Animal Physiology and Neurobiology, Department of Biology, KU Leuven, Leuven, Belgium.
PLoS One. 2023 Aug 1;18(8):e0289326. doi: 10.1371/journal.pone.0289326. eCollection 2023.
Entomopathogenic nematodes, including Steinernema spp., play an increasingly important role as biological alternatives to chemical pesticides. The infective juveniles of these worms use nictation-a behavior in which animals stand on their tails-as a host-seeking strategy. The developmentally-equivalent dauer larvae of the free-living nematode Caenorhabditis elegans also nictate, but as a means of phoresy or "hitching a ride" to a new food source. Advanced genetic and experimental tools have been developed for C. elegans, but time-consuming manual scoring of nictation slows efforts to understand this behavior, and the textured substrates required for nictation can frustrate traditional machine vision segmentation algorithms. Here we present a Mask R-CNN-based tracker capable of segmenting C. elegans dauers and S. carpocapsae infective juveniles on a textured background suitable for nictation, and a machine learning pipeline that scores nictation behavior. We use our system to show that the nictation propensity of C. elegans from high-density liquid cultures largely mirrors their development into dauers, and to quantify nictation in S. carpocapsae infective juveniles in the presence of a potential host. This system is an improvement upon existing intensity-based tracking algorithms and human scoring which can facilitate large-scale studies of nictation and potentially other nematode behaviors.
昆虫病原线虫，包括斯氏线虫属，作为化学农药的生物替代品，其作用变得越来越重要。这些线虫的侵染期幼虫利用停息行为——动物用尾巴支撑身体站立的行为——作为一种寻找宿主的策略。自由生活的线虫秀丽隐杆线虫的发育等同的 dauer 幼虫也会停息，但这是一种寄生物或“搭便车”到新的食物源的方式。已经为秀丽隐杆线虫开发了先进的遗传和实验工具，但停息行为的手动评分耗时较长，阻碍了对这种行为的理解，而停息所需的纹理化基质也会使传统的机器视觉分割算法受挫。在这里，我们提出了一种基于 Mask R-CNN 的跟踪器，能够在适合停息的纹理化背景上分割秀丽隐杆线虫 dauer 幼虫和斯氏线虫侵染期幼虫，并提出了一种用于评分停息行为的机器学习管道。我们使用我们的系统表明，高密度液体培养物中的秀丽隐杆线虫的停息倾向在很大程度上反映了它们向 dauer 幼虫的发育，并且可以量化潜在宿主存在时斯氏线虫侵染期幼虫的停息行为。与现有的基于强度的跟踪算法和人工评分相比，该系统是一种改进，可以促进停息和潜在其他线虫行为的大规模研究。
