C<JIIIP_ Blo<h m. Phwol. Vol. 7OA. pp 537 o 540. 1981 0300-9629 XI 120537-04302.00 0
P in ed ,n G ea B , aln. 411 igh s exned Copy igh 0 198 I Pe gamon P ess L d
ENERGETIC ADVANTAGES OF SLIGHT DROPS IN BODY
TEMPERATURE IN LITTLE BROWN BATS,
MYOTIS LUCIFUGUS
EUGENE H. STUDIER
Depa men o Biology, Uni e si y o Michigan-Flin , Flin , MI 48503. U.S.A
Abs ac -l. A cons an ambien empe a u es (c) below hei he mal neu al zone (TNZ), li le b own
ba s, Myo is luci uyus, main ain a wide ange o s eady-s a e body empe a u es (&).
2. The ela ionship be ween oxygen consump ion and T&-T, di e en ial a cons an T,s below he TNZ
is cu ihnea .
3. Small d ops in & om high & le els esul in sigm i an ly g ea e ene gy sa ings han subsequen
& educ ions o equal inc emen s.
INTRODUCTION
Deep body empe a u e (G) and oxygen consump ion
(OC) as unc ions o ambien empe a u e (T,) ha e
been de e mined o a wide a ie y o mammals.
Assuming ha he o ganisms unde conside a ion do
no signi ican ly u ilize anae obic ene gy p oducing
me abolic pa hways and Tb is cons an du ing he
pe iod o measu emen , he a e o OC is di ec ly
ela ed, wi h li le e o , o me abolic hea p oduc ion.
Possible in e ela ionships be ween G, OC, and T,
ha e o en been discussed and deba ed (Scholande e
al.. 1950; Kleibe , 1961; King, 1964; Tucke , 1965;
Po e & Ga es, 1969; McNab, 1970; S unk, 1971;
Kleibe , 1972; Calde , 1972; Calde & King, 1972;
S unk cd., 1973; McNab, 1980). O pa icula in e -
es is he ela ionship o OC and he T,-T, di e en ial
(T-T,) in endo he ms a T,s below he he mal neu-
al zone (TNZ). In mammals in which s eady-s a e G
is cons an and independen o T,, i.e. in homeo he -
mic endo he ms, T,T, di e en ial can be ob ained
only by a ying T,. I is, he e o e, impossible o ana-
lyze he ela ion o OC o T,-T, a cons an T, in such
species. Among he e o he mic endo he ms, howe e ,
some da a a e a ailable (S udie & O’Fa ell, 1972,
1976) o OC a a wide ange o s eady-s a e Ths a
cons an T,. This pape epo s he ela ionships
be ween OC and T,T, a cons an T,s below he TNZ
in a he e o he mic endo he m, he li le b own ba ,
M~,o i.s luc~&~us, and commen s on he ene ge ic
ad an ages o his he mo egula o y s a egy.
MATERIALS AND METHODS
Da a analyzed o he p esen s udy a e aken om S u-
die & O’Fa ell (1972). De ails o ma e ials and me hods
used appea in ha pape and will be summa ized he e.
Adul , emale li le b own ba s o a ying ep oduc i e
condi ions (p egnan , lac a ing, pos -lac a ing) collec ed
h oughou he summe om a ma e ni y colony we e
s udied. All labo a o y s udies we e pe o med on he day
o cap u e. S eady-s a e OC and Tb we e eco ded a T,s o
1640°C a 4°C in e als. Labo a o y con olled T,s we e
p og ammed o coincide wi h T,s in he na u al oos .
RESULTS AND DISCUSSIONS
S eady-s a e T,,s o li le b own ba s a a ious con-
olled T,s (shown in Fig. 1) indica e he he e o he -
mic pa e n o he mo egula ion exhibi ed by hese
ba s when es ed on he day o cap u e. Much o he
a iabili y in le el o egula ed Tb is a unc ion o
s age o p egnancy, s age o ep oduc i e cycle, e c.
(S udie & O’Fa ell, 1972).
Da a on OC and T,-T, a a ious con olled T,s
om 1632°C we e analyzed by bo h s epwise poly-
nomial eg ession and by leas squa es eg ession
analysis o ele en possible powe , oo , and ecip ocal
ans o ma ions o bo h OC and T,-T, oge he and
independen ly o de e mine he bes s a is ical de-
sc ip ions o he ela ionships be ween hese a iables.
Reg ession coe icien s o he independen a iable
(T,T,) as a squa ed e m o squa ed ans o ma ion
we e in a iably signi ican , excep a a T, o 32°C.
Based on compa ing coe icien s o de e mina ion ( ’)
o maximal alues, he bes uni o m eg ession analy-
sis, excep a 32”C, we e cu ilinea equa ions o he
o m _V = b.? + u, whe e J is OC in cc/g pe h and x
is T,-T, in ‘C. Equa ions a e gi en in Table 1 and
illus a ed in Fig. 2. The ela ionship o OC o Th-T,
becomes p og essi ely less cu ed as T, ises un il a a
T, o 32 ‘C. which is he he mal neu al empe a u e
o his species (S ones & Wiebe s, 1965), he ela ion-
ship is linea . Since he mal conduc ance (McNab,
1980) is ep esen ed by he slopes o he lines in Fig. 2,
a T,s below he TNZ, he mal conduc ance is no a
cons an . Linea eg ession analysis o hese a iables
(OC and G-T,) will, he e o e, unde es ima e ac ual
he mal conduc ance when T,-T, is la ge and o e es i-
ma e he mal conduc ance when T,-T, is small. As
s a ed ea lie , in homeo he mic endo he ms, he only
me hod o ob aining T,-T, is by modi ying T,. Fo
such species, he mal conduc ance is cha ac e is ically
es ima ed by analyzing he slope o he ela ionship o
OC o T, a T,s below he TNZ. Since Tb is cons an
in such species, he abscissa is ela ed o T,-T, and
esul an igu es show a nega i e slope since T,-T,
dec eases as T, ises. Such g aphic ep esen a ions a e,
EUGENE H. STUDIER
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Fig. 1. S eady-s a e body empe a u es (T,) o adul emale Myo is Iueijiiyus o a ying ep oduc i e
condi ion a cons an ambien empe a u es (T,). Numbe s indica e he numbe o da a poin s a ha
posi ion.
he e o e, in e ed le o igh in compa ison o
Fig. 2. Inspec ion o some published igu es depic ing
OC as a unc ion o T, in homeo he mic endo he ms
Table 1. Reduced s a is ical da a o he ela ionship o
oxygen consump ion (y, in cc/g pe h ) o body empe a-
u e o ambien empe a u e di e en ial (x, in “C) a
a ious ambien empe a u es (7J in Myo is hAjiigus.
Reg ession coe icien s a e o equa ions o he o m
1’ = hx’ + a. P < 0.0005 in all cases. Values in pa en heses
a e s anda d e o s.
Reg ession coe icien s
, (‘C) b a F d. . *
16 0.0192 0.268 203.4 1,29 0.875
(0.0013) (0.154)
20 0.0194 0.149 182.8 ,23 0.888
(0.0014) (0.120)
24 0.0263 0.558 166.8 1,33 0.835
(0.0020) (0.077)
28 0.0430 0.480 48.6 1,29 0.627
(0.0062) (0.096)
32* 0.441 0.271 29.4 I,32 0.487
(0.081) (0.158)
* Reg ession coe icien s a e o he linea equa ion:
!’ = bx + a.
shows ela ionships which appea o be cu ilinea
al hough hey a e o en analyzed in ec ilinea ashion
(e.g. Banholze , 1976; G an & Dawson, 1978;
Kamau e al., 1979; Degab iele & Dawson, 1979:
Riibsamen & Ke embeil, 1980). The ec ilinea i y o
his ela ionship has been ques ioned p e iously
(T acy, 1972). Fu he mo e, when he mal conduc-
ance is calcula ed on indi idual measu emen s o Th
and OC, i is appa en o many species ha he mal
conduc ance is no cons an (McNab, 1980). Since
me hods a e a ailable o cu ilinea (polynomial)
eg ession analysis, such analysis should be pe o med
o de e mine he bes desc ip i e s a is ics o da a
such as OC as a unc ion o T, in homeo he mic
endo he ms. Such analysis would yield mo e accu a e
es ima es o minimal s anda d me abolism and he -
mal neu al empe a u e (S udie al., 1975).
The cu ilinea i y o he ela ionship o OC o
G-x a cons an T,s in M. ~~c~u~u.s (Fig. 2) would
no appea o be ela ed o changes in he ba s’ physi-
cal en i onmen bu p obably e lec s some animal-
egula ed p ope y. Possibili ies include animal egu-
la ed di e ences in me abolic hea p oduc ion and/o
in hea Row h ough changes in conduc i i ies o he
shell (King & Fa ne , 1961) o in pe iphe al blood
low, e c. The ela i ely linea , uppe po ions o he
OC o T,T, ela ions (Fig. 2) may well be pa allel
Ene gy sa ings due o lowe ed K in ba s 539
80 -
70 -
2 6.0 _
E
P
s 50-
s
;
4.0 _
5
% 30-
E
0
16 disp opo iona ely less ene gy han a e y high Y&, se
poin .
Acknowledym~en s-I hank D s B uce Wunde and
William A. Calde o many use ul commen s on an ea lie
e sion o his manusc ip and D Richa d W. Dapson o
his c i icisms h oughou he de elopmen o his manu-
sc ip .
Tb - T0 , ‘C
Fig. 2. Reg ession equa ions a a ious ambien empe a-
u es o he ela ionship o oxygen consump ion o body
empe a u e o ambien empe a u e di e en ial (T,-T,) in
M~0 i.s /uc~~ i~gu.s.
and indica e uni o m ene ge ic esponses a a ious
T,s when T,-T, di e en ial exceed a c i ical le el. The
lowe ing o z alues as T, inc eases indica es ha
G-T, di e en ial explains p og essi ely less o he
a iabili y in OC.
While a s a is ically signi ican ec ilinea ela ion-
ship exis s be ween OC and T,-T, a all T,s analyzed,
he ela ionship is bes desc ibed by a cu ilinea
equa ion excep a a T, o 32°C. Use o a ec ilinea
equa ion p edic s equal educ ions in OC o any in-
c emen al educ ion in Tb whe eas he cu ilinea
equa ions show la ge educ ions in OC when Tb is
educed in equal inc emen s om a high se poin . As
an example, a a T, o 2O’C a d op in Th om 37°C
(5.76 cc/g pe h ) o 33’C (3.43 cc/g pe h ) esul s in a
educ ion o OC o 2.33 cc/g pe h . Using 4.8 Cal/cc
o oxygen as an ene gy equi alen , his is a sa ings o
11.2 Cal/g pe h . A u he d op in T om 33°C o
29°C (1.72 cc/g pe h ) esul s in a conside ably
educed ene gy sa ings o only 8.2 Cal/g pe h .
I is also use ul o conside ene gy equi emen s o
aising Tb. A a T, o 16”C, minimum OC in M. luci-
uy~s, when T,-T, = 0, is 0.268 cc/g pe h . A doubling
o OC, o 0.536 cc/g pe h , yields a T,-T, o 3.7”C; a
ipling o OC yields a T,--T, o 53°C; and, a quad u-
pling o minimal OC gi es a T,T, o 6.5”C. F om his
pe spec i e, he cu ilinea i y o he ela ion o OC o
Y&T, suppo s he hypo heses ha homeo he my
e ol ed g adually (Dawson ul., 1979) o in s ep-
wise in e als (C omp on e al., 1978) a he han as a
single majo jump (Dawson & Hulbe , 1970), since
he in e media e se poin s o con olled Tb equi e
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