DISSERTATION RESEARCH: Experimental miniaturization of guppy offspring

这个项目将研究在两个可能的原因中，饲养困难或发展限制，哪一个是设定鱼类尺寸下限的原因。这一发现将有助于检验生命史进化理论，并为海洋渔业招募限制提供发展和功能方面的见解。个体的大小跨越了许多数量级，但受物理原理的限制，在大和小的极端上是有限的。随着生物变得越来越小，它们周围的世界对它们的运动变得越来越有阻力，这被认为限制了鱼类后代的大小，不小于4.5毫米。这种大小的鱼幼虫很难进食。另外，出生时的体型也与发育成熟所需的时间有关。本项目将使用孔雀鱼作为模型系统来测试这些替代方案。该项目包括本科生指导和研究培训。此外，该项目将利用孔雀鱼作为当地高中课堂上进化论和生态学教学的模型。该项目涉及两个小型化操作：水动力和发展。在第一个操作中，研究人员将使用右旋糖酐增加水的粘度，从而有效地缩小后代的尺寸，但不是发育。在第二次操作中，研究人员将从发育中的胚胎中取出蛋黄，从而使胚胎小型化并提前分娩。因为孔雀鱼是活的，卵黄操作需要在体外培养孔雀鱼胚胎，以便进入卵黄囊。用拉出的毛细管，卵黄将被移除，这样孔雀鱼胚胎将被迫在大约4.4毫米的外源喂养。将比较水动力和发育操作之间的摄食率，以确定在以悬浮食物为食时，大小或成熟度是否是限制特征。喂食试验将使用高速视频拍摄，以测量颚部运动学，并确定在吸入喂食过程中喂食装置运行的雷诺数。

This project will examine which of two possible causes, difficulty in feeding or constraints on development, are responsible for setting the lower limit for the size of fish. The findings will help test theories of life-history evolution, and provide developmental and functional insights into limitations on recruitment in marine fisheries. The size of individuals spans many orders of magnitude, but is constrained at the large and small extremes by principles of physics. As organisms become smaller, the world surrounding them becomes more resistive to their movements, which are thought to limit the size of fish offspring to no smaller than 4.5 mm. At this size, fish larvae experience difficulty feeding. Alternatively, size at birth is also related to the time it takes to reach maturity. This project will test these alternatives using guppies as a model system. The project incorporates undergraduate mentoring and research training. Additionally, the project will utilize the guppy as a model for the teaching of evolution and ecology within local high school classrooms. This project involves two miniaturization manipulations: hydrodynamic and developmental. In the first manipulation, the researchers will increase the viscosity of water using dextran, thereby effectively miniaturizing the offspring in size, but not development. In the second manipulation, the researchers will remove yolk from the eggs of developing embryos, thereby miniaturizing and prematurely delivering the young. Because guppies are live bearing, the yolk manipulation requires culturing guppy embryos in vitro in order to access the yolk sac. With a pulled capillary tube, yolk will be removed such that guppy embryos will be forced to feed exogenously at approximately 4.4 mm. Feeding rates will be compared between the hydrodynamic and developmental manipulations to determine if size or maturity is the limiting feature when feeding on suspended food items. Feeding trials will be filmed using high-speed video to measure jaw kinematics and determine the Reynolds number under which the feeding apparatus is operating during suction feeding.