Lecture 17. October 15, 2008

Osmoregulation & Excretion

How many students are missing the lab notebook?

Need 2 graduate student volunteers to enter data.

http://www.npr.org/templates/story/story.php?storyId=95567915&live=1&ps=bb1

Deepest Sea Fish Ever Found!!

- Liparidae - Snail Fish Family - Scorpaneiformes- 4.8 miles down- no airspaces- despite no light, it has eyes - presumably to see bioluminescence- if you subject nerves or muscle to that much pressure, they stop working.- must have adaptations that allow for all that pressure

Thought Question

Active fish have higher relative surface areas than inactive fish.

Why don’t all fish have high relative surface areas?

Dissolved Solutes in Different Types of Water

hagfish

Source [Na+] [K+] [Cl-] others urea mOsm

seawater 439 9 513 88 1050

hagfish 486 8 508 20 1035

sharks - hammerhead

Source [Na+] [K+] [Cl-] others urea TMAO mOsm

seawater 439 9 513 88 0 0 1050

shark 255 6 241 103 441 72 1118

Sharks use trimethylamine oxide (TMAO) which protects them from high urea.

toadfish - SW

Source [Na+] [K+] [Cl-] others urea mOsm

seawater 439 9 513 88 1050

toadfish 180 5 196 9 452

goldfish - FW

Source [Na+] [K+] [Cl-] others urea mOsm

freshwater 0.25 0.04 0.23 1 <5

goldfish 130 3 125 3 274

Source [Na+] [K+] [Cl-] others TMAO urea mOsm

freshwater 0.25 0.04 0.23 1 <5

FW stingray 150 - 150 7 - - 308

freshwater stingray

http://www.biology.ualberta.ca/courses/zool241/index.php?Page=1815

Gill Models

Take home point: This is somewhat complex.

Some saltwater teleosts lack a glomerulus in their kidney.

What does a glomerulus do?

Why would this be a good thing for saltwater teleosts?

Thought Questions

1. What properties/traits that affect osmoregulation do you think would change when catadromous eels migrate from f.w. to s.w. to spawn?

2. What properties/traits do you think would change when anadromous lampreys migrate from s.w. to f.w. to spawn?

3. Why are saltwater Elasmobranchs have a slightly higher total ionconcentration than the surrounding seawater?

Review Questions.1. Distinguish between an osmoregulator, an osmoconformer, an ion regulator,and an ion conformer. For each of the following taxa, explain their strategy in regards to ion/water balance: hagfish, shark, toadfish, goldfish, f.w. stingray.

2. Why do inactive fish have low relative gill surface volumes? Why not have alarge gill surface volume to get more O2 in the body? Hint: what problem doeslarge gill surface area lead to?

3. How do fish regulate their pH? Did you read page 91?

4. Why don’t freshwater stingrays maintain urea in their bodies? Why do saltwaterElasmobranchs maintain TMAO in their bodies?

5. What properties/traits that affect osmoregulation do you think would change when catadromous eels migrate from f.w. to s.w. to spawn? What properties/traits do you think would change when anadromous lampreys migrate from s.w. to f.w. to spawn?

6. From the book. What hormones are involved in the transition from freshwaterto saltwater? What hormones are involved in the transition from saltwater to f.w.?

7. Why do some saltwater teleosts lack a glomerulus?