Rare egg capsule production in the invasive terrestrial planarian Bipalium kewense.
The invasive terrestrial planarian Bipalium kewense is found worldwide in tropical and warm temperate zones. The rate of spread and ecological impact of the flatworm will depend in part on its reproductive strategies. Members of this species reproduce primarily by fission of posterior body fragments. Herein we report, for only the second time in over 120 years of international study, the production of a fertile egg capsule by B. kewense. The capsule was produced by a flatworm from Texas, hatched in 21 days, and it contained 7 juveniles. Although the capsule structure, incubation period, and litter size were similar to those characteristic of the sexual species, B. adventitium, the B. kewense capsule was larger (112 mg) and produced larger offspring.