Study to make transparent skeletal specimens in small fish by using dishwashing liquid

Abstract

Glycerol of high purity is generally used in process of making transparent skeletal specimens for permeation and preservation. However, in the field of education, glycerol’s high cost could be a hindrance to its use. In this experiment, we tried to make transparent skeletal specimens using dishwashing liquid instead of glycerol. Medaka (Oryzais latipes) fixed in 10% formalin overnight at room temperature were put in five kinds of dishwashing liquids containing various concentrations of potassium hydroxide at 35°C for 2 weeks. Transparency of all fish specimens was enhanced by potassium hydroxide in dose dependent manner. We also treated the formalin-fixed fish in alizarine red S solution overnight followed by immersion in various dishwashing liquids as above. We found that two dishwashing liquids containing 1% potassium hydroxide could make skeleton transparent without decoloring of hard bone stained by alizarin red S. Dishwashing liquid is considerably inexpensive compared to glycerol of high purity, therefore this procedure will make it easy to use transparent skeletal specimens in schools.