Bursovaginoidea is one of the two orders in the phylum

Gnathostomulida Gnathostomulids, or jaw worms, are a small phylum of nearly microscopic marine animals. They inhabit sand and mud beneath shallow coastal waters and can survive in relatively anoxic environments. They were first recognised and described in 1956. ...

Appearance and anatomy

Bursovaginoids are rather small, ranging from a half of a millimeter to a full millimeter in length. Many species in the order Bursovaginoidea have a narrow neck, making their head stand out more than other bursovagionoids and all filospermoids. Bursovaginoids, unlike filospermoids, have paired

sensory organs A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of stimuli. (For example, in the human body, the brain which is part of the central nervous system rec ...

and a

penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males do n ...

. Also, all species in Bursovaginoidea have a sperm-storage organ called a

bursa ( grc-gre, Προῦσα, Proûsa, Latin: Prusa, ota, بورسه, Arabic:بورصة) is a city in northwestern Turkey and the administrative center of Bursa Province. The fourth-most populous city in Turkey and second-most populous in the ...

. In suborder Scleroperalia, the bursa is cuticular, while in Conophoralia it is not. Species in order Conophoralia tend to have larger

sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, whi ...

than those in Sceloperalia.

Distribution

Sightings of bursovaginoids have been reported in various parts of the world, including

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

and the north-western and south-eastern parts of the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

. Bursovaginoids mostly live in oceans near the coasts, in depths of under 500 meters (1650 feet), most commonly around 300.

Families

The order Bursovaginoidea contains 73 - 75 species and 24 genera in the following 10 families: * Suborder Conophoralia ** Austrognathiidae (27 species in 4 genera) * Suborder Scleroperalia ** Agnathiellidae (3 species in 2 genera) ** Clausognathiidae (1 species in 1 genus) ** Gnathostomariidae (1 species in 1 genus) ** Gnathostomulidae (23 - 25 species in 5 genera) ** Mesognathariidae (6 species in 3 genera) ** Onychognathiidae (9 species in 5 genera) ** Paucidentulidae (1 species in 1 genus) ** Problognathiidae (1 species in 1 genus) ** Rastrognathiidae (1 species in 1 genus)

References

{{Taxonbar, from=Q275668 Gnathostomulida Marine animals