Placentonema gigantissima
{{Short description|Species of roundworm}}
{{Speciesbox
| image = Placentonema gigantissima from Dailey 1985.png
| image_alt = a large parasitic worm in the placenta of a whale, black and white photo
| image_caption = Placentonema gigantissima in the placenta of a sperm whale (Physeter macrocephalus)
| genus = Placentonema
| species = gigantissima
| authority = (Gubanov, 1951)
| synonyms =
| synonyms_ref =
}}Placentonema gigantissima is a giant nematode that parasitizes the placenta and other tissues of the sperm whale. With a length of {{convert|8.4|m|ft}} and a diameter of {{convert|2.5|cm|in}}, it is potentially the largest nematode worm ever described, inhabiting one of the largest mammals in the world.{{Cite journal |last=Jairajpuri |first=Shamim |date=2005-01-01 |title=Parasite diversity with specific reference to nematodes |url=https://www.wikidata.org/wiki/Q124216019 |journal=Journal of Parasitic Diseases |volume=29 |issue=2 |pages=81–84}} It was discovered in the 1950s around the Kuril Islands.{{cite journal |last1=Gubanov |first1=Nikolai Mikhailovich |date=21 April 1951 |title=Гигантская нематода из плаценты китообразных Placentonema gigantissima nov. gen., nov. sp |trans-title=Giant nematoda from the placenta of Cetacea; Placentonema gigantissima nov. gen., nov. sp |url=http://www.mactode.com/page21/files/Placentonema_gigantissima.pdf |journal=Doklady Akademii Nauk SSSR |language=ru |volume=77 |issue=6 |pages=1123–1125 |pmid=14822893 |archive-url=https://web.archive.org/web/20131215144805/http://www.mactode.com/page21/files/Placentonema_gigantissima.pdf |archive-date=15 December 2013}}
Taxonomy
Placentonema gigantissima was described in 1951 by Russian parasitologist and helminthologist Nikolai Mikhailovich Gubanov.
Originally described from the family Crassicaudidae, 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".
Description
The body is very long, cylindrical, tapering at the ends, with a transparent cuticle. The oral orifice is oval shaped with two simple lateral lips, while the esophagus is divided into two parts, one muscular and glandular.
Males are 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. Mature eggs are oval, 0.05 mm long by 0.03 mm wide, and the young inside the eggs are completely formed.
Life cycle
Placentonema gigantissima utilizes nutrients found in the endometrium of female sperm whales. It forms spiriud (small, embroyonated) eggs.{{cite journal |last1=Juan-Sallés |first1=Carles |last2=Garner |first2=Michael M. |date=2019 |title=67 - Avian Spirurids |url=https://www.sciencedirect.com/science/article/pii/B9780323552288000679 |journal=Fowler's Zoo and Wild Animal Medicine Current Therapy |volume=9 |page=471 |doi=10.1016/B978-0-323-55228-8.00067-9 |isbn=9780323552288 |s2cid=239100923|url-access=subscription }}
It can parasitize not only the placenta, but also the uterus, reproductive tract, mammary glands, and subdermis of the sperm whale.{{Cite journal |last=Hermosilla |first=Carlos |last2=Hirzmann |first2=J. |last3=Silva |first3=L. M. R. |last4=Brotons |first4=J. M. |last5=Cerdà |first5=M. |last6=Prenger-Berninghoff |first6=E. |last7=Ewers |first7=C. |last8=Taubert |first8=A. |date=2018 |title=Occurrence of anthropozoonotic parasitic infections and faecal microbes in free-ranging sperm whales (Physeter macrocephalus) from the Mediterranean Sea |url=http://link.springer.com/10.1007/s00436-018-5942-3 |journal=Parasitology Research |language=en |volume=117 |issue=8 |pages=2531–2541 |doi=10.1007/s00436-018-5942-3 |issn=0932-0113|url-access=subscription }} It is commonly found in pregnant sperm whales.
Much of the life cycle of P. gigantissima is unknown.{{Citation |last=Dailey |first=Murray D. |title=Diseases of Mammalia: Cetacea |date=1985-01-01 |url=https://www.wikidata.org/wiki/Q124216210 |work=Diseases of Marine Animals. Vol. 4 part 2, ed. Otto Kinne |pages=805–848 |access-date=2024-01-09 |language=English}}
Distribution
This species is found inside female sperm whales that inhabit lower latitudes of the southern hemisphere.{{Cite journal |last=Dailey |first=Murray D. |last2=Vogelbein |first2=Wolfgang K. |date=1991-01-01 |title=Parasite fauna of 3 species of Antarctic whales with reference to their use as potential stock indicators |url=https://www.wikidata.org/wiki/Q124215458 |journal=Fishery Bulletin |language=English |volume=89 |issue=3 |pages=355–365}}
External links
{{Commons}}Placentonema gigantissima was discussed on RNZ Critter of the Week, [https://www.rnz.co.nz/national/programmes/afternoons/collections/critter-of-the-week/audio/2018917554/critter-of-the-week-the-giant-nematode 24 November 2023]
References
{{Reflist}}
{{Taxonbar|from=Q3017044}}
Category:Nematodes described in 1951
Category:Parasitic nematodes of mammals
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