What characteristics do polychaetes have?
The known species of polychaetes share only a few characteristics. Each has a head, a tail and a segmented body, and typically each body segment has a pair of leg-like parapodia with spiny bristles sticking out. It’s these bristles that give the worms their name: “polychaete” is Greek for “with much hair.”
What is unusual about the jaws of some polychaetes?
In general, however, they possess a pair of jaws and a pharynx that can be rapidly everted, allowing the worms to grab food and pull it into their mouths. In some species, the pharynx is modified into a lengthy proboscis.
What type of worms are polychaetes?
Polychaetes, which include rag worms, lugworms, bloodworms, sea mice, and others, are marine worms notable for well-defined segmentation of the body. Unique among annelids, most polychaete body segments bear a pair of parapodia (flat, lobelike outgrowths) with setae, or tiny bristles.
What do polychaete worms show?
Some species bear a specialized band of segments known as a clitellum. Annelids show the presence numerous chitinous projections termed chaetae, and polychaetes possess parapodia. Suckers are seen in order Hirudinea.
What are the ecological roles of polychaetes?
Polychaetes are extremely abundant in some areas. They play essential ecological roles, serving on one hand as predators on small invertebrates, and on the other as food for fish and large invertebrates.
Why is nereis called a polychaete?
Nereis possess setae and parapodia for locomotion. They may have two types of setae, which are found on the parapodia. Locomotor chaetae arefor crawling, and are the bristles thatare visible on the exterior of thePolychaeta. they are cylindrical in shape.
Why nereis is called polychaete?
Why are polychaetes good environmental indicators?
Among benthic groups, polychaetes are, in fact, one of the best indicators of environmental disturbance, since this taxon contains both sensitive and tolerant species in a gradient from pristine to heavily disturbed habitats (Pocklington and Wells, 1992).
Where are polychaete worms found?
oceans
Polychaetes are multi-segmented worms living in all environments in the world’s oceans, present from abyssal depths to shallow estuaries and rocky shores, and even free swimming in open water. They are strictly aquatic annelids, but are the most abundant and diverse group of Phylum Annelida.
How do polychaete worms reproduce?
Earthworms reproduce sexually by aligning their bodies and exchanging sperm. On the other hand, polychaetes, which are mostly marine, reproduce asexually. One way they might do this is by fission, which is when the worm makes an exact copy of its DNA and then splits into two.
How do polychaetes move?
Locomotion in free-moving polychaetes is accomplished by circular, longitudinal, and parapodial muscles and by coelomic fluid. Body undulations, which help the worm to move rapidly, are produced by the contraction of longitudinal muscles stimulated by the backward stroke of parapodium of a particular segment.
What do you mean by polychaete?
polychaete. / (ˈpɒlɪˌkiːt) / noun. any marine annelid worm of the class Polychaeta, having a distinct head and paired fleshy appendages (parapodia) that bear bristles (chaetae or setae) and are used in swimming: includes the lugworms, ragworms, and sea mice.
What kind of animal is a Nereis sand worm?
Nereis or Neanthes is a marine polychaete annelid that lives in burrows in sea bottom and comes out in night to prey upon small animals. N. virens (Sandworm), N. pelagica (Type-species) and N. succinea (Clam worm) are common species of Nereis.
What kind of appendages does a Nereis have?
Nereis – The Clam Worm Or Sandworm. Both lobes carry thread-like appendages called dorsal and ventral cirri. The two lobes of parapodium are supported internally by two chitinous rods known as aciculum, on the apical part of which there are bundles of long, chitinous setae or chaetae which project beyond the outer margin.
What kind of locomotion does a Nereis have?
LOCOMOTION. Nereis can crawl, burrow and swim actively. Crawling is done by parapodia, while swimming involves lateral undulations of body, brought about by wave-like contractions of longitudinal muscles and use of parapodia in oar-like fashion.
How big does a Eunice aphroditois polychaete get?
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.