Flatworm

Flatworms (Phylum Platyhelminthes) are relative simple unsegmented, soft-bodied invertebrates commonly called flatworms. This group includes cestodes (tapeworms) and trematodes (flukes) which have complex life-cycles, with mature stages that live as parasites in the digestive systems of fish and land vertebrates,  and intermediate stages that infest secondary hosts.

Main Photo Credit:
"Fluke (Flatworm), Ontario, Canada" by Oshii, 2024. CC BY-NC 2.0.

Description: Wikipedia