Erythrocyte dimensions, counts, and plasma protein concentrations of six species of antarctic birds.

Erythrocyte measurement Total- plasma

RBC countHematocritLengthWidthDepth Volume proteinpeciesNumber(RBC/m13)(percent)(ii) (,.)()(.8)(g/lOO ml)

o penguin12

1 .8 X 106 +.5

52.6 ±2.4

15.2± .3

9.6±.2

3.7

284

5.98:rap penguin5

2. 1 X 106 -+. 1

47.0 ±4.2

14.5± .4

9.4± .1

3.1

224

5.06penguin9

I .9X106 ± . 4

47.8 ± 4.7

16.6± .3

9.4± .2

3.3

2394.94yed shag10

2.4X106 ± . 3

55.9 ± 3.0

13.8± .1

8.0± .5

3.9

228

4.14polar skua8

3.2X106 ± . 2

45.5 ±2.4

13.4± .2

8.4± .2

2.4

143

3.65petrel

9

2.6X106 ± . 4

44.9 ±2.9

13.7±.4

8.5± .2

2.9

175

3.60

20

0 Gentoo Penguin• Adelie Penguin •

* Giant PSkuaC1

I-)

° Blue-eyed Shag 0

etrel

15If)Co

Li,

E5

the loss of body heat. The blue-eyed shag is a divingbird and also spends considerable time in the water.Their plasma protein concentration, erythrocyte vol-ume, and viscosity at low temperatures is intermediatebetween the penguins and the giant petrel and skua,neither of which spends much time in the water.

Mr. Block was in the field from December 16,1973, to February 27, 1974. This work was supportedby National Institutes of Health grant HL-14640-02and National Science Foundation grant Gv-35343.

ReferencesLjj 10

< IL 0a-II 20'II

38'

150

200 250300ERYTHROCYTE VOLUME, j.3

Figure 2. Relationship between the calculated erythrocyte volumeand apparent viscosity of blood from antarctic birds.

volume has a greater influence on apparent viscosityas the temperature decreases. At 0°C., the apparentviscosity of 50 percent hematocrit blood of the gentoopenguin, with its large red blood cell volume, is 1.4times that of the south polar skua.

Penguins can be considered aquatic birds since theyspend as many as 8 months of the year away fromland and in antarctic waters. The unfeathered legsand feet and the poorly insulated flippers are areaswhere considerable body heat could be lost to thecold water. The high plasma protein concentrationand the large erythrocyte size may be an adaptationof these birds to the cold acquatic environment. Theycontribute to the high viscosity at low blood tempera-tures in penguins. This would tend to increase thevascular resistance and hence decrease the flow ofblood into cold extremities. The lower volume ofblood, coupled with the countercurrent vascular heatexchanger in these extremities, would greatly reduce

Guard, C. L., and D. E. Murrish. 1973. Temperature de-pendence of blood viscosity in antarctic homeotherms.Antarctic Journal of the U.S., VIII(4)197-198.

Murrish, D. E., and C. L. Guard. 1973. Peripheral vascularcontrol mechanisms in the giant petrel, Macronectesgiganteus. Antarctic Journal of the U.S., VIII(4): 199-200.

Osmoregulation and thermoregulationstudies of the Adélie penguin

H. T. HAMMEL, J . A. MAGGERT, and R. KAULScripps Institution of OceanographyUniversity of California, San Diego

La Jolla, California 92037

Altering the temperature of the rostral brainstemin animals elicits thermoregulatory responses thatchange the deep body temperature in the oppositedirection. Altering the temperature of the same neuraltissue in the Adélie penguin has almost no effect uponits deep body temperature but it does elicit osmoregu-latory responses. Two pairs of thermodes wereimplanted stereotaxically to straddle the preoptic andanterior hypothalamic (P0AH) nuclei of the penguin.A reentrant tube also was implanted in the mid-line,into which a thermocouple could be inserted to

July-August 1974 99

measure the temperature of the brainstem nuclei whentheir temperature was altered by circulating waterthrough the thermodes. The temperature of the POAHnuclei could be maintained in this way at tempera-tures between 34° and 42° C. When heating thisneural tissue to 42 0 C., the penguins were induced toeat snow or ice and the activity of the salt gland wasreadily affected by heating or by cooling these nuclei.

Dr. Hammel and Messrs. Maggert, Kaul, andF. Todd (of Sea World) were at McMurdo from lateOctober to early December 1973 and obtained 25Adélie penguins from Cape Bird. Twelve of thesebirds were implanted with thermodes while atMcMurdo. These prepared penguins were returnedto our California laboratory in December 1973 forcontinuing thermoregulation and osmoregulationstudies.

In collaboration with Dr. L. Crawshaw, John B.Pierce Laboratory, Yale University, heating and cool-ing the POAH nuclei failed to alter oxygen consump-tion. Even when shivering was induced by forcedingestion of ice, the level of oxygen consumption couldnot be increased by cooling and could not be decreasedby heating the POAH tissue. Only sometimes couldslight vasomotor responses be induced, and onlyslight changes in core temperature were inducedthereby.

In collaboration with Dr. E. Simon, KerckhoffInstitute, Bad Nauheim, Germany, penguins receiveda continuous infusion of 1.0 molar sodium chlorideat a rate of 0.7 milliosmol per minute, into the gut.The birds excreted sodium chloride from both orbitalsalt glands at about the same rate at a normal POAHtemperature of 39°C. Increasing the POAH tempera-ture to 41°C. increased the excretion rate to 1.1milliosmol per minute, while cooling to 34'C. reducedthe excretion rate to nearly zero for periods of a halfhour. The sensitivity of the response was 0.1 to 0.15milliosmol minute -10C.-1.

We suppose this osmoregulatory response to a local-ized increase in temperature in neural tissue is un-natural; it may be induced thermal activity of soluteswithin neurones, while solutes diffuse from the extra-cellular fluid of the heated tissue. These results compelus to consider whether thermoregulatory responsesinduced by localized altering of temperature in thebrain, in the spinal cord, and in other neural elementsin the core may also be attributed to osmotic effectswithin the neural elements. Perhaps only the cutane-ous temperature transducers are excited naturally bythis osmotic process.

This research was supported by National ScienceFoundation grant GB-40176X.

Studies of the brain-blood barrier inantarctic organisms

CARLOS E. TRADATTI, MIGUEL A. ESBRY,RUBIN DIPAOLA, and EMANUEL LEVIN

Direccion Nacional del AntarticoBuenos Aires, Argentina

Brain-blood barrier phenomena (i.e. those ruling thetransport of substances to and from the encephlon)in organisms of conventional habitats are influencedby temperature. Hibernation is one method that notonly modifies the transport of substances into l thecentral nervous system but also affects its normalfunctioning.

It has been shown that many free amino cidspresent in the central nervous system fulfill importantfunctions. This is the case for gamma-aminob tyricacid and for glycine, both proposed as neurot ans-mitters of an inhibitory type, and for others likeglumatic acid (an excitatory agent). The exist nceof a barrier to the transport of these amino acid hasbeen determined in mammals.

Experimental studies, carried out during 197 inAntarctica, established that the brain amino acidcontent in some fishes of the Notothenidae familyhave some peculiarities not present in other ani4ials.Such peculiarities particularly referred to the braingamma-aminobutyric acid content in Trematmusbernachii, which was found to be higher than that ofits metabolic precursor, glutamic acid; this suggeststhat part of the brain gamma-aminobutyric acidcould be blood-transported. The presence of ganma-aminobutyric acid in the blood, in the liver, in. thegonads, and in the kidney was established and indi-cates that the blood-brain barrier for gamma-amino-butyric acid probably is not present.

Experiments were done on fishes and penguinsto determine how 3H-gamma-aminobutyric acid istransported from blood to brain. Preliminary resultsindicate a penetration of this amino acid in i thecentral nervous system. At Palmer Station, duringJanuary and February 1974, experiments concen-trated on the blood-brain barrier to gamma-amino-butyric acid in fishes of the Notothenidae family(Notothenia gibberifrons, Trematomus bernachii,and Trematomus newnesi) and in other homeo-thermal organisms of the region such as the Adéliepenguin (Pygoscelis adéliae) and the blue-eyed bor-morant (Phalacrocorax atriceps) . Experiments studiedthe time course of gamma-aminobutyric acid pene-tration into the brain in different species to see ifthe preliminary results in fishes could be extendedto all antarctic organisms. Samples also were col-

100 ANTARCTIC JOURNAL