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Species of roundworm From Wikipedia, the free encyclopedia
Placentonema gigantissima is a giant nematode that parasitizes the placenta of the sperm whale. With a length of 8.4 metres (28 ft) and a diameter of 2.5 centimetres (0.98 in), it is potentially the largest nematode worm ever described, inhabiting the largest mammals of the world.[1] It was discovered in the 1950s around the Kuril Islands.[2]
| Placentonema gigantissima | |
|---|---|
| |
| Placentonema gigantissima in the placenta of a sperm whale (Physeter macrocephalus) | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Chromadorea |
| Order: | Rhabditida |
| Family: | Tetrameridae |
| Genus: | Placentonema |
| Species: | P. gigantissima |
| Binomial name | |
| Placentonema gigantissima (Gubanov, 1951) | |
Placentonema gigantissima was described in 1951 by Russian parasitologist and helminthologist Nikolai Mikhailovich Gubanov.[2]
Originally described from the family Crassicaudidae,[2] it is now classified in the subfamily Crassicaudinae of the roundworm family, Tetrameridae.
It is a monotypic genus that differs from the only other genus in the subfamily, Crassicauda, by its "caudal alae, stub-like papillae and multiple uterus branching into 32 uteri".[2]
Body very long, cylindrical, tapering at the ends, with a transparent cuticle.[2] Oral orifice oval shaped with two simple lateral lips, esophagus with two parts, one muscular and glandular.[2]
Males up to 3.75 m long and 9 mm wide; females up to 8.4 m long and 2.5 cm wide, with up to 32 ovaries.[2][1] Mature eggs oval, 0.05 mm long by 0.03 mm wide, and the young inside the eggs are completely formed.[2]
Placentonema gigantissima develops its parasitic nature by utilizing nutrients found in the endometrium of female sperm whales and forming as spiriud (small, embroyonated) eggs.[3]
It can parasitize not only the placenta, but also the uterus, reproductive tract, mammary glands, or subdermis of the sperm whale.[4] It is commonly found in pregnant sperm whales.[5]
Much of the life cycle of P. gigantissima is unknown.[5]
P. gigantissima is found inside female sperm whales that inhabit lower latitudes of the southern hemisphere.[6]
Placentonema gigantissima discussed on RNZ Critter of the Week, 24 November 2023
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