Brodkin Marc, Vatnick Itzick, Simon Martin, Hopey Hollyann, Butler-Holston Kristine, Leonard Michelle
Department of Biology, Science Division, Widener University, Chester, Pennsylvania 19013, USA.
J Exp Zool A Comp Exp Biol. 2003 Jul 1;298(1):16-22. doi: 10.1002/jez.a.10270.
The decline in frog populations is a well-recognized worldwide phenomenon and infectious disease has been implicated as a major cause in the global decline of amphibian populations. Rana pipiens are disappearing from many habitats where they used to flourish, and environmental acidification has been considered as a possible contributor to this disappearance. We present a model that integrates the results of several experiments on the effects of acid exposure on natural resistance and mortality of adult Rana pipiens. These studies suggest that different components of the natural defense mechanisms of these frogs have different acid sensitivities. We have shown previously that exposure to pH 5.5 leads to a reduction in splenic white blood cell number, viability, and to colonization of the spleen with both Gram positive and Gram negative bacteria. In this paper we show that exposure to pH 6.0 did not affect the number or viability of splenic white blood cells but did result in colonization of the spleen by bacteria. We also show that cold exposure by itself does not cause a systemic bacterial infection in adult Rana pipiens, but acid stress following cold exposure does. The data presented in this paper provide empirical evidence to support the hypothesis that acid stress may be a contributor to the decline of Rana pipiens in the northeastern region of the United States.
青蛙数量的减少是一个全球公认的现象，传染病被认为是两栖动物数量全球减少的主要原因。北美豹蛙正在从许多它们曾经繁盛的栖息地消失，环境酸化被认为可能是导致这种消失的一个因素。我们提出了一个模型，该模型整合了多项关于酸暴露对成年北美豹蛙自然抵抗力和死亡率影响的实验结果。这些研究表明，这些青蛙自然防御机制的不同组成部分具有不同的酸敏感性。我们之前已经表明，暴露于pH 5.5会导致脾脏白细胞数量减少、活力下降，并导致脾脏被革兰氏阳性菌和革兰氏阴性菌定植。在本文中，我们表明暴露于pH 6.0不会影响脾脏白细胞的数量或活力，但确实会导致细菌在脾脏定植。我们还表明，单独的冷暴露不会在成年北美豹蛙中引起全身性细菌感染，但冷暴露后的酸应激会导致感染。本文所呈现的数据提供了实证证据，以支持酸应激可能是美国东北部北美豹蛙数量减少的一个因素这一假设。
