Water-Pretreatment Squash Technic: A New and Simple Practical Method for the Chromosome Study of Animals

Abstract

To simplify the staining of animal chromosomes (especially in insect testes) the authors have borrowed (with necessary modifications) the squash technic of plant cytology. The method has four steps: (1) Water pretreatment. This step requires only about 5–10 minutes either in water at room temperature or in water kept at about 38°C. in a water bath. (2) Fixation. Ordinarily only 5 minutes in 10–15% aqueous solution of glacial acetic acid is necessary. (3) Staining. The fixed tissue is rinsed in two or three changes of distilled water and then placed in a solution of basic fuchsin: either 1% in 30% ethyl alcohol, or 0.2–0.4% in 5–10% lactic acid. In the former solution the staining period should be about 2 minutes: in the latter, 5–20 minutes. The time is not critical. (4) Squashing. The material is rinsed in several changes of distilled water, placed on a clean slide and squashed under a cover glass. Such preparations last 4–5 weeks, and a technic is described for removing the cover glass in order to mount in Euparal and to make them permanent. The authors list various species of vertebrates as well as invertebrates in which the technic has given good chromosome staining, as shown by illustrations.