Section 8 — Cytatoxonomy and Experimental Taxonomy 



8.18. Chromosome Studies of Domestic Mammals. 



J. F. Lopez-Saez and G. Gimenez-Martin 

 (Madrid, Spain). 



In this work the chromosome complement(s) 

 of the horse (Equus caballus), ass (Equus asinus), 

 mule {Equus caballus X Equus asinus), bull (Bos 

 taurus), sheep (Ovis aries), goat (Capra hircus) 

 and domestic pig (Sus scrofa domesticus) are 

 studied. The karyotype of each species is as 

 follows: 



The horse {Equus caballus) 2n = 64. The X 

 chromosome has submedian centromere and is 

 in size the second of the complement ; the Y chro- 

 mosome is telocentric or apparently telocentric, 

 being in the complement two pairs smaller than it. 



The ass (E. asinus) In = 62. The X chromo- 

 some has subterminal centromere and is in length 

 the fourth pair of the complement; the Y chromo- 

 somes, with submedian centromere, is the small- 

 est chromosome. 



The mule (E. caballus, E. asinus) 2« = 63. 

 The male has the X chromosome of the horse and 

 the Y chromosome of the ass; the female has the 

 X chromosome of the horse and the X chromo- 

 some of the ass. 



The bull (Bos taurus) 2n = 60. The sex chro- 

 mosomes are the only ones with metacentric or 

 submetacentric centromere. The X chromosome 

 is the longest of the idiogram and the Y chro- 

 mosome is among the five shortest chromosomes, 

 but it has median centromere. 



The sheep (Ovis aries) 2n = 54. The X chro- 

 mosome is the longest of the telocentric or ap- 

 parently telocentric chromosomes and the Y, 

 also telocentric, is the smallest of the idiogram. 



The goat (Capra hircus) 2n = 60. All chromo- 

 somes are telocentric or apparently telocentric. 

 The X chromosome is the second in the haploid 

 idiogram and the Y is the smallest of the comple- 

 ment 



The pig (Sus scrofa domesticus) 2n = 38. The 

 X chromosome is metacentric and the Y chro- 

 mosome is the smallest of the karyotype. This is 

 characterized by a median centromere. 



8.19. The Karyotype of Normal Pigs and of One 

 Intersex. B. Henricson and L. Backstrom 

 (Stockholm, Sweden). 



The karyotype of a swine intersex has been 

 analyzed in blood leucocytes grown in tissue 

 culture. Also external and internal genitalia have 

 been investigated. 



As the karyotype of normal swine has been 

 described in only a few earlier works, this is also 

 presented here with suggestions for grouping and 

 numerical classification. 



The intersex investigated had a karyotype 

 which contained 36 apparently normal auto- 

 somes with sex chromosomes of the XX type. 



The external genitalia consisted of a vagina 

 with a relatively big clitoris. There were two 

 testicles of about normal size. One was situated 

 in the scrotum, the other was abdominal. No 

 germ cells were present, only Sertoli cells in well- 

 defined tubuli and Leydig cells in the intersti- 

 tium. No ovarial tissue could be detected. Pri- 

 itive ductuli deferentes from the testicles went 

 over in a rather well-developed uterus. 



Pictures are presented. 



8.20. Classification of the Chromosomes of the Mouse 

 Karyotype. Marco Crippa (Rome, Italy). 



Actively proliferating cultures of cells obtained 

 by trypsinization from embryonic kidneys of 

 C3H and albino Swiss mice were submitted to 

 the techniques usually employed for chromosome 

 studies: colchicine and hypotonic treatment, 

 air-drying and orcein staining. By arranging the 

 40 chromosomes of the normal mouse diploid 

 number according to the criterion of decreasing 

 length, it was possible to subdivide them into 

 five distinct groups, each composed by chromo- 

 somes of similar length. The first group includes 

 4 chromosomes, the second 7 chromosomes in 

 the male and 8 in the female, the third 20 chromo- 

 somes, the fourth 6 chromosomes and the fifth 

 3 chromosomes in the male and 2 in the female. 

 According to this classification it seems reason- 

 able to assume that the X chromosome belongs 

 to the second group and the Y chromosome to 

 the fifth group. The X chiomosome was never 

 observed to have any peculiarity like hetero- 

 chromatic traits or secondary constrictions which 

 could differentiate it from the autosomes of the 

 same group. Nor was it possible to identify the 

 Y chromosome within the small chromosomes of 

 the last group. The length of each chromosome 

 was measured and the data obtained were statis- 

 tically evaluated by using the analysis of variance. 

 This analysis showed that the differences in 

 chromosome length among the five groups are 

 highly significant, although a variability among 

 different mitoses is present to a certain extent. 

 Further details concerning the data obtained by 

 the statistical analysis will be discussed. 



8.21. On the Chromosomes of the Geometrid Moths 

 Cidaria. E. Suomalainen (Helsinki, Finland). 



In the species-rich Geometrid moth genus. 



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