Developmental determination of fish jaw protrusion mechanics

该项目旨在了解进化成功的发展基础。将进行实验以确定颅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。三分之一的现存脊椎动物属于两种鱼类，它们独立地进化出了在进食时将上颚从脸部向前伸出的能力。这两个谱系有非常相似的突出机制，在这两种情况下，上颌形状的微小变化都会显著改变突出距离。由于对不同食物类型的专业化，具有广泛突出的鱼类与具有有限突出的鱼类占据不同的生态位。下颌突出直到发育晚期才出现，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子。初步数据表明，甲状腺激素水平的变化对突出能力的发展有显著的影响。在发育后期，我们对颅骨形成的控制知之甚少，但正是在这一时期，大多数生物开始重塑它们的身体，使它们能够占据它们成年后的生态位。这个项目有可能阐明一个具有极端进化意义的发育时期，但尚未得到太多的研究关注。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纳入了他们生物学课程的所有单元，学生们正在课堂上对鱼类头骨的发育进行研究。鱼类在进食过程中颚部的突出与非凡的进化成功有关。本研究将进一步整合进化功能形态学和发育生物学领域，研究颅骨形态发生的发育后期控制。关于头骨力学的演变，我们已经知道了很多，但大多数研究都是在检查成年标本。也有大量关于头骨发育的文献，但大多数研究都是在生命早期阶段进行的。成人颅骨力学出现在发育后期从少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，幼鱼的饮食和甲状腺激素信号通过影响上颌前骨的形成而成为突出能力的重要决定因素。前颌的形状决定了最大的突出能力。本项目将研究前颌形状变化的发育决定因素，以便更好地了解下颌突出的可进化性。研究将检查斑马鱼和两个具有不同突出能力的密切相关物种的下颌突出的发育控制。本项目的目的是：1)确定甲状腺激素的产生是否影响斑马鱼颌突的发展；2)确定生物力学上不同的饵料是否会影响斑马鱼和两个近缘物种的突起发育；3)确定甲状腺激素分泌的改变是否影响发育中的斑马鱼颌部mRNA的表达水平；4)鉴定与下颌突出能力相关的基因位点。

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.