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Earthworms have many internal parasites, including protozoa, platyhelminthes, mites, and nematodes; they can be found in the worms' blood, seminal vesicles, coelom, or intestine, or in their cocoons (e.g. the mite Histiostoma murchiei is a parasite of earthworm cocoons [53]).
Earthworms and their kin, in the subclass Oligochaeta, lack eyes but have photoreceptor cells in the skin, especially in the dorsal portion of the anterior end. They also lack parapodia and appendages on the prostomium, the body and the periproct (terminal segment on which the anus is located).
Oligochaetes ("with few hairs"), which includes earthworms. Oligochaetes have a sticky pad in the roof of the mouth. [8] Most are burrowers that feed on wholly or partly decomposed organic materials. [13] Hirudinea, whose name means "leech-shaped" and whose best known members are leeches. [8]
Oligochaetes are well-segmented worms and most have a spacious body cavity (coelom) used as a hydroskeleton.They range in length from less than 0.5 mm (0.02 in) up to 2 to 3 metres (6.6 to 9.8 ft) in the 'giant' species such as the giant Gippsland earthworm (Megascolides australis) and the Mekong worm (Amynthas mekongianus).
In polychaetes, these papillae are tiny, fleshy projections on the worm's body or parapodia, often associated with sensory and locomotive functions. [2] Some papillae have sensory receptors to help the worm detect environmental changes , such as touch, water currents , or chemical signals, and support movement by working with parapodia to aid ...
In Britain, it is primarily called the common earthworm or lob worm (though the name is also applied to a marine polychaete). In North America , the term nightcrawler (or vitalis ) is also used, and more specifically Canadian nightcrawler , referring to the fact that the large majority of these worms sold commercially (usually as fishing bait ...
An invasive jumping earthworm – known for its aggressive behavior and ability to severely damage plants in its way – has been spotted in the Midwest. They're back: Invasive jumping earthworms ...
Historically the group has been assigned to the echinoderms, barnacles, annelids and mollusks. Relationships to other Cambrian forms (such as the Halkieriids) have been proposed and discounted. [8] In 2008, the discovery of a fossil preserving soft tissue (including chaetae and parapodia) established an annelid affinity.