Valls J Hunter, Mills Nathan E
Department of Biology, Harding University, Searcy, AR 72149, USA.
J Exp Biol. 2007 Jul;210(Pt 14):2430-5. doi: 10.1242/jeb.003541.
The spotted salamander Ambystoma maculatum breeds in shallow freshwater pools and imbeds its eggs within a common outer jelly matrix that can limit oxygen availability. The eggs are impregnated with the unicellular alga Oophilia amblystomatis, which produces oxygen during the day but consumes oxygen at night. This daily cycle of algal oxygen production drives a diurnal fluctuation of oxygen partial pressure (PO2) within the eggs, the magnitude of which depends on the distance of an egg from the exterior of the jelly matrix and on the ambient PO2 of the pond. We subjected A. maculatum eggs to fluctuating oxygen levels with a variable minimum PO2 and an invariable maximum, to simulate natural conditions, and measured differences in developmental rate, day and stage at hatching, and egg capsule conductance (GO2). Lower minimum PO2 slowed development and resulted in delayed, yet developmentally premature hatching. GO2 increased in all treatments throughout development, but PO2 had no detectable effect on the increase. Intermittent hypoxia caused comparable but less pronounced developmental delays than chronic hypoxia and failed to elicit the measurable change in GO2 seen in ambystomatid salamander eggs exposed to chronic hypoxia.
斑点钝口螈（Ambystoma maculatum）在浅淡水池塘中繁殖，并将卵嵌入共同的外部胶状基质中，这可能会限制氧气的供应。这些卵中含有单细胞藻类——钝口螈嗜卵藻（Oophilia amblystomatis），该藻类在白天产生氧气，但在夜间消耗氧气。藻类氧气产生的这种日常循环驱动了卵内氧分压（PO2）的昼夜波动，其波动幅度取决于卵与胶状基质外部的距离以及池塘的环境PO2。我们让斑点钝口螈的卵暴露于具有可变最低PO2和恒定最高PO2的波动氧气水平下，以模拟自然条件，并测量发育速率、孵化时的天数和阶段以及卵囊传导率（GO2）的差异。较低的最低PO2会减缓发育，并导致孵化延迟，但发育上过早。在整个发育过程中，所有处理组的GO2都增加了，但PO2对这种增加没有可检测到的影响。间歇性缺氧导致的发育延迟与慢性缺氧相当，但程度较轻，并且未能引发在暴露于慢性缺氧的钝口螈科蝾螈卵中观察到的GO2的可测量变化。
