Hox genes are the key determinants of different morphogenetic events in all bilaterian animals. These genes are probably responsible for the maintenance of regenerative capacities by providing positional information in the regenerating animal body. Polychaetes are well known for their ability to regenerate the posterior as well as the anterior part of the body. We have recently described the expression of 10 out of 11 Hox genes during postlarval growth of Alitta (Nereis) virens. Hox genes form gradient overlapping expression patterns, which probably do not contribute to the morphological diversity of segments along the anterior-posterior axis of the homonomously segmented worm. We suggest that this gradient expression of Hox genes establishes positional information along the body that can be used to maintain coordinated growth and regeneration.
Novikova, E. L., Bakalenko, N. I., Nesterenko, A. Y., & Kulakova, M. A. (2013). Expression of Hox genes during regeneration of nereid polychaete Alitta (Nereis) virens (Annelida, Lophotrochozoa). EvoDevo, 4(1). https://doi.org/10.1186/2041-9139-4-14