RECENT FINDINGS IN THE INHIBITION OF AVIAN SPERMATOGENESIS 
Bernard C. Wentworth 
1. Introduction. 
The list of agents, both physical and chemical, which 
affect spermatogenesis, includes changes in environment, nutri- 
tion, genetics, short wave radiation and a host of pharmacologi- 
cally active substances. 
The primordial germ cells in the male chick embryo 
begin to divide actively on or after the thirteenth day of in- 
cubation (Swift, 1916). This early germinal cell division is 
not a characteristic of all avian species. Kirschbaun and Ringaen 
(1936) found in the House Sparrow (Passer domesticus), which has 
been used extensively in the study of spermatogenesis, that the 
germinal cells begin to divide only a few weeks before the first 
spermatozoa mature. Like the spermatozoa of other animals, 
avian sperm cells normally do not show motility within the 
testes. The capacity to move is gradually acquired during pas- 
sage through theepididymis and vasa deferentia (Anderson, 1922; 
Munro, 1938), a process which requires from 1 to 4 days in the 
chicken, depending on mating activity. 
The spermatozoa of passerine birds are distinguished 
by one outstanding feature, namely, their predominantly spiral 
configuration. 
2. Environment 
The observation by Rowan (1925), that the testes of 
the Junco (Junco hyemalis) can be stimulated during the winter 
by increasing the day length with artificial light has stimu- 
lated extensive investigation. The seasonal nature of repro- 
ductive activity in birds is due to the extrinsic factor of 
light affecting the gonads which acts through the mediation of 
the anterior pituitary gland (Benoit, 1935). 
In practically all wild birds, reproductive activity 
is a seasonal phenomenon. Breeding generally occurs during the 
spring and early summer. The gonads then regress to a quiescent 
state and remain inactive until the approach of the breeding 
season of the following year. Domestic birds do not conform 
strictly to this cyclic pattern, although as Parker and McSpadden 
(1943) demonstrated, domestic chickens produce the greatest 
density and volume of semen in April at a mean témperature of 
520F, They also found that the lowest fertility was obtained in 
September at a mean temperature of 68°F. Gamal et al. (1959) 
found the lowest semen quality in December and January. 
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