A PCR assay was employed to detect sequences homologous to the transpo
sase gene of the Tc1 family of transposable elements in a wide variety
of animals. Amplification products of the appropriate size were obtai
ned from most insects (92 of 108 examined; 85%), most other invertebra
tes (33 of 43; 77%), and many vertebrates (18 of 36; 50%). Sequencing
a sample of cloned PCR products from eight insects, one hydra, and two
frogs revealed that each had multiple distinct members of the family
in their genomes. In the most extreme case, the horn fly Haematobia ir
ritans yielded evidence of seventeen distinct types of Tc1 family elem
ents. Most of the sequences obtained indicate that the elements are wi
thin the range of variation already known from fungi, nematodes, flies
, fish and frogs. Some, however, had novel length variants or divergen
t sequences, indicating that they represent new subfamilies of these t
ransposons. These results indicate that this family of transposons is
extremely common in animal genomes, with multiple representatives in m
ost genomes.