844 



SPERM, OVA, AND PREGNANCY 



Fig. 14.16. Somewhat flattened, living rat ovum 

 with 13 accessory spermatozoa in the perivitelline 

 space and a single fertilizing spermatozoon in the 

 ooplasm. X 450. 



broken vip into globules that are dispersed 

 throughout the egg cytoplasm. The remains 

 of the axial filament have been observed in 

 the 2-cell stage of the bat (Van der Stricht, 

 1902), guinea pig (Lams, 1913), and vole 

 (Austin, 1957) and as late as the blastocyst 

 stage of the rat (Blandau and Odor, 1952). 

 Van der Stricht (1902) and Lams (1913) 

 believed that, in the 2-cell stage of the 

 bat and guinea pig, the sperm tail is pres- 

 ent in only one of the blastomeres. This 

 was partially substantiated for the rat by 

 Blandau and Odor, who noted that in 58 

 per cent of 329 2-celled ova a greater por- 

 tion of the axial filament was located within 

 one blastomere and that in 12 per cent it 

 lay entirely within a single blastomere. 

 In the remaining 30 per cent, the axial 

 filament was equally divided between the 

 two. The significance of the various posi- 

 tions of the axial filament in the cleaving 

 egg is not clear. It may represent merely 

 the mechanical difficulty of moving an inert 

 body. Of greater significance is the meaning 

 of the cytoplasmic contribution of the sperm 

 midpiece to the developing embryo in those 

 animals in which its component parts are 

 despersed within the vitellus. 



J. SUPERNUMERARY SPERMATOZOA AND 

 POLYSPERMY IN MAMMALIAN OVA 



The terms "supernumerary sperm," "ac- 

 cessory sperm," and "polyspermy" have 

 been used to mean either the penetration 



of more than one spermatozoon into the 

 ooplasm with the subseciuent development 

 of multiple sperm nuclei, or the location of 

 one or more spermatozoa in the perivitelline 

 space. Inasmuch as polyspermy is used 

 widely in the literature of invertebrates 

 to designate the penetration of the ooplasm 

 by multiple spermatozoa, it is suggested 

 that this meaning should be retained for 

 mammals and that the terms supernumerary 

 or accessory spermatozoa should be utilized 

 just to indicate the presence of nonfertiliz- 

 ing spermatozoa in the perivitelline space. 



Intact spermatozoa have been observed 

 many times within the perivitelline spaces 

 of ova of various mammals (Sobotta and 

 Burckhard, 1910, Gilchrist and Pincus, 

 1932, Odor and Blandau, 1949, Austin, 

 1951b, in the rat; Lams and Doorme, 1908, 

 Lewis and Wright, 1935, in the mouse; Van 

 der Stricht, 1910, in the bat; Hcnsen, 1876, 

 Lams, 1913, in the guinea pig; Hill and 

 Tribe, 1924, in the cat; Heajie, 1886, in the 

 mole; Harvey, 1958, in the i)ika; Pincus 

 and Enzmann, 1932, Chang, 1951c, in the 

 rabbit; Hancock, 1959, in the pig). Quanti- 

 tative data on the presence of supernumer- 

 ary spermatozoa are available for the rat 

 and several strains of mice. Austin (1953) 

 and Odor and Blandau (1951) found that 

 approximately 23 per cent of seminated rat 

 ova contained supernumerary spermatozoa. 

 The number of sperm per egg ranged from 

 1 to 23 (Fig. 14.16). After mating various 

 strains of mice, Braden (1958a, b); and 

 Piko, 1958) reported that the percentage 

 of ova containing more than one sperm 

 was more significantly related to the strain 

 of the male than to the female. Matings 

 with C57 males resulted in a consistently 

 higher number of eggs with more than one 

 sperm, irespective of the strain of the fe- 

 males used. 



Apparently supernumerary spermatozoa 

 have no effect on the rate of development 

 of the ovum. In the rat, at least, the fluids 

 of the perivitelline space offer an environ- 

 ment which is considerably more favorable 

 for these spermatozoa than that of the 

 oviduct. Except for a separation of the 

 head from the neck-piece, the accessory 

 spermatozoa in the rat, at least, show no 

 evidence of cytolysis in any of the de- 



