EFFECT OF COLCHICINE ON THE DEVELOPMENT OF THE FISH EMBRYO, ORYZIAS LATIPES

¹ From the Thompson Biological Laboratory, Williams College

1. The action of colchicine on the differentiation of embryonic structures of the fish embryo has been studied by exposing four different developmental stages of Oryzias latipes, i.e. early cleavage to optic cup stages, to various concentrations for different lengths of time.

2. The sensitivity of both the whole organism and its constituent parts decreases with age and differentiation. Abnormalities were produced whose type and degree depend upon the concentration of the alkaloid, length of exposure and the stage of development. Concentrations of 1-100,000 to 1-1,000 were employed but the latter proved to be most useful.

3. In addition to general retardative and inhibitory effects on cleavage and development, other types of abnormalities included variation in the pigmentation of the eyes and body, cyclopian-like eyes, retardation and inhibition of the development of the tail, irregularities in the heart and yolk-sac vessels, abnormal blood formation, disturbance of body flexures especially the tail, and disturbances in the development of parts of the brain. Apparently when gastrulation occurred, it was typical.

4. In cases where development had ceased entirely during exposure and slight degeneration had set in, differential recovery was seen to take place especially in the formation of pigment and heart development.

5. The alkaloid penetrates the egg chorion very quickly. In weaker concentrations the older embryos showed some adaptation during long exposures. Some of the described effects are similar to those caused by dinitrophenol and x-rays.