Stages of the moult cycle of the amphipod Gammarus pulex have been previously characterised based on the examination of either apolysis of the 3rd dactyl, or the whole body and eye appearance. In the current study the aim was to compare these two established moult staging techniques with a novel X-ray micro-computed tomography (micro-CT) scan method. The micro-CT provides information on the degree of calcification of the external integument and of the internal structures, such as the gastric mill. The degree of calcification is predicted to change during the moult cycle. Successful micro-CT scans were obtained from 80 G. pulex specimens and the radiological appearance of the 28 specimens immediately immersed in 4 % PFA were not different to the 52 specimens stored in 4 % PFA for at least 28 days prior to scanning. These specimens could be classified into moult stages A, B, C, early D or late D based on the degree of calcification. Good agreement was obtained between all three methods of moult stage classification if fresh specimens were used, but if specimens had been preserved in 4% Paraformaldehyde (PFA) for more than 24 hours the loss of colour from the whole body and eye meant these methods were not suitable. This is the first time that a micro-CT method has been used to study G. pulex and shows that this method of moult staging is accurate and reliable.

中文翻译：

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使用 X 射线显微计算机断层扫描研究淡水片脚类动物 Gammarus pulex 的换羽周期

片脚类动物 Gammarus pulex 的蜕皮周期的各个阶段之前已经根据对第三指的分离或整个身体和眼睛外观的检查进行了表征。在目前的研究中，目的是将这两种已建立的换羽分期技术与新型 X 射线显微计算机断层扫描 (micro-CT) 扫描方法进行比较。显微 CT 提供有关外部珠被和内部结构（如胃磨）钙化程度的信息。钙化程度预计会在换羽周期中发生变化。从 80 G. pulex 标本获得了成功的显微 CT 扫描，立即浸入 4% PFA 的 28 个标本的放射学外观与扫描前在 4% PFA 中储存至少 28 天的 52 个标本没有区别。这些标本可根据钙化程度分为换羽期 A、B、C、早期 D 或晚期 D。如果使用新鲜标本，所有三种换羽阶段分类方法都获得了良好的一致性，但如果标本已在 4% 多聚甲醛 (PFA) 中保存超过 24 小时，全身和眼睛的颜色损失意味着这些方法是不合适。这是首次使用显微 CT 方法研究 G. pulex，表明这种换羽分期方法准确可靠。但如果标本在 4% 多聚甲醛 (PFA) 中保存超过 24 小时，全身和眼睛的颜色就会消失，这意味着这些方法不适合。这是首次使用显微 CT 方法研究 G. pulex 并表明这种换羽分期方法准确可靠。但如果标本在 4% 多聚甲醛 (PFA) 中保存超过 24 小时，全身和眼睛的颜色就会消失，这意味着这些方法不适合。这是首次使用显微 CT 方法研究 G. pulex，表明这种换羽分期方法准确可靠。