Department of Biological Sciences, University of Rhode Island, Kingston, Rhode Island, USA.
Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil.
J Morphol. 2024 Aug;285(8):e21754. doi: 10.1002/jmor.21754.
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.
硬骨鱼类的机械感觉侧线（LL）系统一直是比较形态学研究和行为与生理流动感应能力分析的焦点，但在任何一个物种中，其形态和发育都没有得到详细研究。在这里，我们使用活荧光染色（4-Di-2-ASP）、扫描电子显微镜、μCT 和透明和染色来可视化神经丘和颅 LL 管发生的过程，描述了布鲁克鳟鱼（Salvelinus fontinalis）的颅 LL 系统的胚胎后发育。我们检查了 LL 发育的时间与鲑鱼延长的生命周期之间的关系，以及潜在的生态影响。LL 系统由七个含有管神经丘（CN）和四个皮肤表面神经丘（SN）的管组成。在幼鱼（幼虫）阶段，CN 和 SN 的数量和大小增加。当管形态发生开始时，CN 数量稳定，但直到幼鱼（幼鱼）阶段，SN 数量仍在增加。CN 变得比 SN 更大更长，但在两种类型的神经丘中，感觉毛细胞的相对面积在个体发育过程中减小。神经丘中心的管形态发生在幼鱼（卵黄囊幼虫）中开始，当它们从砾石巢中游到水柱中（受精后约 4 个月），此时卵黄囊吸收完成并开始外源性进食。管系列内和管系列之间的管形态发生是异步进行的，直到受精后约 8 个月（幼鱼期）才完成。在 LL 系统和相关的真皮骨中使用三个特征来识别其他肉鳍鱼类的同源物，并考虑 LL 管减少的进化，从而证明了鲑鱼对 LL 进化研究的价值。布鲁克鳟鱼延长的生命周期和游泳时开始的管形态发生预计将对这些关键行为和生态过渡时的神经丘功能产生影响。
