BACKGROUND The experimental approach to the evolution and development of the vertebrate skeleton has to a large extent relied on "direct-developing" amniote model organisms, such as the mouse and the chicken. These organisms can however only be partially informative where it concerns secondarily lost features or anatomical novelties not present in their lineages. The widely used anamniotes Xenopus and zebrafish are "indirect-developing" organisms that proceed through an extended time as free-living larvae, before adopting many aspects of their adult morphology, complicating experiments at these stages, and increasing the risk for lethal pleiotropic effects using genetic strategies. RESULTS Here, we provide a detailed description of the development of the osteology of the African mouthbrooding cichlid Astatotilapia burtoni, primarily focusing on the trunk (spinal column, ribs and epicentrals) and the appendicular skeleton (pectoral, pelvic, dorsal, anal, caudal fins and scales), and to a lesser extent on the cranium. We show that this species has an extremely "direct" mode of development, attains an adult body plan within 2 weeks after fertilization while living off its yolk supply only, and does not pass through a prolonged larval period. CONCLUSIONS As husbandry of this species is easy, generation time is short, and the species is amenable to genetic targeting strategies through microinjection, we suggest that the use of this direct-developing cichlid will provide a valuable model system for the study of the vertebrate body plan, particularly where it concerns the evolution and development of fish or teleost specific traits. Based on our results we comment on the development of the homocercal caudal fin, on shared ontogenetic patterns between pectoral and pelvic girdles, and on the evolution of fin spines as novelty in acanthomorph fishes. We discuss the differences between "direct" and "indirect" developing actinopterygians using a comparison between zebrafish and A. burtoni development.

中文翻译：

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牛膝菌的骨骼发育-直接生长模型的硬骨体计划的发展。

背景技术脊椎动物骨骼进化和发育的实验方法在很大程度上依赖于“直接发育”的羊膜动物模型生物，例如小鼠和鸡。然而，这些生物仅在涉及其谱系中不存在的继发丧失的特征或解剖学新颖性的情况下才部分提供信息。广泛使用的羊膜非洲爪蟾和斑马鱼是“间接发育”的生物，它们作为自由幼体在很长的时间内进行，然后采用其成年形态的许多方面，使这些阶段的实验复杂化，并增加使用致死性多效作用的风险遗传策略。结果在这里，我们提供了非洲口育丽鱼科丽鱼阿斯通蒂罗非鱼的骨病学发展的详细描述，主要集中在躯干（脊柱，肋骨和中央）和阑尾骨架（胸，骨盆，背，肛门，尾鳍和鳞片）上，而在颅骨上则较少。我们显示该物种具有极为“直接”的发育模式，在受精后2周内达到成年人体计划，而仅依靠蛋黄供应，并且不会经历延长的幼体期。结论由于该物种的饲养容易，生成时间短且该物种适合通过显微注射进行遗传靶向策略，因此我们建议使用这种直接发育的丽鱼科鱼将为研究脊椎动物提供有价值的模型系统计划，特别是在涉及鱼类或硬骨性状的演变和发展方面。根据我们的研究结果，我们评论了颈尾鳍的发展，胸鳍和骨盆带之间共同的个体发育模式以及棘棘鱼在新棘鱼中的进化。我们通过使用斑马鱼和burtoni发育之间的比较讨论“直接”和“间接”发展放线翅目之间的差异。