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Water balance and body fluids of Salamandra salamandra (L.) In their natural habitats in summer and winter
Camp.
Biochem.
Physiol.
Vol. 82A,
No.
2. pp.
419-482,
1985
0300-9629/85
$3.00
+ 0.00
0 1985Pergamon Press Ltd
Printed in Great Britain
WATER BALANCE AND BODY FLUIDS OF SALAMANDRA SALAMANDRA (L.) IN THEIR NAThAL HABITATS IN SUMMER AND WINTER GAD DEGANI MIGAL Galilee Technological Center, Kiriat Shmona, 10200, Israel. Telephone: (067) 44981 (Received 11 February 1985) Abstract-l. The water balance and compositions of plasma and urine of Salamundru salumundra in xeric and moist habitats were studied in winter and summer. 2. Water turnover (WTO) of salamanders from both habitats was significantly lower in August (about 455 pg/g/day), than in January (about 970 pg/g/day). 3. The mean blood plasma and urine concentration were higher at the end of the summer (xeric habitats, 341 mOsm/kg; moist habitats 339 mOsm/kg), than in the winter (xeric habitats, 267 mOsm/kg; moist habitats, 221 mOsm/kg), in salamanders from both localities. 4. Only the urine volume of salamanders from xeric habitats was significantly higher (maximum volume 19% body weight) than the urine volume of salamanders from moist habitats (maximum volume 11% body weight).
INTRODIJCIION Salamandra salamandra is a terrestrial urodele found throughout Europe, reaching the limit of its distribution in Israel and North Africa (Eisalt, 1958). After metamorphosis, salamanders live in different habitats. In Israel, three isolated localities of S. salamandra populations are found (Degani and Warburg, 1978; Degani, 1982): (1) on Mount Carmel; (2) in western and central Galilee, where some of the ponds and streams are dry in summer; (3) Tel Dan around the Dan stream, where water is available throughout the entire year (Degani and Mendelssohn, 1979). There are several studies on urodele water economy (Littleford et al., 1947; Cohen, 1952; Rosenthal, 1957; Spight, 1968; Spotila, 1972; Walter and Greenwald, 1977; Brown et al., 1977), of which a few studied the water economy of xeric species (Alvarado, 1967; Whitford, 1968; Warburg, 1971; Degani and Warburg, 1980). Most terrestrial amphibians appear to show adaptive changes in tolerance to high percentages of water loss. The range of change in body fluid was studied in terrestrial anura (Shoemaker et al., 1969; McClanahan, 1972; Katz, 1973; Degani et al., 1981) and urodela (Delson and Whitford, 1973; Degani, 1981a,b, 1982). The papers published to date on population structure, life history and habitats of Salamandra salamandra within the southern limits of its distribution in Israel (Degani and Warburg, 1976, 1978; Warburg et al., 1979; Degani et al., 1980; Degani and Mendelssohn, 1979, 1980) show many differences between populations from various habitats. Degani (1982) found a morphological difference between the salamanders from xeric habitats are bigger than the salamanders from moist habitats. These differences are influenced by the rate of dehydration, and therefore the salamanders from moist habitats are less tolerant of dry conditions than salamanders from xeric habitats (Degani, 198 1b). The
plasma osmolality of salamanders from xeric habitats is found to be higher after dehydration, by comparison with salamanders from moist habitats (Degani, 1981a), and the water turnover of salamanders from xeric habitats was lower than that of the salamanders from moist habitats only measured under laboratory conditions (Degani, 1982). However, there is no previous work on water balance of plasma and urine osmolality of S. salamandra and other urodeles
in their natural
habitats
MATERIALS AND
at different
seasons.
METHODS
Collection and maintenance Adult Salamandra salamandra were collected in the Tel Dan area (moist habitat), and in the Mount Meron area in central Galilee (xeric habitat) between October and November, as described previously by Degani and Warburg (1978) (see the description of habitats in Degani and Warburg, 1978; Degani and Mendelssohn, 1980). Each salamander was marked by toe clipping. Those from moist habitats weighed 18-42g; Those from xeric habitats weighed 55-84 g. In each locality, five salamanders from that locality were placed inside an enclosure (10 m2). In the “semi-arid” enclosure, small pools (1 m2) were arranged similarly to rock pools in the area (Degani and Warburg, 1978; Degani and Mendelssohn, 1979). A small stream 40 cm wide flowed through the “moist” habitat enclosure. Water turnover (IWO) WTO rates of salamanders were measured in summer (August) and winter (January). Salamanders were weighed to +O.Ol g and then injectedintraperitoneally with 0.5mCi tritium in 0.5 ml saline solution. The same quantity, 0.5 mCi of tritium, was injected into 30 ml of distilled water where salamanders from a moist habitat were measured, and into 60 ml of distilled water where salamanders from semi-arid habitats were measured to compare their rates of radioactive decay as described previously by Degani (1982). Urine (approximately 100 ~1) was collected at 08.00 am by cannula from the bladder just before the injection, and during the seven days after the injection. Fifty microliters of each
479
GAD DECANI
480
urine sample was mixed with 2 ml scintillate solution (Bary solution) and the radioactivity determined in a scintillation counter. The decrease in log concentration of the marker during
the sampling period was extrapolated to “zero”, from which total body water (‘I’BW)was assessed. WTO was calculated, as described previously by Degani (1982).
I -
I
Xeric
m-Moist
Body Juid
Urine and blood samples were taken, as described previously by Degani (198la), from each salamander in May, June, July, October and January. Plasma and Urine osmolality, Na+, Cl-, K+ and urea were determined, as described by Degani (1981a). Analysis
The statistical significance of the results was estimated by r-test, Mean +- SEM. RESULTS
Water turnover (WTO)
WTO of Salamandra salamandra from both semiarid and moist habitats was significantly lower (P < 0.001) in summer (August) than in winter (January). However, no significant difference (P > 0.1) was found between salamanders from semi-arid habitats and from moist habitats (Table 1). ”
Blood plasma concentration
and constituents
Tima
Plasma solute concentration of salamanders from both habitats (xeric and moist) was lower in winter (January), and increased during summer to reach a maximum concentration at the end of the summer (October) (Fig. 1). The difference between the plasma concentration at the end of the summer and winter was found to be significant for both salamander populations (P < 0.05). However, statistically significant differences between blood plasma concentrations of salamanders from semi-arid habitats and those from moist habitats were found only in winter. The mean of Na+, Cl-, K+ and urea concentration in plasma was higher at the end of the summer, but a significant difference was found only in the Na+ concentration (P c 0.05). The change of Na+ in salamanders from xeric habitats was between 117 and 116mM (49x), and in moist habitats between 113 and 157 mM (46%). The change of Cl- concentration was found to be lower in both salamander populations. In salamanders from xeric habitats the difference was 38x, and in salamanders from moist habitats the difference was 28%. However, the percentage change of urea concentration was very high, and was even higher in blood plasma of salamanders from semi-arid habitats (269x), than in blood plasma of salamanders from moist habitats (88%) (Fig. 1). Urine volume and concentration The urine volume of salamanders from xeric habitats was found to be significantly higher (P < 0.05)
“!
Yl,
(months)
Ylll
Locality
Tel Dan Tel Dan
than the urine volume of salamanders from moist habitats (Table 2.). The difference between urine volume of salamanders from semi-arid and moist habitats was also significant when the urine was calculated per body weight, excluding statistics for the month of January (Table 2). The urine was found to be hypoosomotic to plasma during all the seasons. No statistically (t-test) significant difference was found between the urine concentration of salamanders from xeric habitats compared with those. from moist habitats during the summer. The other components of the urine are described in Table 3. The most important component of the urine is urea, and the urea content is sometimes high in the urine, and at other times low. DISCUSSION
Salamandra salamandra is found in different habitats in Israel (Degani and Warburg, 1978; Degani and Mendelssohn, 1980). They are active mostly during the rainy season and seasons of high humidity (SO-100% relative humidity (RH)) and low temperature (2-20°C.) (Degani and Warburg, 1978). The difference between the activities may reflect different habitats. The salamanders from moist habitats are
Date
Water turnover pi/g/day
xeric habitat
12-18 August 15-23 January
430 f 170 1030 + 160
moist habitat
22-28 August Cl2 January
480+4O 910 * 50
N = 5 for each locality.
I
Fig. 1. Plasma osmolality and plasma constituents in salamanders. (N = 5 for each locality). x-xeric habitat; Mmoist habitat.
Table 1. Water turnover in salamanders in the natural habitats Galilee Galilee
ox
(1990 - l9fll)
481
Water balance in Salamandra Table 2. Bladder volume of S&man&a Locality Galilee Galilee Galilee Galilee Galilee Tel Tel Tel Tel Tel
Date
xeric habitat
Dan Dan Dan Dan Dan 1
moist habitat
during summer
Volume (ml k SD)
“/, Body weight
27.5.81 27.6.81 25.7.81 3.9.81 9.1.81
3*1 12k6 18f9 7i4 4*1
4 13 19 8 5
27.5.81 27.6.81 25.7.81 3.9.81 9.1.81
1*1 1*1 5fl 1*1 1*1
2 4 11 5 4
n = 5 for each population. Table 3. Urine osmolality and urine constituents Date Xeric habitat 27.5.81 27.6.81 25.7.81 3.9.81 9.1.81 Moist habitat 27.5.81 27.6.81 25.7.81 3.9.81 9.1.81
Osmolality (mOsm/kg f SD)
(mM:z
SD)
(mM 1”: SD)
(mM 15 SD)
Urea WM f SD)
88 f 19 111*4 50* II 164k38 130f51
14*5 7*2 11*4 22+ 11 24k2
3*3 3*1 2*0 15k8 7~t6
4*:2 4*2 I*1 8zt2 13*4
55*8 75 * 30* 63 + 26 +
137 f 57 106 f 54 46f28 136+ 13 51 f 12
17*9 10*2 17 * 10 10*3 11*1
1*0 1+1 1*0 8*4 2*1
15+2 8&4 1+1 7*2 3*2
66 f 9 64*4 16 k 8 54k20 24&5
7 10 24 10
N = 5 for each locality.
found on the ground and breed throughout the year, whilst salamanders from xeric habitats are mainly active and breed in winter. During the dry periods the salamander is found in places where the soil is moist and the temperature low. The differences in adaptation to terrestrial life of salamanders from those habitats was found mostly when the salamanders were exposed to dry conditions, 5% (R.H.) (Degani, 1981b). For example, the salamanders from xeric habitats can survive long periods of water loss (15 days) at 5% R.H. and 25°C as compared to those of moist habitats (8 days), found at the same conditions. The plasma concentration of salamanders from xeric habitats was higher than the plasma concentration of salamanders from moist habitats during dehydration at 5% R.H. and 25°C (Degani, 198 la). Moreover, the salamanders from xeric habitats were more successfully acclimatized to higher concentrations of saline solutions than the salamanders from moist habitats (Degani, 198la), and WTO of salamanders from xeric habitats was lower only when the salamanders maintained a constant body weight on the limited dried soil moisture (Degani, 1982). However, in all these parameters, no signiffcant difference was found when the salamanders were exposed to moist conditions and low temperatures, as when they are found in water, in both habitats. In this study, the salamanders were found in natural habitats and were not exposed to extreme conditions. Therefore, in most of the cases, the changes of body fluids and WTO were significant between the end of the summer and onset of winter, and not between the populations from the different habitats. Degani (1982) found that the WTO rate of salamander from moist and xeric habitat on moist soil was higher than that of the same salamanders on lower moisture soil. Wurburg (1971) and Warburg
CBP 82,2,-P
and Degani (1979) show that the evaporation water loss of S. salamandra increased with temperature and lower humidities. This condition is found in summer in both habitats. The ability of amphibians to absorb moisture from moist substrate has been demonstrated by Heatwole and Lim (1961). Spight (1968) found that Plethodon cinerus could absorb moisture even from sand of 12% moisture content. Warburg and Degani (1979) studied the water uptake of S. salamandra from the soil. The high water uptake occurred with high soil moisture. For example, the rate of water uptake by juvenile S. salamandra from 26.9% soil moisture was 110 g/hr x 10e4, while the rate of water uptake from 15.4% soil moisture was only 20 g/g/hr x 10w4. The change of the plasma concentrations of salamanders found in xeric and moist habitats were lower, compared to the limit of tolerance of salamanders, as was found in the laboratory. For example, the maximum plasma concentration of salamanders from xeric habitats was 768 mOsm/kg, and from wetter habitats, 655 mOsm/kg, after a long period of dehydration (1.5 months) on soil (Degani, 198lb). In this situation the urea accumulation in the plasma reached a very high concentration, -223 mM, in blood plasma in salamanders from semi-arid habitats, and 125 mM, in blood plasma of salamanders from moist habitats. Thus, a higher concentration of urea is found in other terrestrial urodela, e.g. Ambystoma tigrinum (220mM urea; Delson and Whitford, 1973) during long dehydration in soil at the laboratory. Only one quality that appears in natural surroundings also appears in this controlled study: The salamanders from xeric habitats store water in the bladder. The urine volume of these salamanders is very high. This storage of water would help the salamander to survive dry periods. In xeric habitats
GALIDEGANI
482
some of the ponds and streams dry up in summer. Terrestrial amphibia store water in the bladder (Bentley, 1972). the water passes from the bladder to the plasma due to hyperosmolality of the plasma compared to the urine. This difference between the plasma and urine occurs because of the active transport of Na+ from the bladder and kidney to plasma (Whitting and Brown, 1977). In conclusion, water balance and body fluid concentrations differ in summer and winter, but the difference between salamanders from moist habitats and xeric habitats is very small. My hypothesis is that the salamander from xeric habits is better adapted to terrestrial life because of its ability to store water in the bladder and survive even the periods of drought which occurs every few years. One such year was 1977 when some of the ponds did not fill with water; (unpublished data). wish to thank Prof. A. Shkolnik and Prof. H. Mendelssohn for their help and advice.
Acknowledgements-I
Degani G. and Warburg M. R. (1976) The biology and ecology of Salamandra salamandra (L.) in Israel. Israel J. Zool. 25, 206-207.
Degani G. and Warburg M. R. (1978). Population structure and seasonal activity of the adult Salamandra salamandra (L.) (Amphibia, Urodela, Salamandridae) in Israel. J. Herpetol.
12, 427-444.
Degani G. and Warburg M. R. (1980) The response to substrate moisture of juvenile and adult Salamandra salamandra (L.) (Amphibia, Urodela). Biol. Behav. 5, 281-290.
Delson J. and Whitford W. G. (1973) Adaptation of the salamander Ambystoma tigrittum to arid habitats. Comp. Biochem. Physiol. 46A, 631-638. Eiselt J. (1958) Der Feuersalamandra Salamandra salamandra (L.) Beitrag N einer taxonomischen synthese. Abh. Ber. Mus. Naturk. u. Vorgech. (Magdeburg) 10, 77-154. Heatwole H. and Lim K. (1961) Relation of substrate moisture to absorption and loss of water by the salamander, Plethodon cinereus. Ecology 42, 814-819. Katz U. (1973) Studies on the adaptation of the toad Bufo viridis to high salinities: oxygen consumption, plasma concentration and water content of the tissues. J. exp. Biol. 58, 785-796.
REFERENCES
Alvarado R. H. (1967) The significance of grouping on water conservation in Ambystoma. Cope& 667-668. Bentley P. J. (1972) Endocrine and osmoregulation, a Comparative Account of the Regulation of Water and Salt Vertebrates. pp. 161-179. Springer-Verlag, Berlin.
Brown P. S., Hastings S. A. and Frye B. E. (1977) A comparison of the water balance response in five species of plethodentid salamandra. Physiol. Zool. SO, 203-214. Cohen N. W. (1952) Comparative rate of dehydration and hydration in some California salamanders. Ecology 33, 462-479.
Degani G. (1979) Morphological and biochemical differences between the Salamandra salamandra (L.) populations in Israel. Israel J. Zool. 28, 54-55. Degani G. (198la) Salinity tolerance and osmoregulation in Salamandra salamandra (L.) from different populations. J. camp. Physiol.
145, 133-137.
Degani G. (198lb) The adaptation of Salamandra salamandra (L.) from different habitats to terrestrial life. Br. J. Herpetol.
6, 169-172.
Degani G. (1982) Water balance of salamanders (Salamandra salamandra (L.)) from different habitats. Amph. Rept. 2, 309-314.
Degani G., Silanikove N. and Shkolnik A. (1981) Osmotic and urea concentration of blood plasma in burrowing green toads. Israel J. Zool. 30, 96.* Deaani G.. Goldbera S. and Warbure M. R. (1980) Canniglistic phenomeni in Salamandr~salamandra larvae in certain water bodies and under experimental conditions. Hydrobiology
75, 123-128.
Degani G. and Mendelssohn H. (1979) The food of Salamandra salamandra (L.) tadpoles in Israel in different habitats. Proc. Xth Sci. Co& Israel Ecol. Sot. Cl9-C45. Degani G. and Mendelssohn H. (1980) Moisture as an inthtencing factor on the hiding places of juvenile Salamandra salamandra (L.) from semi-arid habitats. Israel ecol. Sot. 49-56.
Littleford R. A., Keller W. F., Phillips N. E. (1947) Studies in the vital limits of water loss in the plethodontid salamanders. Ecology 28, 446-447. McClanahan L. (1972) Changes in body fluid as a function of water potential. Copeia 209-216. Rosenthal G. M. (1957) The role of moisture and temperature in the local’ distribution of the plethodontid salamander Aneides luzubris. Univ. Calif Publ. Zool. 54, 370-420.
Shoemaker V. H., McClanahan L. and Ruibal R. (1969) Seasonal changes in a field population of the spadefoot toads. Copeia 3, 505-591. Spight T. M. (1968) The water economy of salamanders: Evaporative water loss. Physiol. Zool. 41, 195-203. Spotila J. R. (1972) Role of temperature and water in the ecology of lungless salamanders. Ecol. Monogr. 42, 95-125.
Walter D. J. and Greenwald L. (1977) Physiological adaptations of aquatic newts (Notophtalmus viridiscens) to terrestrial environment. Physiol. Zool. 50, 88-98. Warburg M. R. (1971) The water economy of Israeli amphibians: the Urodela Triturus vittatus (Jenyns) and Salamandra salamandra (L.). Comp. Biochem. Physiol. 4OA, 1055-1063. Warburg M. R., Degani G. and Warburg I. (1979) Growth and population structure of Salamandra salamandra (L.) larvae in different limnological conditions. Hydrobiology 64, 147-155.
Warburg M. R. and Degani G. Evaporative water loss and uptake in juvenile and adult Salamandra salamandra (L.) (Amphibia, urodela). Comp. Biochem. Physiol. 62A, 1071-1075.
Whitford W. G. (1968) Physiological responses to temperature and desiccation in the endemic New Mexico plethodontids, Plethodon neomexicanus and Aneides hardii. Copeia. 247-256.
Whitting K. P. and Brown S. C. (1977) Sodium balance in the newt Notophtalmus viridiscens. Comp. Biochem. Physiol. 58A. 49-52.
Biochem.
Physiol.
Vol. 82A,
No.
2. pp.
419-482,
1985
0300-9629/85
$3.00
+ 0.00
0 1985Pergamon Press Ltd
Printed in Great Britain
WATER BALANCE AND BODY FLUIDS OF SALAMANDRA SALAMANDRA (L.) IN THEIR NAThAL HABITATS IN SUMMER AND WINTER GAD DEGANI MIGAL Galilee Technological Center, Kiriat Shmona, 10200, Israel. Telephone: (067) 44981 (Received 11 February 1985) Abstract-l. The water balance and compositions of plasma and urine of Salamundru salumundra in xeric and moist habitats were studied in winter and summer. 2. Water turnover (WTO) of salamanders from both habitats was significantly lower in August (about 455 pg/g/day), than in January (about 970 pg/g/day). 3. The mean blood plasma and urine concentration were higher at the end of the summer (xeric habitats, 341 mOsm/kg; moist habitats 339 mOsm/kg), than in the winter (xeric habitats, 267 mOsm/kg; moist habitats, 221 mOsm/kg), in salamanders from both localities. 4. Only the urine volume of salamanders from xeric habitats was significantly higher (maximum volume 19% body weight) than the urine volume of salamanders from moist habitats (maximum volume 11% body weight).
INTRODIJCIION Salamandra salamandra is a terrestrial urodele found throughout Europe, reaching the limit of its distribution in Israel and North Africa (Eisalt, 1958). After metamorphosis, salamanders live in different habitats. In Israel, three isolated localities of S. salamandra populations are found (Degani and Warburg, 1978; Degani, 1982): (1) on Mount Carmel; (2) in western and central Galilee, where some of the ponds and streams are dry in summer; (3) Tel Dan around the Dan stream, where water is available throughout the entire year (Degani and Mendelssohn, 1979). There are several studies on urodele water economy (Littleford et al., 1947; Cohen, 1952; Rosenthal, 1957; Spight, 1968; Spotila, 1972; Walter and Greenwald, 1977; Brown et al., 1977), of which a few studied the water economy of xeric species (Alvarado, 1967; Whitford, 1968; Warburg, 1971; Degani and Warburg, 1980). Most terrestrial amphibians appear to show adaptive changes in tolerance to high percentages of water loss. The range of change in body fluid was studied in terrestrial anura (Shoemaker et al., 1969; McClanahan, 1972; Katz, 1973; Degani et al., 1981) and urodela (Delson and Whitford, 1973; Degani, 1981a,b, 1982). The papers published to date on population structure, life history and habitats of Salamandra salamandra within the southern limits of its distribution in Israel (Degani and Warburg, 1976, 1978; Warburg et al., 1979; Degani et al., 1980; Degani and Mendelssohn, 1979, 1980) show many differences between populations from various habitats. Degani (1982) found a morphological difference between the salamanders from xeric habitats are bigger than the salamanders from moist habitats. These differences are influenced by the rate of dehydration, and therefore the salamanders from moist habitats are less tolerant of dry conditions than salamanders from xeric habitats (Degani, 198 1b). The
plasma osmolality of salamanders from xeric habitats is found to be higher after dehydration, by comparison with salamanders from moist habitats (Degani, 1981a), and the water turnover of salamanders from xeric habitats was lower than that of the salamanders from moist habitats only measured under laboratory conditions (Degani, 1982). However, there is no previous work on water balance of plasma and urine osmolality of S. salamandra and other urodeles
in their natural
habitats
MATERIALS AND
at different
seasons.
METHODS
Collection and maintenance Adult Salamandra salamandra were collected in the Tel Dan area (moist habitat), and in the Mount Meron area in central Galilee (xeric habitat) between October and November, as described previously by Degani and Warburg (1978) (see the description of habitats in Degani and Warburg, 1978; Degani and Mendelssohn, 1980). Each salamander was marked by toe clipping. Those from moist habitats weighed 18-42g; Those from xeric habitats weighed 55-84 g. In each locality, five salamanders from that locality were placed inside an enclosure (10 m2). In the “semi-arid” enclosure, small pools (1 m2) were arranged similarly to rock pools in the area (Degani and Warburg, 1978; Degani and Mendelssohn, 1979). A small stream 40 cm wide flowed through the “moist” habitat enclosure. Water turnover (IWO) WTO rates of salamanders were measured in summer (August) and winter (January). Salamanders were weighed to +O.Ol g and then injectedintraperitoneally with 0.5mCi tritium in 0.5 ml saline solution. The same quantity, 0.5 mCi of tritium, was injected into 30 ml of distilled water where salamanders from a moist habitat were measured, and into 60 ml of distilled water where salamanders from semi-arid habitats were measured to compare their rates of radioactive decay as described previously by Degani (1982). Urine (approximately 100 ~1) was collected at 08.00 am by cannula from the bladder just before the injection, and during the seven days after the injection. Fifty microliters of each
479
GAD DECANI
480
urine sample was mixed with 2 ml scintillate solution (Bary solution) and the radioactivity determined in a scintillation counter. The decrease in log concentration of the marker during
the sampling period was extrapolated to “zero”, from which total body water (‘I’BW)was assessed. WTO was calculated, as described previously by Degani (1982).
I -
I
Xeric
m-Moist
Body Juid
Urine and blood samples were taken, as described previously by Degani (198la), from each salamander in May, June, July, October and January. Plasma and Urine osmolality, Na+, Cl-, K+ and urea were determined, as described by Degani (1981a). Analysis
The statistical significance of the results was estimated by r-test, Mean +- SEM. RESULTS
Water turnover (WTO)
WTO of Salamandra salamandra from both semiarid and moist habitats was significantly lower (P < 0.001) in summer (August) than in winter (January). However, no significant difference (P > 0.1) was found between salamanders from semi-arid habitats and from moist habitats (Table 1). ”
Blood plasma concentration
and constituents
Tima
Plasma solute concentration of salamanders from both habitats (xeric and moist) was lower in winter (January), and increased during summer to reach a maximum concentration at the end of the summer (October) (Fig. 1). The difference between the plasma concentration at the end of the summer and winter was found to be significant for both salamander populations (P < 0.05). However, statistically significant differences between blood plasma concentrations of salamanders from semi-arid habitats and those from moist habitats were found only in winter. The mean of Na+, Cl-, K+ and urea concentration in plasma was higher at the end of the summer, but a significant difference was found only in the Na+ concentration (P c 0.05). The change of Na+ in salamanders from xeric habitats was between 117 and 116mM (49x), and in moist habitats between 113 and 157 mM (46%). The change of Cl- concentration was found to be lower in both salamander populations. In salamanders from xeric habitats the difference was 38x, and in salamanders from moist habitats the difference was 28%. However, the percentage change of urea concentration was very high, and was even higher in blood plasma of salamanders from semi-arid habitats (269x), than in blood plasma of salamanders from moist habitats (88%) (Fig. 1). Urine volume and concentration The urine volume of salamanders from xeric habitats was found to be significantly higher (P < 0.05)
“!
Yl,
(months)
Ylll
Locality
Tel Dan Tel Dan
than the urine volume of salamanders from moist habitats (Table 2.). The difference between urine volume of salamanders from semi-arid and moist habitats was also significant when the urine was calculated per body weight, excluding statistics for the month of January (Table 2). The urine was found to be hypoosomotic to plasma during all the seasons. No statistically (t-test) significant difference was found between the urine concentration of salamanders from xeric habitats compared with those. from moist habitats during the summer. The other components of the urine are described in Table 3. The most important component of the urine is urea, and the urea content is sometimes high in the urine, and at other times low. DISCUSSION
Salamandra salamandra is found in different habitats in Israel (Degani and Warburg, 1978; Degani and Mendelssohn, 1980). They are active mostly during the rainy season and seasons of high humidity (SO-100% relative humidity (RH)) and low temperature (2-20°C.) (Degani and Warburg, 1978). The difference between the activities may reflect different habitats. The salamanders from moist habitats are
Date
Water turnover pi/g/day
xeric habitat
12-18 August 15-23 January
430 f 170 1030 + 160
moist habitat
22-28 August Cl2 January
480+4O 910 * 50
N = 5 for each locality.
I
Fig. 1. Plasma osmolality and plasma constituents in salamanders. (N = 5 for each locality). x-xeric habitat; Mmoist habitat.
Table 1. Water turnover in salamanders in the natural habitats Galilee Galilee
ox
(1990 - l9fll)
481
Water balance in Salamandra Table 2. Bladder volume of S&man&a Locality Galilee Galilee Galilee Galilee Galilee Tel Tel Tel Tel Tel
Date
xeric habitat
Dan Dan Dan Dan Dan 1
moist habitat
during summer
Volume (ml k SD)
“/, Body weight
27.5.81 27.6.81 25.7.81 3.9.81 9.1.81
3*1 12k6 18f9 7i4 4*1
4 13 19 8 5
27.5.81 27.6.81 25.7.81 3.9.81 9.1.81
1*1 1*1 5fl 1*1 1*1
2 4 11 5 4
n = 5 for each population. Table 3. Urine osmolality and urine constituents Date Xeric habitat 27.5.81 27.6.81 25.7.81 3.9.81 9.1.81 Moist habitat 27.5.81 27.6.81 25.7.81 3.9.81 9.1.81
Osmolality (mOsm/kg f SD)
(mM:z
SD)
(mM 1”: SD)
(mM 15 SD)
Urea WM f SD)
88 f 19 111*4 50* II 164k38 130f51
14*5 7*2 11*4 22+ 11 24k2
3*3 3*1 2*0 15k8 7~t6
4*:2 4*2 I*1 8zt2 13*4
55*8 75 * 30* 63 + 26 +
137 f 57 106 f 54 46f28 136+ 13 51 f 12
17*9 10*2 17 * 10 10*3 11*1
1*0 1+1 1*0 8*4 2*1
15+2 8&4 1+1 7*2 3*2
66 f 9 64*4 16 k 8 54k20 24&5
7 10 24 10
N = 5 for each locality.
found on the ground and breed throughout the year, whilst salamanders from xeric habitats are mainly active and breed in winter. During the dry periods the salamander is found in places where the soil is moist and the temperature low. The differences in adaptation to terrestrial life of salamanders from those habitats was found mostly when the salamanders were exposed to dry conditions, 5% (R.H.) (Degani, 1981b). For example, the salamanders from xeric habitats can survive long periods of water loss (15 days) at 5% R.H. and 25°C as compared to those of moist habitats (8 days), found at the same conditions. The plasma concentration of salamanders from xeric habitats was higher than the plasma concentration of salamanders from moist habitats during dehydration at 5% R.H. and 25°C (Degani, 198 la). Moreover, the salamanders from xeric habitats were more successfully acclimatized to higher concentrations of saline solutions than the salamanders from moist habitats (Degani, 198la), and WTO of salamanders from xeric habitats was lower only when the salamanders maintained a constant body weight on the limited dried soil moisture (Degani, 1982). However, in all these parameters, no signiffcant difference was found when the salamanders were exposed to moist conditions and low temperatures, as when they are found in water, in both habitats. In this study, the salamanders were found in natural habitats and were not exposed to extreme conditions. Therefore, in most of the cases, the changes of body fluids and WTO were significant between the end of the summer and onset of winter, and not between the populations from the different habitats. Degani (1982) found that the WTO rate of salamander from moist and xeric habitat on moist soil was higher than that of the same salamanders on lower moisture soil. Wurburg (1971) and Warburg
CBP 82,2,-P
and Degani (1979) show that the evaporation water loss of S. salamandra increased with temperature and lower humidities. This condition is found in summer in both habitats. The ability of amphibians to absorb moisture from moist substrate has been demonstrated by Heatwole and Lim (1961). Spight (1968) found that Plethodon cinerus could absorb moisture even from sand of 12% moisture content. Warburg and Degani (1979) studied the water uptake of S. salamandra from the soil. The high water uptake occurred with high soil moisture. For example, the rate of water uptake by juvenile S. salamandra from 26.9% soil moisture was 110 g/hr x 10e4, while the rate of water uptake from 15.4% soil moisture was only 20 g/g/hr x 10w4. The change of the plasma concentrations of salamanders found in xeric and moist habitats were lower, compared to the limit of tolerance of salamanders, as was found in the laboratory. For example, the maximum plasma concentration of salamanders from xeric habitats was 768 mOsm/kg, and from wetter habitats, 655 mOsm/kg, after a long period of dehydration (1.5 months) on soil (Degani, 198lb). In this situation the urea accumulation in the plasma reached a very high concentration, -223 mM, in blood plasma in salamanders from semi-arid habitats, and 125 mM, in blood plasma of salamanders from moist habitats. Thus, a higher concentration of urea is found in other terrestrial urodela, e.g. Ambystoma tigrinum (220mM urea; Delson and Whitford, 1973) during long dehydration in soil at the laboratory. Only one quality that appears in natural surroundings also appears in this controlled study: The salamanders from xeric habitats store water in the bladder. The urine volume of these salamanders is very high. This storage of water would help the salamander to survive dry periods. In xeric habitats
GALIDEGANI
482
some of the ponds and streams dry up in summer. Terrestrial amphibia store water in the bladder (Bentley, 1972). the water passes from the bladder to the plasma due to hyperosmolality of the plasma compared to the urine. This difference between the plasma and urine occurs because of the active transport of Na+ from the bladder and kidney to plasma (Whitting and Brown, 1977). In conclusion, water balance and body fluid concentrations differ in summer and winter, but the difference between salamanders from moist habitats and xeric habitats is very small. My hypothesis is that the salamander from xeric habits is better adapted to terrestrial life because of its ability to store water in the bladder and survive even the periods of drought which occurs every few years. One such year was 1977 when some of the ponds did not fill with water; (unpublished data). wish to thank Prof. A. Shkolnik and Prof. H. Mendelssohn for their help and advice.
Acknowledgements-I
Degani G. and Warburg M. R. (1976) The biology and ecology of Salamandra salamandra (L.) in Israel. Israel J. Zool. 25, 206-207.
Degani G. and Warburg M. R. (1978). Population structure and seasonal activity of the adult Salamandra salamandra (L.) (Amphibia, Urodela, Salamandridae) in Israel. J. Herpetol.
12, 427-444.
Degani G. and Warburg M. R. (1980) The response to substrate moisture of juvenile and adult Salamandra salamandra (L.) (Amphibia, Urodela). Biol. Behav. 5, 281-290.
Delson J. and Whitford W. G. (1973) Adaptation of the salamander Ambystoma tigrittum to arid habitats. Comp. Biochem. Physiol. 46A, 631-638. Eiselt J. (1958) Der Feuersalamandra Salamandra salamandra (L.) Beitrag N einer taxonomischen synthese. Abh. Ber. Mus. Naturk. u. Vorgech. (Magdeburg) 10, 77-154. Heatwole H. and Lim K. (1961) Relation of substrate moisture to absorption and loss of water by the salamander, Plethodon cinereus. Ecology 42, 814-819. Katz U. (1973) Studies on the adaptation of the toad Bufo viridis to high salinities: oxygen consumption, plasma concentration and water content of the tissues. J. exp. Biol. 58, 785-796.
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