Researches on the development of Xenopus laevis larvae fed on Tubifex tubifex. I. Presence of liposoluble vitamins in the lipid extract from Tubifex worms.

Vitamin E acetate (alpha-tocopheryl acetate) and related tocopherols, vitamin A acetate (dehydroretinyl acetate), vitamin A alcohol (retinol), and cholesterol were identified by thin-layer chromatography in the lipid extract from Tubifex tubifex worms. Compounds (perhaps vitamin D precursors, or seroidal substances) absorbing short wave UV light and/or reacting with antimony trichloride were also present but not identified. The results are discussed in relation to the growth, metamorphosis and possible appearance of malformations in Xenopus laevis specimens reared on Tubifex alone or on diets integrated with Tubifex. The hypothesis of the presence of tossic substances in Tubifex as a cause of malformations in Xenopus is also discussed.