Question

How do flatworms reproduce sexually?

Answer 1

Flatworms also called as helminths belong to platyhelminthes group. They are long and soft flattened body structures. There are flatworm species which are free-living and parasitic, that means living and feeding on other animal’s bodies. Flatworms have radial symmetry and also bilateral symmetry. Platyhelminthes do not have cilia.

Complete answer:
Flatworms have reproduction different from other organisms. They are hermaphrodites meaning have both male and female sex organs. Flatworms can produce through sexual methods as well as asexual methods. Mostly reproduction through sexual methods.
Cross fertilization is the way in which flatworms reproduce sexually. As the flatworms are hermaphrodite, they can produce eggs within the body and by themselves fertilize them by the presence of sperm generated in its body.
Another way of reproducing sexually can be piercing into skin of a mother flatworm where two flatworms involved in physical contact and one flatworm pierce its penis into the mother’s skin. Hence, eggs get fertilized and encased in the protective cocoon inside the flatworm’s body.
The cocoon’s function is to nourish the eggs and they get released into the environment via different methods- water weeds. The cocoon later hatches into new individuals. The advantages of reproducing sexually are- they can regenerate from organisms from a single piece from themselves.

Note:
Platyhelminthes has no backbone and there is a vertical line in the middle of the organism which is exactly mirrored on the right side. The flatworm is a C shaped organism curled up if kept inside the container, they are triploblastic animals and found parasitizing on other animals such as dogs, cats and cows including humans.