![]() Probably the longest worm on confirmed records is Amynthas mekongianus that extends up to 3 m (10 ft) in the mud along the banks of the 4,350 km (2,703 mi) Mekong River in Southeast Asia.įrom front to back, the basic shape of the earthworm is a cylindrical tube-in-a-tube, divided into a series of segments (called metameres) that compartmentalize the body. When mating, two individual earthworms will exchange sperm and fertilize each other's ova.ĭepending on the species, an adult earthworm can be from 10 mm (0.39 in) long and 1 mm (0.039 in) wide to 3 m (9.8 ft) long and over 25 mm (0.98 in) wide, but the typical Lumbricus terrestris grows to about 360 mm (14 in) long. ![]() Įarthworms are hermaphrodites: each worm carries male and female reproductive organs and genital pores. Similar sets of muscles line the gut tube, and their actions propel digested food toward the worm's anus. Circumferential and longitudinal muscles edging each segment let the worm move. Large numbers of chemoreceptors concentrate near its mouth. Įarthworms have a central nervous system consisting of two ganglia above the mouth, one on either side, connected to an axial nerve running along its length to motor neurons and sensory cells in each segment. As soft-bodied invertebrates, they lack a true skeleton, but their structure is maintained by fluid-filled coelom chambers that function as a hydrostatic skeleton. They have a double transport system made of coelomic fluid that moves within the fluid-filled coelom and a simple, closed circulatory system, and respire (breathe) via cutaneous respiration. They have a cosmopolitan distribution wherever soil, water and temperature conditions allow. They are one of nature's most important detritivores and coprophages, and also serve as food for many low-level consumers within the ecosystems.Įarthworms exhibit an externally segmented tube-within-a-tube body plan with corresponding internal segmentations, and usually have setae on all segments. An earthworm's digestive system runs the length of its body. Įarthworms are commonly found in moist, compost-rich soil, eating a wide variety of organic matters, which include detritus, living protozoa, rotifers, nematodes, bacteria, fungi and other microorganisms. The megadriles are characterized by a distinct clitellum (more extensive than that of microdriles) and a vascular system with true capillaries. Larger terrestrial earthworms are also called megadriles (which translates to "big worms") as opposed to the microdriles ("small worms") in the semiaquatic families Tubificidae, Lumbricidae and Enchytraeidae. Other slang names for earthworms include "dew-worm", "rainworm", "nightcrawler", and "angleworm" (from its use as angling hookbaits). Theoretical cladistic studies have placed them in the suborder Lumbricina of the order Haplotaxida, but this may change. In classical systems, they were in the order of Opisthopora since the male pores opened posterior to the female pores, although the internal male segments are anterior to the female. The term is the common name for the largest members of the class (or subclass, depending on the author) Oligochaeta. An unidentified earthworm species with a well-developed clitellumĪn earthworm is a soil-dwelling terrestrial invertebrate that belongs to the phylum Annelida.
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