Mayagaya Valeriana Simon, Ntamatungiro Alex John, Moore Sarah Jane, Wirtz Robert Andrew, Dowell Floyd Ercell, Maia Marta Ferreira
Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania.
London School of Hygiene & Tropical Medicine, Keppel Street, WC1E 7HT, London, UK.
Parasit Vectors. 2015 Jan 27;8:60. doi: 10.1186/s13071-015-0661-4.
Near-infrared spectroscopy (NIRS) has been successfully used on fresh and RNAlater-preserved members of the Anopheles gambiae complex to identify sibling species and age. No preservation methods other than using RNAlater have been tested to preserve mosquitoes for species identification using NIRS. However, RNAlater is not the most practical preservative for field settings because it is expensive, requires basic laboratory conditions for storage and is not widely available in sub-Saharan Africa. The aim of this study was to test several cheaper and more field-friendly preservation methods for identifying sibling species of the An. gambiae complex using NIRS.
In this study we describe the use of NIRS to identify sibling species of preserved An. gambiae s. s. and An. arabiensis. Mosquitoes of each species were placed in sample tubes and preserved using one of the following preservation methods: (i) refrigeration at 4°C, (ii) freezing at -20°C, (iii) drying over a silica-gel desiccant, (iv) submersion in RNAlater at room temperature, (v) submersion in RNAlater at 4°C, and (vi) submersion in RNAlater at -20°C. Mosquitoes were preserved for 1, 4, 10, 32 or 50 weeks before they were scanned.
Storage at 4°C was the only preservation method that, up to 32 weeks, did not result in significantly lower predicted values than those obtained from fresh insects. After 50 weeks, however, refrigerated samples did not give meaningful results. When storing for 50 weeks, desiccating samples over silica gel was the best preservation method, with a partial least squares regression cross-validation of >80%. Predictive data values were analyzed using a generalized linear model.
NIRS can be used to identify species of desiccated Anopheles gambiae s.s. and Anopheles arabiensis for up to 50 weeks of storage with more than 80% accuracy.
近红外光谱技术（NIRS）已成功应用于新鲜的以及用RNA Later保存的冈比亚按蚊复合体成员，以鉴别同胞物种和年龄。除了使用RNA Later外，尚未测试其他保存方法用于保存蚊子以使用NIRS进行物种鉴定。然而，RNA Later并非野外环境中最实用的防腐剂，因为它价格昂贵，储存需要基本的实验室条件，且在撒哈拉以南非洲地区并不广泛可得。本研究的目的是测试几种更便宜且更适合野外的保存方法，以使用NIRS鉴别冈比亚按蚊复合体的同胞物种。
在本研究中，我们描述了使用NIRS鉴别保存的冈比亚按蚊指名亚种和阿拉伯按蚊的同胞物种。将每个物种的蚊子放入样品管中，并使用以下保存方法之一进行保存：（i）4°C冷藏，（ii）-20°C冷冻，（iii）在硅胶干燥剂上干燥，（iv）室温下浸入RNA Later，（v）4°C下浸入RNA Later，以及（vi）-20°C下浸入RNA Later。蚊子在扫描前保存1、4、10、32或50周。
4°C储存是唯一一种在长达32周内预测值不会显著低于新鲜昆虫所得值的保存方法。然而，50周后，冷藏样品未得出有意义的结果。储存50周时，在硅胶上干燥样品是最佳保存方法，偏最小二乘回归交叉验证>80%。使用广义线性模型分析预测数据值。
NIRS可用于鉴别干燥保存长达50周且准确率超过80%的冈比亚按蚊指名亚种和阿拉伯按蚊的物种。
