myxinomorphi)

Answer 21

Have 4 hearts (primary 4 chambered heart near the gills, and then 3 auxiliary 1 chambered heart. One behind mouth (re-establish flow), one mid body (portal heart, cardinal vein + intestine -> liver), one at the end of tail (re-establish flow)).

Question 22

Circulation (Petromyzontomorphi)

Answer 22

Partially open circulation, more closed than hagfish. 1 heart, posterior to gills, cutaneous respiration.

Question 23

Circulation (Chondrichthyes/Actinopterygii)

Answer 23

Behind gills, 4 chambers. Sinus venosus (reservoir to collect blood), atrium, ventricle (pump), conus/bulbus arteriosus.
Sinoatrial and atrioventricular valve maintain unidirectional flow.