Circular form of regeneration in an unidentified species of land planarians, Bipalium sp.

The communication describes an interesting and possibly novel finding regarding a species of land planarians (Bipalium sp.) from a high altitude of Himalayan range. The regeneration in Bipalium sp. is highly interesting and the process takes about a fortnight for the completion. Accumulation of numerous basophilic cells in parenchyma at the blastema region occurs within 5 days after excision and in 7 to 9 days the head and tail regions become reorganized with the formation of functional pharynx in the tail piece. The neoblast cells in the mesenchyme and the gastrodermis cells proliferate continuously replenishing the population of stem cell for growth, reproduction, and regeneration. Many undifferentiated cells are present even in completely regenerated specimens. Sometimes middle piece regenerates apparently fuse at the blastema surface forming a peculiar circular form of Bipalium sp. where both the head and tail cut ends join completely. These regenerated individuals excepting the middle piece regenerate behave in a normal fashion within 12-14 days.