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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 ...
Water vascular system. The water vascular system is a hydraulic system used by echinoderms, such as sea stars and sea urchins, for locomotion, food and waste transportation, and respiration. [1] The system is composed of canals connecting numerous tube feet. Echinoderms move by alternately contracting muscles that force water into the tube feet ...
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 ...
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 ...
Caenorhabditis elegans (/ ˌsiːnoʊræbˈdaɪtəs ˈɛləɡæns / [6]) is a free-living transparent nematode about 1 mm in length [7] that lives in temperate soil environments. It is the type species of its genus. [8] The name is a blend of the Greek caeno- (recent), rhabditis (rod-like) [9] and Latin elegans (elegant).
Invasive species of earthworms from the suborder Lumbricina have been expanding their range in North America. [1] Earthworms are considered one of the most abundant macroinvertebrates in the soil of ecosystems in temperate and tropical climates. [2] There are around 3,000 species known worldwide. [2] They are considered keystone species in ...
Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks[a] (/ ˈmɒləsks /). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. [4] The number of additional fossil species is estimated between 60,000 and 100,000, [5] and the ...
Acorn worms have an open circulatory system, in which the blood flows through the tissues sinuses. A dorsal blood vessel in the mesentery above the gut delivers blood to a sinus in the proboscis that contains a muscular sac acting as a heart. Unlike the hearts of most other animals, however, this structure is a closed fluid-filled vesicle whose ...