Turbellarian Life Cycle

Turbellarian is a class of flatworms. There are 4,500 species in the class, and it is a very diverse class. Most flatworms are not parasitic and find their own food. Some are nearly 2 feet long, while others are a little less than 1 inch long. Most turbellarians share the same life cycle.

  1. Fission

    • There are species of turbellarians that will reproduce asexually. Asexual reproduction means that there is only one member of the species required for reproduction. This is more common in simple organisms, like turbellarians. Planarians are one of the turbellarians that reproduce asexually. They use fission, which means that they simply pull their bodies apart until they split in two. The body then grows back any part that was missing in the division. Most turbellarians do not reproduce this way.

    Sex

    • Most turberallians are not a single sex. They are hermaphrodites. This means they contain both male and female sex organs. However, unlike some hermaphroditic species, they cannot self-fertilize. They need the sperm of another turbellarian to reproduce. The turbellarian will entwine with another turbellarian and they will both share their sperm with each other. Being hermaphroditic is an evolutionary advantage. Instead of worrying about male and female, the turbellarian can reproduce en masse by mating with any member of its species.

    Fertilization

    • When a turbellarian mates, the eggs in the cocoon on its body are fertilized by the sperm from the other turbellarian. Sometimes there is only one egg in the cocoon; other times, there are many more. It depends solely on the turbellarian. This cocoon will be where the embryos grow. The cocoon will help keep the embryos safe from any outside contaminate that could affect their growth.

    Feeding

    • Now that there are embryos, they must feed to grow. The yolk in the fertilized egg helps serve as nourishment while the embryos grow. There are also special cells inside the cocoon that serve as nutrition. They contain the same high protein of the yolk in the eggs. These cells are included in case the egg yolk is either missing in the egg or is simply not enough to nourish the growing embryos.

    Hatching

    • After a few days of nourishment, the turbellarian are hatched from their eggs and released from the turbellarian parent. Both of the mating turbellarian will be releasing their children at similar times. Most of these hatching turbellarians will not be mature. They will be unable to mate until they age more. However, turbellarians often hatch turbellarians that are capable of sexual reproduction when they are born. This makes them unique among most creatures.