eBooksRead.com books search new books
William E. (William Ernest) Castle.

Studies of inheritance in guinea-pigs and rats online

. (page 1 of 20)
Online LibraryWilliam E. (William Ernest) CastleStudies of inheritance in guinea-pigs and rats → online text (page 1 of 20)
Font size
QR-code for this ebook
IIOLOGY UBRARY

)rnla Institute of Technology



14 - DAYS



STUDIES OF



INHERITANCE IN GUINEA-PIGS AND RATS




BY



W. E. CASTLE AND SEWALL WRIGHT




PUBLISHED BY THE CARNEGIE INSTITUTION or WASHINGTON
WASHINGTON, 1916



CARNEGIE INSTITUTION OF WASHINGTON, PUBLICATION No. 241



PAPER No. 26 OF THE STATION FOR EXPERIMENTAL EVOLUTION
AT COLD SPRING HARBOR, NEW YORK

FROM THE LABORATORY OF GENETICS
OF THE BUSSEY INSTITUTION



Copies of this Book

were first issued

SEP 20 1916



PRESS OF GIBSON BROTHERS, INC.
WASHINGTON



CONTENTS.

PART I. AN EXPEDITION TO THE HOME OF THE GUINEA-PIG AND SOME BREEDING
EXPERIMENTS WITH MATERIAL THERE OBTAINED. BY W. E. CASTLE.

PAGE.

Introduction 3

Some observations on guinea-pigs in Peru 5

Hybridization experiments with Cavia cutleri 8

Life history of C. cutleri 8

Crosses of C. cutleri males with guinea-pig females 13

Color inheritance among the F 2 hybrids 13

(a) Cross 9 albino (race B) X d" C. cutleri 13

(6) Cross 9 albino (race C) X d" C. cutleri 14

(c) Cross 9 brown-eyed cream (race C) X d" C. cutleri 16

(d) Results from (6) and (c) combined 16

(e) Intensity and dilution among the hybrids 17

(/) Significance of the results observed 18

Hybridization experiments with a race of feral guinea-pigs from lea, Peru 20

Origin and characteristics of the lea race 20

Crosses between the lea race and guinea-pigs of race C 23

The F 2 generation 24

Summary on the lea race 29

Hybridization experiments with a domesticated guinea-pig from Arequipa 31

d 1 1002 and his FI offspring 31

F, offspring of d" 1002 33

Back-cross and other offspring of d" 1 1002 35

Miscellaneous matings of the descendants of d" 1002 36

Summary on the Arequipa domesticated race 41

Size inheritance in guinea-pig crosses 42

Previous work on size inheritance 42

Weights and growth curves of C. cutleri, of various guinea-pig races, and of their

hybrids 43

Skeletal measurements of C. cutleri, of various races of guinea-pigs, and of their

hybrids 47

The C. cutleri hybrids 48

Hybrids of the Arequipa d" 1002 52

The lea hybrids 53

Theoretical explanations of size inheritance and of "blending inheritance"

in general 54

PART II. AN INTENSIVE STUDY OF THE INHERITANCE OF COLOR AND OF OTHER COAT
CHARACTERS IN GUINEA-PIGS, WITH ESPECIAL REFERENCE TO GRADED VARIATIONS.
BY SEW ALL WRIGHT.

PAGE.

Color and its inheritance in guinea-pigs 59

Skin, fur, and eye colors of guinea-pigs 59

Color of Cavia cutleri 59

Melanin pigment 59

Primary classification of fur colors 59

Yellow group of colors 60

Dark group of colors 60

Skin colors 61

Eye colors 62

Definitions of fur colors by Ridgway's charts 62

Definitions of eye colors 63

Heredity of fur and eye color 63

Color factors of guinea-pigs 63

Classification of color factors . . 63



IV CONTENTS.

Color and its inheritance in guinea-pigs Continued. PAGE.

Heredity of fur and eye color Continued.

Color vs. white 64

Intensity of general color development 64

Dark vs. yellow color 65

Variations of dark color 66

Table of factor combinations 66

Hereditary factors and the physiology of pigment 67

Discussion of experiments 74

Material 74

Systematic position 74

Description of stocks 74

Problems 77

Inheritance of dilution 77

The red-eye factor 77

Dilution 79

The dilution factor 80

Inheritance of minor variations in intensity 85

Methods and accuracy of grading 85

Variations in intense guinea-pigs and albinos 85

Multiple allelomorphs 86

The relations of imperfect dominance, stock, and age to grades of intensity . . 87

Variations of yellow 89

Variations of sepia 92

Variations of eye color 93

Summary " 93

Inheritance of variations in the agouti pattern 94

Previous work 95

The inheritance of the agouti of C. rufescens 96

Minor variations 99

The inheritance of the agouti of C. cutleri 100

Inheritance of rough fur 100

Classification 102

Previous work 102

Material 103

Problems 104

Inheritance of rough as opposed to smooth 105

Inheritance of major variations 106

Possibilities of linkage among rough and color factors 113

Summary of rough tables 115

Minor variations 116

Roughness of series II 117

Summary 118

General conclusion 119

Experimental data 121

Explanation of tables 62 to 137 121

PART III. FURTHER STUDIES OF PIEBALD RATS AND SELECTION, WITH OBSERVATIONS
ON GAMETIC COUPLING. BY W. E. CASTLE.

PAGE.

The progeny of hooded rats twice crossed with wild rats 163-168

A second report on mass selection of the hooded pattern of rats 168-172

Further observations on the mutant series 173-174

Gametic coupling in yellow rats 175-180

Tables 181-187

BIBLIOGRAPHY 188-190

EXPLANATION OP PLATES. . . ... 191-192



PART I

AN EXPEDITION TO THE HOME OF THE GUINEA-PIG

AND SOME BREEDING EXPERIMENTS WITH

MATERIAL THERE OBTAINED



BY W. E. CASTLE



INTRODUCTION.

For several years I have been engaged in studies of heredity in
guinea-pigs. In the course of these studies all the common varieties
of guinea-pigs have been investigated by the method of experimental
breeding and something has been learned concerning their inter-
relationships and probable mode of origin. The actual origin of most
of these varieties is, however, unknown, as is true also concerning
most varieties of domesticated animals. One or two varieties have,
however, been made synthetically in the laboratory and it is conceivable
that, if we had the original wild stock to work with, from which the
domesticated guinea-pig has arisen, some or all of the existing varieties
might be synthesized anew and perhaps still others might be obtained,
and that in this way something might be learned of the method by
which new varieties arise. From considerations such as these I have
for several years been seeking to obtain living specimens of the wild
species which most closely resemble guinea-pigs. In 1903 I received
from Campinas, Brazil, 3 wild-caught individuals referred at the tune
to the species Cavia aperea, but since found to agree better with the
description of C. rufescens. From two of these animals young were
obtained, and crosses, the results of which have been described in
detail by Dr. Detlefsen (1914), were made with domesticated guinea-
pigs. It may be noted that all male FI hybrids were sterile, but that
the FI females were fertile, and that upon repeated crossing of these
with male guinea-pigs, a race of fertile hybrids was at last obtained,
these being, in the language of breeders, about guinea-pig, | rufescens.
From this result it seems doubtful whether C. rufescens has any close
genetic relationship to the domesticated guinea-pig, although by
hybridization it has been found possible to produce races (f or more
guinea-pig) which have derived certain characters from a rufescens
ancestor.

Cavia aperea from Argentina has been crossed with the guinea-pig
by Nehring (1893, 1894) in Berlin, with the production of fully fertile
hybrids. This result indicates a closer relationship with the guinea-pig
than C. rufescens manifests. Darwin (1876), however, did not regard
aperea as the ancestor of the guinea-pig, because he found it to be
infested with a different species of louse. I have not myself been able
as yet to obtain specimens of C. aperea. Nehring (1889) has argued
with much plausibility that Cavia cutleri of Peru is more probably the
ancestor of the guinea-pig, for (1) it agrees closely with the guinea-pig
in cranial characters and it occurs in a region where guinea-pigs have
been for a long time kept in domestication, as is shown by the occurrence
of mummified guinea-pigs which had been buried with the dead. Natu-
rally I formed a strong desire to secure living specimens of C. cutleri for

3



4 INTRODUCTION.

experimental study, but for several years I was unable to do so.
Through correspondence with Professor S. I. Bailey, who was at the
tune director of the Harvard Astronomical Observatory at Arequipa,
Peru, I ascertained that a wild species of cavy occurred in that locality.
Professor Bailey kindly captured some of the cavies and attempted
repeatedly to forward them to me, but without success. The steam-
ship companies refused to accept them for transportation on the ground
that they might lead to detention or quarantining of their vessels,
since all rodents were suspected of being carriers of bubonic plague.
After several years of waiting and fruitless negotiation with every
chance traveler to Peru with whom I came in contact, I resolved to
go to Peru myself and get the desired specimens. Through a grant
made by the Carnegie Institution of Washington I was enabled, in the
fall of 1911, to carry this resolution into effect.

The Carnegie Institution of Washington and the Bussey Institution
have together provided means for carrying out the breeding experi-
ments described in this paper. I wish to express my gratitude to both
institutions and to thank the director and other officers of the Harvard
College Observatory for hospitality and generous assistance given me
at the Arequipa station. I am indebted also to Professor C. J. Brues
for kindly bringing me a stock of guinea-pigs obtained by him near
Lima, Peru, in 1912.



SOME OBSERVATIONS ON GUINEA-PIGS IN PERU.

On a midsummer day in December 1911 I arrived as a guest at the
Harvard College Observatory in Arequipa, Peru, where I went in
search of guinea-pigs, wild and domesticated, to be used in breeding
experiments.

The day after my arrival at the observatory I walked a short dis-
tance up the highway through a group of adobe cabins, straw-thatched
and without chimney or windows, and with a single door. On looking
in at the open door of one of the cabins, I was pleased to see a domesti-
cated guinea-pig of the common spotted black-and-white sort familiar
to lovers of pet-stock throughout the world. In other near-by cabins
I found considerable numbers of guinea-pigs were kept, in one as many
as 40. They were fed on fresh-cut alfalfa or the green leaves of maize,
receiving apparently no other food and no water. At the back or
sides of the cabin was a sort of shelf or bench of stone used as a seat
or couch, underneath which the guinea-pigs had their home. Their
escape through the open door was prevented by a high lintel of stone,
perhaps 15 inches (38 cm.) high, over which one has to step in entering.
In these cabins were seen most of the common color varieties of guinea-
pigs known to us, agouti, black, yellow, and white (albino). None of
the colored individuals which I saw was self-colored; all were spotted
with white or with yellow or in both ways. The same predilection for
spotting is seen in the other important native domesticated animal, the
llama. I saw no llamas except such as were spotted; some were black
spotted with white, but the majority were of a soft shade of buff or
fawn spotted with white. The common spotted condition of our
guinea-pigs is undoubtedly one of long standing; indeed it would seem
that the Peruvian natives breed no other variety except such as are
either white spotted or all white. The unspotted or " self-colored "
varieties now kept by fanciers in Europe and America have probably
been produced by selection from stock originally spotted. This is
indicated by the great difficulty in securing a self-colored race entirely
free from spotted individuals. Most self-colored races, even when bred
for many generations from self-colored ancestors exclusively, will pro-
duce an occasional individual bearing a few hairs or a patch of hairs of
some other color, or of white.

Among the guinea-pigs kept by the natives near Arequipa, I observed
an occasional animal having a rough or resetted coat. This variety is
known to fanciers in Europe and the United States under the name
Abyssinian. (See Castle, 1905.) It is said, on the authority of
Geoffrey Saint-Hilaire, to have been introduced from Peru into Europe
about the year 1872 in a rough-coated, long-haired individual received
at the Jardin d'Acclimatation, Paris. In conformity with this account

5



6 INHERITANCE IN GUINEA-PIGS.

it may be said that the rough-coated long-haired variety has ever since
its introduction been called by fanciers " Peruvian." I saw no long-
haired individuals, either rough-coated or smooth, among the guinea-
pigs kept by the natives at Arequipa, and the short-haired rough-coated
ones observed had imperfectly developed rosettes, much inferior to
the best standard-bred resetted Abyssinians of fanciers in Europe and
the United States. For this reason I infer that no particular attention
was given to this character in the breeding of the guinea-pigs which I
saw, though this may very likely have been done in other parts of the
country. But the unit-character variation which is responsible for the
resetted condition of the coat in Abyssinian guinea-pigs was plainly
represented in the stocks kept by the natives in Arequipa and needed
only selection to bring it up to the standards of fanciers.

Eight independent mendelizing unit-character variations had been
recognized as affecting the coat characters of guinea-pigs up to this
time. Six of these were represented among the four or five dozen
guinea-pigs which I actually saw in the cabins of natives, the other
two unit characters being (1) the long-haired variation which, as
already noted, is said to have been brought originally from Peru to
Europe; and (2) the brown variation which first came to the notice
of fanciers in England about 1900 and was certainly in existence before
that time in the United States, as I can state from personal knowledge.
It is uncertain whether or not this last variation had already occurred
in Peru and was thence transferred to Europe, but it is certain that all
the other 7 had done so, and it is very probable that this also originated
in Peru. Further, a ninth wholly independent unit-character variation
(presently to be described, viz, the pink-eyed variation) has made its
appearance in stocks of domesticated guinea-pigs obtained by me at
Arequipa in 1911 and by my colleague, Professor C. T. Brues, at Luna,
in 1912. So it is clear that this variation also is widely disseminated
among domesticated guinea-pigs kept by the natives in Peru and which
have never been in the hands of European fanciers at all.

It can be stated, therefore, with probable correctness, that the guinea-
pig has undergone in domestication more extensive variation in color
and coat characters than any other mammal, and that this variation
has occurred almost if not quite exclusively under the tutelage of the
natives of Peru. This conclusion points either to a great antiquity
of the guinea-pig as a domesticated animal or to more rapid evolution by
unit character variation than by other natural processes.

That the natives do give careful attention to the selection of animals
for breeding is shown by the following incident : In the cabin near the
observatory, where I first saw guinea-pigs in Peru, and where I ulti-
mately secured two pairs of animals, one of which I brought back with
me, I observed a very large individual which I desired to purchase,
and though other individuals were offered me at a very reasonable price,



GUINEA-PIGS IN PERU. 7

this particular one could not be had because, I was assured, he was the
"padre" (sire) of the entire family. Size seemed to be the point
especially emphasized in the breeding of guinea-pigs hi this cabin, as
would naturally be the case when the animals formed the meat-supply
of the family, as they do now among the native poor of Peru and doubt-
less have done since ancient times.

But the chief object of my journey to Peru was the study not of the
domesticated guinea-pigs of the country, but of their wild progenitors.
Accordingly special efforts were made to secure specimens of the wild
cavy, which Professor Bailey had found to be abundant hi the locality.
Once or twice, when riding along a road between irrigated fields, I had
seen a cavy scurry to cover in a pile of rocks; further, I had observed
droppings of the animals in the rocky wall of a cattle corral in an
alfalfa field. But how to capture the animals alive was a problem
which baffled immediate solution. It seemed likely that the natives
would know better how to go about this than I did. Accordingly word
was passed around among the near-by villages that a good price would
be paid at the observatory for wi!4 cavies, either alive or dead.
Within a few hours boys began to arrive with the coveted specimens
and for the next week I was kept busy preparing skins and saving bones
of the animals which were received dead, or making cages and caring
for such as arrived alive. In this way 11 cavies (all I could hope to
transport safely) and about a dozen skins were soon secured, and
preparations were made for the return journey. In due time the
journey was accomplished, and with such success that three new races
of guinea-pigs were added to our experimental stocks, viz, (1) a wild
species, the probable ancestor of the domesticated guinea-pig, identified
as Cavia cutleri Bennett; (2) a feral race from lea, probably identical
with that described by Von Tschudi; (3) domesticated guinea-pigs,
such as are at present kept by the natives of Peru.



8 INHERITANCE IN GUINEA-PIGS.



HYBRIDIZATION EXPERIMENTS WITH CAVIA CUTLERI.
LIFE HISTORY OF CAVIA CUTLERI.

The primary object of my journey to Peru was to secure representa-
tives of the wild species of cavy, Cavia cutleri Bennett, known to exist
there. Four pairs of these animals captured at Arequipa were suc-
cessfully installed in cages at the Bussey Institution in January 1913.

One of the males soon died without leaving descendants; the other
7 animals (4 females and 3 males) produced offspring in captivity, which
have continued to breed succesfully, though the stock has at times
been seriously reduced by disease in cold weather. Three generations
of descendants have been reared from the original stock of 7 animals.
Together they number 100 individuals, of which 47 are males and 53
females. All are very uniform in color, size, general appearance, and
behavior.

Their color is a dull leaden gray-brown, well adapted to escape notice
amid the arid surroundings of their native habitat. The fur is agouti-
ticked and the belly light, but the yellow of the ticking and belly is so
pale as to resemble a dirty white or very light cream shade. The color
is much paler than that of the Brazilian species, Cavia rufescens, studied
by Detlefsen. The fur is also finer and softer, in which respect it
resembles the guinea-pig. The size of C. cutleri is about the same as
that of C. rufescens, and between one-third and one-half that of the
guinea-pig. The maximum weight of an adult male is about 525 grams ;
that of a domesticated male guinea-pig obtained in Arequipa (of 1002)
is nearly three times this amount.

In wildness Cavia cutleri is very much like C. rufescens. The animals
live contentedly in small cages, 2 feet 6 inches square, but invariably
retreat under their box or conceal themselves in the hay if anyone
approaches.

The extreme savageness toward each other of individuals of Cavia
cutleri makes it difficult to rear large numbers of them in captivity. It
is seldom possible to keep more than a single pair in a cage together
for any length of tune. Two adult males will not five together peace-
ably under any circumstances, and if two females are placed together
in a cage with one male persecution of one female by the other usually
follows. Even when the young are allowed to grow up in the same
cage with their parents, family dissensions are likely to arise as soon as
the young become mature.

The period of gestation (minimum interval between litters) averages 3
or 4 days shorter than in guinea-pigs, being 60 to 70 days, and the number
of young to a litter varies from 1 to 4. Fifty-three litters born in captivity
include exactly 100 young, an average of 1.89 young to a litter. The
size of litter occurring most frequently is 2, which has been recorded



CAVIA CUTLERI.



9



TABLE 1. Number and size of litters produced by each mother, Cavia cutleri.



Mother and date of her birth.


Date of litter.


Size of
litter.


Mother's
age at
birth of
young.


Days
since
last
litter.


9 2 (caught wild) ; born March 1911 (?)


Mar. 5, 1913


2


months
24




9 3 (caught wild) ; born May 1911 (?)


June 28, 1913
Aug. 29, 1913
Nov. 4, 1913

May 29, 1912


2
2
2

3


27
29
31

12


62
67


9 5 (caught wild) ; born Jan. 1910 (?)


Oct. 3, 1912
Dec. 26, 1912
July 5, 1913
Dec. 15, 1913

July 12, 1912


3
1
3
1

3


17
20
26
32

18




9 6 (caught wild) ; born Jan. 1910 (?)


Sept. 12, 1912
Nov. 15, 1912
Jan. 22, 1913

Sept. 6, 1912


3
3
2

3


20
22

24

20


62
64
68


9 11; May 29, 1912


Sept. 26, 1912


1


4




9 15; July 12, 1912


Dec. 10, 1912


2


5




926; Sept. 6, 1912 ,.


Feb. 17, 1913
June 30, 1913
Oct. 1, 1913
Aug. 15, 1914
Dec. 2, 1914

July 5, 1912


1
3
2
2
1

1


7
12
15
25
29

10


69


927; Sept. 6, 1912


Sept. 4, 1912
Nov. 4, 1912

Apr. 25, 1913


2
2

1


12
14

7


61
61


9 36; Oct. 3, 1912


June 25, 1913
Aug. 25, 1913

June 17, 1913


1
1

1


9
11

8


61
61


942; Nov. 15, 1912


Oct. 16, 1913
Aug. 3, 1914
Nov. 2, 1914

July 26, 1913


4
2
2

2


12
22
25

8




965; Jan. 22, 1913


Sept. 20, 1913
Aug. 25, 1914
Nov. 2, 1914

July 26, 1913


2
2
2

2


10
21
24

6


56
69


966; Jan. 22, 1913


Nov. 1, 1913
Dec. 27, 1913

June 25, 1913


2
3

2


9
11

5


56


9 79; March 5, 1913


Aug. 29, 1913
June 28, 1913


2
1


7
3|t


65


9 118; June 28, 1913


Sept. 4, 1913
Nov. 4, 1913


2
1


6
4


68


9 124; June 30, 1913


Jan. 5, 1914
Nov. 1 1913


1
3


6
4


62


9129; July 5, 1913


Dec. 27, 1913


2


6




9 184; Sept. 4, 1913


Mar. 1, 1914
Mar. 15, 1914


1
1


8
6


64


9224; Oct. 16, 1913


May 18, 1914
July 20, 1914

July 30, 1913


1
2

1


8
10

9


64
63


9 241 ; Nov. 4, 1913


Dec. 8, 1913
Jan. 12, 1915


1
2


14
14















10



INHERITANCE IN GUINEA-PIGS.



24 times; litters of 1 have been recorded 18 times, litters of 3, 10 times,
and a litter of 4 once. Factors which influence size of litter are evi-
dently age and state of nourishment of the mother. Table 2 shows the
relation of age of mother to size of litter. Very young mothers (age
4 months or less) have only 1 young at a birth. The females become
sexually mature at a very early age, as do female guinea-pigs. Well-
nourished females may breed at 2 months of age, when they are less
than half-grown, full growth not being attained until they are 12 or 13
months old. Females over 4 months but under 12 months of age
produce usually 1 or 2 young at a birth, rarely 3; those which are 1 or
2 years old produce the maximum number of young, usually 2 or 3,
rarely 1 or 4. After the age of 2 years the number of young again

TABLE 2. Relation between age of mother and size of litter, Cavia cuileri.



Age of mother
in months.


Size of litters and number of
each size.


Age of mother
in months.


Size of litters and number of
each size.


1 in
litter.


2 in

litter.


3 in

litter.


4 in
litter.


1 in
litter.


2in
litter.


3 in

litter.


4 in
litter.


4


3


2
3
1
1
1
2


1
1




12 to 15


1


3
1
2
6
2


2
2
3
1


1


5


16 to 19


6


1
3
3
2
1
1


20 to 23


1


7


24 to 27


8


28 to 31


1
1


9


32


10


Total litters. . .


11


18


24


10


1





decreases to 1 or 2. The oldest female known to have borne young
(one of the original stock) had at the time been in captivity over 2
years and her estimated age was 32 months. None of the females
born in captivity has given birth to young at a more advanced age
than 29 months. Our records accordingly indicate that females rarely
breed after they have attained the age of 1\ years. The duration of
the breeding period in the case of males is more extended. It is prob-
able that males do not attain sexual maturity quite so early as females,
for females may breed when less than 2 months old, but we have no
evidence that males can breed before they are 3 months old. 1 But the
capacity to breed once attained continues indefinitely. One male
(cT4) caught wild in December 1911 and estimated then to have been
6 months old is still siring young, more than 3 years after his capture,
being, it is estimated, nearly 4 years old.

Females are capable of breeding again immediately after the birth


1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Online LibraryWilliam E. (William Ernest) CastleStudies of inheritance in guinea-pigs and rats → online text (page 1 of 20)
Using the text of ebook Studies of inheritance in guinea-pigs and rats by William E. (William Ernest) Castle active link like:
read the ebook Studies of inheritance in guinea-pigs and rats is obligatory.

Leave us your feedback | Links exchange | RSS feed 

Online library ebooksread.com © 2007-2014