Cloacal Water Absorption/ T & Q II / kinda long...sorry

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Posted by BabyHerp on May 05, 2000 at 12:56:28:

In response to the question posted by T about where I was able to find info that Iguanas DO NOT absorb water thru their vents ....the BEST fieldwork done by a university which I thought I bookmarked...cannot be found (at this time anyway;-) I can however post numerous snipets from articles Ive read regarding permeability of skin, and function of the cloaca and you decide. The only time I have EVER come across something regarding cloaca & being able to absorb EXTERNAL water was in an Iguana Iguana Newsletter article Vol 5 I think....in response to a letter from a person worried about her iguana and kidney disease. Here is THAT response/snipet:

******Soak her in a warm water bath every day to encourage pooping and to help with hydration. You can even put Pedialyte in the water as iguanas can absorb fluids through their cloaca vent*******

I have never come across a scientific paper that substantiates this for iguanas in my search to date. I too used to advocate people soaking their iguana in Gatorade or Pedialyte to increase internal hydration...but I truly think NOW that I was full of it! Oops forgot two letters there. Numerous species of turtles, some tortoises *are* able to absorb water via the cloaca from external sources however and Ive read papers (scientific, academic research articles) that substantiate this.

BUT: what I HAVE found thru reading numerous articles that the cloaca acts as a resevoir where water is "resorbed" into the bloodstream NOT "absorbed" from external forces. Absorbed and resorbed are really two different things. The correct term should be resorbed in regards to water & cloaca. Iguana takes in water by mouth (food or drink)...once ingested nutrients and liquids find way to cloaca were it is resorbed. Here is a bunch of related snipets from various articles regarding reptiles ability to take in water, and skin permeability (all snipets about reptiles or lizards). Some of it may not be very noteworthy....but draw your own conclusions.
*****
Reptiles---problem: desication
Kidney--scant isotonic urine
Cloaca -- resorbs water
Nitrogen waste--uric acid
*****
Terrestrial species face problems with fluid conservation. Water loss occurs at skin, lungs and kidney. Water and electrolyte balance depend upon gut and kidney. Kidney must eliminate waste while conserving water.
******
Most reptiles do not experience the benefits or costs of water movement through the skin -- reptile skin is so impermeable owing to a lipid layer.
******
Reptiles do, however, uptake water through the mouth. Usually by drinking directly from pools.
******
In semiarid environments where ponds and pools are not available, they display other interesting adaptations:

Fog collection - e.g., Namib Desert Vipers

Dew collection - lizards

Rain collection behaviors and structures - turtles

Active maintenance of water holes - tortoises
***********
Uptake: Preformed water

Water in tissues of food also forms an important component of water uptake -- and often is the only source for desert species (e.g., Galapagos tortoises).
**************

Other herps have the best mixture of water and ions, but plants and insects are also important sources. Reptiles will stop eating certain plants if their water or ion content unfavorable.
********************
Uptake: Metabolic water
Metabolized from food - 1 g starch produces 0.556 g water and 1 g fat to 1 g water. With proteins, nitrogen wastes must be dealt with: 1 g protein to 0.4 g water (urea) or 0.5 g water (uric acid) plus nitrogenous wastes.

Metabolizing fat in reptiles can be a particularly important source of metabolic water during drought periods -- e.g., tortoises.

Loss: Evaporation

Mainly regulated through changes in skin permeability and behavior
*******************
Modifying skin permeability -- Case study:

Phyllomedusa spp. (large South American hylids, semiarboreal and in semiarid regions -- always in danger of dehydration). Secrete mixture of waterproofing agents, smears them over body with limbs, and substantially decreases skin permeability. Risks overheating but waxy cover actually melts and animal opens eyes wide to cool brain at high temperatures (thereby reverting to evaporative cooling).
********
Reduce exposure of moist surfaces by closing eyes, tucking limbs, curling body, crouching or clustering with others
*********

Cloaca -- Several turtles have bursae in cloaca and rarely surface for air, but constantly pump water in and out of cloaca at 1-5 s intervals, e.g., Podocnemis.
***********
3. Reptiles have a thick, scaly skin that is keratinized and impermeable to water; keratin is protein found also in hair, fingernails, and feathers; this protective skin prevents water loss but requires several molts a year.
*******
Reptiles have a lower metabolic demand (oxygen demand) than birds and mammals. As a result they can go underwater for extensive periods without any specializations because of their 3 chambered heart.
***********
Reptiles, birds and mammals live in a dry environment and need to drink or eat all their water. This may be hard to come by so their kidneys conserve water. Birds and reptiles process nitrogenous waste into uric acid (uricotelic). This is not water soluble so little water is needed. Salt is excreted in the urine or by salt glands. They don't make a watery urine, most water is reabsorbed and a white paste is formed.
********
Characteristics of reptiles
- stronger skeleton than amphibians
- pelvic girdle attaches to vertebral column by at least 2
sacral vertebrae
- skull - deeper and narrower
- outer skin - horny scales that conserve water
*********
Water Conservation
Impervious skin: horny scales, keratin
- phospholipids bound to keratin --> water-proofing skin, phosopholipids important
************
Despite having waterproof skins most land animals still lose water via lungs, skin, urine, f�ces.
**************
b. Water sources are food, drink, metabolic water.
i. Some animals get most of their water by oxidation of food.
ii. The end-products of cell respiration are CO2 and water.
*****************
In many species from arid environments, the hindgut ends in a cloaca rather than an anus. The distinction here is that the urethra from the bladder terminates in a common chamber with the undigested food from the intestine, rather than through it=s own independent opening through the external genitalia (cloaca is latin for sewer). The advantage of this is that water can then be re-absorbed from the urine also resulting in the formation of a semi-solid paste and a further reduction in water loss.
***************
reptiles possess a cloaca allows even better retention of water/electrolytes beyond that of the large intestine.
*****************
In reptiles the resorption of water from the urine mainly takes place in the cloaca and not in the kidneys themselves. Most reptiles produce mainly urates (a white deposit) as the end-product of their protein metabolism.
******************
>>>>>>>The only reason why we keep a humid enviroment, spray, bath, our iguanas imo is to PREVENT water loss/osmolarity.....they do NOT "absorb" anything skin or cloaca ....only whats ingested. Dehydration is a very important factor....no doubt in preventing kidney disease....but what I starting to find out....kidney disease in our captive igs has more to do with the PROTEIN (plant) content of their foods/over supplementation of vitamins & the types of calcium given. Im not sure if this helps....but its all I got right now.....I'll try and find that one research article that
made up my mind FINALLY ....about this issue.
Until then....goodnight!!
Gina

Follow Ups:

DATA! Bwahahaha I'm rolling in it! Iguanamomma 05/06/00 (0)
Re: "It's all I've got right now..." ROTFLMAO!!!!! T and Q 05/05/00 (2)
- Re: "It's all I've got right now..." ......... (more) iZ's mom 05/05/00 (1)
  - Re: Ok you guys are you done ROTFLYAO?? much more :-O BabyHerp 05/05/00 (0)

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: In response to the question posted by T about where I was able to find info that Iguanas DO NOT absorb water thru their vents ....the BEST fieldwork done by a university which I thought I bookmarked...cannot be found (at this time anyway;-) I can however post numerous snipets from articles Ive read regarding permeability of skin, and function of the cloaca and you decide. The only time I have EVER come across something regarding cloaca & being able to absorb EXTERNAL water was in an Iguana Iguana Newsletter article Vol 5 I think....in response to a letter from a person worried about her iguana and kidney disease. Here is THAT response/snipet: : ******Soak her in a warm water bath every day to encourage pooping and to help with hydration. You can even put Pedialyte in the water as iguanas can absorb fluids through their cloaca vent******* : I have never come across a scientific paper that substantiates this for iguanas in my search to date. I too used to advocate people soaking their iguana in Gatorade or Pedialyte to increase internal hydration...but I truly think NOW that I was full of it! Oops forgot two letters there. Numerous species of turtles, some tortoises *are* able to absorb water via the cloaca from external sources however and Ive read papers (scientific, academic research articles) that substantiate this. : BUT: what I HAVE found thru reading numerous articles that the cloaca acts as a resevoir where water is "resorbed" into the bloodstream NOT "absorbed" from external forces. Absorbed and resorbed are really two different things. The correct term should be resorbed in regards to water & cloaca. Iguana takes in water by mouth (food or drink)...once ingested nutrients and liquids find way to cloaca were it is resorbed. Here is a bunch of related snipets from various articles regarding reptiles ability to take in water, and skin permeability (all snipets about reptiles or lizards). Some of it may not be very noteworthy....but draw your own conclusions. : ***** : Reptiles---problem: desication : Kidney--scant isotonic urine : Cloaca -- resorbs water : Nitrogen waste--uric acid : ***** : Terrestrial species face problems with fluid conservation. Water loss occurs at skin, lungs and kidney. Water and electrolyte balance depend upon gut and kidney. Kidney must eliminate waste while conserving water. : ****** : Most reptiles do not experience the benefits or costs of water movement through the skin -- reptile skin is so impermeable owing to a lipid layer. : ****** : Reptiles do, however, uptake water through the mouth. Usually by drinking directly from pools. : ****** : In semiarid environments where ponds and pools are not available, they display other interesting adaptations: : Fog collection - e.g., Namib Desert Vipers : Dew collection - lizards : Rain collection behaviors and structures - turtles : Active maintenance of water holes - tortoises : *********** : Uptake: Preformed water : Water in tissues of food also forms an important component of water uptake -- and often is the only source for desert species (e.g., Galapagos tortoises). : ************** : Other herps have the best mixture of water and ions, but plants and insects are also important sources. Reptiles will stop eating certain plants if their water or ion content unfavorable. : ******************** : Uptake: Metabolic water : Metabolized from food - 1 g starch produces 0.556 g water and 1 g fat to 1 g water. With proteins, nitrogen wastes must be dealt with: 1 g protein to 0.4 g water (urea) or 0.5 g water (uric acid) plus nitrogenous wastes. : Metabolizing fat in reptiles can be a particularly important source of metabolic water during drought periods -- e.g., tortoises. : Loss: Evaporation : Mainly regulated through changes in skin permeability and behavior : ******************* : Modifying skin permeability -- Case study: : Phyllomedusa spp. (large South American hylids, semiarboreal and in semiarid regions -- always in danger of dehydration). Secrete mixture of waterproofing agents, smears them over body with limbs, and substantially decreases skin permeability. Risks overheating but waxy cover actually melts and animal opens eyes wide to cool brain at high temperatures (thereby reverting to evaporative cooling). : ******** : Reduce exposure of moist surfaces by closing eyes, tucking limbs, curling body, crouching or clustering with others : ********* : Cloaca -- Several turtles have bursae in cloaca and rarely surface for air, but constantly pump water in and out of cloaca at 1-5 s intervals, e.g., Podocnemis. : *********** : 3. Reptiles have a thick, scaly skin that is keratinized and impermeable to water; keratin is protein found also in hair, fingernails, and feathers; this protective skin prevents water loss but requires several molts a year. : ******* : Reptiles have a lower metabolic demand (oxygen demand) than birds and mammals. As a result they can go underwater for extensive periods without any specializations because of their 3 chambered heart. : *********** : Reptiles, birds and mammals live in a dry environment and need to drink or eat all their water. This may be hard to come by so their kidneys conserve water. Birds and reptiles process nitrogenous waste into uric acid (uricotelic). This is not water soluble so little water is needed. Salt is excreted in the urine or by salt glands. They don't make a watery urine, most water is reabsorbed and a white paste is formed. : ******** : Characteristics of reptiles : - stronger skeleton than amphibians : - pelvic girdle attaches to vertebral column by at least 2 : sacral vertebrae : - skull - deeper and narrower : - outer skin - horny scales that conserve water : ********* : Water Conservation : Impervious skin: horny scales, keratin : - phospholipids bound to keratin --> water-proofing skin, phosopholipids important : ************ : Despite having waterproof skins most land animals still lose water via lungs, skin, urine, f�ces. : ************** : b. Water sources are food, drink, metabolic water. : i. Some animals get most of their water by oxidation of food. : ii. The end-products of cell respiration are CO2 and water. : ***************** : In many species from arid environments, the hindgut ends in a cloaca rather than an anus. The distinction here is that the urethra from the bladder terminates in a common chamber with the undigested food from the intestine, rather than through it=s own independent opening through the external genitalia (cloaca is latin for sewer). The advantage of this is that water can then be re-absorbed from the urine also resulting in the formation of a semi-solid paste and a further reduction in water loss. : *************** : reptiles possess a cloaca allows even better retention of water/electrolytes beyond that of the large intestine. : ***************** : In reptiles the resorption of water from the urine mainly takes place in the cloaca and not in the kidneys themselves. Most reptiles produce mainly urates (a white deposit) as the end-product of their protein metabolism. : ****************** : >>>>>>>The only reason why we keep a humid enviroment, spray, bath, our iguanas imo is to PREVENT water loss/osmolarity.....they do NOT "absorb" anything skin or cloaca ....only whats ingested. Dehydration is a very important factor....no doubt in preventing kidney disease....but what I starting to find out....kidney disease in our captive igs has more to do with the PROTEIN (plant) content of their foods/over supplementation of vitamins & the types of calcium given. Im not sure if this helps....but its all I got right now.....I'll try and find that one research article that : made up my mind FINALLY ....about this issue. : Until then....goodnight!! : Gina

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