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Oxygen consumption of a fresh water crab, Paratelphusa hydrodromous, in relation to salinity stress
Comp. Biochem. Physiol., 1967, Vol. 23, pp. 599 to 605. Pergamon Press. Printed in Great Britain
OXYGEN CONSUMPTION OF A FRESH WATER CRAB,
PARATELPHUSA HYDRODROMOUS, IN RELATION TO SALINITY STRESS* R. R A M A M U R T H I t Department of Biology, University of Oregon, Eugene, Oregon
(Received 23 May 1967) Almtraet--1. The fresh water field crab Paratelphusa hydrodromous exhibits good tolerance to saline media up to 100% sea water. 2. The crabs show minimal oxygen consumption in 50% sea water and roaTimal oxygen consumption in tap water and in 100~/osea water. The variation in the pattern of metabolic response to salinity appears to be related to the chloride ion gradient existing between the blood and the medium. The direction of the C1- gradient influences the Oi consumption of the crabs. INTRODUCTION Trm COrC~LICTING reports on the relationship between the O3 consumption and the water and salt balance in crustaceans have been well documented (Beadle, 1957; Remane & Schlieper, 1958; Florkin, 1960; Kinne, 1964; Ports & Parry, 1964). Even though the osmotic and ionic regulatory mechanisms of crustaceans have been very thoroughly studied (Robertson, 1960; Lockwood, 1962; Scheer, 1965; Florkin, 1966), the metabolic implications of these phenomena have not been fully understood. Since an understanding of the problems involved in the conquest of inland waters is intimately connected with and dependent upon our understanding of the patterns of respiratory metabolism of fresh water forms, the present investigation to follow the variations in the metabolic response of the fresh water field crab, Paratelphusa hydrodromous, to osmotic stress, was undertaken. MATERIALS AND METHODS The details of the maintenance of the crabs in the laboratory and collecting of the blood for analysis were described in an earlier paper (Padmanabhanaidu & Ramamurthi, 1961). Total osmotic pressure, Na +, K +, Mg ~+, Ca 2+, C1- and SO42were determined by the methods reported by Padmanabhanaidu (1966). Oxygen consumption was measured by the method reported by Saroja (1959). The dissolved oxygen content of the water samples was determined by the Winkler's procedure as given in Welsh & Smith (1953). Sea water was collected from Madras Coast. The salinity of full strength sea water was 32~oo. 10%, 25%, 37.5%, 50%, * Supported in part by NIH Grant AM 03539 to Dr. B. T. Seheer. I" On leave from Sri Venkateswara University, Tirupati, India. 599
600
R. ~ T , - * I
62.5%, and 75% sea water were prepared by diluting 100% sea water. The oxygen consumption was measured in a sequence in all salinities starting from tap water. The animals were left for 15 min after they were transferred into each next higher salinity before the 0 2 consumption was measured. The respiratory chambers were coated with black paint in order to avoid changes in the activity of the animal due to illumination. The experimental temperature was 27°+ I°C. O~ consumption was measured in 34 crabs and the data were plotted against size (body weight) on a double logarithmic paper. The weight regression curves were fitted by the method of least squares. In Fig. 1, a and b, the size-metabolism curves in various 3,O'-
n
2.O~
S
,.oL
/11./ •
-'-
./..;./ 0"7
•
~o, E
.,,~/io/
3.c
f
/ b
e,
,.c 2. °.,
°"-i
~.f/C'¢~ .~.~:°5"
I LI,I o
I
I
20
30
Weight,
I
40
I 80I ,il I10
g
FIG. 1. Weight regression lines of oxygen consumption of P. hydrodromous in
different salinities. Double logarithmic grid. (a) T a p w a t e r 100% sea water 50% s e a w a t e r 75% sea water
................ . . . . . . . . .
(b) T a p water 25% sea water 37"5% s e a w a t e r . . . . . . . . . 62"5% s e a w a t e r . . . . . . . . . . . . . . . .
salinities are presented together to facilitate comparison, omitting the individual points for the purpose of clarity. For the analysis of the blood of the crabs in different salinities, the crabs were treated in the same way as they were treated during the respiratory measurements (1 hr in each medium). RESULTS
Salinity tolerance. The salinity tolerance of P. hydrodromous was determined by upgrading 24 individuals through various grades of sea water (25, 50, 75, and
OXYGEN
CONSUMPTION
OF FRESH WATER
CRAB, P A R A T E L P H U S A
HYDRODROMOUS
601
100%), keeping the animals for two days in each medium. The crabs exhibited good tolerance to all these concentrations of sea water and survived well for prolonged periods without any apparent Rl effects. Sets of 12 crabs each were transferred directly to various concentrations of sea water from tap water. The crabs withstood direct transfer, even to undiluted sea water. N o weight changes could be detected when the crabs were weighed after keeping them for ½ hr in each of the saline media. Oxygen consumption. The maximal oxygen consumption was recorded in tap water and in 100% sea water. The crabs showed minimal oxygen consumption in 50% sea water (Fig. la and b). For a 20 g crab the sequence in the metabolic level from top to bottom in various salinities is as follows: Tap water-100% s.w.75% s.w.-25% s.w.-62.5% s.w.-37.5% s.w.-50°//o s.w. For any given CI- gradient the percent increase in oxygen consumption is greater in the hypotonic media than in hypertonic media, as far as CI- gradient is concerned, indicating that the direction of the C1- gradient influences the oxygen consumption (Fig. 2).
" •135 o J~
13o-
.
125
~"
120
._~ c o
o
I10
I00'
I
50
I
I
150
I
I
250
Chloride g r a d i e n t ,
I
I
550
I
4.5o
mM/L.
Fxo. 2. Comparison of oxygen consumption (% basal, taking the Os consumption in 50% sea water as basal) of P. hydrodromousas a function of CI- ion difference between the blood and the medium. "Hypertonic" represents media that offer positive chloride gradient (medium-blood), and "hypotonic" represents media that offer negative chloride gradient (medium-blood) to the crabs.
Ionic compositionof the blood. The total osmotic pressure and the concentration of different inorganic ionic species are presented in Table 1. There is an increase in the total osmotic pressure, Na + and C1- ion concentration of the blood when the crabs are upgraded through different salinities, but the rise is negligible when compared to the increase in osmotic pressure and the concentration of other ions in the medium. DISCUSSION It is well known that the ability to tolerate different concentrations of salt water varies very much in different species of fresh water crustaceans. Potamobius
602
R. ~ T m
fazcyiatilis was shown to survive up to a concentration of about 370 mM NaCI/1. (Bogucki, 1934). Astacus fluviatilus (Hermarm, 1931) and Asellus aquaticus (Lockwood, 1959) do not survive in higher concentrations of sea water. Saduria entomon (Lockwood & Croghan, 1957) and Caecosphaeroma tmrgundam (DrescoDerouet, 1959) can be adapted to full strength sea water. Duval (1925) found that Telphusa (Potamon edule) could withstand direct transfer to 100% sea water. TABLE 1 - - I O N I C
COMPOSITION OF THE BLOOD OF
P. hydrodromous*
(Weight range: 18-22 g)
Medium
Osmotic pressure CI SOa Na K Mg Ca (% NaCl) (mM/l.) (mM/1.) (mM/1.) (mM/l.) (mM/l.) (mM]l.)
Tap water 25% sea water 37"5% sea water 50% sea water 62.5% sea water 75% sea water 100% sea water
0"60 0"62 -0"79 -0.90 1.10
255 248 265 262 278 288 286
14.75 14.47 11.97 11.13 11.08 8"31 5.43
330 339 337 345 342 363 360
6'80 7.40 7.51 7"38 7.75 7"96 8.28
Ionic composition of sea water
3"10
567
23
558
9"5
7.83 8.29 7.69 6.30 6.36 5.52 5'31 39.4
7"78 10-25 8.39 12"86 11.70 10"31 9"39 9.40
* Each value represents the mean of six separate determinations.
Paratelphusa hydrodromous (present investigation) resembles Telphusa in its ability to tolerate saline media. Shaw (1959) reported that Potamon niloticus, the East African fresh water crab, fails to survive in undiluted sea water. Permeability of the animal to water and ions, relative concentrations of ions in the blood, and isosmotic intracellular regulation, mostly by amino acids, are the major factors that determine the salt-tolerating ability of a species. The fact that no weight changes could be detected when the crabs were weighed in different salinities indicates that P. hydrodromous achieved a great reduction in permeability. Duval (1925) suggested that crustaceans with high blood concentration have greater ability to tolerate salt water. P. hydrodromous has high blood chloride and sodium concentration and this, together with the extremely low permeability to water may be of importance in the successful survival of the crab in higher salinities. It would be of interest to see whether the intraceUular isosmotic regulation by the active modification of amino acids (Duchateau & Florkin, 1956) is in operation in this crab to prevent cellular dehydration in full strength sea water. The crabs showed maximal oxygen consumption in tap water and in 100% sea water. The minimal oxygen consumption was recorded in 50% sea water. Similar observations on other fresh-water crustaceans have earlier been reported. The oxygen consumption of crayfish is 40% higher in its natural medium of fresh
OXYGEN CONSUMPTION OF FRESH WATER CRAB, P A R A T E L P H U S A
HYDRODROMOUS
603
water than in isotonic sea water (Peters, 1935). Fresh water G a ~ r ~ pu~x and Asellus aquaticus have higher rates of 0 8 uptake than their related marine species Garamarus marinus and Idotea neglects (Fox & Simmonds, 1933). Krogh (1939) suggested that the "escape reaction" induced in an animal when it is exposed to an osmotic stress, might be responsible for the increase in the oxygen consumption. Gross (1957) concluded that the increase in the O~ uptake of (/ca after the imposition of osmotic stress is due to increased locomotor activity. This suggestion does not apply for P. hydrodromous since the maximal O ~ uptake was recorded in fresh water, which is the natural medium of the animal and hence cannot induce any "escape reaction". Brackish water which is new to the crab should really induce an "escape reaction" and result in an increased Oa uptake, but the results do not indicate this. P. hydrodromous showed minimal 0 2 consumption in 5 0 0 sea water. But Ports (1954) showed on a theoretical basis, assuming that animals are semipermeable, that only 0.5% of the total metabolic energy is utilized for the osmotic work done in Eriocheir. The relationship between the increases in O ~ consumption and the osmotic regulation has been reported (Lofts, 1956; Remane & Schlieper, 1958; Pampapathi Rao, 1958; Dehnel, 1960; Madanamohan Rao & Pampapathi Rao, 1962). The results of the present investigation indicate that the changes in the oxygen consumption in various salinities are more closely related to ionic regulation rather than to total osmotic pressure regulation. P. hydrodromous maintains the chloride and sodium concentrations in the blood at a relatively steady level in different salinities. The crabs experienced the largest chloride ion gradient between the blood and the medium when they were in tap water and in 100% sea water, and the maximal O~ consumption was recorded in these media. The Oz consumption was minimal in 50% sea water, which offered the lowest chloride ion gradient to the crab. A similar relationship between the O~ consumption and chloride ion regulation was shown in Ocypode albicans (Flemister & Flemister, 1951). The metabolism of P. hydrodromous is about 30% higher in media of extreme chloride gradient (tap water and 100% sea water) than in 50°/0 sea water. A part of this increase may be a reflection of energy expenditure for various active processes in the gills and the excretory organs that are involved in osmotic and ionic regulation. Lofts (1956) reported that marsh pool individuals of Palaemonetes varians show a 600~/o increase in the O~ consumption in media of extreme salinity over that in the isotonic medium. Such great differences in oxygen consumption may not be due to osmotic effect alone. Several other factors, of which we know little, may be influencing the metabolic response of crustaceans to osmotic and ionic stress. The mechanisms and energetics involved in the isosmotic intracellular regulation in crustaceans have not been fully understood. The whole animal respiration (Schwabe, 1933) and the gill tissue respiration (Florkin, 1960) of Eriocheir do not show any variation in different salinities. The gill respiration rate of summer Heraigrapsus increases in lower salinities, which is related to an increase in osmotic gradient (Dehnel & McCaughran, 1964). Schlieper (1936) suggested that hydration of ceils might be responsible for the increase of oxygen consumption in dilute media. King (1965) showed in several species of marine and brackish 2O
604
R. ~ ~ , ~ i
water crustaceans that the tissue respiration does not always parallel the whole animal respiration, and also, neither hydration of cells nor the osmotic work could account completely for the increase in Os uptake in dilute media. R a m a m u r t h i (1966) found that succinic dehydrogenase activity in gill and hepatopancreas of Paratelphusa hydrodromous as a function of salinity does not follow the same trend shown by the total oxygen consumption of the crab. T h i s indicates that investigations at molecular level m i g h t help in understanding different types and magnitudes of metabolic response to changes in the salinity of the medium. AcknowledgementsmI am grateful to Professor K. Pampapathirao, Professor and Head of the Department of Zoology, Sri Venkateswara University, Tirupati, India, under whose guidance this work was carried out. My sincere thanks are due to the late Dr. W. J. Gross of the University of California at Riverside, Calif., to Professor B. T. Scheer of the University of Oregon, Eugene, Oregon, and Professor Marcel Florkin of the University of Liege, Belgium, for critically going through the manuscript and offering valuable suggestions. I am thankful to Mrs. Elsie Mumbach for her timely help during the preparation of the manuscript. REFERENCES BEADLE L. C. (1957) Comparative Physiology: Osmotic and ionic regulation in aquatic animals. A. Rev. Physiol. 19, 329-358. BOGUCKIM. (1934) Ionic and osmotic regulation in crayfish. Archs int. Physiol. 38, 172-179. DEHNEL P. A. (1960) Effect of temperature and salinity on the oxygen consumption of two intertidal crabs. Biol. Bull. mar. biol. Lab., Woods Hole 118, 215-249. DEHNEL P. A. & McCAUOHRANA. (1964) Gill tissue respiration in two species of estuarine crabs. Comp. Biochem. Physiol. 13, 233-259. DImSCO-I~RoUET Louise (1959) Contributions/~ l'~tude de la biologie de deux crustac~s aquatiques cavernicoles, Caecosphaeroma burgundum D. et Niphargus orcinus Virei Ch. Vie Milieu 10, 321-346. DUCHATEAUG. & FLORKINM. (1955) Concentration du milieu ext~rieur et ~tat stationnaire du pool des acides amln~s non prot~iques des muscles. Archs int. Physiol. 67, 489-500. DUCAL M. (1925) Researches physico-chimiques et physiologiques sur le milieu int~rieur des animaux aquatiques. Ann. Inst. Ocdanogr. Monaco, (New Series) 2, 233--407. FLEMISTERL. J. ~ FLEMISTERS. C. (1951) Chloride ion regulation and oxygen consumption in the crab, Ocypode albicans (Bosq). Biol. Bull. mar. biol. lab., Woods Hole 101, 259-273. FLORKIN M. (1960) In: Ecology and Metabolism in the Physiology of Cr~stacea. (Edited by WATSaM~ T. H.) Vol. I, pp. 395410. Academic Press, New York. FLORKINM. (1966) Aspects moldculaires de l'adaptation et de la phylogdnie. Chap. V. Mason et Cie, Paris. Fox M. H. & SIMMONDSB. G. (1933) Metabolic rates of aquatic arthropods from different habitats. J. exp. Biol. 10, 67-74. GROSS W. J. (1957) A behavioral mechanism for osmotic regulation in a semi-terrestrial crab. Biol. Bull. mar. biol. Lab., Woods Hole 113, 268-273. Hm~m~ANNF. (1931) Ober den wasserhaushalt des flusskrebses. Z. Vergl. Physiol. 7, 15-26. KING E. N. (1965) The oxygen consumption of intact crabs and excised gills as a function of decreased salinity. Comp. Biochem. Physiol. 15, 93-102. KINNE O. (1964) The effects of temperature and salinity on marine and brackish water animals. II. Salinity and temperature-salinity combinations. Oceanogr. Mar. Biol. ~Inn. Rev. 2, 281-339. KaOGH A. (1939) Osmotic Regulation in Aquatic Animals. Cambridge University Press.
OXYGEN CONSUMPTION OF FRESH WATER CRAB~ PARATELPHUSA HYDRODROMOUS
605
LOCKWOOD A. P. M. (1959) The osmotic and ionic regulation of Asellus aquaticus (L). J. exp. Biol. 36, 546-555. LOCKWOODA. P. M. (1962) The osmoregulation of crustacea. Biol. Rev. 37, 257-305. LOCKWOODA. P. M. & CROGR~'~ P. C. (1957) The chloride regulation of the brackish and fresh water races of Mesidotea entoraon (L.). •. exp. Biol. 34, 253-258. LOFTS B. (1956) The effects of salinity changes on the respiratory of the prawn Palaemonetes Parians (Leach). J. exp. Biol. 33, 730-736. M ~ a ) A N M O ~ O G. & PAMPAPATm~O K. (1962) Oxygen consumption in a brackish water crustacean Sesarma plicatum (Latrielle) and a marine crustacean, Lepas anatifera (L.). Crustaceana 4, 75-81. PADMANABR~qAIDUB. & RAMAMU~THIR. (1961) The influence of sex and size on the osmotic pressure, the chloride and the free amino acids of the blood of the fresh water field crab, Paratelphusa sp. and the fresh water mussel, Lamellidens marginalis. J. exp. Biol. 38, 35--41. P A D ~ A . ~ A I D U B. (1966a) Ionic composition of the blood and the blood volume of the scorpion, Heterometrus fulvipes. Comp. Biochem. Physiol. 17, 157-166. PAMPAPATHIRAOK. (1958) Oxygen consumption as a function of size and salinity in Metapenaeus monoceros (Fab.) from marine and brackish water environments, y. exp. Biol. 35, 307-313. PE~as H. (1935) l~ber den Einfluss des Salzgehaltes im Aussenmedium auf den Ban und die Funktion der Exkretionsorgane dekapoder crustaceen (Nach Untersuchungen an Potamobius fluviatilis und Homarus vulgaris). Z. Morph. Okol. Tiere 30, 355-381. POTTS W. T. W. (1954) The energetics of osmoregulation in brackish and fresh water animals..7, exp. Biol. 31, 618-630. POTTS W. T. W. & PARRY G. (1964) Osmotic and Ionic Regulation in Animals. Chap. 8, Pergamon Press, London. RAMAMtraTm R. (1966) Succinic dehydrogenase activity in a fresh water crab in relation to salinity stress. Comp. Biochem. Physiol. 19, 645--648. R~MANE A. & SCHLIEPERC. (1958) Die Biologie des Brackwassers. Ira: D/e Binnengewasser (THmNEMANN A. Hm~uSG), Bd. 22, S. 348. Schweizerbart, Stuttgart. ROBERTSONJ. D. (1960) Ionic regulation in the crab Carcinus maenas (L.) in relation to the moulting cycle. Comp. Biochem. Physiol. 1, 183-212. SAROJAK. (1959) Studies on the oxygen consumption in tropical poikilotherms. II. Oxygen consumption in relation to body size and temperature in the earthworm, Megascolex mauritii, when kept submerged underwater. Proc. Ind. Acad. Sci., X L I X (13), 183-193. SCH~R B. T. (1965) Salt and water balance of invertebrates. Archs anat. microscp. 54(1), 531-546. SCHLmPEa C. (1936) Die Abhangigkeit der Atmungsintensitat der Organismen Vom Wassergehalt und dem Kolloidalen Zustand des Protoplasmas. Biol. Zbl. 56, 87-94. SCHWAnE E. (1933) l~ber die Osmoregulation Verschiedener Krebse (Malacostracen). Z. vergl. Physiol. 19, 183-236. SHAW J. (1959) Salt and water balance in the East African freshwater crab, Potamon niloticus. ft. exp. Biol. 36, 157-176. WELSH H. • SMITH R. I. (1953) Laboratory Exercises in Invertebrate Physiology. Burgess, Minneapolis.
OXYGEN CONSUMPTION OF A FRESH WATER CRAB,
PARATELPHUSA HYDRODROMOUS, IN RELATION TO SALINITY STRESS* R. R A M A M U R T H I t Department of Biology, University of Oregon, Eugene, Oregon
(Received 23 May 1967) Almtraet--1. The fresh water field crab Paratelphusa hydrodromous exhibits good tolerance to saline media up to 100% sea water. 2. The crabs show minimal oxygen consumption in 50% sea water and roaTimal oxygen consumption in tap water and in 100~/osea water. The variation in the pattern of metabolic response to salinity appears to be related to the chloride ion gradient existing between the blood and the medium. The direction of the C1- gradient influences the Oi consumption of the crabs. INTRODUCTION Trm COrC~LICTING reports on the relationship between the O3 consumption and the water and salt balance in crustaceans have been well documented (Beadle, 1957; Remane & Schlieper, 1958; Florkin, 1960; Kinne, 1964; Ports & Parry, 1964). Even though the osmotic and ionic regulatory mechanisms of crustaceans have been very thoroughly studied (Robertson, 1960; Lockwood, 1962; Scheer, 1965; Florkin, 1966), the metabolic implications of these phenomena have not been fully understood. Since an understanding of the problems involved in the conquest of inland waters is intimately connected with and dependent upon our understanding of the patterns of respiratory metabolism of fresh water forms, the present investigation to follow the variations in the metabolic response of the fresh water field crab, Paratelphusa hydrodromous, to osmotic stress, was undertaken. MATERIALS AND METHODS The details of the maintenance of the crabs in the laboratory and collecting of the blood for analysis were described in an earlier paper (Padmanabhanaidu & Ramamurthi, 1961). Total osmotic pressure, Na +, K +, Mg ~+, Ca 2+, C1- and SO42were determined by the methods reported by Padmanabhanaidu (1966). Oxygen consumption was measured by the method reported by Saroja (1959). The dissolved oxygen content of the water samples was determined by the Winkler's procedure as given in Welsh & Smith (1953). Sea water was collected from Madras Coast. The salinity of full strength sea water was 32~oo. 10%, 25%, 37.5%, 50%, * Supported in part by NIH Grant AM 03539 to Dr. B. T. Seheer. I" On leave from Sri Venkateswara University, Tirupati, India. 599
600
R. ~ T , - * I
62.5%, and 75% sea water were prepared by diluting 100% sea water. The oxygen consumption was measured in a sequence in all salinities starting from tap water. The animals were left for 15 min after they were transferred into each next higher salinity before the 0 2 consumption was measured. The respiratory chambers were coated with black paint in order to avoid changes in the activity of the animal due to illumination. The experimental temperature was 27°+ I°C. O~ consumption was measured in 34 crabs and the data were plotted against size (body weight) on a double logarithmic paper. The weight regression curves were fitted by the method of least squares. In Fig. 1, a and b, the size-metabolism curves in various 3,O'-
n
2.O~
S
,.oL
/11./ •
-'-
./..;./ 0"7
•
~o, E
.,,~/io/
3.c
f
/ b
e,
,.c 2. °.,
°"-i
~.f/C'¢~ .~.~:°5"
I LI,I o
I
I
20
30
Weight,
I
40
I 80I ,il I10
g
FIG. 1. Weight regression lines of oxygen consumption of P. hydrodromous in
different salinities. Double logarithmic grid. (a) T a p w a t e r 100% sea water 50% s e a w a t e r 75% sea water
................ . . . . . . . . .
(b) T a p water 25% sea water 37"5% s e a w a t e r . . . . . . . . . 62"5% s e a w a t e r . . . . . . . . . . . . . . . .
salinities are presented together to facilitate comparison, omitting the individual points for the purpose of clarity. For the analysis of the blood of the crabs in different salinities, the crabs were treated in the same way as they were treated during the respiratory measurements (1 hr in each medium). RESULTS
Salinity tolerance. The salinity tolerance of P. hydrodromous was determined by upgrading 24 individuals through various grades of sea water (25, 50, 75, and
OXYGEN
CONSUMPTION
OF FRESH WATER
CRAB, P A R A T E L P H U S A
HYDRODROMOUS
601
100%), keeping the animals for two days in each medium. The crabs exhibited good tolerance to all these concentrations of sea water and survived well for prolonged periods without any apparent Rl effects. Sets of 12 crabs each were transferred directly to various concentrations of sea water from tap water. The crabs withstood direct transfer, even to undiluted sea water. N o weight changes could be detected when the crabs were weighed after keeping them for ½ hr in each of the saline media. Oxygen consumption. The maximal oxygen consumption was recorded in tap water and in 100% sea water. The crabs showed minimal oxygen consumption in 50% sea water (Fig. la and b). For a 20 g crab the sequence in the metabolic level from top to bottom in various salinities is as follows: Tap water-100% s.w.75% s.w.-25% s.w.-62.5% s.w.-37.5% s.w.-50°//o s.w. For any given CI- gradient the percent increase in oxygen consumption is greater in the hypotonic media than in hypertonic media, as far as CI- gradient is concerned, indicating that the direction of the C1- gradient influences the oxygen consumption (Fig. 2).
" •135 o J~
13o-
.
125
~"
120
._~ c o
o
I10
I00'
I
50
I
I
150
I
I
250
Chloride g r a d i e n t ,
I
I
550
I
4.5o
mM/L.
Fxo. 2. Comparison of oxygen consumption (% basal, taking the Os consumption in 50% sea water as basal) of P. hydrodromousas a function of CI- ion difference between the blood and the medium. "Hypertonic" represents media that offer positive chloride gradient (medium-blood), and "hypotonic" represents media that offer negative chloride gradient (medium-blood) to the crabs.
Ionic compositionof the blood. The total osmotic pressure and the concentration of different inorganic ionic species are presented in Table 1. There is an increase in the total osmotic pressure, Na + and C1- ion concentration of the blood when the crabs are upgraded through different salinities, but the rise is negligible when compared to the increase in osmotic pressure and the concentration of other ions in the medium. DISCUSSION It is well known that the ability to tolerate different concentrations of salt water varies very much in different species of fresh water crustaceans. Potamobius
602
R. ~ T m
fazcyiatilis was shown to survive up to a concentration of about 370 mM NaCI/1. (Bogucki, 1934). Astacus fluviatilus (Hermarm, 1931) and Asellus aquaticus (Lockwood, 1959) do not survive in higher concentrations of sea water. Saduria entomon (Lockwood & Croghan, 1957) and Caecosphaeroma tmrgundam (DrescoDerouet, 1959) can be adapted to full strength sea water. Duval (1925) found that Telphusa (Potamon edule) could withstand direct transfer to 100% sea water. TABLE 1 - - I O N I C
COMPOSITION OF THE BLOOD OF
P. hydrodromous*
(Weight range: 18-22 g)
Medium
Osmotic pressure CI SOa Na K Mg Ca (% NaCl) (mM/l.) (mM/1.) (mM/1.) (mM/l.) (mM/l.) (mM]l.)
Tap water 25% sea water 37"5% sea water 50% sea water 62.5% sea water 75% sea water 100% sea water
0"60 0"62 -0"79 -0.90 1.10
255 248 265 262 278 288 286
14.75 14.47 11.97 11.13 11.08 8"31 5.43
330 339 337 345 342 363 360
6'80 7.40 7.51 7"38 7.75 7"96 8.28
Ionic composition of sea water
3"10
567
23
558
9"5
7.83 8.29 7.69 6.30 6.36 5.52 5'31 39.4
7"78 10-25 8.39 12"86 11.70 10"31 9"39 9.40
* Each value represents the mean of six separate determinations.
Paratelphusa hydrodromous (present investigation) resembles Telphusa in its ability to tolerate saline media. Shaw (1959) reported that Potamon niloticus, the East African fresh water crab, fails to survive in undiluted sea water. Permeability of the animal to water and ions, relative concentrations of ions in the blood, and isosmotic intracellular regulation, mostly by amino acids, are the major factors that determine the salt-tolerating ability of a species. The fact that no weight changes could be detected when the crabs were weighed in different salinities indicates that P. hydrodromous achieved a great reduction in permeability. Duval (1925) suggested that crustaceans with high blood concentration have greater ability to tolerate salt water. P. hydrodromous has high blood chloride and sodium concentration and this, together with the extremely low permeability to water may be of importance in the successful survival of the crab in higher salinities. It would be of interest to see whether the intraceUular isosmotic regulation by the active modification of amino acids (Duchateau & Florkin, 1956) is in operation in this crab to prevent cellular dehydration in full strength sea water. The crabs showed maximal oxygen consumption in tap water and in 100% sea water. The minimal oxygen consumption was recorded in 50% sea water. Similar observations on other fresh-water crustaceans have earlier been reported. The oxygen consumption of crayfish is 40% higher in its natural medium of fresh
OXYGEN CONSUMPTION OF FRESH WATER CRAB, P A R A T E L P H U S A
HYDRODROMOUS
603
water than in isotonic sea water (Peters, 1935). Fresh water G a ~ r ~ pu~x and Asellus aquaticus have higher rates of 0 8 uptake than their related marine species Garamarus marinus and Idotea neglects (Fox & Simmonds, 1933). Krogh (1939) suggested that the "escape reaction" induced in an animal when it is exposed to an osmotic stress, might be responsible for the increase in the oxygen consumption. Gross (1957) concluded that the increase in the O~ uptake of (/ca after the imposition of osmotic stress is due to increased locomotor activity. This suggestion does not apply for P. hydrodromous since the maximal O ~ uptake was recorded in fresh water, which is the natural medium of the animal and hence cannot induce any "escape reaction". Brackish water which is new to the crab should really induce an "escape reaction" and result in an increased Oa uptake, but the results do not indicate this. P. hydrodromous showed minimal 0 2 consumption in 5 0 0 sea water. But Ports (1954) showed on a theoretical basis, assuming that animals are semipermeable, that only 0.5% of the total metabolic energy is utilized for the osmotic work done in Eriocheir. The relationship between the increases in O ~ consumption and the osmotic regulation has been reported (Lofts, 1956; Remane & Schlieper, 1958; Pampapathi Rao, 1958; Dehnel, 1960; Madanamohan Rao & Pampapathi Rao, 1962). The results of the present investigation indicate that the changes in the oxygen consumption in various salinities are more closely related to ionic regulation rather than to total osmotic pressure regulation. P. hydrodromous maintains the chloride and sodium concentrations in the blood at a relatively steady level in different salinities. The crabs experienced the largest chloride ion gradient between the blood and the medium when they were in tap water and in 100% sea water, and the maximal O~ consumption was recorded in these media. The Oz consumption was minimal in 50% sea water, which offered the lowest chloride ion gradient to the crab. A similar relationship between the O~ consumption and chloride ion regulation was shown in Ocypode albicans (Flemister & Flemister, 1951). The metabolism of P. hydrodromous is about 30% higher in media of extreme chloride gradient (tap water and 100% sea water) than in 50°/0 sea water. A part of this increase may be a reflection of energy expenditure for various active processes in the gills and the excretory organs that are involved in osmotic and ionic regulation. Lofts (1956) reported that marsh pool individuals of Palaemonetes varians show a 600~/o increase in the O~ consumption in media of extreme salinity over that in the isotonic medium. Such great differences in oxygen consumption may not be due to osmotic effect alone. Several other factors, of which we know little, may be influencing the metabolic response of crustaceans to osmotic and ionic stress. The mechanisms and energetics involved in the isosmotic intracellular regulation in crustaceans have not been fully understood. The whole animal respiration (Schwabe, 1933) and the gill tissue respiration (Florkin, 1960) of Eriocheir do not show any variation in different salinities. The gill respiration rate of summer Heraigrapsus increases in lower salinities, which is related to an increase in osmotic gradient (Dehnel & McCaughran, 1964). Schlieper (1936) suggested that hydration of ceils might be responsible for the increase of oxygen consumption in dilute media. King (1965) showed in several species of marine and brackish 2O
604
R. ~ ~ , ~ i
water crustaceans that the tissue respiration does not always parallel the whole animal respiration, and also, neither hydration of cells nor the osmotic work could account completely for the increase in Os uptake in dilute media. R a m a m u r t h i (1966) found that succinic dehydrogenase activity in gill and hepatopancreas of Paratelphusa hydrodromous as a function of salinity does not follow the same trend shown by the total oxygen consumption of the crab. T h i s indicates that investigations at molecular level m i g h t help in understanding different types and magnitudes of metabolic response to changes in the salinity of the medium. AcknowledgementsmI am grateful to Professor K. Pampapathirao, Professor and Head of the Department of Zoology, Sri Venkateswara University, Tirupati, India, under whose guidance this work was carried out. My sincere thanks are due to the late Dr. W. J. Gross of the University of California at Riverside, Calif., to Professor B. T. Scheer of the University of Oregon, Eugene, Oregon, and Professor Marcel Florkin of the University of Liege, Belgium, for critically going through the manuscript and offering valuable suggestions. I am thankful to Mrs. Elsie Mumbach for her timely help during the preparation of the manuscript. REFERENCES BEADLE L. C. (1957) Comparative Physiology: Osmotic and ionic regulation in aquatic animals. A. Rev. Physiol. 19, 329-358. BOGUCKIM. (1934) Ionic and osmotic regulation in crayfish. Archs int. Physiol. 38, 172-179. DEHNEL P. A. (1960) Effect of temperature and salinity on the oxygen consumption of two intertidal crabs. Biol. Bull. mar. biol. Lab., Woods Hole 118, 215-249. DEHNEL P. A. & McCAUOHRANA. (1964) Gill tissue respiration in two species of estuarine crabs. Comp. Biochem. Physiol. 13, 233-259. DImSCO-I~RoUET Louise (1959) Contributions/~ l'~tude de la biologie de deux crustac~s aquatiques cavernicoles, Caecosphaeroma burgundum D. et Niphargus orcinus Virei Ch. Vie Milieu 10, 321-346. DUCHATEAUG. & FLORKINM. (1955) Concentration du milieu ext~rieur et ~tat stationnaire du pool des acides amln~s non prot~iques des muscles. Archs int. Physiol. 67, 489-500. DUCAL M. (1925) Researches physico-chimiques et physiologiques sur le milieu int~rieur des animaux aquatiques. Ann. Inst. Ocdanogr. Monaco, (New Series) 2, 233--407. FLEMISTERL. J. ~ FLEMISTERS. C. (1951) Chloride ion regulation and oxygen consumption in the crab, Ocypode albicans (Bosq). Biol. Bull. mar. biol. lab., Woods Hole 101, 259-273. FLORKIN M. (1960) In: Ecology and Metabolism in the Physiology of Cr~stacea. (Edited by WATSaM~ T. H.) Vol. I, pp. 395410. Academic Press, New York. FLORKINM. (1966) Aspects moldculaires de l'adaptation et de la phylogdnie. Chap. V. Mason et Cie, Paris. Fox M. H. & SIMMONDSB. G. (1933) Metabolic rates of aquatic arthropods from different habitats. J. exp. Biol. 10, 67-74. GROSS W. J. (1957) A behavioral mechanism for osmotic regulation in a semi-terrestrial crab. Biol. Bull. mar. biol. Lab., Woods Hole 113, 268-273. Hm~m~ANNF. (1931) Ober den wasserhaushalt des flusskrebses. Z. Vergl. Physiol. 7, 15-26. KING E. N. (1965) The oxygen consumption of intact crabs and excised gills as a function of decreased salinity. Comp. Biochem. Physiol. 15, 93-102. KINNE O. (1964) The effects of temperature and salinity on marine and brackish water animals. II. Salinity and temperature-salinity combinations. Oceanogr. Mar. Biol. ~Inn. Rev. 2, 281-339. KaOGH A. (1939) Osmotic Regulation in Aquatic Animals. Cambridge University Press.
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