Using wintergreen oil for mounting mosquito larvae: a safer alternative to xylene

Abstract

Permanent mounting of fourth instar mosquito larvae is essential for identifying Aedes spp. This procedure requires extensive exposure to xylene, a clearing agent in the mounting process. We investigated wintergreen oil as a substitute for xylene. Five hundred larvae were mounted on slides to evaluate shrinkage or expansion of specimens after clearing using xylene or wintergreen oil. We examined the ventral brush and siphonal hair tufts for species identification and for preservation of morphological characteristics after clearing specimens in xylene or wintergreen oil. Shrinkage of the length of whole larvae and width of the head, thorax and abdomen after mounting was significantly greater after clearing with xylene than with wintergreen oil. The length of the comb scale nearest the ventral brush was similar for both clearing agents. The clarity of the specimens after mounting was improved by clearing with wintergreen oil, but the integrity of the ventral brush and siphonal hair tufts were similar for both clearing agents.

Key words::

• Aedes
• clearing
• dengue
• laboratory technicians
• larvae
• methyl salicylate
• mosquito
• mounting
• occupational hazard
• shrinkage
• wintergreen oil
• xylene

Acknowledgments

We acknowledge the Faculty of Medicine, Universiti Kebangsaan Malaysia Medical Center (UKMMC) for permission and funding to conduct this research. We thank the Department of Parasitology and Medical Entomology for laboratory space and technical support. We are grateful to Ahmad Firdaus Mohd Salleh for helping us with laboratory work. Help with the statistics by Associate Professor Najib Mahmood Rafee is appreciated. This work was funded by UKMMC Fundamental Grant (FF-2013-479).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this paper.