CORRELATION BETWEEN THE POSSESSION OF A CHITINOUS CUTICLE AND SENSITIVITY TO DDT

¹ Zoology Department, University of Pennsylvania; Marine Biological Laboratory, and Division of Entomology, University of Minnesota

1. Throughout the animal phyla there is a correlation between the presence of a chitinous cuticle and susceptibility to external applications of DDT. Those aquatic animals with a chitinous cuticle (arthropods and certain coelenterates) are highly sensitive to external applications of DDT, other animals are not so susceptible although there is considerable variability.

2. The correlation to a chitinous cuticle is supported by studies on various coelenterates, on adsorption, and on temperature coefficients. Coelenterata with respectively a complete, partial, and no chitinous perisarc are respectively highly sensitive, somewhat sensitive, and nearly insensitive to DDT. DDT can be adsorbed by chitin and chitinous cuticles and at low concentrations shows a negative temperature coefficient for toxicity to arthropods.

3. From these data a hypothesis is proposed that chitinous cuticles facilitate the entry of DDT into the animal body by selectively concentrating the compound by adsorption phenomena.

4. This is the first demonstration that an insecticide can be adsorbed by chitinous cuticles and the first direct evidence that such adsorption actually can play a role in insecticide action.

5. The present paper does not consider the nature of the toxicity of DDT to protoplasm. The data given here refer only to the selective action of DDT as a function of penetration facilitated by chitinous exoskeletons. The shift to a positive temperature coefficient at higher concentrations, the lack of effect from injecting DDT emulsions into snails, and the variability in median lethal doses for injected DDT emulsions in different animals, all indicate that the selective adsorption of DDT by chitinous cuticles is only a part of the story of the toxic action of this compound.

This article has been cited by other articles:

				R. A. Hoffman, A. R. Roth, A. W. Lindquist, and J. S. Butts Absorption of DDT in Houseflies over an Extended Period Science, March 21, 1952; 115(2986): 312 - 313. [PDF]