Annelid
Classification- Segmented worms make up the Phylum Annelida. The phylum includes earthworms and their relatives, leeches, and a large number of mostly marine worms known as polychaetes. Various species of polychaete are known as lugworms, clam worms, bristleworms, fire worms, sea mice. Annelids can be identified by their segmented bodies. There are about 9000 species of annelid known today.
Diversity- Annelids are coelomate animals; they have a fluid-filled body cavity in which the gut and other organs are suspended. Oligochaetes and polychaetes typically have spacious coeloms; in leeches, the coelom is reduced to a system of narrow canals, and archiannelids may lose the coelom entirely. The coelom is divided into separate compartments by partitions called septa, which give the "segmented worms" their segmented appearance.
Life History- They number more than 9,000 species that have been distributed among three classes: the marine worms (Polychaeta), which are divided into free-moving and sedentary. And then there is the tube-dwelling, forms; the earthworms (oligchaeta) and the leeches (Hirudinea).
Ecological Roles- Annelids have radiated into a number of niches. Some are parasitic, notably the leeches and myzostomarians; others filter-feed or prey on other invertebrates. However, probably the most significant ecological role played by annelids is reworking of soil and sediments. Many polychaetes and oligochaetes, and even a few leeches, are burrowers that constantly rework the sediment through which they burrow; in addition, they may ingest and excrete large quantities of sediments or soils. Soils may harbor 50 to 500 earthworms per square meter; they keep soils aerated, and their castings fertilize the soil. Traditionally the annelids have been divided into two major groups, the polychaetes and clitellates. In turn the clitellates were divided into oligochaetes, which include earthworms, and hirudinomorphs, whose best-known members are leeches. For many years there was no clear arrangement of the approximately 80 polychaete familes into higher-level groups.
Human Impacts- The presence of earthworms in soil increases crop production. The burrows they produce improve aeration of the soil, facilitating water movement, while their castings readily combine with organic debris to form humus and improve fertility of the soil. Generally people cringe when even the slightest mention of a leech is made. Their parasitic blood sucking mode of feeding stirs emotions of disgust, but medicinally harnessed, this ability has been used for centuries in blood-letting and a number of other procedures, including reconstructive surgery of severed digits and plastic surgery. Polychaetes play a role in biomonitoring of the marine environment and are commonly used as bait organisms, but may be destructive as demonstrated by their boring and fouling activity.Accounts of the use of leeches for the medically dubious practise of blood-letting have come from China around 30 AD, India around 200 AD, ancient Rome around 50 AD and later throughout Europe. In the 19th century medical demand for leeches was so high that some areas' stocks were exhausted and other regions imposed restrictions or bans on exports, and Hirudo medicinalis is treated as an endangered species by both ICUN and CITES. More recently leeches have been used to assist in microsurgery, and their saliva has provided anti-inflammatory compounds and several important anticoagulants, one of which also prevents tumors from spreading.
Classification- Segmented worms make up the Phylum Annelida. The phylum includes earthworms and their relatives, leeches, and a large number of mostly marine worms known as polychaetes. Various species of polychaete are known as lugworms, clam worms, bristleworms, fire worms, sea mice. Annelids can be identified by their segmented bodies. There are about 9000 species of annelid known today.
Diversity- Annelids are coelomate animals; they have a fluid-filled body cavity in which the gut and other organs are suspended. Oligochaetes and polychaetes typically have spacious coeloms; in leeches, the coelom is reduced to a system of narrow canals, and archiannelids may lose the coelom entirely. The coelom is divided into separate compartments by partitions called septa, which give the "segmented worms" their segmented appearance.
Life History- They number more than 9,000 species that have been distributed among three classes: the marine worms (Polychaeta), which are divided into free-moving and sedentary. And then there is the tube-dwelling, forms; the earthworms (oligchaeta) and the leeches (Hirudinea).
Ecological Roles- Annelids have radiated into a number of niches. Some are parasitic, notably the leeches and myzostomarians; others filter-feed or prey on other invertebrates. However, probably the most significant ecological role played by annelids is reworking of soil and sediments. Many polychaetes and oligochaetes, and even a few leeches, are burrowers that constantly rework the sediment through which they burrow; in addition, they may ingest and excrete large quantities of sediments or soils. Soils may harbor 50 to 500 earthworms per square meter; they keep soils aerated, and their castings fertilize the soil. Traditionally the annelids have been divided into two major groups, the polychaetes and clitellates. In turn the clitellates were divided into oligochaetes, which include earthworms, and hirudinomorphs, whose best-known members are leeches. For many years there was no clear arrangement of the approximately 80 polychaete familes into higher-level groups.
Human Impacts- The presence of earthworms in soil increases crop production. The burrows they produce improve aeration of the soil, facilitating water movement, while their castings readily combine with organic debris to form humus and improve fertility of the soil. Generally people cringe when even the slightest mention of a leech is made. Their parasitic blood sucking mode of feeding stirs emotions of disgust, but medicinally harnessed, this ability has been used for centuries in blood-letting and a number of other procedures, including reconstructive surgery of severed digits and plastic surgery. Polychaetes play a role in biomonitoring of the marine environment and are commonly used as bait organisms, but may be destructive as demonstrated by their boring and fouling activity.Accounts of the use of leeches for the medically dubious practise of blood-letting have come from China around 30 AD, India around 200 AD, ancient Rome around 50 AD and later throughout Europe. In the 19th century medical demand for leeches was so high that some areas' stocks were exhausted and other regions imposed restrictions or bans on exports, and Hirudo medicinalis is treated as an endangered species by both ICUN and CITES. More recently leeches have been used to assist in microsurgery, and their saliva has provided anti-inflammatory compounds and several important anticoagulants, one of which also prevents tumors from spreading.