Water metabolism and the distribution of two species of australian murids,Rattus rattus and Rattus villosissimus

• 1.1. The ad libitum water requirement of Rattus villosissimus in the laboratory is significantly less than that of R. rattus. There are corresponding differences in the quantities of water eliminated via the urine, skin and lungs, although faecal water losses are similar.
• 2.2. R. rattus and R. villosissimus reduce body weight, urinary and faecal water loss, and probably food intake, when deprived of drinking water.
• 3.3. R. rattus is unable to limit body weight loss to the same degree as R. villosissimus when deprived of drinking water. This is partly due to inferior renal performance, although other factors such as higher evaporative water loss and lower food intake are probably involved.
• 4.4. The current distributions of R. rattus and R. villosissimus on the Australian mainland can be correlated with the known water metabolism of the two species.

     

Water fluxes and urine production in blue crabs (Callinectes sapidus) as a function of environmental salinity

• 1.1. Water efflux and urine production rates were measured in blue crabs acclimated to several salinities.
• 2.2. In 100% seawater the mean rate of water efflux (31.3 ml/100g hr⁻¹) was significantly greater than that in 50% seawater (18.9 ml/100 g hr⁻¹.
• 3.3. Water efflux was directly related to body weight.
• 4.4. The mean urine production rate was significantly greater in crabs acclimated to 50% and 30% seawater (0.17 and 0.18 ml/100g hr⁻¹) than in animals conditioned to 100% seawater (0.09 ml/100 g hr⁻¹).
• 5.5. The difference between theoretical net water fluxes for crabs exposed to 100% seawater and 50% seawater was similar to the difference in urine output in the same salinities, demonstrating the importance of the antennal gland in volume regulation.

     

Adaptations of Crocodylus acutus and Alligator for life in saline water

• 1.1. American crocodiles (C. acutus) weighing less than 200 g are unable to grow when kept in 35 ppt sea water in the laboratory. Yet paradoxically there are some highly saline areas in south Florida where rapid growth occurs. It is possible that these conflicting observations can be reconciled by behavioral osmoregulation of young crocodiles.
• 2.2. Hatching occurs during the rainy season and small crocodiles may drink from the brackish “lens” available during and after rainfall.
• 3.3. Using a weekly regime of alternating exposure to 35 ppt (6 days) and 4 ppt (12–24 hr), it has been demonstrated that growth of small crocodiles occurs. Feeding takes place primarily when brackish water is available. Salinities as high as 18 ppt were drunk when crocodiles were dehydrated by 15–20% of initial mass.
• 4.4. C. acutus and Alligator have a rather low rate of water efflux in sea water (0.2ml/100g-hr).
• 5.5. Sodium influx in sea water of C. acutus is low, but higher than efflux. Thus there is no evidence yet for a significant role of the lingual salt glands in sodium excretion.
• 6.6. The major adaptations to saline water of hatchling C. acutus are a low intake of sodium, an ability to selectively drink water of lower salinities, and to grow very rapidly (within 3–4 months) to a size much more tolerant of immersion in 35 ppt sea water.

     

Sodium balance in adult atlantic salmon (Salmo salar L.) during migration into neutral and acid fresh water

• 1.1. In sea-water, adult salmon (S. salar) exchange an average of 12.6% of total body sodium/hr.
• 2.2. Following transfer to fresh water sodium uptake follows Michaelis-Menton kinetics. F_max = 2.40 mmol Na/1 ECF/hr, K_m = 0.26 mmol Na/1. The uptake system is fully activated immediately following transfer to fresh water.
• 3.3. Post smolts adapted to sea-water for 3 months take up sodium at only one third of the rate of adult fish following return to fresh water.
• 4.4. The concentration of prolactin in the plasma is low in sea-water adapted fish and does not rise during the first 8 hr in fresh water.
• 5.5. At pH 5 sodium uptake is reduced by almost 90%, even in the absence of aluminium, but recovers immediately on return to neutral water.
• 6.6. At pH 5 and 20 μmol Al/1 there is little further effect on sodium uptake but after 6 hr in aluminium the inhibition of sodium uptake continues after return to neutral aluminium fresh water and uptake is only 50% of normal 24 hr later.

     

Changes in the EEL intestine during seawater adaptation

• 1.1. Rate of fluid absorption by eel (Anguilla rostrata) intestinal sacs in vitro reached seawater adapted values 3 days after transfer from freshwater to seawater.
• 2.2. After 3 days in seawater oxygen consumption and Na-K-ATPase activity of intestinal mucosa had not increased over freshwater values.
• 3.3. The weight of intestinal mucosa increased 32% during seawater adaptation as a result of an increase in the number of mucosal cells (hyperplasia).
• 4.4. The rate of intestinal fluid absorption was reduced by 10⁻⁴ M ouabain and was not affected by 10⁻⁴ M acetazolamide.

     

Difference in the specific activity of tritium labelled water in blood,urine and evaporative water in rabbits

• 1.1. After a single injection of tritium labelled water (THO) into rabbits the specific activity was measured in blood, urine and evaporative water.
• 2.2. The specific activity in urine was similar to that in blood, the specific activity in pulmocutaneous evaporate was 5–8% below that of blood.
• 3.3. The permeability coefficient of the urinary bladder wall for THO was 44 ± 11 cm/sec × 10⁻⁶.
• 4.4. Maximum differences in the specific activity between blood and urine due to the accumulation of urine in the bladder were calculated as up to 1.8%.
• 5.5. In the state of equilibrium the specific activity in urine water, but not in evaporative water. can be used for the estimation of total body water.

     

Seawater drinking in eared seals

• 1.1. Behavior resembling seawater drinking (mariposia) was observed in four species of otariids (fur seals and sea lions).
• 2.2. Among territorial males drinking frequency was greatest in the morning hours, it did not increase with high environmental temperatures, and it decreased as a function of days spent on territory.
• 3.3. Mariposia may function in nitrogen excretion among fasting animals.

     

Effects of angiotensin II and bladder condition on hydration behavior and water uptake in the toad,Bufo woodhousei

• 1.1. Water absorption response (WR) behavior and water weight gain were examined in hydrated toads, Bufo woodhousei, treated with angiotensin II (All) or with a control Ringer's solution. The effects of urinary bladder condition (ad lib. bladder urine or empty bladder) were examined concurrently.
• 2.2. Toads treated with All (100μg/100g body weight), spent more time in WR posture and absorbed more water than Ringer's-injected toads.
• 3.3. Toads with empty bladders maintained WR posture for longer periods of time and gained more weight than toads whose bladders were not emptied.
• 4.4. The effects of All and bladder urine on water absorption by B. woodhousei appear to be separate and additive.

     

Factors regulating the functioning of the in vitro perfused aglomerular kidney of the anglerfish,Lophius piscatorius L.

• 1.1. Kidneys of Lophius were perfused from the renal portal vein with a Ringer's solution.
• 2.2. Mammalian and piscine neurohypophysial hormones (in doses of 20–500 ng/kg body wt) did not affect the rate of urine production or the urinary concentration of inorganic ions.
• 3.3. The rate of urine production and the urinary concentration of magnesium and sodium ions varied with the concentration of magnesium in the perfusate.
• 4.4. The rate of urine production was positively correlated with urine magnesium concentration (r = 0.83 ± 0.04) and negatively correlated with that of sodium (r = −0.40).
• 5.5. The urinary concentration of sodium ions varied inversely with that of magnesium ions (r = −0.89).
• 6.6. Ouabain treatment (0.1–0.8 mM/l) reduced the rate of urine production by over 60% and altered, to varying extents, the pattern of electrolyte excretion. A simple model for the mode of formation of urine by the aglomerular kidney, based on the present results and other observations is suggested.

     

Effects of salinity and temperature on oxygen consumption in a freshwater population of Palaemonetes antennarius (Crustacea,decapoda)

• 1.1. After step-like increases in salinity the shrimps exhibit the smallest increase in oxygen consumption in the lower salinity range. At higher salinities the shrimps show longer recovery times and greater increases in the metabolic rate after salinity shock.
• 2.2. In steady-state experiments, the shrimps display the lowest oxygen consumption rates near the isosmotic point. The lowest metabolic rates occur at salinities of 3‰ and 10‰ At salinities of 20‰ and above the rate of metabolism increases by 20–30%.
• 3.3. The calculated osmoregulatory work for animals in fresh water amounts to only 2.7% of routine metabolism and drops to 1.1% for shrimps in 3‰ and 0.7% in 5‰ salinity.
• 4.4. Locomotory activity in the form of position change was not responsible for the increased oxygen consumption of the animals after salinity shocks. A “tentative swimming activity” by fast and frequent beating of the pleopods without position change may be an important factor in the increase of metabolic rates.
• 5.5. In its temperature response, the brackish water population has a higher metabolic rate than the freshwater one. Between 5 and 35°C Q ₁₀-values range from 4.01 to 1.37.

     

Na+/H+ exchange in the kidneys of eels (Anguilla anguilla) adapted to sea water or to freshwater environments: Studies with brush border membrane vesicles

• 1.1. In brush border membrane vesicles isolated from eel kidneys, adapted either to sea water or freshwater environments, a Na⁺/H⁺ antiporter is present.
• 2.2. Using a calibration plot it is possible to evaluate the amount of protons that this antiporter can accumulate inside the vesicular space.
• 3.3. The activity of the antiporter seems to be affected by the salinity of the water; it is higher in animals adapted to seawater.
• 4.4. This adaptation seems to occur by a J_max regulation of the antiporter.

     

A comparison of the effects of saline imbibition and water deprivation on the composition of the blood,urine and pituitary neural lobe of the gerbil (Meriones unguiculatus)

• 1.1. The effects of 2% saline imbibition and water deprivation on the water balance of the gerbil were compared.
• 2.2. The unchanged fluid intake and losses, body weight and several blood indices suggested little alteration in the state of hydration after saline imbibition.
• 3.3. After 5 days water deprivation the animals lost weight and evidence of haemoconcentration was observed. These changes took place despite reductions in water loss (via the urine and faeces) and evidence of secretion of vasopressin and the two principal acidic neural lobe proteins.
• 4.4. The gerbil appeared to be better adapted to water stress induced by saline imbibition than by water deprivation and this may be related to its habitat in Northern Asia.

     

Effects of feeding on water balance and cutaneous drinking in the toad (Bufo bufo L.)

• 1.1. Toads fed mealworms ad libitum for 24-hr periods once a week retained water in the body in amounts that varied with meal size, as well as temporally.
• 2.2. The ratio between masses of water retained and mealworms eaten increased from about 0.5 in May to about 1.3 by mid-July, and declined again at the end of the seasonal feeding period. li[3. It is argued that this pattern reflects seasonal variation in the secretion of digestive (gastric) juice in response to meal size.
• 3.4. The cutaneous drinking response, reflected in number of visits to the water source, increased in strength with successive feedings.
• 4.5. It is suggested that the drinking response to feeding included a secondary, behavioural component, superimposed upon a primary response to feeding.

     

Adaptation of rainbow trout (Salmo gairdnerii) to sea water: Changes in calcitonin levels

• 1.1. The calcitonin content of the ultimobranchial body (UBB) and plasma levels of calcitonin, calcium and phosphate were measured in rainbow trout (Salmo gairdnerii) following their transfer from fresh to sea water.
• 2.2. The plasma calcium level remained unchanged throughout the experiment while the UBB calcitonin content, plasma calcitonin and plasma phosphate rose significantly during the hours immediately following transfer.
• 3.3. The levels of all three subsequently fall so that, 8–15 days later, a new equilibrium was established with lower than control (fresh water) levels of UBB calcitonin, plasma calcitonin and plasma phosphate.
• 4.4. It would appear, from these data, that calcitonin plays some part in the endocrine regulation of sea water transfer.

     

Salt and water balance in the sipunculan phascolopsis gouldi: is any animal a “simple osmometer”?

• 1.1. Phascolopsis gouldi, the commonly studied sipunculan of the Woods Hole area, Massachusetts, can tolerate a salinity range from about 45% seawater to at least 100% SW, with literature records extending to about 160% SW. There was no survival at 40% SW.
• 2.2. Over this salinity range, P. gouldi is an osmotic and ionic conformer.
• 3.3. The osmotic and sodium concentrations of the coelomic fluid are the same as that of the medium; the chloride concentration is about 9% less than that of the medium; the potassium concentration is about 30% higher.
• 4.4. Analysis of water content regulation by two different approaches shows that P. gouldi does have a limited ability for volume regulation, restricted to salinities higher than 58% SW.
• 5.5. P. gouldi is not a “simple osmometer”.

     

Renal function in migrating adult atlantic salmon,Salmo salar L.

• 1.1. Renal function in migrating adult Atlantic salmon was studied in sea-water (SW) and following abrupt transfer to fresh water (FW).
• 2.2. Urine flow rate of SW-adapted fish, 0.72 ml/kg/hr, increased 6.3-fold to 4.55 ml/kg/hr after 2–3 days in FW, later decreasing to around 1 ml/kg/hr.
• 3.3. Changes in glomerular filtration rate and ion filtration rates largely paralleled changes in urine flow. In SW-adapted salmon about 4% of excreted magnesium is filtered. Tubular magnesium secretion declined within 1 day of FW transfer.
• 4.4. During the period of maximum diuresis, urinary sodium loss is 77% of the branchial sodium uptake rate. This falls to less than 20% in FW-adapted fish.

     

In situ perfusion study of sodium transport across the nephridia of a marine invertebrate Sabella pavonia S. (Polychaeta; Annelida)

• 1.1. A suitable perfusion rate (0.110μl/min) was calculated after measuring nephridial volume and urine transit time.
• 2.2. Neither inulin nor albumin were found suitable as water movement markers for nephridia.
• 3.3. There was no net sodium flux through the nephridial wall.
• 4.4. Measurements of net nsodium flux through the nephridia showed that, in normal sea water, Sabella could not transport large amounts of sodium against a concentration gradient. A unidirectional sodium flux of about 10nequiv/min per cm crossed the nephridia.

     

Organ specific changes in energy metabolism due to anaerobiosis in the sea mussel Mytilus edulis (L.)

• 1.1. Anaerobic energy metabolism was investigated in different organs of Mytilus edulis and the whole animal.
• 2.2. Succinate accumulates to high levels in most organs but remains low in the hemolymph.
• 3.3. After 16 hours propionate accumulation is observed in all organs. Experimental evidence is not sufficient yet to point out organs that produce more propionate than others.
• 4.4. Acetate is a minor end product.
• 5.5. Acetate and propionate are found in the hemolymph in amounts equal to those in the organs.
• 6.6. Animals incubated in oxygen-free seawater accumulate more end products than animals exposed to air, in the form of volatile fatty acids that are excreted into the incubation water.
• 7.7. Alanine and glutamine increase in the posterior adductor muscle. Aspartate decreases in the total animal, posterior adductor muscle and gills, while in the hemolymph decrease in alanine, asparagine, serine, threonine and proline are observed.

     

Osmoregulation in the brook trout,Salvelinus fontinalis—II. Effects of size,age and photoperiod on seawater survival and ionic regulation

• 1.1. Brook trout (Salvelinus fontinalis) of a single genetic stock, and hatched at the same time, were raised under two photoperiod and two feeding regimes to obtain fish of the same age but with different sizes and photoperiod experiences. In 11 experiments over 1.5 firs, fish were gradually exposed to 32 ppt seawater for 20 days to investigate the ontogeny of salinity tolerance.
• 2.2. Daily changes in plasma osmolarity, [Na⁺], [Cl⁻], [K⁺], [Mg²⁺], thyroxine, hematocrit and gill Na⁺,K⁺-ATPase during adaptation to 10, 20 and 32 ppt were examined in one experiment.
• 3.3. Size was the primary determinant of seawater survival (r² = 0.77) the effect of size on seawater survival slowed after fish reached a fork length of 14 cm. The effect of age on seawater survival (r² = 0.65) was through its covariance with size.
• 4.4. Photoperiod affected seawater survival only through its influence on the timing of male maturation, which decreased salinity tolerance.
• 5.5. Regulation of plasma osmolarity, [Na⁺], [Cl⁻], [K²⁺], [Mg²⁺] and hematocrit in sea water increased linearly with size over the entire range of sizes (6–32 em).
• 6.6. Gill Na⁺,K⁺-ATPase activity after 20 days in seawater decreased with increasing size of brook trout, possibly reflecting decreased demand for active ion transport in larger fish.
• 7.7. Plasma thyroxine concentrations declined in seawater, but no definitive role of this hormone in seawater adaptation was found.
• 8.8. Size dependent survival and osmoregulatory ability of brook trout is compared to other salmonids and a conceptual model is developed.

     

The effect of salinity on the osmotic,sodium and chloride concentrations in the hemolymph of euryhaline shrimp of the genus Penaeus

• 1.1. The hemolymph is isosmotic to seawater at 745 mOs/kg in P. aztecus, 768 mOs/kg in P. duorarum, 680 mOs/kg in P. setiferus, 699 mOs/kg in P. stylirostris, and 718 mOs/kg in P. vannamei.
• 2.2. The hemolymph is hyperosmotic to seawater at salinities below the isosmotic concentrations and hypoosmotic to those above.
• 3.3. With respect to sodium and chloride, the hemolymph is hyperionic to seawater at low salinities and hypoionic to seawater at high salinities.
• 4.4. P. aztecus and P. duorarum are weaker osmotic and ionic regulators at low salinities than P. setiferus, P. stylirostris, and P. vannamei.
• 5.5. There are no significant differences in the osmotic and ionic regulatory capabilities of all five species at high salinities.