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Some physiological and biochemical adaptations to diving in three species of ducks
Camp.Biochem.Phwiul..1977. Vol.57A. pp. 227 fo 228. Pergamon
Press. Prinrrd
in GrvurBritain
SOME PHYSIOLOGICAL AND BIOCHEMICAL ADAPTATIONS TO DIVING IN THREE SPECIES OF DUCKS P. A. COOK. W. R. SIEGFRIED AND P. G. H. FROST Department of Zoology and Fitzpatrick Institute. University of Cape Town. Rondebosch 7700, South Africa (Recriord
21 September
1976)
Abstract-l.
Heart rates before, during and after diving and serum lactate concentrations before and after diving were measured in three species of ducks (Oxyura macoa, Netta erythrophthalmu and Anus smithii) which differ in their feeding behaviour and diving ability. 2. Oxyura muccon (a specialist diver) showed a greater diving bradycardia and a greater post-dive tachycardia than either of the other species, but the build-up of serum lactate during diving was less in 0. maccoa than in either of the other species. 3. It is concluded that, in the three species of ducks. physiological and biochemical adaptations are positively correlated with feeding behaviour and diving ability.
INTRODUCTION
The physiological
mechanisms which permit diving animals to survive long periods of hypoxia have been reviewed by Scholander (1961) and Andersen (1966). It is well known that the heart rate of many animals. including ducks, is reduced whilst the animal is submerged (Catlett & Johnston, 1974). Physiological adaptations do not, however, fully explain the tolerance of diving animals to hypoxia and biochemical adaptations may be involved. For example, in the Pond Turtle (Pseudomys scripta) survival during prolonged periods of anaerobiosis is facilitated by a biochemical adaptation involving the enzyme lactate dehydrogenase (Simon et nl., 1974). whilst in the Weddell Seal (Leptonychotes weddelli) prolonged diving ability is associated with high activity of pyruvate kinase in the heart and brain (Altman & Robin, 1969). The three species of ducks reported on here occupy similar habitats, but differ in their feeding behaviour. The Cape Shoveller (Anas smithii) is normally found in fertile, shallow-water pans, from which it obtains its food by paddling along the surface with its beak submerged, sieving out fine edible particles by means of its beak lamellae. It occasionally submerges its head, but rarely dives. The Maccoa Duck (Ouyura maccoa), on the other hand, relies almost entirely on diving to obtain chironomid midge larvae and pupae. which form its chief food. Whilst feeding it remains submerged for up to 30 set at a time. then surfaces and rests for about 10 set between dives. One individual which was observed continuously for 6 hr spent 177 min diving and a total of 133 min underwater. The Southern Pochard (Netra erythrophthalma) is intermediate between the other two species, with respect to feeding behaviour. It feeds mainly near the edges of lakes, sometimes paddling with its beak submerged and sometimes diving for short periods. The purpose of this investigation was to determine whether differences in feeding behaviour were reflected in physiological and biochemical adaptations to diving.
MATERIALS
AND METHODS
The heart rate of the ducks was measured using a George Washington 400 MD2 oscillograph with an FC124 input coupler. Normal pre-dive heart rate was determined on ducks which had been fasted for about four hours and strapped to a restraining board for at least 30min before the beginning of the experiment. Heart rate whilst diving was measured by tilting the restraining board so that the entire body of the animal was submerged. The diving schedule adopted for all three species was 20 set submergence followed by 1Osec on the surface, continued for a total of 30min. The immediate post-dive heart rate was measured during the first minute of emergence after the final dive. Blood samples were taken before and after the dive schedule and serum lactate concentration was determined according to the method of Hohorst (1962). The experiment was repeated on at least two specimens of each species. RESULTS
The Maccoa. an active diver, experiences much greater bradycardia than the Shoveller, while the Pochard is intermediate (Table 1). Post-dive tachycardia was also much greater in the Maccoa than in either of the other two species. The build-up of lactic acid in the blood during diving shows the opposite trend, in that the concentration in the Maccoa increases only slightly whilst that in the Shoveller more than doubles. The Pochard again is intermediate between the other two (Table 1). DISCUSSION
It appears that the Maccoa is much better adapted to diving than either the Pochard or the Shoveller, while the Pochard is slightly better adapted than the Shoveller. It seems likely that the metabolic rate of the submerged Maccoa is reduced so as to conserve oxygen. In the Shoveller, however. the metabolic rate is reduced only slightly and, thus during experimental dives, it is forced to obtain its required energy through anaerobic glycolysis once all of its available 227
228
P. A. Coon. W. R.
SEGFRIEU) AND
P. G. H. F~os’r
Table I. Heart Rate (beat+nin) before. during and after diving, and serum lactate concentrations (mgj100 ml) before and after diving in three species of wild ducks Shoveller Pre-dive heart rate Heart rate during dive Dive rate as “,, of pre-dive rate Post-dive heart rate Pre-dive lactate cont. Post-dive lactate cont. “O increase in lactate cont.
oxygen has been used up. This is reflected in a large build”~tp of lactic acid in its blood. The Maccoa is
further adapted in that it is capable of a considerable increase in its heart rate immediately after surfacing, which would help in repaying any oxygen debt which may have been built up during the dive. AckrroM?Irdgralrnts-We are grateful to the Cape Department of Nature and environmental conservation for the loan of the experimental animals. REFERENCES
ALTMANM. & ROBIN E. D. (1969) Survival during prolonged anaerobiosis as a function of an unusual adap-
Pochard
M accoa
138 Xl 58.7 195 64.0 139.8
1x5 57 30.X 213 76.6 104.3
173 -ti 24.7 426 60.5 77.0
118.5
36.’
2x.5
tation involving lactate dehydrogenase subunits. Camp. Bj~c~~~~.Pension. 30. I I7YY1187. ANDERSEN H. T. (1966)Physiological adaptations in diving vertebrates. Physiol. Rec. 46, 21 t-243. CATLETTR. H. & JOHNSTON B. L. (1974) Cardiac response to diving in wild ducks. Cornp. Biochem. Physiol. 47A. 925-93 I. HOHORSTH. J. (1962) In Methods qf’ En,-ymaric .4rrufysis (Edited by BERGMEYEK H. U.). 1st Edn. 622 pp. Vet-lag Chemie, Weinheim. S~HOLA~‘DEK P. F. (1961) Physiological adaptations to diving in animals and man. Hurrry Lect. 57, 93-I IO. SIMONL. M., RABIN E. D.. ELSNERR., VAN KESSELA. L. G. J. & THEODOKCJ. (1974) A biochemical basis for differences in maximal diving time in aquatic animals. Camp.
Biochem.
Physiol.
47B.
209-215.
Press. Prinrrd
in GrvurBritain
SOME PHYSIOLOGICAL AND BIOCHEMICAL ADAPTATIONS TO DIVING IN THREE SPECIES OF DUCKS P. A. COOK. W. R. SIEGFRIED AND P. G. H. FROST Department of Zoology and Fitzpatrick Institute. University of Cape Town. Rondebosch 7700, South Africa (Recriord
21 September
1976)
Abstract-l.
Heart rates before, during and after diving and serum lactate concentrations before and after diving were measured in three species of ducks (Oxyura macoa, Netta erythrophthalmu and Anus smithii) which differ in their feeding behaviour and diving ability. 2. Oxyura muccon (a specialist diver) showed a greater diving bradycardia and a greater post-dive tachycardia than either of the other species, but the build-up of serum lactate during diving was less in 0. maccoa than in either of the other species. 3. It is concluded that, in the three species of ducks. physiological and biochemical adaptations are positively correlated with feeding behaviour and diving ability.
INTRODUCTION
The physiological
mechanisms which permit diving animals to survive long periods of hypoxia have been reviewed by Scholander (1961) and Andersen (1966). It is well known that the heart rate of many animals. including ducks, is reduced whilst the animal is submerged (Catlett & Johnston, 1974). Physiological adaptations do not, however, fully explain the tolerance of diving animals to hypoxia and biochemical adaptations may be involved. For example, in the Pond Turtle (Pseudomys scripta) survival during prolonged periods of anaerobiosis is facilitated by a biochemical adaptation involving the enzyme lactate dehydrogenase (Simon et nl., 1974). whilst in the Weddell Seal (Leptonychotes weddelli) prolonged diving ability is associated with high activity of pyruvate kinase in the heart and brain (Altman & Robin, 1969). The three species of ducks reported on here occupy similar habitats, but differ in their feeding behaviour. The Cape Shoveller (Anas smithii) is normally found in fertile, shallow-water pans, from which it obtains its food by paddling along the surface with its beak submerged, sieving out fine edible particles by means of its beak lamellae. It occasionally submerges its head, but rarely dives. The Maccoa Duck (Ouyura maccoa), on the other hand, relies almost entirely on diving to obtain chironomid midge larvae and pupae. which form its chief food. Whilst feeding it remains submerged for up to 30 set at a time. then surfaces and rests for about 10 set between dives. One individual which was observed continuously for 6 hr spent 177 min diving and a total of 133 min underwater. The Southern Pochard (Netra erythrophthalma) is intermediate between the other two species, with respect to feeding behaviour. It feeds mainly near the edges of lakes, sometimes paddling with its beak submerged and sometimes diving for short periods. The purpose of this investigation was to determine whether differences in feeding behaviour were reflected in physiological and biochemical adaptations to diving.
MATERIALS
AND METHODS
The heart rate of the ducks was measured using a George Washington 400 MD2 oscillograph with an FC124 input coupler. Normal pre-dive heart rate was determined on ducks which had been fasted for about four hours and strapped to a restraining board for at least 30min before the beginning of the experiment. Heart rate whilst diving was measured by tilting the restraining board so that the entire body of the animal was submerged. The diving schedule adopted for all three species was 20 set submergence followed by 1Osec on the surface, continued for a total of 30min. The immediate post-dive heart rate was measured during the first minute of emergence after the final dive. Blood samples were taken before and after the dive schedule and serum lactate concentration was determined according to the method of Hohorst (1962). The experiment was repeated on at least two specimens of each species. RESULTS
The Maccoa. an active diver, experiences much greater bradycardia than the Shoveller, while the Pochard is intermediate (Table 1). Post-dive tachycardia was also much greater in the Maccoa than in either of the other two species. The build-up of lactic acid in the blood during diving shows the opposite trend, in that the concentration in the Maccoa increases only slightly whilst that in the Shoveller more than doubles. The Pochard again is intermediate between the other two (Table 1). DISCUSSION
It appears that the Maccoa is much better adapted to diving than either the Pochard or the Shoveller, while the Pochard is slightly better adapted than the Shoveller. It seems likely that the metabolic rate of the submerged Maccoa is reduced so as to conserve oxygen. In the Shoveller, however. the metabolic rate is reduced only slightly and, thus during experimental dives, it is forced to obtain its required energy through anaerobic glycolysis once all of its available 227
228
P. A. Coon. W. R.
SEGFRIEU) AND
P. G. H. F~os’r
Table I. Heart Rate (beat+nin) before. during and after diving, and serum lactate concentrations (mgj100 ml) before and after diving in three species of wild ducks Shoveller Pre-dive heart rate Heart rate during dive Dive rate as “,, of pre-dive rate Post-dive heart rate Pre-dive lactate cont. Post-dive lactate cont. “O increase in lactate cont.
oxygen has been used up. This is reflected in a large build”~tp of lactic acid in its blood. The Maccoa is
further adapted in that it is capable of a considerable increase in its heart rate immediately after surfacing, which would help in repaying any oxygen debt which may have been built up during the dive. AckrroM?Irdgralrnts-We are grateful to the Cape Department of Nature and environmental conservation for the loan of the experimental animals. REFERENCES
ALTMANM. & ROBIN E. D. (1969) Survival during prolonged anaerobiosis as a function of an unusual adap-
Pochard
M accoa
138 Xl 58.7 195 64.0 139.8
1x5 57 30.X 213 76.6 104.3
173 -ti 24.7 426 60.5 77.0
118.5
36.’
2x.5
tation involving lactate dehydrogenase subunits. Camp. Bj~c~~~~.Pension. 30. I I7YY1187. ANDERSEN H. T. (1966)Physiological adaptations in diving vertebrates. Physiol. Rec. 46, 21 t-243. CATLETTR. H. & JOHNSTON B. L. (1974) Cardiac response to diving in wild ducks. Cornp. Biochem. Physiol. 47A. 925-93 I. HOHORSTH. J. (1962) In Methods qf’ En,-ymaric .4rrufysis (Edited by BERGMEYEK H. U.). 1st Edn. 622 pp. Vet-lag Chemie, Weinheim. S~HOLA~‘DEK P. F. (1961) Physiological adaptations to diving in animals and man. Hurrry Lect. 57, 93-I IO. SIMONL. M., RABIN E. D.. ELSNERR., VAN KESSELA. L. G. J. & THEODOKCJ. (1974) A biochemical basis for differences in maximal diving time in aquatic animals. Camp.
Biochem.
Physiol.
47B.
209-215.