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Fat content, fatty acid composition and estimates of energy metabolism of adélie penguins (Pygoscelis adeliae) during the early breeding season fast
Comp. Biochem. Physiol., 1973, Vol. 45B, pp. 709 to 719. Pergamon Press. Printed in Great Britain
FAT CONTENT, FATTY ACID COMPOSITION AND ESTIMATES OF ENERGY METABOLISM OF AD]~LIE PENGUINS (PYGOSCELIS ADELI./IE) DURING THE EARLY BREEDING SEASON FAST S T E P H E N R. J O H N S O N and G E O R G E C. W E S T Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska 99701 (Received 13 September 1972)
Abstract--1. Ad61ie penguins (Pygoscelis adeliae) breeding at Cape Crozier, Antarctica, arrive in the colony from the sea in October at the beginning of the austral summer. Both sexes fast while on the breeding colony for 3-6 weeks before returning to the sea to feed. 2. Six individuals collected during the first fast period showed decreased blubber thickness and a linearly corresponding decrease in ether extractable fat with time after arrival in the breeding area. Birds contained about 45 per cent of dry weight as fat upon arrival, and in a typical incubation, males decreased to about 20 per cent after day 27. 3. The decrease in fat represents approximately 56 g of fat used per day by fasting male Ad61ies for the 27-day period. On the basis of this value, it has been estimated that 490 keal/bird per day approximates energy demands for these fasting birds during the early part of the breeding season. 4. Fatty acid compositions of total ether extractable lipids, subcutaneous fat and abdominal depot fat did not differ significantly except in a few of the longchain acids. Depot fat fatty acids of normal breeding birds did not change significantly from arrival on the colony to day 27. 5. Proportions of fatty acids in Ad61ie penguin depot fat correspond with the proportions of fatty acids in their normal diet of In-ill (Euphausia superba). INTRODUCTION ONE OF THE MOST abundant and widely distributed species among the Antarctic pygoscelid penguins is the Ad~lie (Pygoscelis adeh'ae) which breeds along the coast of Antarctica, the South Orkney Islands and the South Shetland Islands. The breeding biology and behavior of P. adeliae have been thoroughly reviewed by Sladen (1958), Sapin-Jaloustre (1960) and Penney (1968). In general, the older established breeders (4 to 7 + years old) trek several miles across the sea ice in the austral spring and arrive at the breeding colonies first, followed by the younger birds. Territory formation and mate selection precede laying of the normal two-egg clutch; the incubation period usually lasts for 33-38 days with the male taking the first incubation "shift". Both parents fast during these periods of occupation, with the first fast by the males sometimes lasting 6 weeks. T h e female's fast, after that of the male, is shorter, usually lasting only 2-3 weeks. 709
710
STSPH~ R. JOHNSON AND GEORGE C. WEST
O u r small but well-documented sample (six birds) of Ad61ie carcasses were taken f r o m Cape Crozier, Ross Island, Antarctica, during the early part of the breeding season when males were establishing territories, selecting mates and incubating, all of which occur during a period of prolonged fast. I n this paper we have estimated various energetic parameters of fasting Ad61ies, namely weight loss due primarily to fat catabolism in fasting males, fasting energy requirements as calculated f r o m fat utilization, and possible changes in fatty acid composition in the various fat storage areas in adult fasting Ad61ies. MATERIALS AND METHODS
During the 1968 austral summer, six fresh Ad~lie penguins were collected from the Cape Crozier breeding colony on Ross Island, Antarctica. Their frozen carcasses were shipped to Fairbanks, Alaska, and stored frozen at the Institute of Arctic Biology. The five groups of birds were: A. B-9, male, killed on arrival at the breeding colony; B-6, female, killed on arrival at the breeding colony. B. B-14, male, kiUed 10 days after arrival at the breeding colony and found wandering throughout the colony. C. C-23, female, killed approximately 15 days after arrival at the breeding colony. She lost her mate and started the first incubation shift, but later abandoned the nest and was killed on her return to the sea. D. B-18, male, killed 20 days after arrival at the breeding colony and during the first incubation shift. E. B-19, male, killed 28 days after arrival at the breeding colony and during the first incubation shift. The total lipid content of each bird was determined from six randomly chosen subsamples after each bird had been diced, thoroughly mixed and freeze-dried. Total lipids were extracted with petroleum ether (30-60°C) in soxhlet extraction columns. Two replications of this extraction process were made, which resulted in about half of each bird being analyzed for total lipid content. Fatty acid composition of depot and subcutaneous fat from each bird was determined by sampling and analyzing fat from visceral and axillary regions respectively, and a portion of the total lipid extraction was used to determine the fatty acid composition of total body fat. Samples of fat were saponified in ethanolic KOH and the fatty acid salts were converted with 12% HCI and recovered in petroleum ether (Meng et al., 1969). Methylation was accomplished by boiling in borontrifluoride methanol for 3-5 min. The methyl esters were analyzed on an F & M Model 810 gas chromatograph with a hydrogen flame detector. Helium was used as the carrier gas and both diethyleneglycolsuccinate (20% DEGS) and ethyleneglycoladipate (10% EGA) were used as column stationary phases and the 8 ft x ~ in. cohamas were packed with 60/80 mesh Chromosorb W. The majority of the samples were analyzed on the DEGS columns; EGA was used to separate and help identify certain questionable acids which required more complete separation. Identification of peaks was made by using Supelco fatty acid standards RM-3, PUFA-1 and GLC-110 and by graphing relative retention times as described by Ackman (1963). Thin-layer chromatography techniques were used to check for possible incomplete methylation of fatty acids (Wood et al., 1964). The double-bond index was also calculated for each sample as a measure of the degree of unsaturation of the total sample (the summation of the percentage of each acid in the sample multiplied by the number of double bonds it contains divided by 100, Richardson
711
ENERGY METABOLISM OF AD~,LIE P E N G U I N S
al., 1961). Relative amounts of acids were calculated from triangulation of the chromatographic peaks.
et
RESULTS AND DISCUSSION Carcass fat content and metabolism The amount of total extractable lipid decreased throughout the fast period. Figure 1 expresses this decrease as the percentage fat of dry carcass weight in the five penguins during progressively longer fasts at the breeding colony at Cape Crozier. Carcass water content gradually increased from 48 to 60 per cent during the same period in the same birds. 50
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FIO. 1. Decrease in per cent fat of lean dry weight in fasting Ad~lie penguins during the breeding season at Cape Crozier, Ross Island, Antarctica. The majority of the fat stored by these penguins was deposited subcutaneously and was used progressively during the fast which resulted in a decrease in the thickness of the blubber layer (Fig. 2). Similarly, Fig. 3 shows the loss of weight associated with the catabolism of these energy stores during the fast by four males. The majority of the weight loss is probably associated with fat catabolism. However, during rapid starvation in small birds, protein is also catabolized (Evans, 1969), and in fasting, some protein must be catabolized to provide necessary blood glucose for maintenance of central nervous function (Kety, 1957; Sokoloff, 1960). Benedict & Lee (1937), in their classic study of lipogenesis in the domestic goose, found that the amount of protein entering into fasting metabolism was between 4 and 7 per cent for adult geese whose initial weights were approximately 4 kg. If we assume, therefore, that 93-97 per cent of the weight loss of the penguins was due to fat catabolism, the average daily metabolic rate of fasting males during the early part of the breeding season at Cape Crozier can be estimated.
712
STEPHEN R. JOHNSON AND GEORGE C. WEST
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FIG. 2. Reduction in blubber layer during the fast or period of heavy fat utilization.
The slope of the weight loss regression line (0"056, Fig. 3) represents the mean decrease in weight in kg per day by males. In other words, the average amount of fat used to satisfy energy requirements during the fast was 52-54 g/bird per day and the amount of protein used was between 2 and 4 g/day. Fat yields 9-0 kcal/g and protein 4.0 kcal/g when metabolized by animals (Maynard & Loosli, 1962). Therefore, the total catabolism ranged from 486 to 495 kcal/bird per day for fasting males'during the early part of the breeding season at Cape Crozier.
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FIG. 3. T o t a l w e i g h t loss since first arrival at t h e b r e e d i n g c o l o n y a n d e x t e n d i n g t h r o u g h t h e p e r i o d o f fast b y m a l e s .
ENERGY METABOLISM OF AD~LIE PENGUINS
713
The amount of energy required for caged existence at 0°C for a 5-kg bird, according to Kendeigh (1970), would be 428 kcal]bird per day. However, as Kendeigh states, "The cost of free existence is greater than that of caged existence in proportion to the amount of locomotor activity involved." Since Kendeigh's equation is based on metabolic rates of caged birds, the actual existence energy of free-living Ad~lie penguins would probably be greater than the 428 kcal/bird per day. Furthermore, temperatures during the breeding season at the Cape Crozier rookery are well below 0°C (average temperatures approximate -5°C), and winds up to 100 m.p.h, at the same time are not uncommon (Boyd & Sladen, 1971). Wind at moderate velocities has been shown to increase the resting metabolic rate even of well-insulated arctic birds such as the snowy owl (Nyctea scandiaca) (Gessaman, 1972), so we would expect an increase in metabolic rate with the high winds encountered by birds on the penguin rookeries. With these factors in mind, the calculated values of 485-495 kcal/bird per day do not seem too high. The metabolic rates of three incubating adult Ad61ie penguins measured by LeResche & Boyd (1969) in the field at Cape Crozier averaged only 370 kcal/bird per day. This would indicate that existence energy plus activities associated with incubation accounted for about 75 per cent of the total energy demands during that period while the balance is required for locomotion, territory defense, replacing heat loss due to high winds, etc.
Surface area measurements Since analyses of fatty acid composition were also being conducted on our small sample of Ad61ie penguin carcasses, no attempts were made to determine thermal conductance directly for fear that heating and cooling of the carcasses could alter certain fatty acids. However, on one carcass (C-23, female, unfeathered weight 2.569 kg), surface area determined directly by use of a coating of silicone sealer (Johnson, 1972) and plumage weight were found to be 1652 cm2 and 195.2 g (7.6 per cent of the body weight) respectively. We present these values since others (Drent & Stonehouse, 1971) working with penguins have mentioned that no surface area values were available for this group of birds. Drent & Stonehouse (1971) also mentioned that penguin carcasses are probably as far from standard avian configuration as any group of birds. However, upon visual inspection, we found that the one plucked penguin carcass conformed surprisingly well to general avian morphological configuration, and, in fact, the measured surface area deviated only 13 per cent from the value predicted by Meeh's formula (SA = 10wt°'eT), which is well within the range of deviation exhibited by other species (Drent & Stonehouse, 1971).
Fatty acid composition A total of forty-five different fatty acids were identified from Ad~lie penguin fat; a representative list of some of these acids from various tissues in one fasting male (B-14) is given in Table 1. The percentage fatty acid composition by carbon family, by the number of double bonds and the double-bond index for the five
714
S T E P H ~ R. JOHNSON AND GEORGE C. WEST
penguins during the fast are shown in Tables 2-4. Data given to two decimals does not imply this order of accuracy, but are intended only to show the relative proportions of minor components. T h e largest percentages of fatty acids in total extractable body fat were comprised of oleic (Cls:l), myristic (Clan), palmitic (Cxen), palmitoleie (Cle:l) and some of the very long-chain polyunsaturated acids such as docosapentaenoic (C~:5) and docosahexaenoic (C~2:e) acids. Similarly, visceral depot and subcutaneous fat were comprised mostly of 14, 16, 18 and 22 carbon acids (Tables 2-4). Percentages of the various fatty acids were remarkably similar in all five birds analyzed, with the only significant difference being the relatively smaller amount of 16- and the greater amount of 20-carbon acids in the total extractable and depot
TABLE1--FATTY ACID COMPOSITION OF TOTAL LIPID AND TWO STORAGE AREAS IN ONE FASTING ADELIE PENGUIN, NO. B--14
Fatty acid
Total fat (%)
Depot Subcutaneous fat fat (%) (%)
12" 13 Iso 13 n 13:1 14 n 14:1 15 Iso 15 Anteiso 15 n 15:1 16 Iso 16 Anteiso 16 n 16:1 17 Anteiso 17 n 17:1 18 Iso 18 Anteiso 18 n 18:1 18:2
0"05 0.04 0"01 Tr 0.02 0.01 0.02 0-02 6'08 6.51 0"01 Tr 0.86 0.60 0.14 0.04 0.44 0.37 0"02 0.10 0"20 0.08 -0.01 14.56 20.39 8.51 7.50 0"15 0-09 0"28 0.52 1"23 1"21 0"21 0"29 0"18 0.25 3"17 3"35 31.69 30.13 3"65 3.04
0"05 0"01 0"03 0"01 6"34 Tr 0"72 0"18 0"46 0.13 0.04 0.01 20"50 6"38 0"12 0"59 2"01 0"55 0.05 4-05 34.42 2"86
Fatty acid
Total fat (%)
Depot fat (%)
Subcutaneous fat (%)
18:3" 19 Iso 19 Anteiso 19:1 20 Iso 20 Anteiso 20 n 20:1 20:2 20:3 20:4 20:5 21 Anteiso 21:1 22 Iso 22 n 22:1 22:4 22:5 22:6 23:1
1"08 -Tr 0"80 0"03 -0"28 5"16 0"43 0"12 Tr 2"09 0"19 0"48 0.08 -5"01 0"14 2-13 8.59 2"81
0.53 --0.29 0"21 -0.78 4-95 -0"36 -0.40 -0.22 0"23 Tr 1-74 -2-32 8-65 0.35
0"31 Tr
* Carbon number followed by number of double bonds. Tr, trace.
0.61 0.24 0.15 0.33 6"06 ---2.72 -2-05 0.35 Tr 2"05 1.73 4.82 Tr
1.371
Double bond Index
1.407
26"93 55"74 4.08 1-20 0"14 4"24 8"59
0"05 0"05 6"09 1"46 23"27 1"66 39"98 0"80 8"11 0"67 15"95 2"81 --
B-14
1.189
24'97 62-70 2"42 0"37 1.11 3"04 5"22
-0"08 5"26 2"71 12"72 3"44 38"91 0"33 20"65 -13-76 Tr 1 "82
C-23
1.373
32"51 49"08 2"81 1"80 -5"61 8"32
0"09 0"02 10"58 1"75 2"57 2"28 40"92 0"32 8"80 0"99 11"92 ---
B-18
* Values listed are percentages of the total composition.
32"72 47"41 3"18 1-64 1"34 5"82 7"71
0"07* 0"02 8"21 1"58 26"09 1"95 41"56 0"43 7"16 0"22 11"84 0'02 --
B-9
Saturates I II III IV V VI
No. of double bonds
12 13 14 15 16 17 18 19 20 21 22 23 24
Carbon No.
Bird No.
1.162
31 '40 54"05 4.91 1"01 0"61 3"10 5"30
0"01 0"02 9"94 0"55 25"24 0"88 43"28 0"34 6"70 0"32 11"56 0"39
B-19
T A B L E 2 - - F A T T Y ACID COMPOSITION OF TOTAL EXTRACTABLE BODY FAT
1"252
27"73 58-66 3-10 0"61 0"27 4"60 5.81
0-05* 0"04 5.44 2"13 27"97 2"00 43"36 0"10 12"73 -8"77 -0"13
B- 9
1"408
33"77 46"51 3"04 0"89 ~ 6"72 8"65
0"04 0"03 6"53 1-11 27"98 1"82 37"59 0"29 10"70 0"22 12"94 0"35 --
B-14
1"391
21 "34 63"60 3'41 0"43 -5"60 6"62
0"07 0"03 6"61 0"92 12"10 0"66 37"17 0"44 24"42 0"31 11"43 0"96 2"14
C-23
1-461
28"95 53"41 2"50 Tr 0"22 7"26 8"51
0"11 0-07 6-58 2"17 25"36 1 "86 40"61 0"69 9"47 0-22 12"43 0-25 --
B-18
* Values listed are percentages of the total composition.
Double bond index
Saturates I II III IV V VI
No. of double bonds
12 13 14 15 16 17 18 19 20 21 22 23 24
Carbon No.
Bird No.
T A B L E 3 - - F A T T Y ACID COMPOSITION OF DEPOT FAT
1-428
5"75 8-94
25"83 57"68 0"52 0"71
0"13 0"04 5"38 2"23 21 "95 3"16 39"12 2"66 9"41 0'31 14"11 0"26 1"10
B-19
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716
STEPHEN R. JOHNSON AND GEORGE C. WEST TABLE 4----FATTY ACID COMPOSITION OF SUBCUTANEOUSFAT
Bird No. Carbon No. 12 13 14 15 16 17 18 19 20 21 22 23 24
B-9
B-14
C-23
B-18
B-19
0"02* 0"05 3"66 1"44 25"17 3"14 44"47 0"19 9"19 -11"52 0"17 0"33
0"05 0"05 6"34 1"49 26"93 2"72 42"24 0"61 9"50 2"05 8"95 Tr --
0"17 0"02 10"91 1"79 21"48 0"69 32"26 0"57 14"55 0"25 16"41 0"07 0"86
0"22 0"10 12"43 2"55 18"66 2"27 42"69 -7"69 -12"88 -0"33
0"02 0"06 2"44 1"32 17"65 3"77 51"32 0"38 9"93 -11"98 0"20 0"79
33"52 50-81 2"86 0"73 -6-01 6"60
34"77 53"72 2"86 0"31 0"14 4"45 4"82
31-30 49"90 4"50 0"31 0"20 4-14 9"73
32"44 48"18 3-35 1"10 0'95 5"10 8"33
22"45 64"46 2"70 0"70 1.10 3"34 5"00
No. of double bonds Saturates I II III IV V VI Double bond index
1-232
1"120
1"394
1"379
1"239
*Values listed are percentages of the total composition. fat components from bird C-23. In the subcutaneous fraction from C-23, the percentages of both 16- and 18-carbon acids were smaller, although less so than in the other two fractions (depot fat and total body fat), and percentages of 20and 22-carbon acids were relatively greater than in the other four birds analyzed. T w o possibilities exist for the explanation of the differences between C-23 and the other birds. Firstly, C-23 was a female that had laid eggs and had thus utilized lipid reserves in egg production. Secondly, she had to assume the first incubation shift, a task normally undertaken by the male. Although it is possible that a change in behavior pattern may have caused the observed differential utilization of fatty acids, we prefer to suspect that egg production resulted in the observed differences between the female and the males. Fatty acid composition of depot lipids of most wild birds thus far studied can be well correlated with the fatty acids in the diet (Walker, 1966; Moss & Lough, 1968; West & Meng, 1968a, b). T h e penguins' diet is made up largely of krill and
717
ENERGY METABOLISM OF AD,~I.IE PENGUINS
other marine invertebrates which are known to have relatively unsaturated fatty acid compositions due to the large amounts of long-chain polyunsaturated acids (Lovern, 1964; Lewis, 1967; Krzeczkowski, 1970, 1971; Sidhu et al., 1970). Both krill (Euphausia superba) and Ad61ie penguins have high amounts of oleic and palmitic acids, comparable amounts of several other acids and essentially the same double-bond index (Table 5). The penguins have a greater variety of fatty acids that are present in more than 1 per cent of the total than do the krill which indicates either endogenous synthesis, preferential accumulation of certain acids or that the birds are obtaining these acids from another food source. TABLE5~PERCENTAGE
COMPOSITION OF THE PRINCIPAL FATTY ACIDS OF THE TOTAL LIPIDS OF KRILL (E. ~perba) AND OF ADI~LIE PENGUIN DEPOT FAT
Fatty acid 14 16 16:1 17:1 18 18:1 18:2 20:1 20:5 22:1 22:5 22:6 Double bond index*
KriU (from Sidhu et al., 1970) 18"7 24"0 11"2 -0-9 20"5 2"3 0"6 -Tr 13"2 5"9 1.40
Penguin (from Table 1) 6"5 20.5 7"5 1.2 3.9 30.1 3.0 5.0 4.4 1"7 2"3 8"7 1"41
* Calculated from the total composition. It could be hypothesized that penguins would prepare for their fast by depositing certain fatty acids that could be more easily mobilized for egg production and for such energy demanding activities as incubation and thermoregulation in the cold in the absence of dietary intake of either protein or carbohydrate. Unfortunately, we do not have samples nor know of studies of fatty acids of penguins taken during the non-breeding season for comparison. We are, however, becoming convinced that birds are capable of selective fatty acid deposition depending at least on the conditions of captivity and probably also on the normal seasonal shifts of their physiological state in the wild (West & Meng, 1968a). It is known that environmental factors and extreme abnormal physiological states such as starvation affect the fatty acid composition of animals. In general, both cold and starvation increase the proportion of unsaturated acids in tissue lipids (Kodama & Pace, 1963; Chalvardjian, 1964; Williams & Platner, 1967; West & Meng, 1968b; Meng et aL, 1969). From this, we could postulate that
718
STEPHEN R. JOHNSON AND GEORGE C. WEST
fasting b y penguins might also result in a gradual increase in unsaturation. H o w ever, no obvious trend in this direction is noticeable in our results. Therefore, we m u s t conclude that fasting by penguins, an annual event for which the birds are adapted, is physiologically different f r o m starvation which occurs in animal species not adapted to going without food for long periods of time. Acknowledgements--This research was supported by N.S.F. Grant No. GB-12076 to George C. West. We wish to thank Robert E. LeResche for obtaining the penguin specimens and for reviewing early stages of the manuscript and Marilyn Modafferi for assistance in the chromatographic analyses of fatty acid composition. REFERENCES
ACKMANR. G. (1963) Structural correlation of unsaturated fatty acid esters through graphic comparison of gas-liquid chromatographic retention times on a polyester substrate..7. Am. Oil chem. Soc. 40, 558-564. BENEDICT F. & LEE R. C. (1937) Lipogenesis in the animal body, with special reference to the physiology of the goose. Carnegie Inst. of Wash. Publ. No. 489. BOYD J. C. & SLADF.~W. J. L. (1971) Telemetry studies of the internal body temperatures of Adrlie and Emperor penguins at Cape Crozier, Ross Island, Antarctica. Auk 88, 366-380. CHALVARDJIANA. M. (1964) Fatty acids of brown and yellow fat in rats. Biochem. ft. 90, 518-521. DRENT R. H. & STONEHOUSEB. (1971) Thermoregulatory responses of the Peruvian penguin, Spheniscus humboldti. Comp. Biochem. Physiol. 40A, 689-710. EVANS P. R. (1969) Winter fat deposition and overnight survival of yellow buntings (Emberiza citrinella L.). ft. anim. Ecol. 38, 415-423. GESSAMANJ. A. (1972) Bioenergetics of the snowy owl (Nyctea scandiaca), ft. Arctic Alpine Res. 4, 223-238. JOHNSON S. R. (1972) Thermal adaptation in North American Sturnidae. Ph.D. thesis, University of British Columbia, Vancouver. KENDEICH S. C. (1970) Energy requirements for existence in relation to size of bird. Condor 72, 60-65. K ~ ' ¢ S. S. (1957) The Metabolism of the Central Nervous System (Edited by RICHTERD.). Pergamon Press, London. KODAMa A. & PACE N. (1964) Effect of environmental temperature on hamster body fat composition, ft. appl. Physiol. 19, 863-867. KaZECZKOWSKIR. A. (1970) Fatty acids in raw and processed Alaska pink shrimp. )t. Am. Oil chem. Soc. 47, 451-452. KaZECZKOWSKXR. A., Tmq~Y R. D. & KELLEY C. (1971) Alaska king crab: fatty acid composition, carotenoid index and proximate analysis, ft. Food Sci. 36, 604-606. LERESeh'~ R. & BoYo J. C. (1969) Response to acute hypothermia in Ad~lie penguin chicks. Commun. Behav. Biol. 4, 85-89. LEWIS R. W. (1967) Fatty acid composition of some marine animals from various depths. ft. Fish Res. Bd Can. 24, 1101-1115. Lowm~ J. A. (1964) The lipids of marine organisms. In Oceanogr. Mar. Biol. Rev. (Edited by BARNESH.), Vol. 2, pp. 169-191. George Allen & Unwin, London. M A ~ h t ~ L. A. & LOOSLIJ. K. (1962) Animal Nutrition. McGraw-Hill, New York. Mm~G M. S., WmT G. C. & IRVING L. (1969) Fatty acid composition of caribou bone marrow. Comp. Biochem. Physiol. 30, 187-191. Moss R. & LOUGHA. K. (1968) Fatty acid composition and depot fats in some game birds (Tetraonidae). Comp. Biochem. Physiol. 25, 559-562.
ENERGY METABOLISM OF ADI~.LIE PENGUINS
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Pin,mY R. L. (1968) Territorial and social behavior in the Ad61ie penguin. In Antarctic Res. Series 12, Antarctic Bird Studies (Edited by AUSTINO. L.), pp. 83-131. American Geophysical Union, Nat. Acad. Sci., Nat. Res. Council. RICHARDSONT., TAPPEL A. L. & GROCERA. H., JR. (1961) Essential fatty acids of mitochondria. Archs Biochem. Biophys. 94, 1--6. SAPIN--JALOUSTR~J. (1960) Ecologie du Manchot Addlie. Hermann, Paris. SIDHU G. S., MONTGOMERYW. A., HOLLOWAYG. L., JOHNSON A. R. & WALKERD. M. (1970) Biochemical composition and nutritive value of kriU (Euphausia superba Dana). ~. Sci. Fd Agric. 21, 293-296. SLADEN W. J. L. (1958) The pygoscelid penguin--1 and 2. Scientific Reports, Falkland Islands Dependency Survey 17, 1-97. SOKOLOFF L. (1960) Metabolism of the central nervous system in vivo. In Handbook of Physiology (Edited by FIELD J.), American Physiological Society, Washington, D.C., Vol. III, pp. 1843-1864. WALKERA. T. (1964) Major fatty acids in migratory bird fat. Physiol. ZoSl. 372 57-64. WEST G. C. • MENG M. S. (1968a) Seasonal changes in body weight and fat and the relation of fatty acid composition to diet in the willow ptarmigan. Wilson Bull. 80, 426-441. WEST G. C. & MENG M. S. (1968b) The effect of diet and captivity on the fatty acid composition of redpoll (Acanthisflammea) depot fats. Comp. Biochem. Physiol. 25, 535-540. WILLIAMSD. D. & PLATNERW. S. (1967) Cold-induced changes in fatty acids of the rat and hamster. Am.y. Physiol. 212, 167-172. Wool) P., IMAICHIK., KNOWLESJ., MICHAELO G. & KINSELL L. (1964) The lipid composition of human plasma chylomicrons, o~. Lipid Res. 5, 225-231.
Key Word Index--Adglie penguin; Pygoscelis addlie; fasting penguins; fatty acids in penguin; energy requirements of penguins.
FAT CONTENT, FATTY ACID COMPOSITION AND ESTIMATES OF ENERGY METABOLISM OF AD]~LIE PENGUINS (PYGOSCELIS ADELI./IE) DURING THE EARLY BREEDING SEASON FAST S T E P H E N R. J O H N S O N and G E O R G E C. W E S T Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska 99701 (Received 13 September 1972)
Abstract--1. Ad61ie penguins (Pygoscelis adeliae) breeding at Cape Crozier, Antarctica, arrive in the colony from the sea in October at the beginning of the austral summer. Both sexes fast while on the breeding colony for 3-6 weeks before returning to the sea to feed. 2. Six individuals collected during the first fast period showed decreased blubber thickness and a linearly corresponding decrease in ether extractable fat with time after arrival in the breeding area. Birds contained about 45 per cent of dry weight as fat upon arrival, and in a typical incubation, males decreased to about 20 per cent after day 27. 3. The decrease in fat represents approximately 56 g of fat used per day by fasting male Ad61ies for the 27-day period. On the basis of this value, it has been estimated that 490 keal/bird per day approximates energy demands for these fasting birds during the early part of the breeding season. 4. Fatty acid compositions of total ether extractable lipids, subcutaneous fat and abdominal depot fat did not differ significantly except in a few of the longchain acids. Depot fat fatty acids of normal breeding birds did not change significantly from arrival on the colony to day 27. 5. Proportions of fatty acids in Ad61ie penguin depot fat correspond with the proportions of fatty acids in their normal diet of In-ill (Euphausia superba). INTRODUCTION ONE OF THE MOST abundant and widely distributed species among the Antarctic pygoscelid penguins is the Ad~lie (Pygoscelis adeh'ae) which breeds along the coast of Antarctica, the South Orkney Islands and the South Shetland Islands. The breeding biology and behavior of P. adeliae have been thoroughly reviewed by Sladen (1958), Sapin-Jaloustre (1960) and Penney (1968). In general, the older established breeders (4 to 7 + years old) trek several miles across the sea ice in the austral spring and arrive at the breeding colonies first, followed by the younger birds. Territory formation and mate selection precede laying of the normal two-egg clutch; the incubation period usually lasts for 33-38 days with the male taking the first incubation "shift". Both parents fast during these periods of occupation, with the first fast by the males sometimes lasting 6 weeks. T h e female's fast, after that of the male, is shorter, usually lasting only 2-3 weeks. 709
710
STSPH~ R. JOHNSON AND GEORGE C. WEST
O u r small but well-documented sample (six birds) of Ad61ie carcasses were taken f r o m Cape Crozier, Ross Island, Antarctica, during the early part of the breeding season when males were establishing territories, selecting mates and incubating, all of which occur during a period of prolonged fast. I n this paper we have estimated various energetic parameters of fasting Ad61ies, namely weight loss due primarily to fat catabolism in fasting males, fasting energy requirements as calculated f r o m fat utilization, and possible changes in fatty acid composition in the various fat storage areas in adult fasting Ad61ies. MATERIALS AND METHODS
During the 1968 austral summer, six fresh Ad~lie penguins were collected from the Cape Crozier breeding colony on Ross Island, Antarctica. Their frozen carcasses were shipped to Fairbanks, Alaska, and stored frozen at the Institute of Arctic Biology. The five groups of birds were: A. B-9, male, killed on arrival at the breeding colony; B-6, female, killed on arrival at the breeding colony. B. B-14, male, kiUed 10 days after arrival at the breeding colony and found wandering throughout the colony. C. C-23, female, killed approximately 15 days after arrival at the breeding colony. She lost her mate and started the first incubation shift, but later abandoned the nest and was killed on her return to the sea. D. B-18, male, killed 20 days after arrival at the breeding colony and during the first incubation shift. E. B-19, male, killed 28 days after arrival at the breeding colony and during the first incubation shift. The total lipid content of each bird was determined from six randomly chosen subsamples after each bird had been diced, thoroughly mixed and freeze-dried. Total lipids were extracted with petroleum ether (30-60°C) in soxhlet extraction columns. Two replications of this extraction process were made, which resulted in about half of each bird being analyzed for total lipid content. Fatty acid composition of depot and subcutaneous fat from each bird was determined by sampling and analyzing fat from visceral and axillary regions respectively, and a portion of the total lipid extraction was used to determine the fatty acid composition of total body fat. Samples of fat were saponified in ethanolic KOH and the fatty acid salts were converted with 12% HCI and recovered in petroleum ether (Meng et al., 1969). Methylation was accomplished by boiling in borontrifluoride methanol for 3-5 min. The methyl esters were analyzed on an F & M Model 810 gas chromatograph with a hydrogen flame detector. Helium was used as the carrier gas and both diethyleneglycolsuccinate (20% DEGS) and ethyleneglycoladipate (10% EGA) were used as column stationary phases and the 8 ft x ~ in. cohamas were packed with 60/80 mesh Chromosorb W. The majority of the samples were analyzed on the DEGS columns; EGA was used to separate and help identify certain questionable acids which required more complete separation. Identification of peaks was made by using Supelco fatty acid standards RM-3, PUFA-1 and GLC-110 and by graphing relative retention times as described by Ackman (1963). Thin-layer chromatography techniques were used to check for possible incomplete methylation of fatty acids (Wood et al., 1964). The double-bond index was also calculated for each sample as a measure of the degree of unsaturation of the total sample (the summation of the percentage of each acid in the sample multiplied by the number of double bonds it contains divided by 100, Richardson
711
ENERGY METABOLISM OF AD~,LIE P E N G U I N S
al., 1961). Relative amounts of acids were calculated from triangulation of the chromatographic peaks.
et
RESULTS AND DISCUSSION Carcass fat content and metabolism The amount of total extractable lipid decreased throughout the fast period. Figure 1 expresses this decrease as the percentage fat of dry carcass weight in the five penguins during progressively longer fasts at the breeding colony at Cape Crozier. Carcass water content gradually increased from 48 to 60 per cent during the same period in the same birds. 50
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FIO. 1. Decrease in per cent fat of lean dry weight in fasting Ad~lie penguins during the breeding season at Cape Crozier, Ross Island, Antarctica. The majority of the fat stored by these penguins was deposited subcutaneously and was used progressively during the fast which resulted in a decrease in the thickness of the blubber layer (Fig. 2). Similarly, Fig. 3 shows the loss of weight associated with the catabolism of these energy stores during the fast by four males. The majority of the weight loss is probably associated with fat catabolism. However, during rapid starvation in small birds, protein is also catabolized (Evans, 1969), and in fasting, some protein must be catabolized to provide necessary blood glucose for maintenance of central nervous function (Kety, 1957; Sokoloff, 1960). Benedict & Lee (1937), in their classic study of lipogenesis in the domestic goose, found that the amount of protein entering into fasting metabolism was between 4 and 7 per cent for adult geese whose initial weights were approximately 4 kg. If we assume, therefore, that 93-97 per cent of the weight loss of the penguins was due to fat catabolism, the average daily metabolic rate of fasting males during the early part of the breeding season at Cape Crozier can be estimated.
712
STEPHEN R. JOHNSON AND GEORGE C. WEST
2.O-
J
Pygosce/i$ odelioe
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FIG. 2. Reduction in blubber layer during the fast or period of heavy fat utilization.
The slope of the weight loss regression line (0"056, Fig. 3) represents the mean decrease in weight in kg per day by males. In other words, the average amount of fat used to satisfy energy requirements during the fast was 52-54 g/bird per day and the amount of protein used was between 2 and 4 g/day. Fat yields 9-0 kcal/g and protein 4.0 kcal/g when metabolized by animals (Maynard & Loosli, 1962). Therefore, the total catabolism ranged from 486 to 495 kcal/bird per day for fasting males'during the early part of the breeding season at Cape Crozier.
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FIG. 3. T o t a l w e i g h t loss since first arrival at t h e b r e e d i n g c o l o n y a n d e x t e n d i n g t h r o u g h t h e p e r i o d o f fast b y m a l e s .
ENERGY METABOLISM OF AD~LIE PENGUINS
713
The amount of energy required for caged existence at 0°C for a 5-kg bird, according to Kendeigh (1970), would be 428 kcal]bird per day. However, as Kendeigh states, "The cost of free existence is greater than that of caged existence in proportion to the amount of locomotor activity involved." Since Kendeigh's equation is based on metabolic rates of caged birds, the actual existence energy of free-living Ad~lie penguins would probably be greater than the 428 kcal/bird per day. Furthermore, temperatures during the breeding season at the Cape Crozier rookery are well below 0°C (average temperatures approximate -5°C), and winds up to 100 m.p.h, at the same time are not uncommon (Boyd & Sladen, 1971). Wind at moderate velocities has been shown to increase the resting metabolic rate even of well-insulated arctic birds such as the snowy owl (Nyctea scandiaca) (Gessaman, 1972), so we would expect an increase in metabolic rate with the high winds encountered by birds on the penguin rookeries. With these factors in mind, the calculated values of 485-495 kcal/bird per day do not seem too high. The metabolic rates of three incubating adult Ad61ie penguins measured by LeResche & Boyd (1969) in the field at Cape Crozier averaged only 370 kcal/bird per day. This would indicate that existence energy plus activities associated with incubation accounted for about 75 per cent of the total energy demands during that period while the balance is required for locomotion, territory defense, replacing heat loss due to high winds, etc.
Surface area measurements Since analyses of fatty acid composition were also being conducted on our small sample of Ad61ie penguin carcasses, no attempts were made to determine thermal conductance directly for fear that heating and cooling of the carcasses could alter certain fatty acids. However, on one carcass (C-23, female, unfeathered weight 2.569 kg), surface area determined directly by use of a coating of silicone sealer (Johnson, 1972) and plumage weight were found to be 1652 cm2 and 195.2 g (7.6 per cent of the body weight) respectively. We present these values since others (Drent & Stonehouse, 1971) working with penguins have mentioned that no surface area values were available for this group of birds. Drent & Stonehouse (1971) also mentioned that penguin carcasses are probably as far from standard avian configuration as any group of birds. However, upon visual inspection, we found that the one plucked penguin carcass conformed surprisingly well to general avian morphological configuration, and, in fact, the measured surface area deviated only 13 per cent from the value predicted by Meeh's formula (SA = 10wt°'eT), which is well within the range of deviation exhibited by other species (Drent & Stonehouse, 1971).
Fatty acid composition A total of forty-five different fatty acids were identified from Ad~lie penguin fat; a representative list of some of these acids from various tissues in one fasting male (B-14) is given in Table 1. The percentage fatty acid composition by carbon family, by the number of double bonds and the double-bond index for the five
714
S T E P H ~ R. JOHNSON AND GEORGE C. WEST
penguins during the fast are shown in Tables 2-4. Data given to two decimals does not imply this order of accuracy, but are intended only to show the relative proportions of minor components. T h e largest percentages of fatty acids in total extractable body fat were comprised of oleic (Cls:l), myristic (Clan), palmitic (Cxen), palmitoleie (Cle:l) and some of the very long-chain polyunsaturated acids such as docosapentaenoic (C~:5) and docosahexaenoic (C~2:e) acids. Similarly, visceral depot and subcutaneous fat were comprised mostly of 14, 16, 18 and 22 carbon acids (Tables 2-4). Percentages of the various fatty acids were remarkably similar in all five birds analyzed, with the only significant difference being the relatively smaller amount of 16- and the greater amount of 20-carbon acids in the total extractable and depot
TABLE1--FATTY ACID COMPOSITION OF TOTAL LIPID AND TWO STORAGE AREAS IN ONE FASTING ADELIE PENGUIN, NO. B--14
Fatty acid
Total fat (%)
Depot Subcutaneous fat fat (%) (%)
12" 13 Iso 13 n 13:1 14 n 14:1 15 Iso 15 Anteiso 15 n 15:1 16 Iso 16 Anteiso 16 n 16:1 17 Anteiso 17 n 17:1 18 Iso 18 Anteiso 18 n 18:1 18:2
0"05 0.04 0"01 Tr 0.02 0.01 0.02 0-02 6'08 6.51 0"01 Tr 0.86 0.60 0.14 0.04 0.44 0.37 0"02 0.10 0"20 0.08 -0.01 14.56 20.39 8.51 7.50 0"15 0-09 0"28 0.52 1"23 1"21 0"21 0"29 0"18 0.25 3"17 3"35 31.69 30.13 3"65 3.04
0"05 0"01 0"03 0"01 6"34 Tr 0"72 0"18 0"46 0.13 0.04 0.01 20"50 6"38 0"12 0"59 2"01 0"55 0.05 4-05 34.42 2"86
Fatty acid
Total fat (%)
Depot fat (%)
Subcutaneous fat (%)
18:3" 19 Iso 19 Anteiso 19:1 20 Iso 20 Anteiso 20 n 20:1 20:2 20:3 20:4 20:5 21 Anteiso 21:1 22 Iso 22 n 22:1 22:4 22:5 22:6 23:1
1"08 -Tr 0"80 0"03 -0"28 5"16 0"43 0"12 Tr 2"09 0"19 0"48 0.08 -5"01 0"14 2-13 8.59 2"81
0.53 --0.29 0"21 -0.78 4-95 -0"36 -0.40 -0.22 0"23 Tr 1-74 -2-32 8-65 0.35
0"31 Tr
* Carbon number followed by number of double bonds. Tr, trace.
0.61 0.24 0.15 0.33 6"06 ---2.72 -2-05 0.35 Tr 2"05 1.73 4.82 Tr
1.371
Double bond Index
1.407
26"93 55"74 4.08 1-20 0"14 4"24 8"59
0"05 0"05 6"09 1"46 23"27 1"66 39"98 0"80 8"11 0"67 15"95 2"81 --
B-14
1.189
24'97 62-70 2"42 0"37 1.11 3"04 5"22
-0"08 5"26 2"71 12"72 3"44 38"91 0"33 20"65 -13-76 Tr 1 "82
C-23
1.373
32"51 49"08 2"81 1"80 -5"61 8"32
0"09 0"02 10"58 1"75 2"57 2"28 40"92 0"32 8"80 0"99 11"92 ---
B-18
* Values listed are percentages of the total composition.
32"72 47"41 3"18 1-64 1"34 5"82 7"71
0"07* 0"02 8"21 1"58 26"09 1"95 41"56 0"43 7"16 0"22 11"84 0'02 --
B-9
Saturates I II III IV V VI
No. of double bonds
12 13 14 15 16 17 18 19 20 21 22 23 24
Carbon No.
Bird No.
1.162
31 '40 54"05 4.91 1"01 0"61 3"10 5"30
0"01 0"02 9"94 0"55 25"24 0"88 43"28 0"34 6"70 0"32 11"56 0"39
B-19
T A B L E 2 - - F A T T Y ACID COMPOSITION OF TOTAL EXTRACTABLE BODY FAT
1"252
27"73 58-66 3-10 0"61 0"27 4"60 5.81
0-05* 0"04 5.44 2"13 27"97 2"00 43"36 0"10 12"73 -8"77 -0"13
B- 9
1"408
33"77 46"51 3"04 0"89 ~ 6"72 8"65
0"04 0"03 6"53 1-11 27"98 1"82 37"59 0"29 10"70 0"22 12"94 0"35 --
B-14
1"391
21 "34 63"60 3'41 0"43 -5"60 6"62
0"07 0"03 6"61 0"92 12"10 0"66 37"17 0"44 24"42 0"31 11"43 0"96 2"14
C-23
1-461
28"95 53"41 2"50 Tr 0"22 7"26 8"51
0"11 0-07 6-58 2"17 25"36 1 "86 40"61 0"69 9"47 0-22 12"43 0-25 --
B-18
* Values listed are percentages of the total composition.
Double bond index
Saturates I II III IV V VI
No. of double bonds
12 13 14 15 16 17 18 19 20 21 22 23 24
Carbon No.
Bird No.
T A B L E 3 - - F A T T Y ACID COMPOSITION OF DEPOT FAT
1-428
5"75 8-94
25"83 57"68 0"52 0"71
0"13 0"04 5"38 2"23 21 "95 3"16 39"12 2"66 9"41 0'31 14"11 0"26 1"10
B-19
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716
STEPHEN R. JOHNSON AND GEORGE C. WEST TABLE 4----FATTY ACID COMPOSITION OF SUBCUTANEOUSFAT
Bird No. Carbon No. 12 13 14 15 16 17 18 19 20 21 22 23 24
B-9
B-14
C-23
B-18
B-19
0"02* 0"05 3"66 1"44 25"17 3"14 44"47 0"19 9"19 -11"52 0"17 0"33
0"05 0"05 6"34 1"49 26"93 2"72 42"24 0"61 9"50 2"05 8"95 Tr --
0"17 0"02 10"91 1"79 21"48 0"69 32"26 0"57 14"55 0"25 16"41 0"07 0"86
0"22 0"10 12"43 2"55 18"66 2"27 42"69 -7"69 -12"88 -0"33
0"02 0"06 2"44 1"32 17"65 3"77 51"32 0"38 9"93 -11"98 0"20 0"79
33"52 50-81 2"86 0"73 -6-01 6"60
34"77 53"72 2"86 0"31 0"14 4"45 4"82
31-30 49"90 4"50 0"31 0"20 4-14 9"73
32"44 48"18 3-35 1"10 0'95 5"10 8"33
22"45 64"46 2"70 0"70 1.10 3"34 5"00
No. of double bonds Saturates I II III IV V VI Double bond index
1-232
1"120
1"394
1"379
1"239
*Values listed are percentages of the total composition. fat components from bird C-23. In the subcutaneous fraction from C-23, the percentages of both 16- and 18-carbon acids were smaller, although less so than in the other two fractions (depot fat and total body fat), and percentages of 20and 22-carbon acids were relatively greater than in the other four birds analyzed. T w o possibilities exist for the explanation of the differences between C-23 and the other birds. Firstly, C-23 was a female that had laid eggs and had thus utilized lipid reserves in egg production. Secondly, she had to assume the first incubation shift, a task normally undertaken by the male. Although it is possible that a change in behavior pattern may have caused the observed differential utilization of fatty acids, we prefer to suspect that egg production resulted in the observed differences between the female and the males. Fatty acid composition of depot lipids of most wild birds thus far studied can be well correlated with the fatty acids in the diet (Walker, 1966; Moss & Lough, 1968; West & Meng, 1968a, b). T h e penguins' diet is made up largely of krill and
717
ENERGY METABOLISM OF AD,~I.IE PENGUINS
other marine invertebrates which are known to have relatively unsaturated fatty acid compositions due to the large amounts of long-chain polyunsaturated acids (Lovern, 1964; Lewis, 1967; Krzeczkowski, 1970, 1971; Sidhu et al., 1970). Both krill (Euphausia superba) and Ad61ie penguins have high amounts of oleic and palmitic acids, comparable amounts of several other acids and essentially the same double-bond index (Table 5). The penguins have a greater variety of fatty acids that are present in more than 1 per cent of the total than do the krill which indicates either endogenous synthesis, preferential accumulation of certain acids or that the birds are obtaining these acids from another food source. TABLE5~PERCENTAGE
COMPOSITION OF THE PRINCIPAL FATTY ACIDS OF THE TOTAL LIPIDS OF KRILL (E. ~perba) AND OF ADI~LIE PENGUIN DEPOT FAT
Fatty acid 14 16 16:1 17:1 18 18:1 18:2 20:1 20:5 22:1 22:5 22:6 Double bond index*
KriU (from Sidhu et al., 1970) 18"7 24"0 11"2 -0-9 20"5 2"3 0"6 -Tr 13"2 5"9 1.40
Penguin (from Table 1) 6"5 20.5 7"5 1.2 3.9 30.1 3.0 5.0 4.4 1"7 2"3 8"7 1"41
* Calculated from the total composition. It could be hypothesized that penguins would prepare for their fast by depositing certain fatty acids that could be more easily mobilized for egg production and for such energy demanding activities as incubation and thermoregulation in the cold in the absence of dietary intake of either protein or carbohydrate. Unfortunately, we do not have samples nor know of studies of fatty acids of penguins taken during the non-breeding season for comparison. We are, however, becoming convinced that birds are capable of selective fatty acid deposition depending at least on the conditions of captivity and probably also on the normal seasonal shifts of their physiological state in the wild (West & Meng, 1968a). It is known that environmental factors and extreme abnormal physiological states such as starvation affect the fatty acid composition of animals. In general, both cold and starvation increase the proportion of unsaturated acids in tissue lipids (Kodama & Pace, 1963; Chalvardjian, 1964; Williams & Platner, 1967; West & Meng, 1968b; Meng et aL, 1969). From this, we could postulate that
718
STEPHEN R. JOHNSON AND GEORGE C. WEST
fasting b y penguins might also result in a gradual increase in unsaturation. H o w ever, no obvious trend in this direction is noticeable in our results. Therefore, we m u s t conclude that fasting by penguins, an annual event for which the birds are adapted, is physiologically different f r o m starvation which occurs in animal species not adapted to going without food for long periods of time. Acknowledgements--This research was supported by N.S.F. Grant No. GB-12076 to George C. West. We wish to thank Robert E. LeResche for obtaining the penguin specimens and for reviewing early stages of the manuscript and Marilyn Modafferi for assistance in the chromatographic analyses of fatty acid composition. REFERENCES
ACKMANR. G. (1963) Structural correlation of unsaturated fatty acid esters through graphic comparison of gas-liquid chromatographic retention times on a polyester substrate..7. Am. Oil chem. Soc. 40, 558-564. BENEDICT F. & LEE R. C. (1937) Lipogenesis in the animal body, with special reference to the physiology of the goose. Carnegie Inst. of Wash. Publ. No. 489. BOYD J. C. & SLADF.~W. J. L. (1971) Telemetry studies of the internal body temperatures of Adrlie and Emperor penguins at Cape Crozier, Ross Island, Antarctica. Auk 88, 366-380. CHALVARDJIANA. M. (1964) Fatty acids of brown and yellow fat in rats. Biochem. ft. 90, 518-521. DRENT R. H. & STONEHOUSEB. (1971) Thermoregulatory responses of the Peruvian penguin, Spheniscus humboldti. Comp. Biochem. Physiol. 40A, 689-710. EVANS P. R. (1969) Winter fat deposition and overnight survival of yellow buntings (Emberiza citrinella L.). ft. anim. Ecol. 38, 415-423. GESSAMANJ. A. (1972) Bioenergetics of the snowy owl (Nyctea scandiaca), ft. Arctic Alpine Res. 4, 223-238. JOHNSON S. R. (1972) Thermal adaptation in North American Sturnidae. Ph.D. thesis, University of British Columbia, Vancouver. KENDEICH S. C. (1970) Energy requirements for existence in relation to size of bird. Condor 72, 60-65. K ~ ' ¢ S. S. (1957) The Metabolism of the Central Nervous System (Edited by RICHTERD.). Pergamon Press, London. KODAMa A. & PACE N. (1964) Effect of environmental temperature on hamster body fat composition, ft. appl. Physiol. 19, 863-867. KaZECZKOWSKIR. A. (1970) Fatty acids in raw and processed Alaska pink shrimp. )t. Am. Oil chem. Soc. 47, 451-452. KaZECZKOWSKXR. A., Tmq~Y R. D. & KELLEY C. (1971) Alaska king crab: fatty acid composition, carotenoid index and proximate analysis, ft. Food Sci. 36, 604-606. LERESeh'~ R. & BoYo J. C. (1969) Response to acute hypothermia in Ad~lie penguin chicks. Commun. Behav. Biol. 4, 85-89. LEWIS R. W. (1967) Fatty acid composition of some marine animals from various depths. ft. Fish Res. Bd Can. 24, 1101-1115. Lowm~ J. A. (1964) The lipids of marine organisms. In Oceanogr. Mar. Biol. Rev. (Edited by BARNESH.), Vol. 2, pp. 169-191. George Allen & Unwin, London. M A ~ h t ~ L. A. & LOOSLIJ. K. (1962) Animal Nutrition. McGraw-Hill, New York. Mm~G M. S., WmT G. C. & IRVING L. (1969) Fatty acid composition of caribou bone marrow. Comp. Biochem. Physiol. 30, 187-191. Moss R. & LOUGHA. K. (1968) Fatty acid composition and depot fats in some game birds (Tetraonidae). Comp. Biochem. Physiol. 25, 559-562.
ENERGY METABOLISM OF ADI~.LIE PENGUINS
719
Pin,mY R. L. (1968) Territorial and social behavior in the Ad61ie penguin. In Antarctic Res. Series 12, Antarctic Bird Studies (Edited by AUSTINO. L.), pp. 83-131. American Geophysical Union, Nat. Acad. Sci., Nat. Res. Council. RICHARDSONT., TAPPEL A. L. & GROCERA. H., JR. (1961) Essential fatty acids of mitochondria. Archs Biochem. Biophys. 94, 1--6. SAPIN--JALOUSTR~J. (1960) Ecologie du Manchot Addlie. Hermann, Paris. SIDHU G. S., MONTGOMERYW. A., HOLLOWAYG. L., JOHNSON A. R. & WALKERD. M. (1970) Biochemical composition and nutritive value of kriU (Euphausia superba Dana). ~. Sci. Fd Agric. 21, 293-296. SLADEN W. J. L. (1958) The pygoscelid penguin--1 and 2. Scientific Reports, Falkland Islands Dependency Survey 17, 1-97. SOKOLOFF L. (1960) Metabolism of the central nervous system in vivo. In Handbook of Physiology (Edited by FIELD J.), American Physiological Society, Washington, D.C., Vol. III, pp. 1843-1864. WALKERA. T. (1964) Major fatty acids in migratory bird fat. Physiol. ZoSl. 372 57-64. WEST G. C. • MENG M. S. (1968a) Seasonal changes in body weight and fat and the relation of fatty acid composition to diet in the willow ptarmigan. Wilson Bull. 80, 426-441. WEST G. C. & MENG M. S. (1968b) The effect of diet and captivity on the fatty acid composition of redpoll (Acanthisflammea) depot fats. Comp. Biochem. Physiol. 25, 535-540. WILLIAMSD. D. & PLATNERW. S. (1967) Cold-induced changes in fatty acids of the rat and hamster. Am.y. Physiol. 212, 167-172. Wool) P., IMAICHIK., KNOWLESJ., MICHAELO G. & KINSELL L. (1964) The lipid composition of human plasma chylomicrons, o~. Lipid Res. 5, 225-231.
Key Word Index--Adglie penguin; Pygoscelis addlie; fasting penguins; fatty acids in penguin; energy requirements of penguins.