Nematomorpha

related topics
{specie, animal, plant}
{island, water, area}
{@card@, make, design}

}} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }}

Nematomorpha (sometimes called Gordiacea, and commonly known as horsehair worms or Gordian worms) is a phylum of parasitic animals that are superficially morphologically similar to nematode worms, hence the name. They range in size in most species from 50 to 100 centimetres (20 to 39 in) long and can reach in extreme cases up to 2 meters, and 1 to 3 millimetres (0.039 to 0.12 in) in diameter. Horsehair worms can be discovered in damp areas such as watering troughs, streams, puddles, and cisterns. The adult worms are free living, but the larvae are parasitic on beetles, cockroaches, orthopterans, and crustaceans.[1] About 326 species are known and a conservative estimate suggests that there may be about 2000 species worldwide.[2] The name "Gordian" stems from the legendary Gordian knot. This relates to the fact that nematomorpha often tie themselves in knots.[3]

Contents

Description and biology

Nematomorphs possess an external cuticle without cilia. Internally, they have only longitudinal muscle and a non-functional gut, with no excretory, respiratory or circulatory systems. The nervous system consists of a nerve ring near the anterior end of the animal, and a ventral nerve cord running along the body.[4]

Reproductively, they are dioecious, with the internal fertilization of eggs that are then laid in gelatinous strings. Adults have cylindrical gonads, opening into the cloaca. The larvae have rings of cuticular hooks and terminal stylets that are believed to be used to enter the hosts. Once inside the host, the larvae live inside the haemocoel and absorb nutrients directly through their skin. Development into the adult form takes weeks or months, and the larva moults several times as it grows in size.[4]

The adults are mostly free living in freshwater or marine environments, and males and females aggregate into tight balls (Gordian knots) during mating.[5][6]

In Spinochordodes tellinii, which has orthopterans as its vector, the infection acts on the insect's brain and causes it to seek water and drown itself, thus returning the nematomorph to water.[5] They are also remarkably able to survive the predation of their host, being able to wriggle out of the predator that has eaten the host.[7]

Full article ▸

related documents
Hemichordata
Nymphaeales
Thelypteridaceae
Gymnosphaerid
Xenarthra
Volvox
Amphiuma
Dipper
Echidna
Musaceae
Rodhocetus
Goose
Fabales
Anomalocarid
Oology
Mycology
Eastern Imperial Eagle
Phanerozoic
Genotype-phenotype distinction
Sciaenidae
Larva
Fern ally
Entomology
Sidehill gouger
Hebe (genus)
Himalayan Tahr
Erysimum
Bee Orchid
Gentian
List of freshwater aquarium plant species