Comparison of some parameters of serum and uterine fluid of pregnant, viviparous sharks (Carcharhinus leucas) and serum of their near-term young

Abstract

Abstract-I. In eight females, serum urea concentrations of 134-336 ml\l/l.

Body Fluid Solutes of Juveniles and Adults of the Euryhaline Bull Shark Carcharhinus leucas from Freshwater and Saline Environments

“…The individual urea levels range from well below the fresh-water average (157 compared with 169 mM/liter to approximately the marine average (357 compared with 356 mM/liter). A similar range of urea levels (134-336 mM/ liter) was found in a series of eight pregnant females taken from the same collecting grounds at Barra del Colorado (Thorson and Gerst 1972). From tagging and tracking records (unpublished data) it is known that these sharks move freely in and out of the river mouth and from fresh water to salt water and vice versa.…”

Body Fluid Solutes of Juveniles and Adults of the Euryhaline Bull Shark Carcharhinus leucas from Freshwater and Saline Environments

“…The individual urea levels range from well below the fresh-water average (157 compared with 169 mM/liter to approximately the marine average (357 compared with 356 mM/liter). A similar range of urea levels (134-336 mM/ liter) was found in a series of eight pregnant females taken from the same collecting grounds at Barra del Colorado (Thorson and Gerst 1972). From tagging and tracking records (unpublished data) it is known that these sharks move freely in and out of the river mouth and from fresh water to salt water and vice versa.…”

Living with high concentrations of urea: They can!

“…Most elasmobranches live in seawater and are stenohaline while the stingrays of the genus Potamotrygon are the only elasmobranch permanently adapted to freshwater [45,46]. However a number of species are marginally euryhaline since they can enter in the brackish environment of river mouths [47] and a small number can move from seawater to freshwater, generally on a seasonal basis [13,46,48,49].…”

“…Since the kidney is the primary organ responsible of urea retention and euryhaline elasmobranchs remain ureotelic in environment with a low salinity [30,34,46,[50][51][52] the renal regulation of urea retention in habitat with different salinities is crucial for the osmotic homeostasis of these species. This observation suggests that the activity and/or the expression of urea transporters in renal tubules have to be regulated.…”

Molecular and functional characterization of a urea transporter from the kidney of the Atlantic stingray

“…Most euryhaline elasmobranchs appear to migrate between habitats on a seasonal basis (35,42). However, at least one species (Atlantic stingray) can reproduce and complete its life cycle in freshwater, whereas another (bull shark) has the potential to do so (22,43).…”

“…Interestingly, elasmobranchs remain ureosmotic in low-salinity environments. Urea remains a major osmolyte, contributing 30-40% to the extracellular fluid osmolality (8,10,15,21,34,43,48), and the kidneys remain the primary site for urea retention. The amount of urea reabsorbed by the renal tubules is markedly increased after exposure to a low-salinity environment; i.e., despite a lower fractional reabsorption of urea (decreasing from 90-98% to 66-84%), the increase in the filtered load of urea coupled with the high reabsorptive capacity of the renal tubules results in a large increase in the absolute amount of urea reabsorbed (data recalculated from Refs.…”

Body Fluid Solutes of Juveniles and Adults of the Euryhaline Bull Shark Carcharhinus leucas from Freshwater and Saline Environments

“…The individual urea levels range from well below the fresh-water average (157 compared with 169 mM/liter to approximately the marine average (357 compared with 356 mM/liter). A similar range of urea levels (134-336 mM/ liter) was found in a series of eight pregnant females taken from the same collecting grounds at Barra del Colorado (Thorson and Gerst 1972). From tagging and tracking records (unpublished data) it is known that these sharks move freely in and out of the river mouth and from fresh water to salt water and vice versa.…”

Living with high concentrations of urea: They can!

“…Most elasmobranches live in seawater and are stenohaline while the stingrays of the genus Potamotrygon are the only elasmobranch permanently adapted to freshwater [45,46]. However a number of species are marginally euryhaline since they can enter in the brackish environment of river mouths [47] and a small number can move from seawater to freshwater, generally on a seasonal basis [13,46,48,49].…”

“…Since the kidney is the primary organ responsible of urea retention and euryhaline elasmobranchs remain ureotelic in environment with a low salinity [30,34,46,[50][51][52] the renal regulation of urea retention in habitat with different salinities is crucial for the osmotic homeostasis of these species. This observation suggests that the activity and/or the expression of urea transporters in renal tubules have to be regulated.…”

Molecular and functional characterization of a urea transporter from the kidney of the Atlantic stingray

“…Most euryhaline elasmobranchs appear to migrate between habitats on a seasonal basis (35,42). However, at least one species (Atlantic stingray) can reproduce and complete its life cycle in freshwater, whereas another (bull shark) has the potential to do so (22,43).…”

“…Interestingly, elasmobranchs remain ureosmotic in low-salinity environments. Urea remains a major osmolyte, contributing 30-40% to the extracellular fluid osmolality (8,10,15,21,34,43,48), and the kidneys remain the primary site for urea retention. The amount of urea reabsorbed by the renal tubules is markedly increased after exposure to a low-salinity environment; i.e., despite a lower fractional reabsorption of urea (decreasing from 90-98% to 66-84%), the increase in the filtered load of urea coupled with the high reabsorptive capacity of the renal tubules results in a large increase in the absolute amount of urea reabsorbed (data recalculated from Refs.…”

Body Fluid Solutes of Juveniles and Adults of the Euryhaline Bull Shark Carcharhinus leucas from Freshwater and Saline Environments

“…The individual urea levels range from well below the fresh-water average (157 compared with 169 mM/liter to approximately the marine average (357 compared with 356 mM/liter). A similar range of urea levels (134-336 mM/ liter) was found in a series of eight pregnant females taken from the same collecting grounds at Barra del Colorado (Thorson and Gerst 1972). From tagging and tracking records (unpublished data) it is known that these sharks move freely in and out of the river mouth and from fresh water to salt water and vice versa.…”

Living with high concentrations of urea: They can!

“…Most elasmobranches live in seawater and are stenohaline while the stingrays of the genus Potamotrygon are the only elasmobranch permanently adapted to freshwater [45,46]. However a number of species are marginally euryhaline since they can enter in the brackish environment of river mouths [47] and a small number can move from seawater to freshwater, generally on a seasonal basis [13,46,48,49].…”

“…Since the kidney is the primary organ responsible of urea retention and euryhaline elasmobranchs remain ureotelic in environment with a low salinity [30,34,46,[50][51][52] the renal regulation of urea retention in habitat with different salinities is crucial for the osmotic homeostasis of these species. This observation suggests that the activity and/or the expression of urea transporters in renal tubules have to be regulated.…”

Molecular and functional characterization of a urea transporter from the kidney of the Atlantic stingray

“…Most euryhaline elasmobranchs appear to migrate between habitats on a seasonal basis (35,42). However, at least one species (Atlantic stingray) can reproduce and complete its life cycle in freshwater, whereas another (bull shark) has the potential to do so (22,43).…”

“…Interestingly, elasmobranchs remain ureosmotic in low-salinity environments. Urea remains a major osmolyte, contributing 30-40% to the extracellular fluid osmolality (8,10,15,21,34,43,48), and the kidneys remain the primary site for urea retention. The amount of urea reabsorbed by the renal tubules is markedly increased after exposure to a low-salinity environment; i.e., despite a lower fractional reabsorption of urea (decreasing from 90-98% to 66-84%), the increase in the filtered load of urea coupled with the high reabsorptive capacity of the renal tubules results in a large increase in the absolute amount of urea reabsorbed (data recalculated from Refs.…”