''Sphaerularia vespae'' is an

endoparasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...

that infects the Japanese yellow hornet, ''

Vespa simillima ''Vespa simillima'', the yellow hornet, including the color form known as the , is a common hornet species in the Eastern Hemisphere. The typical mainland color form (Japanese language, Japanese:ケブカスズメバチ, Korean language, Korean: ...

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

Sphaerularia ''Sphaerularia'' is a genus of nematodes belonging to the family Sphaerulariidae Sphaerulariidae is a family of nematodes belonging to the order Tylenchida Tylenchida is an order (biology), order of nematodes. List of families * Superfa ...

''.

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 is a Cities designated by government ordinance of Japan, designated city in Hokkaido, Japan. Located in the southwest of Hokkaido, it lies within the alluvial fan of the Toyohira River, a tributary of the Ishikari River. Sapporo is the capital ...

Hokkaido is the list of islands of Japan by area, second-largest island of Japan and comprises the largest and northernmost prefectures of Japan, prefecture, making up its own list of regions of Japan, region. The Tsugaru Strait separates Hokkaidō fr ...

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

( Hitsujigaoka, Mount Moiwa and Shiraikawa Sapporo), and in Nishi-Nopporo,

Ebetsu is a Cities of Japan, 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 M ...

, 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 (also known as faeces American and British English spelling differences#ae and oe, or fæces; : faex) 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 ...

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

queens Queens is the largest by area of the Boroughs of New York City, five boroughs of New York City, coextensive with Queens County, in the U.S. state of New York (state), New York. Located near the western end of Long Island, it is bordered by the ...

that settle in the soil for

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

. 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