COLD-BLOODED VERTEBRATES 



1059 



arc rt'tainecl in the o\-idu('t, and atrophy 

 after oviposition. 



Corpora lutea occur in both ox'iparuu.s and 

 viviinirous lizards.-" The f^uggestion that a 

 hormone from the corpus luteum })revents 

 further follicular growth and ovulation was 

 made by Cunningham and Smart (1934) 

 and Panigel (1951b). Boyd (1940), calling 

 attention to the corpora lutea of oviparous 

 reptiles, offers the hypothesis that in this 

 vertebrate class the corpus luteum may 

 have evolved before the i^lacenta and only 

 subsequently acquired an endocrine func- 

 tion related to viviparity icf. discussion of 

 corpus luteum function in fish and amphibi- 

 ans). The gestation period in Xantusia lasts 

 about three months; by histologic criteria 

 the corpus luteum appears functional for 

 the first two months (Miller, 1948, 1951). 

 Bilateral ovariectomy or destruction of 

 the corpora lutea at the beginning of preg- 

 nancy in Lacerta vivipara does not inter- 

 rupt gestation or embryonic development 

 (Panigel, 1953, 1956). Hypophysectomy 

 also fails to affect embryonic growth, but 

 both this operation and ovariectomy make 

 parturition difficult, as does the administra- 

 tion of progesterone (Panigel, 1956). 



Corpora lutea have been found in the 

 ovaries of many genera of snakes.-^*^ Corpora 

 may persist during part or all of gestation. 

 Ovariectomy during early and middle preg- 



■" Oviparous: Amphiholunis (Weekes, 1934), 

 Hemidactylus (Dutta, 1944), and Lacerta viridis 

 (Cunningham and Smart, 1934). Viviparous: 

 Hoplodactylus (Boyd, 1940), Xatitusia (Miller, 

 1948, 1951, 1954), Egernia, Lygosoma, and Tiliqua 

 (Weekes, 1927a, 1934), Lacerta (Zuotoca) vivipara 

 (Hett, 1924; Regamey, 1935; Panigel, 1951a), and 

 Anguis (Lucien, 1903; Cunningham and Smart, 

 1934). 



*' Oviparous: Xeiiodon (P'raenkel and Martins, 

 1939). Ovoviviparous: Coronella (Rollinat, 1898) 

 and Dryophylax and Tomodon (Valle and Souza, 

 1942). Viviparous: Natrix {Tropidonotiis) (Rol- 

 Hnat, 1898; Rahn, 1939, 1940b; Bragdon, 1946, 1951 ; 

 Bragdon, Lazo-Wasem, Zarrow and Hisaw, 1954). 

 Potamophis (Rahn, 1939), Storeria (Ralin, 1939), 

 Thamnophis (Rahn, 1939, 1940a, b; Cieslak, 1945; 

 Bragdon, 1946, 1951, 1952; Bragdon, Lazo-Wasem. 

 Zarrow and Hisaw, 1954), Enhydrina (Samuel, 

 1944; Kasturirangan, 1951), Hydropliis (Samuel, 

 1944), Bothrops and Crotrdus (Fraenkel and Mar- 

 tins, 1938, 1939; Fraenkel, Martins, and Mello, 

 1940; Porto, 1941; Rahn, 1942; Valle and Valle, 

 1943). Natrix, Thamnophis, and Crotalus are re- 

 garded as ovoviviparous tiy some investigators. 



nancy of \'arious species of the colubrid 

 snakes Xntrix, Thamnophis, and Storeria 

 was followed by resorption of the embryos 

 or the birth of dead embryos. The injection 

 of progesterone after ovariectomy did not 

 prevent death of the embryos. Ovariectomy 

 late in jiregnancy seemed to have no effect. 

 Hypophysectomy interfered with pregnancy 

 at any stage. Injection of posterior pituitary 

 extract did not influence early or middle 

 pregnancy, but induced delivery thereafter 

 (Clausen, 1940). Removal of all corpora 

 lutea from pregnant Bothrops and Crotalus 

 resulted in cessation of embryonic develop- 

 ment (Fraenkel Martins and Mello, 1940), 

 but, as Bragdon ( 1951 ) suggests, the high 

 postoperative mortality leaves some doubt 

 whether embryonic death was due to loss 

 of the corpora lutea or to other factors. On 

 the other hand, Rahn (1939, 1940b) cas- 

 trated 23 pregnant Thamnophis and Natrix 

 at various stages of jiregnancy and found 

 live young at autopsy up to 25 days later. 

 In Xatrix and Thamnophis neither hy- 

 pophysectomy as early as the first week af- 

 ter ovulation nor ovariectomy interfered 

 with pregnancy (Bragdon, 1942, 1946, 1951. 

 1952). Both operations did interfere with 

 parturition. Bragdon concludes that in these 

 snakes corpora lutea are not essential for 

 the maintenance of pregnancy. Panigel's ex- 

 tensive study of the viviparous lizard iZoo- 

 toca vivipara (1956) supports this opinion. 



Bio-assay of alcoholic extracts of the 

 corpora lutea of Bothrops and Crotalus re- 

 vealed progestin (Porto, 1941), as did bio- 

 assays of plasma from Natrix and Tham- 

 nophis {Bragdon, Lazo-Wasem, Zarrow 

 and Hisaw, 1954). In the latter study, the 

 results, expressed in Progesterone Equiva- 

 lents, were as follows. In two donors with 

 inactive ovaries and two with pre-ovulatory 

 follicles, plasma levels were 0.3, 1.0, 0.3, 

 and 0.3 /xg./ml. Other assays showed, at 

 early ovulation, 2.0 /i,g./ml.; end of first 

 third of pregnancy, 4.0 and 4.0 /xg./ml.; end 

 of second third of jiregnancy, 4.0 and 6.0 

 fig./ml.; full term, 8.0 /xg./ml. 



It is also of interest that bio-assay of 

 plasma from two snakes with testes in full 

 development gave Progesterone Equivalent 

 values of 0.3 and 1.0 /xg./ml. (Bragdon, 

 Lazo-Wasem, Zarrow and Hisaw, 1954). 



