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Most Lizards
Most Lizards
Land-dwelling iguanas, though different species vary signifcantly in habitat and behavior, feed primarily on flowers, foliage and fruit. Above photo is of a Galápagos Land Iguana.
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Marine Iguanas
Marine Iguanas
The only species of lizard known to feed in the sea, the marine iguana has adapted to obtain nutrients in a very unique way. However, by feeding underwater, they ingest a large amount of salt.
Osmoregulation
Osmoregulation
Mass-specific water turnover rates in adult marine iguanas are high compared to other lizards. It's estimated that, while feeding underwater, these iguanas ingest a high amount of seawater, as indicated by the NaCl content of nasal secretions. About 40% of their total water intake is estimated to be from seawater. This high salt intake results in the well-known great secretory capacity of the nasal salt gland of the marine iguana. This high salt intake also affects the way marine iguanas filter and absorbs nutrients.
Filtration
Filtration
The reptilian urinary tract has paired kidneys, which are connected to the cloaca by the ureter. Inside the kidney, there is no pelvis or pyramids, and there are only a few thousand nephrons. The reptilian nephron is 2 to 8mm, and lacks a Loop of Henle, though a glomerulus is still present, which acts as a microscopic filter. The lack of a Loop of Henle means that reptiles are not able to produce hypertonic urine and instead excrete it in more concentrated forms.
Normal kidney in a green iguana (Iguana iguana) (Zwart et al.)
Absorption
Absorption
Marine iguanas have uniquely adapted to reabsorb large amounts of water in their kidneys. They also drink large amounts of water during the day. Their highly efficient salt glands ensure that water and salt are carefully separated, allowing for pure elimination of salt in the form of a sneeze!
Excretion
Excretion
All products of the urinary, digestive, and reproductive systems exit through the vent of the cloaca. The filtered product in the kidneys from the few thousand nephrons drains into a collecting duct. The product moves through the ureter, until reaching the cloaca chamber. Until elimination, this is where all the products from the abovementioned systems reside.
Watch them sneeze!
Watch them sneeze!
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