COLD-BLOODED VERTEBRATES 



1053 



that ovarian hormones are secreted chiefly 

 or only during the breeding season), as does 

 the ei)itheliinn of the urogenital fossa, and 

 seasonal development of all structures there- 

 after, of course, fails to occur (Regamey, 

 1935). Ovariectomy of the snake Natrix 

 causes rapid oviducal atrophy (Takewaki 

 and Hatta, 1941). 



XVI. Effects of Estrogens 

 and Projjesterone 



Female sex hormones when experimentally 

 administered are usually very effective in 

 modifying the reproductive systems of fish, 

 amphibians, and reptiles. 



Fish 



Estrogen is reported to have stimulated 

 spermatogenesis when injected into imma- 

 ture male carp (Castelnuovo, 1937) but to 

 have suppressed spermatogenesis in Platy- 

 poecilus (Cohen, 1946). In the loach, Mis- 

 gurnus, the injection of estrone or estradiol 

 benzoate caused discharge of sperm and in- 

 hibition of spermatogenesis in the male, 

 whereas ovarian development was inhibited 

 in the female. Suppression of the release of 

 gonadotrophin from the pituitary was sug- 

 gested as the underlying mechanism (Egami, 

 1954b, c). The liver of Oryzias and Gaster- 

 osteus during the breeding season is sexually 

 dimorphic in structure, color, and weight. 

 Administration of estrogen to males at this 

 time results in transformation of their livers 

 to the female type (Egami, 1955a; Oguro, 

 1956) . Curiously, in Platypoecilus estradiol 

 and estradiol benzoate had opposite effects. 

 In males less than 18 mm. long, estradiol did 

 not affect the testes but the anal fin grew 

 slightly. In older males, large gonopodia de- 

 veloped and the testes were stimulated. The 

 same hormone caused ovarian degeneration 

 and growth of gonopodia in females. Estra- 

 diol benzoate, however, inhibited testes and 

 ovaries and caused no gonopodial develop- 

 ment (Ta Volga, 1949). 



Pregneninolone, sometimes regarded as a 

 "bisexual" hormone, induced partial mas- 

 culinization of immature female Platypoe- 

 cilus, and evoked typical female body size 

 and bodv index in immature males (Cohen, 

 1946). 



In the years before World War II much 

 interest centered on some experiments on 

 the bitterling, Rhodeus amarus. At breeding 

 time the urogenital papilla of the European 

 cyprinid hypertrophies into a rather lengthy 

 ovipositor; with the latter, eggs are depos- 

 ited in fresh water mussels (Bretschneider 

 and Duyvene de Wit, 1947 ) . In 1932 Fleisch- 

 mann and Kann reported that the injection 

 of follicular hormone into the female bitter- 

 ling during the nonbreeding period resulted 

 in lengthening of the ovipositor. Injections 

 of salt solution or anterior lobe hormone did 

 not give this result. Further, implantation 

 of the bitterling ovary in a castrate female 

 mouse, it was stated, produced estrus. This 

 seemed to show that ovipositor growth was 

 due to estrogen from the fish's ovaries. Ehr- 

 hardt and Kiihn (1933, 1934) found that the 

 addition to 1 liter aquarium water of 5 ml. 

 pregnancy urine, one tablet (150 mouse 

 units) ovarian hormone, or urine extracts 

 also caused ovipositor lengthening. Injec- 

 tion, or addition to aciuarium water, of Pro- 

 gynon (estradiol) produced ovipositor 

 growth in females outside the breeding sea- 

 son and in castrate males (Fleischmann and 

 Kann, 1934). The idea developed that the 

 response might be sensitive and specific 

 enough to provide the basis for a bio-assay 

 for estrogens or progesterone. There is little 

 doubt that the ovipositor responds to rather 

 small amounts of these hormones. ^'•' How- 

 ever, it was discovered that ovipositor 

 growth may also be evoked by adrenal cor- 

 tical hormones, purified male hormones, and 

 male urine, as well as by various alcohols 

 and other solvents and at least one inor- 

 ganic comiiound.-" de Groot and Duyvene 

 de Wit (1949), who have vividly described 

 the oviposition of Rhodeus, found that the 

 ovipositor rapidly elongates in response to 

 copulin, a male hormone which, they postu- 

 lated, is released into the aquarium water 

 by the male bitterling. The bitterling assay 



^'' Floischinanu and Kann, 1935; Duyvene de 

 Wit, 1940; Bretschneider and Duyvene de Wit, 

 1947; van der Veen and Duyvene de Wit, 1951. 



-"Sziisz, 1934; Barnes, Kanter and Klawans. 

 1936; Kleiner, Weisman and Mi.?likind, 1936; 

 Duyvene de Wit, 1938, 1939; Glaser and Ranftl, 

 1938; Fleischmann and Kann, 1938; van Koersveld, 

 1948. 



