Permanent Staining of Tracheae with Trypan Blue
The arrangement of the tracheae in the insect central nervous system (CNS), apart from its own intrinsic interest and the possibility that some insecticides may gain entry to the ganglia along the tracheae (Gerolt, 1969, 1972), is of importance in studies of neuroanatomy because the larger tracheal branches can provide easily identifiable landmarks for locating the positions of nervous structures. Various methods used to stain other elements of the nervous system, most of them described in other chapters of this book, will also reveal the tracheae, for example the Bo-dian protargol silver technique (Chap. 6) (and no doubt other silver-on-the-slide methods, such as described in Chap. 7), Golgi silver block impregnation (Chap. 9; also Pearson, 1971), Kronthal-Corning lead or copper impregnation (Strausfeld, 1976), and Procion yellow used by the immersion method (Chap. 13; illustrated by Gregory, 1974a, Fig. 16). However, these methods all require the material to be sectioned and so are unsuited to the study of the tracheal system in whole ganglia. Superficial tracheae of whole ganglia can be observed in freshly dissected live material under an appropriate saline solution, but only while they remain filled with air. Numerous methods have been put forward for filling the tracheal system of the whole insect more or less permanently, using a variety of colored substances.
KeywordsTrypan Blue Prussian Blue Nerve Cord Ventral Nerve Cord Barium Chloride
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