 Dear students, in this topic we shall discuss the asthma regulators and asthma conformers. The asthma regulators are the animals which actively regulate water and salts to maintain an internal osmolarity which is different from their external medium. Their body fluid concentrations differ noticeably from the outer environment. The internal tissues of asthma regulators are actually very sensitive to minor changes in extracellular osmolarity so they need to regulate water and electrolyte balance or electrolytes to maintain their cell volume which is disturbed by changes in osmolarity. They discharge excess water in hypotonic environments while they excrete salts in hypotonic environments. The asthma regulators include the animals which live in all environments that is marine freshwater and terrestrial environment. But in each environment they have distinct adaptations to regulate the osmotic balance. There are almost all vertebrates, such as elasmobranchs or cartilaginous fishes group elasmobranchs and except for hagg fishes all other vertebrates are asthma regulators. Marine vertebrates live in an environment which is hypotonic. They keep the salts concentration at this level that their bodies are hypotonic to the sea water. For this purpose they regulate the osmolarity to remove excess salts from the body. Freshwater vertebrates who live in a hypotonic environment they maintain high concentration of salts in their bodies so their bodies are hypotonic to the external medium. Invertebrates may have the same amount of fresh water or terrestrial invertebrates. Now we shall discuss osmoconformers. The animals which do not actively control the osmotic conditions of their body are known as osmoconformers. They conform to the osmolarity of their ambient medium. Their body fluids are kept isotonic to the external environment. All marine invertebrates as a rule are osmoconformers. That is they are in osmotic balance with the sea water. Their ion concentrations of body fluids parallel that of the sea water. But vertebrates may have a little vertebrates that is just elasmobranchs or hagg fishes. These are osmoconformers. Osmoconformers have this capacity that their cells have high osmotic tolerance. They tolerate or tolerate the changes that occur on a large scale in the osmolarities and cope with them and maintain their cell volumes. This happens. This ability is produced by increasing the intracellular osmolarities with the intracellular organic osmolites. Osmolites are those substances which reduce the need to maintain osmotic pressure with inorganic ions. Utilized by marine elasmobranchs.