Additionally, the segmentation of the body wall may not correspond to the internal segmentation of the coelomic cavity. This adaptation possibly helps the leeches to elongate when they ingest copious quantities of blood from host vertebrates. The subclass Brachiobdella includes species like Branchiobdella balcanica sketi and Branchiobdella astaci , worms that show similarity with leeches as well as oligochaetes.
Figure 3. The a earthworm, b leech, and c featherduster are all annelids. Phylum Annelida includes vermiform, segmented animals. Segmentation is seen in internal anatomy as well, which is called metamerism. Annelids are protostomes. 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.
Suckers are seen in order Hirudinea. Reproductive strategies include sexual dimorphism, hermaphroditism, and serial hermaphroditism. Internal segmentation is absent in class Hirudinea. Improve this page Learn More. Skip to main content. Module Invertebrates. Search for:. This is a combination video and animation on annelid anatomy.
The annelids include marine forms called Polychaetes, the earthworms, and the leeches. Polychaetes are the most diverse group of annelids and most live in the marine environment. They differ from earthworms and leeches in that they have appendages called parapodia and do not possess a clitellum. In size they range from 1 mm 0. Many species display beautiful coloration and some possess toxic spines. There are 3 basic life forms of polychaetes; free-swimming, sedentary, and boring.
The free-swimming polychaetes are found swimming in the water column, crawling across the seabed, or burrowing beneath the sediments. Most sedentary polychaetes produce tubes within which they live. Some tubes are made of elastic organic material and others are hard, stony, and calcareous.
Most feed on organic material either in the water column or on the seabed but some species collect and consume small invertebrates. There are commensal polychaetes but parasitism is rare. All polychaetes have gills and a closed circulatory system and some have a small heart. As with the other Annelids, polychaetes do have a small brain and are aware of light, touch, and smell; most species dislike light.
Reproduction involves males and females who release their gametes in the water where fertilization occurs and drifting larva form. The tube of a common tubeworm found on panhandle beaches; Diopatra. Photo: University of Michigan. Aside from parasitic tapeworms and leeches, earthworms are one of the more commonly recognized varieties of worms.
Many folks actually raise earthworms for their gardens or for fish bait; a process known as vermiculture. Like the earthworms they also have a clitellum, a region of thickened skin which is only obvious during the reproductive period. Mating involves the intertwining of bodies where each deposits sperm in the others' clitellar area. Rhyncobdellids have no penis but produce sharp packages of sperm which are forced through the body wall. The sperm then make their way to the ovaries where fertilisation takes place.
The clitellum secretes a tough gelatinous cocoon which contains nutrients, and it is in this that the eggs are deposited. The cocoon is either buried or attached to a rock, log or leaf and dries to a foamy crust.
After several weeks or months, the young emerge as miniature adults. Studies show that the cocoons are capable of surviving the digestive system of a duck.
For over years, leeches were needlessly applied for many ailments as an adjunct to blood letting. Their use in Europe peaked between and , but subsequent shortages led to a decline in their use. Today there is a real clinical application in that they are of great value to plastic surgeons when venous congestion of skin and muscle flaps is a problem.
Medical use of leeches also includes treatment of black eyes, and hirudin is used in the treatment of inflammation of the middle ear. Hirudin is also being developed for experimental use as a systemic anticoagulant, and may prove useful in invitro blood sampling. The Sydney suburban sprawl is resulting in houses extending into areas such as wet valleys that leeches normally prefer.
It is therefore less distance for these leeches to travel in wet weather before they end up in backyards and can get a meal from domestic animals or humans living there. Similarly the domestic animals and humans themselves unwittingly bring many leeches home with them from bush walks, holidays, and other travels. If these leeches are adult they will invariably find a suitable damp spot in the garden to lay their eggs and suddenly you have a colony of leeches in your backyard.
The most common enquiry regarding leeches concerns repellents. It is unknown whether a specific preparation is commercially available but there is a plethora of tried and tested, but unproven leech-protection ideas. These include a lather of bath soap smeared on exposed parts and left to dry, applications of eucalyptus oil, tropical strength insect repellent, lemon juice and impenetrable barriers of socks and pantyhose.
The presence of hirudin in the wound following a leech bite may cause oozing to continue for several hours. Although inconvenient, blood loss is not significant. Gut bacteria can cause wound infection. In the post-operative use of leeches this is closely monitored and dealt with by use of the appropriate antibiotic.
There may also be a delayed irritation and itching after a bite. There appears to be no support for the theory that mouthparts left behind after forced removal of the leech causes this reaction. There is no evidence to suggest that they do. The presence of trypanosomes in the gut of jawless leeches has been noted, but jawed leeches do not appear to be hosts.
Trypanosomes cause the African sleeping sickness in humans. Leeches transmit trypanosomes that infect fish, crocodiles and even platypus, but none of them are dangerous to humans. Allergy to leech bite has been reported. Medical opinion should be sought, depending on the severity of the reaction. Trypanosomes of Australian mammals: A review Craig K. Thompson , Stephanie S. Godfrey, R. Andrew Thompson. The Australian Museum respects and acknowledges the Gadigal people as the First Peoples and Traditional Custodians of the land and waterways on which the Museum stands.
Image credit: gadigal yilimung shield made by Uncle Charles Chicka Madden. This website uses cookies to ensure you get the best experience on our website. Learn more. Skip to main content Skip to acknowledgement of country Skip to footer This photo was taken at Somersby Falls, New South Wales, where the leeches were 'searching for blood'.
0コメント