Nematomorpha
From Freepedia
| Horsehair worms | ||||
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Nematomorpha (commonly known as horsehair worms) are a phylum of parasitic animals morphologically and ecologically similar to nematodes. They are, at an average, 1 meter long, and 1 to 3 millimeters in diameter. Horsehair worms can be discovered in damp areas such as watering troughs, streams, puddles, and cisterns. The adult, free living worms are not parasitic of humans or other mammals, but the young worms grow in beetles, cockroaches, or grasshoppers.
A team of biologists from the French National Center for Scientific Reaserch in Montpellier, France studied one species of parasitic hairworms that take refuge in grasshoppers, and found it has a very unusual lifecycle. After it infects its host (how it infests the grasshopper is currently unkown), it procedes to eat the host's innards until it has grown into adulthood. It then produces and injects proteins into its host brain that cause the grasshopper to go searching for a body of water and jump in. The grasshopper drowns, but the worm is returned to water where it can then continue its life cycle.
~320 described species of hair worms
Characteristically they are 1-3mm in diameter and 1m long on average. They have an external cuticle without cilia. Internally, they have a non-functioning gut, with no excretory, respiratory or circulatory system. They also have longitudinal muscles only, similar to nematodes. Adults are free living.
Reproductively they are dioecious, internal fertilization eggs laid in gelatinous strings. Cleavage is unusual. Larval form are parasitic in arthropods.
Order Nectonematoida: Marine, planktonic, with a double row of natotory setae along each side of the body; with dorsal and ventral longitudinal epidermal cords, blastocoelom spacious and fluid filled; gonads single; larvae parasitize decapod crustaceans
Order Gordioidea: Freshwater and semiterrestrial; lack lateral rows of setae; with a single, ventral epidermal cord; blastocoelum filled with mesenchyme in young animals but becomes spacious in older individuals; gonads grasshoppers and crickets.
