HERPETOLOGY OF ZUNI MOUNTAINS — GEHLBACH 



265 



That paedogenesis occurs in larger Zuiii larvae is evidenced by 

 the fact that at least one spechnen (USNM 8240, 103 mm. snout-vent) 

 contains many large yolked eggs. Environmental factors believed 

 to cause neoteny in A. tlgrinum have been widely reviewed. In 

 the present study, transformation, both natural and experimentally 

 tested, seemed to be initiated by shrinkage of the pond environment 

 associated with increased temperatures and decreased oxygen supply. 



MISC. DIPTERA 

 LARVAE 

 ADULT AQUATIC 

 COLEOPTERA 



NOTONECTID 

 NYMPHS 



fHIRUDINEA 27o 



,ANISOPTERA NAIADS 2% 



Figure 6.— Food (in percent of volume) of 36 larvae of Ambysloma tigrinum nebulosum, 

 35-45 mm. in snout-vent length, collected July 16, 1957, at 7800 feet. 



Shufeldt (1885) cited similar evidence for metamorphosis in Zuni 

 larvae as did Durham (1956, p. 220) for A. tigrinum from northern 

 Arizona. Schuierer (1958) said that, among other things, a well 

 oxygenated, constant water supply was impHcated in maintaining 



neoteny. 



Most Zuni larvae forced to gulp air at the surface m laboratory 

 jars metamorphosed within four weeks of capture regardless of size. 

 Specimens under similar conditions remained larval in form when 

 provided with an artificial oxygen supply. Some larvae, approxi- 



