''Sphaerularia vespae'' is an

endoparasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has c ...

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 infects the Japanese yellow hornet, ''

Vespa simillima ''Vespa simillima'', the yellow hornet, including the color form known as the , is a common hornet Hornets (insects in the genus ''Vespa'') are the largest of the eusocial wasps, and are similar in appearance to their close relatives yello ...

''. It invades and resides in the gaster (abdomen) of female hornets where it grows and develops. Because ''S. vespae'' sterilizes its host, it is also known as a

parasitic castrator Parasitic castration is the strategy, by a parasite, of blocking reproduction by its host, completely or in part, to its own benefit. This is one of six major strategies within parasitism. Evolutionary strategy The parasitic castration strateg ...

. After '' S. bombi'', it is the second recognized species of the genus ''

Sphaerularia ''Sphaerularia'' is a genus of nematodes belonging to the family Sphaerulariidae. The species of this genus are found in Europe and Northern America. Species: *''Sphaerularia bombi ''Sphaerularia bombi'' is an entomopathogenic nematode. It ...

''.

Diagnosis

''Sphaerularia vespae'' is characterized by the round, finger-like tip tail of females and the conspicuous male bursa. These features are used to distinguish ''S. vespae'' from ''S. bombi''. In addition, the square head shape of parasitic juveniles also distinguishes ''S. vespae'' from ''S. bombi,'' which have a more round, dome-shaped head.

Distribution

''S. vespae'' has been found at several sites in

Sapporo ( ain, サッ・ポロ・ペッ, Satporopet, lit=Dry, Great River) is a city in Japan. It is the largest city north of Tokyo and the largest city on Hokkaido, the northernmost main island of the country. It ranks as the fifth most populous city ...

Hokkaido is Japan's second largest island and comprises the largest and northernmost prefecture, making up its own region. The Tsugaru Strait separates Hokkaidō from Honshu; the two islands are connected by the undersea railway Seikan Tunnel. The la ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

( Hitsujigaoka,

Mount Moiwa is a mountain located about southwest of the center of Sapporo, Hokkaido and southwest of Sapporo Station. A ropeway Ropeway may refer to: Cable transport * Cableway, or cable transport, a broad class of transport modes that have cables * A ...

and Shiraikawa Sapporo), and in Nishi-Nopporo,

Ebetsu is a city in Ishikari Subprefecture, Hokkaido, Japan. History Ebetsu was settled originally by Japanese people in 1871, who came from the Miyagi Prefecture on Honshu. In 1878, tondenhei began moving into the area. When the Meiji Government, ...

, Hokkaido.

Life cycle

''S. vespae'' has a similar life cycle to that of ''S. bombi''. Juveniles of ''S. vespae'' are passed out in the

feces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...

of the host and deposited in the soil. There, the juveniles grow and develop. Later, fertilized adult females infect healthy hornet

queens Queens is a borough of New York City, coextensive with Queens County, in the U.S. state of New York. Located on Long Island, it is the largest New York City borough by area. It is bordered by the borough of Brooklyn at the western tip of Long ...

that settle in the soil for

hibernation Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most ...

. When these newly infected queens emerge from hibernation they are now carrying adult ''S. vespae'' in their abdomen. In the spring, these parasitized queens display behavior that is inappropriate to the time of the year. Normally, in the fall, healthy queen hornets visit various nooks and crannies, such as decayed logs in the forest, to find a spot to hibernate. When the queen finds a suitable site, she lines it with plant fibers that serve as nesting material. However, queen hornets that have been infected by ''S. vespae'' have become sterilized due to their undeveloped ovaries and start visiting decaying logs much earlier in the year, during early to mid-summer. Parasitized queen hornets never dig or gather nesting materials when they land at different locations. Instead, they fly from one potential hibernation site to another, each time dropping off a load of ''S. vespae'' juveniles. Once deposited in the soil, these juveniles wait for new hosts that settle in for hibernation in the fall and the cycle repeats itself.

References

{{Taxonbar, from=Q16758745 Tylenchida Nematodes described in 2007 Endoparasites