New Method for Automatic Body Length Measurement of the Collembolan, Folsomia candida Willem 1902 (Insecta: Collembola)

The collembolan, Folsomia candida, is widely used in soil ecotoxicology. In recent years, growth rate of collembolans has become as frequently used endpoint as reproduction rate in ecotoxicological studies. However, measuring collembolan body sizes to estimate growth rate is a complicated and time-consuming task. Here we present a new image analysis method, which facilitates and accelerates the body length measurement of the collembolan Folsomia candida. The new software package, called CollScope, consists of three elements: 1) an imaging device; 2) photographing software; 3) an ImageJ macro for image processing, measurement and data analysis. We give a complete description of the operation of the software, the image analyzing process and describe its accuracy and reliability. The software with a detailed usage manual is attached as Supplementary Material. We report a case study to demonstrate that the automated measurement of collembolan body sizes is highly correlated with the traditional manual measurements (estimated measuring accuracy 0.05 mm). Furthermore, we performed a dose-response ecotoxicity test using cadmium-sulfate by using CollScope as well as classical methods for size measurement. Size data measured by CollScope or manually did not differ significantly. Furthermore the new software package decreased time consumption of the measurements to 42% when tested on 35 animals. Consequently, methodological investigations performed in this study should be regarded as a recommendation for any other routine dose-response study where body growth is an endpoint.

弹尾虫（collembolan）白符跳虫（Folsomia candida）被广泛应用于土壤生态毒理学研究领域。近年来，弹尾虫的生长速率已成为生态毒理学研究中与繁殖速率同等常用的观测终点。然而，通过测定弹尾虫体长以估算其生长速率的工作复杂且耗时。本文提出一种新型图像分析方法，可简化并加速白符跳虫（Folsomia candida）的体长测定流程。这款名为CollScope的新型软件包包含三个组成部分：1）成像装置；2）拍摄软件；3）用于图像处理、参数测定与数据分析的ImageJ宏脚本。本文完整阐述了该软件的操作流程、图像分析过程，并对其准确性与可靠性进行了系统说明。本软件附带详细使用手册，以补充材料形式随文附上。本研究通过案例分析证实，弹尾虫体长的自动化测定结果与传统人工测定结果具有极高相关性（测定精度预估为0.05 mm）。此外，本研究分别采用CollScope与传统体长测定方法，针对硫酸镉开展了剂量-反应生态毒理学测试。两种方法获取的体长数据无显著统计学差异。在对35个样本进行测试时，该新型软件包将测定耗时缩减至原方法的42%。因此，本研究开展的方法学探究可作为以体长生长为观测终点的常规剂量-反应研究的参考方案。