Developmental determination of fish jaw protrusion mechanics

这个项目的目标是了解进化成功的发展基础。将进行实验，以确定头骨发育的变化如何改变有史以来最有用的生物力学能力之一：下颌突出。现存的脊椎动物中有三分之一属于两个鱼种，它们独立地进化出在进食过程中上颌骨从面部向前伸出的能力。这两个谱系具有非常相似的突出机制，在两种情况下，上颌形状的微小变化都会显着改变突出距离。由于对不同食物类型的专一性，具有广泛突起的鱼与那些具有有限突起的鱼相比，占据了不同的生态位。颌骨突出直到发育后期才出现，通常是在明显的变态之后。甲状腺激素信号是变态和骨形成的主要调节因素。初步数据表明，甲状腺激素水平的变化可以对突起能力的发展产生显著的影响。人们对发育后期颅骨形成的控制知之甚少，但正是在这一时期，大多数生物开始以允许它们占据成年生态位的方式重塑自己的身体。这个项目有可能阐明一个具有极端进化意义的发展时期，但尚未受到太多研究关注。这项研究是与一位高中生物教师兼科学家合作进行的。这项工作的各个方面都被融入到他们的生物学课程的所有单元中，学生们正在课堂上进行一项关于鱼头骨发育的研究--鱼在进食过程中下巴突出与非凡的进化成功有关。本研究将通过研究颅骨形态发生的后期发育控制，进一步整合进化功能形态学和发育生物学领域。关于颅骨力学的进化，人们知道很多，但大多数研究都是对成人标本的研究。也有大量关于头骨发育的文献，但大多数研究都考察了早期生命阶段。成人的颅骨力学出现在发育后期从幼年到成人的过渡阶段，因此了解影响颅骨进化的发育因素需要对这一时期进行研究。初步数据表明，幼年饮食和甲状腺激素信号通过影响前颌骨的形成，是决定前颌骨前突能力的重要因素。前颌骨形状决定了最大的前伸能力。本课题将探讨前颌骨形态变异的发育决定因素，以更好地了解颌骨前突的进化规律。研究将考察斑马鱼和两个具有不同突出能力的密切相关物种的颌骨突出的发育控制。该项目有以下目标：1)确定甲状腺激素的产生是否影响斑马鱼颌骨突起的发育；2)确定摄食不同生物力学饲料是否影响斑马鱼及其两个近缘物种的颌骨突起发育；3)确定甲状腺激素产生的变化是否影响斑马鱼颌骨发育中的mRNA表达水平；以及4)确定与颌骨突起能力相关的遗传位点。

This project is targeted at understanding the developmental underpinnings of evolutionary success. Experiments will be carried out to determine how changes in skull development alter one of the most useful biomechanical abilities to ever evolve: Jaw protrusion. One third of living vertebrates belong to two fish lineages that independently evolved the ability to project their upper jaws forward from the face during feeding. These two lineages have remarkably similar protrusion mechanisms and in both cases small changes in upper jaw shape dramatically alter protrusion distance. Fishes with extensive protrusion occupy different ecological niches than those that have limited protrusion due to specialization on different food types. Jaw protrusion does not appear until late development, usually after a pronounced metamorphosis. Thyroid hormone signaling is a major regulator of both metamorphosis and bone formation. Preliminary data demonstrate that changes in thyroid hormone levels can have pronounced effects on the development of protrusion ability. Very little is known about the controls of cranial formation during late development, yet it is during this period that most organisms begin to remodel their bodies in ways that allow them to occupy their adult ecological niches. This project has the potential to illuminate a developmental period of extreme evolutionary significance that has not yet received much investigative attention. This research is being performed in collaboration with a high-school biology teacher-scientist. Aspects of the work are being incorporated in to all units of their biology course and students are performing a study of fish skull development in the classroomFish jaw protrusion during feeding is linked to extraordinary evolutionary success. This study will further integrate the fields of evolutionary functional morphology and developmental biology by investigating the late-developmental controls of skull morphogenesis. A great deal is known about the evolution of skull mechanics, but most studies have examined adult specimens. There is also a large literature on skull development, but most studies have examined early life stages. Adult cranial mechanics arise during juvenile to adult transitions in late development, so understanding the developmental factors that have shaped skull evolution requires study of this time period. Preliminary data indicate that juvenile diet and thyroid hormone signaling are important determinants of protrusion ability via their affects on the formation of the premaxillary bone. Premaxilla shape determines maximum protrusion ability. This project will investigate the developmental determinants of premaxilla shape variation in order to better understand the evolvability of jaw protrusion. Research will examine the developmental controls of jaw protrusion in the zebrafish and two closely related species with different protrusion abilities. This project has the following aims: 1) to determine if thyroid hormone production affects the development of zebrafish jaw protrusion; 2) to determine if feeding on biomechanically different diets affects protrusion development in the zebrafish and two closely related species; 3) to determine if altered thyroid hormone production affects mRNA expression levels in developing zebrafish jaws; and 4) to identify genetic loci associated with jaw protrusion ability.