![]() Appendages on each segment are used for walking or swimming. The annelid worms (phylum Annelida) have segmented bodies, distinct heads, digestive tubes, circulatory systems, and brains. (15 cm) long and covered with brown chitin, giving it a stiff appearance since the worms were frequently found in watering troughs, superstition had it that they developed from horsehairs. The larvae are parasitic, first in the bodies of aquatic insects and then within grasshoppers or beetles. Like the nematodes, the hairworms, or horsehair worms, are unsegmented, but they are grouped separately in the phylum Nematomorpha. Other parasitic nematodes include Filaria, the cause of filariasis, which may result in elephantiasis Trichinella, the cause of trichinosis Ascaris, an intestinal parasite of humans, horses, and pigs the pinworm, a parasite common in children the Guinea worm, Dracunculus medinensis, which is ingested as a larva in water and slowly emerges when full grown (up to 3 ft/91 cm) through a painful sore in the skin, but as a result of an eradication program is now found only in Chad, Ethiopia, and South Sudan and various other species that are agricultural pests. Also called roundworms and threadworms, the nematodes include widespread free-living species as well as parasites, such as the hookworm. Of these, the largest phylum is the nematodes, which are probably the most numerous multicellular animals. Pseuodcoelomate worms include those in the phyla Rotifera, Gastrotricha, Kinorhyncha, Nematoda, and Nematomorpha. The smallest species are only a fraction of an inch (less than 2.5 cm) long, while giants of the group range up to 90 ft (27 m) and are the longest of all invertebrates. The nemertines, or ribbon worms (phylum Nemertinea), are often colorful marine carnivores with an extensible proboscis. Members of the phylum Platyhelminthes, or the flatworms, are the most primitive they are generally small and flat-bodied and include the free-living planarians (of the class Turbellaria) as well as the parasitic flukes (class Trematoda) and tapeworms (class Cestoda). Worm, common name for various unrelated invertebrate animals with soft, often long and slender bodies. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |