The Evolution and Diversification of a Symbiotic Bioluminescence Signaling System

美国自然历史博物馆（American Museum of Natural History）的约翰·斯帕克斯博士（Dr. John Sparks）获得了一笔拨款，用于研究马尾鱼科鱼类（马尾鱼）与发光的海洋原核生物光杆菌（Photobacterium leiognathi）之间共生关系的进化、共同进化相互作用和生物地理学。鱼类宿主丰富，经济上重要，广泛分布在整个印度太平洋地区。这种鱼在其内部的食道环结构中拥有密集的细菌共生体，该结构被称为光器官，为细菌提供氧气和营养，并利用细菌的发光进行各种与捕食、反捕食和性别特异性信号有关的展示。大多数种类的雄马鱼表现出很大的、结构复杂的和物种特有的光器官，而雌马鱼的光器官发育相对较差。推测马尾鱼雄性发光信号的性选择与光器官系统（LOS）的形态多样化和物种形成有关。尽管基于物种特异性雄性信号的两性二态生物发光系统的进化和功能在萤火虫中得到了很好的记录，但在脊椎动物中，人们对这些系统知之甚少。马尾鱼提供了一个很好的系统来解决这些问题。利用DNA序列数据和马尾鱼LOS的表型特征，重构马尾鱼的进化关系，并根据共生关系模式进行研究。该项目将深入了解鱼类发光信号系统的进化，性选择在马尾鱼多样化中的作用，细菌每一代获得的共生中的共同进化相互作用，以及共生在鱼类和细菌的生物地理分布中的作用。该项目将为博士后和学生参与者提供系统学、共生、鱼类学、共同进化和生物地理学领域的实地考察和培训。

A grant has been awarded to Dr. John Sparks of the American Museum of Natural History to examine the evolution, coevolutionary interactions and biogeography of the symbiosis between fishes of the family Leiognathidae (ponyfishes) and the luminous marine prokaryote Photobacterium leiognathi. The fish host is abundant, economically important, and widely distributed throughout the Indo-Pacific. The fish harbors a dense population of the bacterial symbiont in an internal circumesophageal structure, called a light organ, providing the bacteria with oxygen and nutrients, and uses bacterial luminescence in various displays associated with predation, anti-predation and sex-specific signaling. Males of most ponyfish species exhibit greatly enlarged, structurally complex and species-specific light organs, whereas those of females are comparatively poorly developed. It is hypothesized that sexual selection for male luminescence signaling is correlated with morphological diversification of the light organ system (LOS) and speciation in ponyfishes. Although the evolution and functions of a sexually-dimorphic bioluminescent system based on species-specific male signaling are well documented in fireflies, in vertebrates these systems are poorly understood. Ponyfishes provide an excellent system in which to address these questions. The evolutionary relationships of ponyfishes will be reconstructed using DNA sequence data and phenotypic features of the fish's LOS, and examined in light of symbiont patterns of relationship. This project will provide insight into the evolution of luminescence-signaling systems in fishes, the role of sexual selection in ponyfish diversification, coevolutionary interactions in a symbiosis in which the bacterium is acquired with each new generation, and the role of the symbiosis in the biogeographic distribution of the fish and bacterium. The project will provide exposure to fieldwork and training to post-doctoral and student participants in the areas of systematics, symbiosis, ichthyology, coevolution, and biogeography.