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The annelids (/ ˈ æ n ə l ɪ d z /), also known as the segmented worms, comprise a large phylum called Annelida (/ ə ˈ n ɛ l ɪ d ə /; from Latin anellus 'little ring'). [ 3 ] [ a ] The phylum contains over 22,000 extant species , including ragworms , earthworms , and leeches .
For much of the year, these worms look like any other burrow-dwelling polychaete, but as the breeding season approaches, the worm undergoes a remarkable transformation as new, specialized segments begin to grow from its rear end until the worm can be clearly divided into two halves. The front half, the atoke, is asexual.
Spaghetti worms have tentacles that extend outside their burrow for a considerable distance. The bodies of spaghetti worms are segmented. The tentacles can grow over one meter long. The tentacles are used to wrap around their prey and bring it closer to the mouth. Eupolymnia crasscornis also has inner and outer lips for food gathering.
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).
Limnodrilus hoffmeisteri is conveyor-belt feeder that ingests particles in deep sediments and egests them on the sediment surface in the form of pseudofeces. [5] [6] The activities of this worm can alter sediment stratification, [6] [7] [8] increase the water content and porosity of sediment, [9] change the distribution of sediment particle size, [6] [10] alter the oxygen and nutrient dynamics ...
The first stage in many forms of bloodworm is a zooplanktonic stage followed by the benthic instar where the familiar segmented red larvae develop protected by silk tubes made in the bottom silt. These larvae progress from tiny pale opaque worms to the larger red larvae of 3 to 10 centimeters (1.2 to 3.9 in) in length or longer over a period as ...
Phyllodocida are segmented worms and range in size from a few millimetres long to over a metre. Each segment bears a pair of paddle-like parapodia.The prostomium generally has one or two pairs of eyes, a dorsal pair of antennae, a ventral pair of sensory palps and a pair of organs on the neck.
Clitellate annelids are segmented worms characterised by the clitellum or girdle which is located near the head end of mature individuals. The mouth is on the ventral surface and is overhung by the prostomium (proboscis). The brain is not located in the head but in one of the body segments.