Overview
- University of Warsaw zoologists Katarzyna Tratkiewicz and Ludwik Gąsiorowski accidentally spotted spontaneous two-headed Stenostomum brevipharyngium in routine lab cultures.
- Microscopy and chemical markers confirmed that a functional head had formed where a tail should be during asexual reproduction.
- When the double-headed worms were cut into sections, the middle fragment regenerated a tail at the opposite end, producing descendants with reversed head–tail polarity.
- Normal offspring from double-headed parents ruled out a heritable genetic cause, pointing to a developmental phenomenon.
- The cause remains unknown and unverified in the wild, though prior work shows double heads can be induced electrically and the authors cite pluripotent stem-cell remodeling as enabling survival and reproduction.