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An earthworm is a soil -dwelling terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (or subclass, depending on the author) Oligochaeta. In classical systems, they were in the order of Opisthopora since the male pores opened posterior to the female pores, although the ...
Oligochaeta (/ ˌɒlɪɡəˈkiːtə, - ɡoʊ -/) [1] is a subclass of soft-bodied animals in the phylum Annelida, which is made up of many types of aquatic and terrestrial worms, including all of the various earthworms. Specifically, oligochaetes comprise the terrestrial megadrile earthworms (some of which are semiaquatic or fully aquatic), and ...
Earthworms are a classic example of biological homonymous metamery – the property of repeating body segments with distinct regions. In biology, metamerism is the phenomenon of having a linear series of body segments fundamentally similar in structure, though not all such structures are entirely alike in any single life form because some of them perform special functions. [1]
The annelids / ˈænəlɪdz / (Annelida / əˈnɛlɪdə /, from Latin anellus, "little ring" [ 3 ][ a ]), also known as the segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecologies – some in marine environments as distinct as ...
Polychaetes are segmented worms, generally less than 10 cm (4 in) in length, although ranging at the extremes from 1 mm (0.04 in) to 3 m (10 ft), in Eunice aphroditois. They can sometimes be brightly coloured, and may be iridescent or even luminescent. Each segment bears a pair of paddle-like and highly vascularized parapodia, which are used ...
The nervous system is also the only place in the nematode body that contains cilia, which are all nonmotile and with a sensory function. [52] [53] The bodies of nematodes are covered in numerous sensory bristles and papillae that together provide a sense of touch. Behind the sensory bristles on the head lie two small pits, or 'amphids'.
Planarians are bilaterian flatworms that lack a fluid-filled body cavity, and the space between their organ systems is filled with parenchyma. [5] [13] Planarians lack a circulatory system, and absorb oxygen through their body wall. They uptake food to their gut using a muscular pharynx, and nutrients diffuse to internal tissues.
The Chaetognatha / kiːˈtɒɡnəθə / or chaetognaths / ˈkiːtɒɡnæθs / (meaning bristle-jaws) are a phylum of predatory marine worms that are a major component of plankton worldwide. Commonly known as arrow worms, they are mostly nektonic; however about 20% of the known species are benthic, and can attach to algae and rocks.