What is a “euryhaline fish”? How do they adjust their physiology to the different salinity environments?
- can tolerate varying levels of salinity
- can rapidly switch between osmoregulatory strategies
- surfaces tend to be more impermeable to water and NaCl
- adults are typically more tolerant to a wider salinity rang
Define anadromous and catadromous
- anadromous: spawn in freshwater, live in ocean
- catadromous: spawn in ocean, live in freshwater
Explain the physiological challenges that salmon face as part of its reproductive cycle
- Freshwater osmoregulation (take up NaCl, pee diluted urine)
- Low [Ca2+] in FW = resorb Ca2+ from bone
- Burst swimming = white muscle
- Reproduction= egg & sperm production, secondary sexual characters (e.g. hooked jaw and hump in males)
How do animals maintain their position in the water column?
- active swimming: requires energy
- buoyancy: saves energy
Describe the general buoyancy strategy
- anything that weighs less than the weight of the water it displaces will float
- accumulate things that are lighter than water to remain buoyant
Provide examples of low density substances used to maintain buoyancy
- ammonium (lighter than sodium)
- fat (lighter than protein or muscle)
- cartilage (lighter than bone)
Why are the concentrations of NH4+ and Na+ inversely related in buoyancy compartments?
- needs to maintain balance of charges, so NH4+ replaces Na+ to be more buoyant
- when one increases, the other must decrease to keep charges the same
Why do sites of NH4+ accumulation for buoyancy have an acidic pH?
- NH4+ prefers the form NH3 at basic pHs, which is a gas that will diffuse out
- must keep pH low to keep in ammonium form
What type of diet do cephalopods have, and why is this essential for their buoyancy strategy?
- carnivorous diet
- use the amino acids from proteins to form ammonium
What other animal seen in this course have a similar type of diet? What is the significance for osmoregulation?
- sharks
- used to create urea to offset osmotic gap
How do sharks and rays achieve buoyancy?
- has cartilage instead of bone
- accumulates squalene (and other lipids) in liver
- pectoral fins and asymmetrical tail provide “dynamic lift”
Describe the experiment that established the relationship between feeding status and buoyancy during shark migrations between California and Hawaii
- White sharks migrate between California and Hawaii and feed on pinnipeds in CA, then barely feed during the migration (use liver lipid stores as their main energy source) and feed again in Hawaii
- drift rate increases during migration, meaning their buoyancy decreases as they use liver lipid stores as energy
- they tend to sink faster and use more energy swimming to stay afloat
What is the major advantage of accumulating gases as a buoyancy mechanism? And the disadvantage?
- very low density, so provides a lot of buoyancy
- can limit rapid movements
- uses energy
What animals have rigid buoyancy gas chambers? What are the advantages and disadvantages?
- cephalopods
- A: a rigid compartment does not change volume with depth/pressure
- D: requires energy, might break at high pressure => limits depth (chambers can get thicker to withstand pressure, but it adds weight so there is a limit), relatively slow
Explain how the cuttlefish gas chamber regulates buoyancy. Use the following terms: cuttlebone, chambers with lamellae, epithelium with cells rich in mitochondria and NKA, blood, NaCl transport, water transport, size of the gas bubble.
- the cuttlefish has a porous cuttlebone that is divided into chambers with lamellae that contain liquid and gas
- the epithelium rich in mitochondria and NKA change the concentration of NaCl in the lamellae using energy from the mitochondria
- NKA drives NaCl absorption from fluid inside the chamber into the blood
- water follows NaCl and leaves the chamber
- N2 gas diffuses from the blood into the chamber, expanding and increasing the size of the gas bubble => more buoyant
What are the two types of fish swim bladders?
- connected to the esophagus (open)
- not connected to the esophagus (closed)
What is the function of the gas gland? What is the function of the oval?
- gas gland acidifies the blood running through blood capillaries (high rates of CO2 and Lactate/H+ production from respiration)
- oval has muscular valve for O2 release, allows the bladder to deflate
Explain the mechanism that fills up a close swim bladder. Use the following terms: Swim bladder, gas gland, metabolic production of lactic acid and CO2, acidification, red blood cells, hemoglobin, Root effect, O2 movement, gas impermeable, rete mirabilis.
- Cells in the gas gland produce CO2 and lactic acid
- acidification induce RBCs to release O2 by the root effect and the bohr effect
- root effect prevents cooperativity so it reduces oxygen carrying capacity
- bohr effect reduces the oxygen affinity
- O2 diffuses into the swim bladder
- rete mirabilis further increases O2 concentration in the capillaries feeding the swim bladder
- the swim bladder is gas impermeable to the accumulated oxygen cannot escape
Why do fishes that live deeper have a longer rete mirabilis in their swim bladders?
-they need to accumulate gas against larger hydrostatic pressure
