What are sedentary polychaetes?
The sedentary polychaetes have its prostomium, proboscis and eyes reduced or absent. Most of them live in tubes constructed by themselves in the mud or sand of the ocean bottom. The tubes are straight or U-shaped with two openings. The glands on the ventral surfaces of the segments secrete the tube-forming materials.
What makes polychaeta different than annelids?
Polychaetes differ from other annelids in having a well differentiated head with specialized sense organs and no clitellum. They have many setae, usually arranged in bundles on the parapodia. The sense organs in polychaetes are more highly developed than in oligochaetes.
What do polychaete worms show?
In Summary: Phylum Annelida These animals have well-developed neuronal and digestive systems. 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.
What is the difference between Errantia and Sedentaria?
The mobile forms (Errantia) tend to have well-developed sense organs and jaws, while the stationary forms (Sedentaria) lack them, but may have specialized gills or tentacles used for respiration and deposit or filter feeding, e.g., fanworms.
What do sedentary polychaetes feed on?
Sedentary polychaetes have greatly modified head regions for specialized feeding habits. Many are adapted for feeding on organic matter deposited on the ocean floor. For example, the lugworms have a simple, thin-walled, jawless proboscis, which is used to draw sand into the gut, where organic matter is removed.
Are bristle worms asexual?
Reproduction and Life Cycle Most bristle worms reproduce by releasing eggs and sperm into the water, though some bristle worms reproduce asexually by budding. Larvae morph from a free-swimming stage to a segmented stage before maturing. A few bristle worm species take care of their young.
What happens if you touch a fireworm?
Fireworms produce a stinging sensation if touched. The body of H. carunculata, found in the coral reefs of the Caribbean Sea, is covered with fine, white, brittle bristles that break if touched; they easily become imbedded in human skin and produce a substance that is highly irritating.
What was the longest earthworm ever found?
The longest earthworm is Microchaetus rappi of South Africa. In 1967 a giant specimen measuring 6.7 m (21 ft) in length when naturally extended and 20 mm (0.8 in) in diameter was found on a road between Alice and King William’s Town.
Do polychaete worms have eyes?
Most Polychaeta have pairs of parapodia, paddle-like appendages, running down the sides of their worm-like bodies. The polychaete Fabricia has eyes at both ends of its body, a useful thing to have, since it usually swims backwards.
What happens if you touch a bristle worm?
Although bristleworms are not aggressive, they may bite when handled, and the bristles or spines (termed chaetea) can penetrate skin (sting when touched). The spines penetrate the skin like cactus spines and can be difficult to remove, and usually cause the most symptoms listed below.
Are earthworms Errantia and Sedentaria?
Based on these results, Annelida was split into two major clades, one clade (the Errantia) adapted to an errant mobile life and the other (the Sedentaria) which includes earthworms and leeches, to a more sessile, sedentary one.
Which is an example of a Sedentary polychaete?
Polychaetes can be separated into two large orders, Errantia and Sedentaria, based on the development of the anterior appendages and life habits. Errant Polychaetes are active swimmer or crawler while Sedentary Polychaetes are burrowers or tube dwellers.
How are parapodia reduced in a polychaete?
The parapodia are reduced in the sedentary polychaetes, and the setae of many tube-dwelling forms are hooked to help the worm hold itself to the wall of its tube. The structure of the digestive tract of polychaetes is variable, reflecting the diversity of feeding types.
Which is the best description of a polychaete?
The class has usually been divided on the basis of mode of existence into two groups, the errantia and the sedentaria. Errant polychaetes include actively crawling or swimming forms which may, however, also spend time in burrows or crevices, or under rocks on the seashore.
Is there an ordinal classification for the Polychaeta?
There is no acceptable ordinal classification for the Polychaeta; the class is divided into Errantia and Sedentaria for convenience but genera belonging to each subclass may not be related. Pick a style below, and copy the text for your bibliography.