A method for paraffin sectioning and identification of indoleamines in the brain of insects with a sclerotized cuticle

Abstract

Sectioning of insects with sclerotized cuticles for histological examination can be challenging and often involves double-embedding, chemical dissolution of the cuticle or long periods of sample preparation. Furthermore, exposure of the tissue to harsh chemical treatments potentially interferes with antibody binding and thus chemical dissolution of the cuticle is undesirable for performing fluorescence immunohistochemistry (IHC). A method for obtaining paraffin sections of compound eye and neural tissue from the Australian black field cricket Teleogryllus commodus, an Orthopteran insect with a sclerotized cuticle, without the need for double embedding and with minimal pre-embedding processing is presented here. This method produced sections with minimal tissue curling or lifting in the tissues of interest. Fluorescence IHC labelling of melatonin and serotonin, comprehensively demonstrating their distribution in the compound eye and the optic lobe of the Orthopteran brain, was also performed. This method provides a framework for sectioning insect tissues with sclerotized cuticles and for IHC labelling of indoleamine compounds in the brain of Orthopteran insects.