PHOTOPERIODISM AND SEASONAL BREEDING IN THE TROPICS

热带地区的光周期和季节性繁殖

• 批准号: 3324623
• 负责人: FRANKLIN H BRONSON
• 金额: $ 10.28万
• 依托单位: UNIVERSITY OF TEXAS AT AUSTIN
• 依托单位国家: 美国
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-05-01 至 1992-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3324623
• 关键词: Marsupialia; anticonvulsants; biological clocks; bioperiodicity; photobiology; photostimulus; reproduction; seasons; sex cycle

An immense amount of effort has been expended in understanding the photoperiodic control of reproduction in mammals. Despite this effort, an ignorance of great proportion still remains. Over three quarters of all mammals live in the tropics, yet the state of photoperiodic regulation remains tied exclusively to animal models drawn from the one quarter living in the temperate zone. We don't know if mammals have the capacity to react reproductively to the small variation in daylength they experience in the tropics. If they do have this capacity we don't know if they use it to regulate their reproduction seasonally. If this capacity is absent we don't know why in genetic and neuroendocrine terms it is absent. The present proposal speaks to all of these questions. Three species of small mammals will be trapped in a seasonally harsh environment in Venezuela where there is one hour of annual variation in daylength: a mouse-sized marsupial that is a rigid seasonal breeder; a rodent that breeds year around, and a rodent that is intermediate in its seasonality. Laboratory bred offspring of these animals will challenged to mature or short daylengths, both with and without added social influence. Where appropriate, critical daylength will be determined and compared with that existing when spermatogenesis and oogenesis start and stop seasonally in the wild. Thus we will learn whether or not these animals are reproductively photoresponsive and if some of them actually use this capacity. Species found to be unresponsive to photoperiod will be tested to determine why they are not responsive. Initial experiments will focus on the way they measure daylength, how they secrete melatonin, how they react to this hormone, and whether or not daylength influences the negative feedback sensitivity of LH secretion to gonadal steriods. Species found to be heterogenously responsive to photoperiod will be subjected to experiments designed to (a) see if reproductive photoresponsiveness can be reestablished in these animals via genetic selection; (b) explore quantitatively the genetic basis for the heterogeneity; and (c) determine how the loci of concern relate to neuroendocrine mechanisms. The results of all of this will be a new set of principles and animal models that are more truly representative of mammals as a whole.

人们花费了大量的努力来了解 哺乳动物繁殖的光周期控制。 尽管 这一努力，很大一部分的无知仍然存在。 超过 四分之三的哺乳动物生活在热带地区， 光周期调节仍然仅限于动物 从生活在温带的四分之一人口中抽取的模型。 我们不知道哺乳动物是否有能力 它们经历的日照长度的微小变化 在热带地区 如果他们真的有这种能力，我们不知道他们是否 用它来调节它们的季节性繁殖。 如果这个能力是 我们不知道为什么在遗传和神经内分泌方面， 缺席。 本提案涉及所有这些问题。 三种小型哺乳动物将被困在一个季节性 委内瑞拉的恶劣环境，每年有一个小时的 昼长的变化：一种老鼠大小的有袋动物， 季节性繁殖动物;一种全年繁殖的啮齿动物， 它的季节性是中等的。 实验室培育的后代 这些动物将受到成年或短日照的挑战， 无论是否有社会影响力。 在适当的情况下， 临界日长将被确定并与之进行比较 存在于精子发生和卵子发生开始和停止时 季节性地在野外。 因此，我们将了解这些 动物的繁殖对光敏感，如果其中一些 实际上是利用这种能力。 将对发现对光周期无反应的物种进行试验， 确定他们没有反应的原因。 初步实验将 关注它们测量白昼长度的方式，它们如何分泌 褪黑激素，它们对这种激素的反应， 日长影响LH的负反馈敏感性 分泌到性腺类固醇中。 发现物种异质 对光周期的反应将进行实验 目的是（a）看看生殖光反应是否可以 通过遗传选择在这些动物中重新建立;（B）探索 从数量上说明异质性的遗传基础;以及（c） 确定关注的位点与神经内分泌的关系 机制等 所有这一切的结果将是一套新的原则和动物 更真实地代表哺乳动物的模型， 整体