''Placentonema gigantissima'' is a giant

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

that parasitizes the placenta of the

sperm whale The sperm whale or cachalot (''Physeter macrocephalus'') is the largest of the toothed whales and the largest toothed predator. It is the only living member of the genus ''Physeter'' and one of three extant species in the sperm whale famil ...

. With a length of and a diameter of , it is potentially the largest nematode worm ever described. It was discovered in the 1950s around the Kuril Islands. The placentonema gigantissima develops its parasitic nature by utilizing nutrients found in the endometrium of female sperm whales and forming as spiriud (small, embroyonated) eggs. It can parasitize not only the placenta, but also the uterus, reproductive tract, mammary glands, or subdermis of the sperm whale.

References

Nematodes described in 1951 Spirurida Parasitic nematodes of mammals Whales {{Secernentea-stub