Abstract：
The mechanosensory lateral line (LL) system of salmonid fishes has been the focus of comparative morphological studies and behavioral and physiological analyses of flow sensing capabilities, but its morphology and development have not been studied in detail in any one species. Here, we describe the post-embryonic development of the cranial LL system in Brook Trout, Salvelinus fontinalis, using vital fluorescent staining (4-Di-2-ASP), scanning electron microscopy, µCT, and clearing and staining to visualize neuromasts and the process of cranial LL canal morphogenesis. We examined the relationship between the timing of LL development, the prolonged life history of salmonids, and potential ecological implications. The LL system is composed of seven canals containing canal neuromasts (CNs) and four lines of superficial neuromasts (SNs) on the skin. CNs and SNs increase in number and size during the alevin (larval) stage. CN number stabilizes as canal morphogenesis commences, but SN number increases well into the parr (juvenile) stage. CNs become larger and more elongated than SNs, but the relative area occupied by sensory hair cells decreases during ontogeny in both types of neuromasts. Neuromast-centered canal morphogenesis starts in alevins (yolk sac larvae), as they swim up into the water column from their gravel nests (~4 months post-fertilization), after which yolk sac absorption is completed and exogenous feeding begins. Canal morphogenesis proceeds asynchronously within and among canal series and is not complete until ~8 months post-fertilization (the parr stage). Three characters in the LL system and associated dermal bones were used to identify their homologs in other actinopterygians and to consider the evolution of LL canal reduction, thus demonstrating the value of salmonids for the study of LL evolution. The prolonged life history of Brook Trout and the onset of canal morphogenesis at swim-up are predicted to have implications for neuromast function at these critical behavioral and ecological transitions.
摘要：
鲑鱼的机械感觉侧线（LL）系统一直是比较形态学研究以及流量感应能力的行为和生理分析的重点，但是它的形态和发育尚未在任何一个物种中进行过详细研究。这里,我们描述了布鲁克鳟鱼颅骨LL系统的胚胎后发育，沙维林，使用活体荧光染色（4-Di-2-ASP），扫描电子显微镜，µCT,以及清除和染色，以可视化神经桅杆和颅骨LL管形态发生的过程。我们研究了LL发育时机之间的关系，鲑鱼的长期生活史，和潜在的生态影响。LL系统由七个包含管神经杆（CN）的管道和皮肤上的四行浅层神经杆（SNs）组成。CN和SN在alevin（幼虫）阶段的数量和大小增加。CN数随着运河形态发生的开始而稳定，但是SN数增加到parr(少年)阶段。CNs比SNs变得更大，更细长，但是感觉毛细胞占据的相对面积在这两种类型的神经腺体的个体发育过程中都会减少。以神经肥大为中心的管形态发生始于alevins（卵黄囊幼虫），当它们从砾石巢游入水柱时（施肥后约4个月），之后，卵黄囊吸收完成，外源喂养开始。运河形态发生在运河系列内部和之间异步进行，直到受精后约8个月（帕尔阶段）才完成。LL系统和相关真皮骨中的三个特征被用来鉴定它们在其他放线体中的同源物，并考虑LL管减少的演变，从而证明了鲑鱼对LL进化研究的价值。预计布鲁克鳟鱼的长期生活史和游泳时运河形态发生的发生将对这些关键的行为和生态转变中的神经肥大功能产生影响。
