MUS MUCULUS AND MUS WAGNERI COMPARED. II. THE BODY WEIGHT

M U S MUCULUS AND M U S W A G N E R I COMPARED.

11. THE BODY WEIGHT

A. B. DROOGLEEVER FORTUYN

Pekiitg Union Medical College, Peiping, China

Received February 27, 1930

In

in three of the races studied for the number of their tailrings and described in the first paper of this series the weight was determined from birth to the age of six months. On the first, the eighth and the fifteenth day the

weight was measured in tenths of grams, for animals of 3 weeks in half

grams and for older animals of 4 to 15 weeks and of 4 to 6 months, in

grams. No pregnant females were used.

The three races used for this investigation were (a) the tame albino

M u s wagmri, W T W, (b) the tame albino M u s musculus, W M, both

derived from hybrids of wagneri and musculus, bought in the local market

in Peking, but carefully selected, the one for wagneri type, the other for

the type of M u s musculus, and (c) the albino M u s musculus, H T M.

The latter is a pure Mus musculus imported from the United States of

America, but selected for the high number of tailrings. Tables 1, 2, and 3

contain the data collected about these races, and figure 1 gives a graphic representation of them.

Only a few observations were made on the body weight of the wild

M u s wagneri, caught in houses in Peking, since the age of such animals is unknown and the data, therefore, are not directly comparable with those obtained in tame races. I n nine wild males, apparently not very young, the weight varied between 10 and 16 grams, in six non-pregnant females

it varied between 9 and 15 grams, whereas two pregnant females weighed

14 and 20 grams respectively. These figures agree very well with those of

table 1 for W T W.

I n the albino M U S

wagneri the male is heavier than the female as is the case in all other

varieties of mice. Mus wagneri is a t every age, on the average, lighter

than Mus musculus. This is a well known fact, but it is here studied in

detail. Those animals which become very heavy do so by accumulating

fat. They differ in general appearance from M u s musculus of the same

weight. I n W T W there is a great variation in body weight, the heaviest

animal being three or even four times as heavy as the lightest animal of The three tables offer many interesting points.

BODY WEIGHT IN MICE 169

the same age. This fact finds its expression in a high coefficient of Yaria- tion.

Table 2 for Mus muscuZus, W M, gives the weight for males and females

separately only after the age of six weeks, as at the time when these data were collected the sexes were not separated before the age of seven weeks,

l Z 3 4 5 6 7 8 9 I O I I l Z 1 3 1 4 I 5 4 m sm s m

Z 6 W

a g e i n w e e k s and m o n t h s

FIGURE 1.-Growth curves for the albino +Ww wugseri, W T W; the albino iMus mvscdus,

W M; and for the albino Mus musculus selected for a high number of tailrings, H T M. After the

age of 4 weeks (in W M 6 weeks) the growth curve for both sexes is given.

which is too late. The table also contains the figures for the weight of

animals of both sexes together after the age of seven weeks, but these

have little significance on account of the marked sexual difference in body weight. At all ages the heaviest animal is only about twice as heavy as

the lightest animal of the same age, and, consequently, the coefficient of

170 A . H. I>ROOGLEEVER FOKTUYN

variation is lower than in W T W. It is slightly higher in the female than

in the male.

Table 3 for the albino Mus muscuZus, H T M, which was imported into

China and probably had no Mus wag.neri among its ancestors gives the

body weight for the age of 14 and 15 weeks, whereas in the other two races the weight a t 13 weeks was followed immediately by the weight a t 4 months. This was done on account of the fact that in both sexes the growth curve went down during the thirteenth week after which the body weight slowly rose again to reach what is apparently its normal figure a t the end of the fourth month. This irregularity in the growth curve is

partly caused by the fact that the group of mice weighed when 12 weeks

old was not identical with the group weighed a t the age of 13 weeks. I n fact, in all three races very few mice were weighed from the beginning to the end of the growth curve. Nevertheless, the growth curves are fairly smooth on account of the large number of mice weighed. Only in race

W RI before the age of 13 weeks and in race H T M after the age of 12

weeks some irregularities occur which must be studied more carefully to be completely understood. In many cases also the individual growth curves of the mice show more than the usual irregularities during these weeks.

Another remarkable fact is the low degree of variation in the body

weight of H T M, especially in the male sex. I n all cases the heaviest male

is only one and a half times as heavy as the lightest male of the same age. The coefficient of variation for the male is generally below 10. I n H T M more than in the other two races it is obvious that the male is less variable than the female in regard to body weight, although, as remarked before, pregnant females were not included in the investigation. I n the albino rat the reverse is true.

Since the low degree of variability in body weight cannot be ascribed to inbreeding, which was practised irregularly and on about the same scale in all three races, it must be a consequence of the selection for a high num- ber of tailrings which had been practised to obtain the race H T M. The

coefficient of variation for the number of tailrings, as given in the first

paper of this series, is highest for W T W and lowest for H T M, whereas

W M has an intermediate position. Exactly the same holds true for the

coefficient of variation of the body weight. The correlation between the

number of tailrings and the body weight must be studied in greater detail,

but so far it seems as if reduction of the variability of the number of

tailrings, by selection, goes parallel with a reduction of the variability in

AQE 1st day 8th day 15th day 3 weeks 4 weeks 5 weeks 6 weeks 7 weeks 8 weeks 9 weeks 10 weeks 11 weeks 12 weeks 13 weeks 4 months 5 months 6 months AVERAQE WEIQET AND MEAN ERROR (zoo'? 0 AND 38')

1.19+0.01 3.21

50.

05

5.37k0.10 7.42k0.11 8.92k0.12 _10.33k0.13

TABLE 1 Body weight of the albino Mus wagneri W T W

,

STANDUD DEVIATION kO.15 k0.70 k1.42 k1.60 k1.82 k1.91

OEFFICIENI F VARIATIOI 12.82 21.98 26.44 21.56 20.40 18.48

AVERAQE WEIQET AND MEAN ERROR (100 0 0 )

9.71k0.16 _10.22

k0. 17 10.49 50. 19 10.91 k0.20 11.69kO. 19

12.2350.21 12.3550.21 12.85

50.24

13.46kO.

25

14.58k0.27 15.31k0.33 16.65

+O

.39

STANDARD DEVIATION k1.62 rt1.79 k1.92 k2.04 k1.93 k2.12 k2.16 k2.41 +_2.59 52.73 rt3.35 k3.98

AVERAQE

WEIQHT

AND

MEAN

ERROR

?OEFFICIENI F

VARIATION 16.68 17.51 18.30 18.69 16.50 _17.33 17.48 18.75 19.24 18.72 _{21.88 23.90}

'

10.9550.19 11.43

k 0.20 12.04 k 0.22 12.90 1 0.22 13.74 3. 0.21 14.11 10.23

14.5450.23 14.803.0.25 15.47

k0.29 17.11 3-0.32 18.76 3. 0.43 19.97 i0.48 (85309

STANDARD DEVIATION k1.98 k2.07 k2.23 k2.26 k2.13 F2.31 k2.39 k2.59 k2.91 k3.71 k4.39 k4.48

;OEFFICIENl F

AQE ~~ 1st day 8th day 15th day 3 weeks 4 weeks 5 weeks 6 weeks 7 weeks 8 weeks 9 weeks 10 weeks 11 weeks 12 weeks 13 weeks 4 month 5 month 6 month

STAND- ARD

DE-

VIATION -1-1.95 f2.25 k2.71 i3.13 -1-3.71 k3.70 f3.37 f2.58 f3.29 +3.19

- TOTAL ?UMBER )F

MICE

-

COEFF'ICIEW OF

VARIATIO

______

12.18 12.72 14.26 16.18 17.90 17.81 15.72 11.36 13.77 13.27

Body s'eigkt of the albiiio Miu musculus, W M, in grams.

BTAND- ARD

DE- VIATION AMRAQE WEIQBT AND MEAN ERROR ---__.___- ~ AMRAQE WEIQRT AND MEAN ERROR 1.31 30.01

3.48f0.07 6.03

k0.08

8.65f0.12 _{11.64f0.13 14.16f0.13 15.38k0.18 16.52k0.16 18.77}

+O.

19

20.08~0.20 20.35

f0. 21 21.72 k0.24 21.90 0.21

22.6950.23 24.30

f

0,23

26.01f0.30 26.78f0.31

COEFFICIENT OF

VARIATION

STAND- bBD

DE-

VIATION k0.17 k0.74 k1.15 C1.42 k1.79 f1.80 k2.19 k1.94 k2.58 f3.01 f3.64 k3.68 k3.43 53.45 f3.23 - f4.12 f4.47

TOTAL _NUMBER OF

0

P

COEFFICIENT OF

VARIATION

~-

13.34 21.26 19.07 16.41 15.37 12.71 14.23 11.74 13.74 14.98 17.88 16.94 15.66 15.20 13.29 15.84 16.69

72 90 _{113 168 109 132 107 100} 93 ₁₀₀

17.05f0.20 19.85+0.25 21.25k0.28 21.95k0.28 22.40

k0.

31

22.95L-0.25 23.96f0.29 26.00f0.31 28.24f0.39 29.53

f0. 38 AVEHAQE WEIQBT AND WEAN ERROR

k1.78 k2.42 f2.89 k3.23 f 3.43 k2.91 f3.02 -1-3.04 f3.76 i3.84

16.00f

0.22

17.68k0.23 19

.OO

+O.

25

19.34k0.24 20.72

k

0.35

20.78-1-0.32 21.42

io,

32

22.70k0.25 23.88

io.

34

24.03f0.31

TOTAL NUMBER OF

$3

~-

TABLE 3 Body weight in grams of the albino Mus musculus, H T M, selected for a high number of tailrilzgs.

STAND- ARD

DE-

VIATION

-___.

G L

I

I

COEFBICIE~ OF

VARIATION AVERAGE WEIGRT AGE AND MEAN ERROR

ir0.17 k0.62 k1.09 k1.32 rt1.69 k1.76 t1.83 k2.25 k2.50 k2.57 k2.64 k2.77 k2.72 k3.06 t3.22 t3.30 f3.55 t3.44 k3.45

---

12.22 15.60 17.50 15.10 14.00 12.03

100 14.15+0.17 11.09 100 15.4650.14 12.36 100 . 16.61+_0.16 12.85 109 ~ 17.66k0.17 12.44 104 18.70k0.19 12.35 ~ 100 19.47k0.23 12.65 102 20.21k0.26 12.17 100 20.62k0.26 13.96 196 19.86+0.19 14.50 103 14.92 115 15.06 144 21.47kO.27 13.98 152 22.4050.23 13.22 104 23.8Sk0.26

1.41k0.01 3.97

k0.04

6.24k0.06 8.

74

k0.09

12.07rt0.11 14.63k0.12 16.49k0.12 18.20rt0.15 19.45k0.16 20.65f0.16 21.36k0.18 21.89

k

0.19

22.34k0.19 21.91k0.15 22.20

k0. 22 22.11 k0.21 23.57 k0. 20

24.59rt0.19 26.09k0.23

lstday Sthday 15thday 3

weeks 4 weeks 5 weeks 6 weeks 7 weeks 8 weeks 9 weeks 10 weeks 11 weeks 12 weeks 13 weeks 14 weeks 15 weeks

4months 5months 6months

'IVJTAL AVERAQE WEIOAT

[

STAND- ARD

DE-

i~~~~~~~~

VlhTXON

9

9

314 200 262 207 200 209 200 200 220 229 200 203 200 408 206 230 288 303 213 %1.64 +1.55 - rti.54 51.63 rt1.73 +1.94 k1.59 k1.70 f2.01 rt2.10 52.16 k2.51 f2.26 52.66

I

I

I

10.87 8.84 7.78 7.65 7.76 8.45 6.74 7.06 8.44 8.65 8.85 9.78 8.41 9.42

174 A. 13. DROOGLEEVER FORTUYN

number of tailrings, because the body weight changes from day to day during the whole life of the individual, whereas the number of tailrings is

constant after the age of 5 weeks. One has, therefore, in selection for the

number of tailrings a valuable means of indirect and provisional selection for body weight which must be of importance in all those cases where the

body weight of mice is studied experimentally:

When the three races of mice are compared it appears that there is very

little difference between W M and H T M, proving that W M, although

of hybrid origin, is a true Mus musculus. On the other hand, the average

body weight of the tame M u s wagneri, W T W, a t all ages and for both

sexes is less than the body weight of Mus musculus. Generally speaking

one may say that the body weight of M u s wagneri is two-thirds of that of

Mus musculus.

SUMMARY

The average body weight of M u s wagneri is two-thirds of that of M u s

I n both species of mice the male is heavier than the female.

There is little difference in body weight between a pure albino M u s

musculus imported from the United States of America into China and an

albino Mus musculus, derived from hybrids with Mus wagneri, bought in

Peking.

I n Mus musculus the coefficient of variation of the body weight is

higher in the female than in the male.

The coefficient of variation of the body weight is highest in the albino

M u s wagne'ri, lower in the albino M u s musculus of hybrid origin and still

lower in the albino M u s musculus selected for a high number of tailrings.

It goes parallel with the coefficient of variation of the number of tailrings in these races.