期刊
PHYSIOLOGICAL AND BIOCHEMICAL ZOOLOGY
卷 75, 期 2, 页码 145-154出版社
UNIV CHICAGO PRESS
DOI: 10.1086/339388
关键词
-
The evolution of reptilian viviparity (live bearing) from oviparity (egg laying) is thought to require transitional stages of increasingly longer periods of embryonic development in utero, that is, longer periods of egg retention by the gravid female. Studies on sceloporine lizards demonstrate that embryonic responses to egg retention that is extended beyond the time of normal oviposition range from developmental arrest to normal development. The present study was designed to test the hypothesis that O-2 availability is the proximate factor that determines the rate and degree of development that reptilian embryos undergo in utero. Eggs of Sceloporus undulatus were incubated under conditions of low (LOX), normal (NOX), and high (HOX) oxygen both early and late in development. The LOX treatment consistently had a negative effect on development in terms of embryonic differentiation and growth, length of incubation, egg mortality, and hatchling size. Moreover, the LOX treatment had a stronger negative effect later in development than earlier in development. The results support the hypothesis that limited oxygen availability in utero acts as a developmental constraint. They further indicate that selection for extended egg retention, per se, will not lead to viviparity unless each incremental increase in the duration of egg retention is coupled with selection for traits (e.g., vascularity of oviduct and chorioallantois, hemoglobin oxygen affinity, etc.) that enhance O-2 availability to embryos. Such selection would be the most efficacious in cold climates where the effects of hypoxia would be the least likely to limit embryonic development.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据