182 



Embryogenesis: Preparatory Phases 



spermatozoa are in a highly active condition 

 (see Lillie, '19; Gray, '28). Along with in- 

 creasing the activity of the spermatozoa the 

 egg water may also increase the rate of 

 oxygen uptake. For example, Gray ('28) 

 found increases ranging from 212 to 425 

 per cent in the sea urchin Echinus esculen- 

 tus, and similar increases have been found 

 by Tyler ('48a) in the keyhole limpet 

 Megathura crcnulata. Hartmann et al. ('39) 

 reported that the agent responsible for the 

 activation of the spermatozoa in Arbacia 

 pustulosa is the pigment echinochrome 

 which is present in the eggs of this species 

 of sea urchin. However, attempts to confirm 

 this were imsuccessful both in a species of 

 sea urchin whose eggs do not contain echino- 

 chrome and in one whose eggs are so pig- 

 mented (Tyler, '39b; Cornman, '41). Tyler 

 and Fox ('39, '40) found the activating 

 agent in the egg waters of Strongylocentrotus 

 and of Megathura to remain associated, after 

 dialysis and precipitation, with the large 

 molecular substance that has aggkitinating 

 action (see below) on the sperm. While such 

 association has also been reported by Corn- 

 man ('41), Kuhn and Wallenfels ('40), and 

 Vasseur and Hagstrom ('46), these workers 

 find the activating agent to be at least par- 

 tially dialyzable. Many years ago Clowes 

 and Bachman ('21) found that distillates of 

 Arbacia egg water would activate the sperm 

 and this was confirmed more recently by 

 Cornman ('41). It would appear, then, that 

 the activating agent in egg water is normally 

 bound to the agglutinating agent, from 

 which it may be split off as a relatively small 

 molecular substance, but its exact chemical 

 nature has not, as yet, been determined. 



LIFE SPAN OF THE GAMETES 



The conditions of insemination in most 

 animals require that the gametes remain in 

 a fertilizable state for a period of time fol- 

 lowing release from the gonads. It is of in- 

 terest, then, to inquire into the factors 

 involved in the aging of the gametes. 



Senescence of Spermatozoa. In some species 

 of animals, such as the bat, the honeybee 

 and certain terrestrial isopods (Vandel, '41) 

 the sperm may survive for periods of several 

 months to several years in the female genital 

 tract. Apart from such special cases the 

 usual life span of shed sperm is of the order 

 of several hours to a few days (see Hart- 

 man, '39). An important factor that is known 

 to affect markedly the functional life span of 

 sperm is dilution. Many workers have shown 



(see Morgan, '27; Gray, '28; Rothschild, 

 '48a, b, c) that the duration of life varies 

 directly with the concentration of the sus- 

 pension. The relative or complete lack of 

 motility of sperm in undiluted semen of sea 

 urchins and other animals has frequently 

 been attributed to a relatively high tension 

 of carbon dioxide. Rothschild ('48b) has 

 shown, however, that lowering the carbon 

 dioxide tension does not induce motility, 

 whereas increasing the oxygen tension ac- 

 tivates the spermatozoa. By exposing the 

 semen alternately to nitrogen and oxygen 

 the spermatozoa could be made alternately 

 inactive and active. Hartmann, Schartau and 

 Wallenfels ('40) had proposed that immo- 

 bility in semen, as well as subsequent senes- 

 cence of sea urchin sperm, was due to a 

 substance, termed androgamone I, that is 

 liberated by the spermatozoa. This view 

 stood in contradiction to observations of 

 Gray ('28) and Hayashi ('45) showing that 

 sea urchin sperm were as motile when di- 

 luted with seminal plasma as with sea water. 

 Rothschild ('48c) showed in addition that 

 the supernatant of a dense two-hour sperm 

 suspension, which is supposed to contain 

 androgamone I, had no inhibitory effect on 

 respiration. These and other experiments 

 show that senescence is not attributable to 

 substances, such as the hypothetical andro- 

 gamone I, diffusing into the medium from 

 the sperm and that the "dilution effect" 

 cannot be explained on the basis of a dilu- 

 tion of such inhibitor. 



More recently it has been shown (Tyler 

 and Atkinson, '50) that the life span of sea 

 urchin sperm can be considerably extended 

 by addition of any one of a number of amino 

 acids to the suspension. Similar results have 

 been obtained in birds and mammals (Lorenz 

 and Tyler, '51; Tyler and Tanabe, '52). It 

 was shown (Tyler and Rothschild, '51) that 

 the amino acid is not utilized metabolically, 

 although it has effects on the respiratory 

 metabolism of the sperm and even enables 

 sea urchin sperm to remain motile anaerobi- 

 cally, whereas they ordinarily die promptly 

 in absence of oxygen. The results suggested 

 that the amino acids act by binding certain 

 trace metals present in the sea water. Tests 

 with other kinds of metal-chelating agents 

 such as ethylenediaminetetraacetic acid 

 (Versene*), diethyldithiocarbamic acid, 8-hy- 

 droxyquinoline, and a-benzoinoxime have 

 given similar prolongation of the life span 

 of the sea urchin spermatozoa (Tyler, '53). 



* Trade name of Bersworth Chemical Co., Fram- 

 ingham, Mass. 



