Describe the osmotic challenge faced by a freshwater teleost?

Answer 1

freshwater fishes face two challenges:
1. absorption of water into the body by osmosis through exposed body surfaces.
2. loss of minerals.
they overcome it by:
1. excreting lots of dilute urine.
2.absorbing minerals against concentration gradient through ionocyte cells in gill membranes

Answer 2

All freshwater animals face major osmosis problems because there are far more soluble molecules present inside them than in the outer water so the water will try to force its way up the concentration gradient to 'dilute' what's inside and the small molecues inside that can exit the organism will be forced out.

not sure what a teleost is but this should be relevant in some way :)

Answer 3

Why should the freshwater teleost be facing an "osmotic challenge"?
Has it been placed in an environment to which it is not suited?
It is osmotically adapted to its environment, so the "challenge" needs to be defined.

Answer 4

Irrespective of the salinity of their external environments, teleost fishes maintain their plasma osmotic concentration about one-third that of seawater. In fresh water this requires counteracting the passive gain of water and loss of ions by producing a copious dilute urine and actively taking up ions across the gills. In seawater, teleosts must counteract the passive gain of ions and loss of water. This is accomplished by drinking seawater, absorbing water and salts across the gut, and secreting excess monovalent ions across the gills and divalent ions through the kidney.1. Morphology and transport mechanisms of gill chloride cells in seawater and fresh water. See text for details of transport mechanisms. Chloride cells are characterized by numerous mitochondria and an extensive tubular system that is continuous with the basolateral membrane. In seawater, chloride cells are generally larger and contain a deep apical cyrpt, whereas in freshwater the apical surface is broad and contains numerous microvilli. In some species, such as tilapia the H+-ATPase and apical sodium channel may be present in pavement cells rather than chloride cells. Recent evidence suggests that individual chloride cells can move between these two mophological states (Hiroi et al., 1999), and also arise from undifferentiated stem cells (Wong and Chan, 1999). Growth hormone and cortisol can individually promote the differentiation of the seawater chloride cell, and also interact positively to control epithelial transport capacity. Prolactin inhibits the formation of seawater chloride cells and promotes the development of fresh water chloride cells. Cortisol also promotes acclimation to fresh water by maintaining ion transporters and chloride cells, and by interacting to some degree with prolactin. PVC = pavement cell

Answer 5

Water will be lost from an area of low solute concentration (the freshwater) to an area of high solute concentration (the fish).

Answer 6

you are getting lazy

Answer 7

sorry havent got a clue .////////////////

Answer 8

.
And do your homework for you ? ......

......... HA HA .......

...............NO ..........