Osmoregulation in Crocodilians

Taplin, L. E.

doi:10.1111/j.1469-185x.1988.tb00721.x

Cited by 60 publications

(59 citation statements)

References 76 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…However, crocodilians kidneys have a limited ability to regulate ureteral urine composition (Taplin, 1988) and cloaca function plays a larger role in osmoregulation (Pidcock et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

Morphology and Histochemistry of Juvenile American Alligator (Alligator mississippiensis) Nephrons

Moore

Hyndman

Cox

et al. 2009

The Anatomical Record

View full text Add to dashboard Cite

Here we present a detailed morphological description of the alligator (Alligator mississippiensis) kidney and nephron. We present a series of histological, histochemical, and immunohistochemical markers that clearly define the seven regions of the alligator nephron. The alligator kidney is composed of many paired (mirrored) lobules on each kidney (lobe). Single nephrons span the width of lobules three times. The fine structure of glomeruli, lying in rows spanning the height of the lobule, is resolved by periodic acid methionine silver (PAMS) and periodic acid Schiff 's (PAS) histochemistry. Glomeruli are connected to the proximal tubule (PT) via a neck segment. The PT is alcian blue-negative, making it distinct from the distal tubule (DT), connecting segment (CS), and collecting duct (CD). The PT is clearly identifiable by a PAS-positive brush border membrane. The PT is connected to the DT via an intermediate segment (IS) that makes a 180 turn to connect these tubules. PAMS-positive material is found in the lumens of the PT, IS, and DT. Also, PAMS-positive granules are found in the DT, CS, and CD. Immunolocalization of the Na þ , K þ -ATPase to the basolateral membrane of the DT, CS, and CD suggests a role of this enzyme in driving primary and secondary transport processes in these segments, including bicarbonate transport into the lumen of the DT (leading to an alkaline urine). Through the techniques described here, we have identified a series of distinct markers to be used by pathologists, veterinarians, and researchers to easily identify alligator nephron segments. Anat Rec, 292:1670Rec, 292: -1676Rec, 292: , 2009. V V C 2009 Wiley-Liss, Inc.Key words: Alligator mississippiensis; kidney; nephron; histochemistry; Na þ , K þ -ATPaseThe kidneys' primary functions, the excretion of nitrogenous wastes and the maintenance of water and ion balance, are achieved through three fundamental mechanisms: glomerular filtration, tubular reabsorption, and secretion. To understand these physiological processes, a description of the morphological structures and kidney cell types is integral. Kidneys from various vertebrate species have been well investigated (Dantzler, 1980;Dantzler and Braun, 1980;Schmidt-Nielsen, 1988;Braun, 1998); whereas, knowledge of the crocodilian kidney is more limited. Previous studies of alligator nephrons have investigated general morphology (Huber, 1917), general nephron composition (Ventura et al.,

show abstract

“…However, crocodilians kidneys have a limited ability to regulate ureteral urine composition (Taplin, 1988) and cloaca function plays a larger role in osmoregulation (Pidcock et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

Morphology and Histochemistry of Juvenile American Alligator (Alligator mississippiensis) Nephrons

Moore

Hyndman

Cox

et al. 2009

The Anatomical Record

View full text Add to dashboard Cite

show abstract

“…Webb et al (1983) noted that the presence of the larger estuarine crocodile, C. porosus, in northern Australian rivers might influence the distribution of C. johnstoni through competition or predation. While this appears likely for rivers such as the Adelaide where C. porosus is abundant, surveys of rivers in the southern Gulf of Carpentaria [Taplin (1988) and unpublished observations] suggest that other factors are also important. In the Limmen Bight and many other southern Gulf rivers, C. porosus is present at extremely low densities (Messel et al 1979(Messel et al -1986Taplin 1990).…”

Section: Discussionmentioning

confidence: 99%

“…The relevance of this distinction to consideration of salt and water balance in crocodilians (and other taxa) has been outlined by Grigg (1981) and Taplin (1984Taplin ( , 1988. The approximate boundaries between continuously and periodically hypo-and hyper-osmotic waters on the Limmen Bight mainstream at the times of our expeditions are shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…These include C. cataphractus, C. novae-guineae, C. palustris, C. rhombifer, C. niloticus and Osteolaemus tetraspis (Taplin 1988). Debate between American and Australian scholars over the significance of lingual salt glands in C. acutus of the southern USA has highlighted the difficulty of reconciling laboratory and field observations in some environments (Taplin 1988).…”

Section: Introductionmentioning

confidence: 99%

“…Hatchlings and juveniles are able to maintain plasma homeostasis and grow in salinities of 0-45 mg.ml -1 at least (Grigg et al 1980;Grigg 1981;Taplin 1984Taplin , 1988. This capability derives in part from active lingual salt glands (Taplin and Grigg 1981) which account for a substantial fraction of Na + efflux in sea water (Taplin 1985;Grigg et al 1986).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Osmoregulation of the Australian freshwater crocodile, Crocodylus johnstoni, in fresh and saline waters

1993

View full text Add to dashboard Cite

Abstract. An unusual saltwater population of the "freshwater" crocodilian, Crocodylus johnstoni, was studied in the estuary of the Limmen Bight River in Australia's Northern Territory and compared with populations in permanently freshwater habitats. Crocodiles in the river were found across a large salinity gradient, from fresh water to a salinity of 24 mg.ml -1 , more than twice the body fluid concentration. Plasma osmolarity, concentrations of plasma Na + , Cl -, and K + , and exchangeable Na + pools were all remarkably constant across the salinity spectrum and were not substantially higher or more variable than those in crocodiles from permanently freshwater habitats. Body fluid volumes did not vary; condition factor and hydration status of crocodiles were not correlated with salinity and were not different from those of crocodiles from permanently fresh water. C. johnstoni clearly has considerable powers of osmoregulation in waters of low to medium salinity. Whether this osmoregulatory competence, extends to continuously hyperosmotic environments is not known, but distributional data suggest that C. johnstoni in hyperosmotic conditions may require periodic access to hypoosmotic water. The study demonstrates a physiological capacity for colonisation of at least some estuarine waters by this normally stenohaline freshwater crocodilian.

show abstract

Osmoregulation by Vertebrates in Aquatic Environments

Lillywhite

Evans

2021

Encyclopedia of Life Sciences

View full text Add to dashboard Cite

Because the salt concentration of body fluids in aquatic vertebrates differs from that of their environment, they face net influx or efflux of water and salt across their permeable skin or exposed membranes. In fishes, these diffusional movements of both salts and water largely involve the gills. Other vertebrates have less permeable body surfaces, but water and salts are gained in drinking that is incidental to eating prey, which also can be an important source of salt intake. Kidneys function importantly in freshwater fishes to remove excess water, and ions are actively transported inwards across gill tissue as well as acquired in food. Marine fishes tend to dehydrate in seawater, so they drink seawater to make up a water deficit and secrete excess salt across the gills. Marine elasmobranch fishes accumulate urea in body fluids to minimise the gradient for osmotic exchange and secrete excess ions via a specialised rectal gland that functions accessory to the kidney. In other vertebrates, inhabitants of fresh water must counteract a key problem of acquiring sufficient ions while excreting nitrogenous waste as ammonia or urea, whereas marine species must avoid excess salt intake while avoiding dehydration. Vertebrates without gills have evolved either extrarenal salt glands that excrete excess salt, or in the case of mammals, a specialised kidney that can excrete highly concentrated urine. Relatively few, non‐fish taxa drink seawater as a route for water gain, while most others have dependency on dietary, metabolic or free drinking water. Osmoregulation involves the maintenance of volume, distribution and ionic composition of body fluids in organisms. With the exception of hagfish, extant vertebrates maintain osmotic concentrations of body fluids at levels that are roughly one‐third that of seawater. Aquatic vertebrates living in fresh water must counteract excessive influx of water and losses of ions to the surrounding environment, whereas those living in marine environments tend to dehydrate and gain excess salt. Freshwater fishes eliminate excess water by means of producing a copious flow of dilute urine, while acquiring ions from surrounding water by transporter mechanisms located in the gills. Marine fishes acquire needed water by drinking seawater and excreting excess salt gained by diffusion and drinking by transport mechanisms in the gills. Marine vertebrates other than fishes and mammals have evolved extrarenal salt glands that excrete excess salts, and water is gained largely from dietary, metabolic and freshwater drinking sources. Marine mammals excrete salt loads and urea from kidneys that have effective concentrating abilities, while gaining water from diet and metabolism.

show abstract

Osmoregulation in Crocodilians

Cited by 60 publications

References 76 publications

Morphology and Histochemistry of Juvenile American Alligator (Alligator mississippiensis) Nephrons

Morphology and Histochemistry of Juvenile American Alligator (Alligator mississippiensis) Nephrons

Osmoregulation of the Australian freshwater crocodile, Crocodylus johnstoni, in fresh and saline waters

Osmoregulation by Vertebrates in Aquatic Environments

Contact Info

Product

Resources

About