Elasmobranchs Flashcards
Why do Elasmobranchs have high levels of TMAO
TMAO neutralises the denaturation effect of UREA on proteins
Describe Elasmobranchs osmolarity
Elasmobranchs are slightly hyper osmotic to their environment. This Is because although with their ions alone they would be isosmotic, their blood contains urea and TMAO which also contributes to osmotic pressure.
What is TMAO
Tri-Methyl-Amine Oxide
How are excess salts removed?
Excess Na+ and Cl- are removed via the rectal gland by active transport.
Do Elasmobranchs drink water?
No - however water does enter passively by diffusion across girls
How do elasmobranchs solve the problem of ions diffusion into their bodies?
The rectal gland - it has a low permeability for ions and a spiral intestine.
Why is the rectal gland dark brown?
The dark brown colour shows there is lots of blood supply and lots of myoglobin collecting oxygen which is needed for high levels of active transport of ions.
Explain the rectal glands structure
The gland has a tubular system which empties into the central canal and then into the spiral intestine. The basolateral membrane is rich in Na+K+ATPase pumps and tight junctions have high permeability for Na+.
How does the Rectal Gland work?
- ATPase builds up Na+ gradient in the cell
- The gradient means that Cl- ions follow in via the NKCC cotransporter
- Cl- then diffuses out of the cell into the seawater
- Tight junctions have a high permeability to Na+ meaning Na+ is drawn out to the seawater from a +ve to a -ve charge (paracellular)
How do elasmobranchs solve the problem of high urea in their blood?
Kidneys reabsorb urea and TMAo (UREA retention), the kidneys have 3/4 loops for reabsorption; TMAO counteracts the denaturation effects of urea on proteins.
