Reese N E, Boyce W M, Gardner I A, Nelson D M
Department of Pathology, Microbiology, and Immunology, University of California, Davis 95616, USA.
J Med Entomol. 1996 Sep;33(5):835-8. doi: 10.1093/jmedent/33.5.835.
Thirteen morphologic characters were evaluated on Psoroptes cuniculi (Delafond) mites to determine if measurements for these variables were influenced by the use of different fixatives and varying periods of fixation. Morphologic structures composed primarily of chitin (outer opisthosomal setal lengths and right 3rd tarsal pedicle length) were not affected by either fixative type or duration of fixation. In contrast, alcohol and formalin fixation both resulted in significant reductions (P < 0.05) in mean body size measurements when compared with mites mounted in Hoyer's medium without prior fixation. The largest reduction in size was seen in mites fixed for the longest period, but there was no apparent association between size reduction and increasing concentration of alcohol or formalin. Surprisingly, when mites were remeasured 4 yr later, Hoyer's mounting medium was found to have had the opposite effect of fixation and caused an increase in body size. Mites mounted in Hoyer's medium without prior fixation had significantly increased body lengths, whereas mites mounted in Hoyer's following fixation in alcohol and formalin had significant increases in both body length and posterior body width. Our results indicate that fixation and mounting can significantly influence the morphometric analysis of mites and other arthropods. We recommend that morphometric studies be conducted using consistent methodology to reduce experimental bias, and these methodologies be reported in publications dealing with morphometric analyses.
对兔痒螨（德拉方）螨的13个形态学特征进行了评估，以确定这些变量的测量是否受到不同固定剂的使用和不同固定时间的影响。主要由几丁质组成的形态结构（体后半部外侧刚毛长度和右第3跗节蒂长度）不受固定剂类型或固定时间的影响。相比之下，与未经预先固定而装在霍耶氏介质中的螨相比，酒精和福尔马林固定均导致平均体型测量值显著降低（P < 0.05）。在固定时间最长的螨中观察到最大的尺寸减小，但尺寸减小与酒精或福尔马林浓度增加之间没有明显关联。令人惊讶的是，4年后对螨进行重新测量时，发现霍耶氏装片介质具有与固定相反的效果，并导致体型增大。未经预先固定而装在霍耶氏介质中的螨体长显著增加，而在酒精和福尔马林中固定后装在霍耶氏介质中的螨体长和体后半部宽度均显著增加。我们的结果表明，固定和装片可显著影响螨类和其他节肢动物的形态测量分析。我们建议使用一致的方法进行形态测量研究，以减少实验偏差，并在涉及形态测量分析的出版物中报告这些方法。
