Microbial Infection, Egg Viability, and the Onset of Incubation in Birds

鸟类的微生物感染、卵子活力和孵化开始

• 批准号: 0517549
• 负责人: Steven Beissinger
• 金额: --
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0517549&HistoricalAwards=false
• 关键词: Microbial; Infection; Egg; Viability; Onset

Microbial Infection, Egg Viability, and the Onset of Incubation in birdsSteven R. Beissinger University of California at BerkeleyBirds can lay no more than one egg a day and influence the synchrony of hatching by determining when to initiate incubation. Yet parents often opt for a pattern of asynchronous hatching that leads to death of last-hatched young due to competition with siblings for food. Most previous studies have assumed embryos are protected within their shells and waiting for bird parents to begin incubation in a manner that creates optimal hatching patterns. An alternative idea is that asynchronous hatching may be the result of a trade-off between the benefits of laying a large clutch to the parent and the costs of delaying incubation to the survival of early-laid eggs. Recent work in tropical forests provides the first evidence that microbes can infect unincubated eggs and that infection greatly reduces hatching success. Preliminary studies in a temperate environment also found high rates of microbial penetration in unincubated eggs. This project will examine how microbes may shape the onset of incubation in birds from three complementary perspectives. 1) The researchers will study the consequences of microbial infection prior to full incubation, approached by measuring the rate of microbial penetration of wild bird eggs exposed to temperate environments, and by examining whether penetration by microbes reduces hatching success. 2) Microbial processes on the eggshell that affect the chance of infection will be studied by determining how microbial communities on eggshells change during incubation, and if change is due to microclimate differences from the incubating female or due to chemical defenses on the feathers or skins of birds. 3) Parental defenses against microbial infection will be examined by studying whether parents disinfect egg contents by partially incubating them, and determining if this increases hatching success. The investigators will test whether parents differentially endow eggs in antibiotic properties by laying order, and whether this provides greater protection. Identifying the impact of microbes on egg viability may provide a new paradigm for understanding the onset of incubation, partial incubation, and other avian reproductive behaviors. Experiments will be conducted at the Hopland Research and Extension Center in Mendocino County, CA, with Western Bluebirds, Tree Swallows, Violet Green Swallows and Oak Titmice. Differences in antimicrobial defenses of eggs within and among species will be tested on these species and on Green-rumped Parrotlets (in Venezuela), Pearly-eyed Thrashers (in Puerto Rico), Blue-winged Teal (in North Dakota), and American Coots (in North Dakota). This project includes a significant training component involving an Asian American female doctoral candidate, a postdoctoral student, and significant numbers of postgraduate and undergraduate students, all of whom will be trained in field and lab skills in behavioral ecology, microbiology and experimental design. Minority recruitment efforts will use Berkeley's program in minority education to attract other candidates. Applying the results of the project to captive rearing of birds may have important impacts. Hatching success of captive-bred endangered birds is almost always much lower than natural incubation, perhaps because partial incubation is rarely employed. The poultry industry must manage microbes to prevent infection of eggs being stored for breeding stock. Both groups will benefit if this project identifies key microbial processes and antimicrobial defenses of wild birds.

鸟类的微生物感染、鸡蛋活力和孵化开始加州大学伯克利分校的史蒂文·R·贝辛格大学鸟牌每天只能下一个蛋，并通过决定何时开始孵化来影响孵化的同步性。然而，由于与兄弟姐妹争夺食物，父母经常选择一种异步孵化的模式，这会导致最后孵化的幼崽死亡。以前的大多数研究都假设胚胎在壳内受到保护，并等待鸟类父母开始孵化，以创造最佳的孵化模式。另一种想法是，异步化孵化可能是在为双亲产下大窝的好处和推迟孵化的成本与早产卵存活之间进行权衡的结果。最近在热带森林的研究首次证明，微生物可以感染未孵化的鸡蛋，而且感染会大大降低孵化成功率。在温带环境中的初步研究也发现，未孵化鸡蛋中的微生物渗透率很高。这个项目将从三个互补的角度研究微生物如何影响鸟类孵化的开始。1)研究人员将在完全孵化之前研究微生物感染的后果，方法是测量暴露在温带环境中的野生鸟蛋的微生物渗透率，并检查微生物的渗透率是否会降低孵化成功率。2)将通过确定蛋壳上的微生物群落在孵化过程中如何变化，以及变化是由于孵化中的雌鸟的小气候差异还是由于鸟类羽毛或皮肤上的化学防御而导致的，来研究影响感染机会的蛋壳上的微生物过程。3)父母对微生物感染的防御将通过研究父母是否通过部分孵化鸡蛋内容物来消毒，并确定这是否会增加孵化成功率来检查父母对微生物感染的防御。调查人员将测试父母是否通过产卵顺序赋予鸡蛋不同的抗生素特性，以及这是否提供了更大的保护。识别微生物对鸡蛋存活率的影响可能为理解孵化、部分孵化和其他鸟类繁殖行为的开始提供一个新的范式。实验将在加利福尼亚州门多西诺县的霍普兰研究和推广中心进行，研究对象包括西方蓝鸟、树燕、紫罗兰绿燕和橡树山雀。将在这些物种以及绿腰鹦鹉(在委内瑞拉)、珠眼短尾鹦鹉(在波多黎各)、蓝翼天鹅(在北达科他州)和美洲库茨(在北达科他州)上测试这些物种和物种之间鸡蛋抗菌防御的差异。该项目包括一个重要的培训部分，涉及一名亚裔美国女博士生、一名博士后学生以及大量的研究生和本科生，他们都将接受行为生态学、微生物学和实验设计方面的实地和实验室技能培训。少数族裔招聘工作将利用伯克利的少数族裔教育计划来吸引其他候选人。将该项目的成果应用于圈养鸟类可能会产生重要的影响。人工饲养的濒危鸟类的孵化成功率几乎总是比自然孵化低得多，可能是因为很少使用部分孵化。家禽业必须对微生物进行管理，以防止被储存为种畜的鸡蛋受到感染。如果该项目确定野生鸟类的关键微生物过程和抗菌防御措施，这两个群体都将受益。