Thyonicola americana is a species of parasitic sea snail, a marine gastropod mollusc in the family Eulimidae. It infests the sea cucumbers Eupentacta quinquesemita and Eupentacta pseudoquinquesemita in Puget Sound and other parts of the northeastern Pacific Ocean.
The adult female Thyonicola americana bears little resemblance to a mollusc, having no shell and a coiled worm-like form.While living in the visceral tissues of its host, its central cavity is connected to the large intestine lumen of its host by a thin stalk, inside which is a tubule lined with cilia. The larvae are recognisable as mollusc larvae and have a shell and foot but no velum. They are benthic and move by crawling.
A female T. americana larva settles on a suitable host and undergoes metamorphosis into a juvenile which makes its way into the host's gut, possibly through the cloaca, and penetrates the gut wall. The adult female is a worm-like organism which when uncurled can be up to 200 mm (8 in) long. The male larva enters the central cavity of the adult female and undergoes metamorphosis into a dwarf adult; it then atrophies apart from its testicular tissues which fertilise the eggs produced by the female. After taking about six months to mature, the parasite can reproduce continually, reaching peak reproduction in late summer. As it matures, the ovaries develop and the interior cavity begins to accumulate egg capsules containing eggs and developing larvae. There may be about 500 capsules each containing 75 to 150 larvae. The larvae are liberated into the host's gut sequentially as they mature. In the autumn, most host sea cucumbers eviscerate, growing a new gut in the spring. Not all individuals eviscerate, but when this occurs, the parasite is expelled (due to its attachment to the gut wall) and dies, and any remaining egg capsules are liberated into the open sea. The parasite seems to be present only in sea cucumbers with entire guts, and more than one parasite may be present in one host.
The adult T. americana lives attached to the hind third of the intestine of the sea cucumber Eupentacta quinquesemita , a common holothurian in the Pacific Northwest,and also to the closely related Eupentacta pseudoquinquesemita ; in Puget Sound, 38% of the latter were found to be parasitised. E. quinquesemita exhibits a seasonal evisceration, expelling its guts in the autumn and growing a new set in the spring. However evisceration of the host results in the death of the parasite, and when this happens many individuals will not have reached full maturity and will fail to complete their life cycles.
The flatworms, flat worms, Platyhelminthes, or platyhelminths are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates. Unlike other bilaterians, they are acoelomates, and have no specialized circulatory and respiratory organs, which restricts them to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion. The digestive cavity has only one opening for both ingestion and egestion ; as a result, the food cannot be processed continuously.
Acanthocephala is a phylum of parasitic worms known as acanthocephalans, thorny-headed worms, or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines, which it uses to pierce and hold the gut wall of its host. Acanthocephalans have complex life cycles, involving at least two hosts, which may include invertebrates, fish, amphibians, birds, and mammals. About 1420 species have been described.
Strongyloides stercoralis is a human pathogenic parasitic roundworm causing the disease strongyloidiasis. Its common name in the US is threadworm. In the UK and Australia, however, the term threadworm can also refer to nematodes of the genus Enterobius, otherwise known as pinworms.
Sea cucumbers are echinoderms from the class Holothuroidea. They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothurian species worldwide is about 1,717 with the greatest number being in the Asia Pacific region. Many of these are gathered for human consumption and some species are cultivated in aquaculture systems. The harvested product is variously referred to as trepang, namako, bêche-de-mer or balate. Sea cucumbers serve a useful role in the marine ecosystem as they help recycle nutrients, breaking down detritus and other organic matter after which bacteria can continue the degradation process.
Dipylidium caninum, also called the flea tapeworm, double-pored tapeworm, or cucumber tapeworm, is a cyclophyllid cestode that infects organisms afflicted with fleas and canine chewing lice, including dogs, cats, and sometimes human pet-owners, especially children.
Taenia pisiformis, commonly called the rabbit tapeworm, is an endoparasitic tapeworm which causes infection in lagomorphs, rodents, and carnivores. Adult T. pisiformis typically occur within the small intestines of the definitive hosts, the carnivores. Lagomorphs, the intermediate hosts, are infected by fecal contamination of grasses and other food sources by the definitive hosts. The larval stage is often referred to as Cysticercus pisiformis and is found on the livers and peritoneal cavities of the intermediate hosts. T. pisiformis can be found worldwide.
Ancylostoma duodenale is a species of the roundworm genus Ancylostoma. It is a parasitic nematode worm and commonly known as the Old World hookworm. It lives in the small intestine of hosts such as humans, cats and dogs, where it is able to mate and mature. Ancylostoma duodenale and Necator americanus are the two human hookworm species that are normally discussed together as the cause of hookworm infection. They are dioecious. Ancylostoma duodenale is abundant throughout the world, including Southern Europe, North Africa, India, China, southeast Asia, some areas in the United States, the Caribbean, and South America.
The Strongylida suborder includes many of the important nematodes found in the gastrointestinal tracts of ruminants, horses, and swine, as well as the lungworms of ruminants and the hookworms of dogs and cats.
Toxocara canis is a worldwide-distributed helminth parasite of dogs and other canids. The name is derived from the Greek word "toxon," meaning bow or quiver, and the Latin word "caro," meaning flesh. They live in the small intestine of the definitive host. In adult dogs, the infection is usually asymptomatic but may be characterized by diarrhea. By contrast, massive infection with Toxocara canis can be fatal in puppies, causing diarrhea, vomiting, an enlarged abdomen, flatulence, and poor growth rate.
Evisceration is a method of autotomy involving the ejection of internal organs used by animals as a defensive strategy. Sea cucumbers (Holothuroidea) eject parts of the gut in order to scare and defend against potential predators such as crabs and fish. The organs are regenerated in a few days by cells in the interior of the sea cucumber.
Toxascaris leonina is a common parasitic roundworm found in dogs, cats, foxes, and related host species. Toxascaris leonina, or T. leonina, is an ascarid nematode, a worldwide distributed helminth parasite which is in a division of eukaryotic parasites that, unlike external parasites such as lice and fleas, live inside their host. The definitive hosts of T. leonina include canids and felines (cats), while the intermediate hosts are usually rodents, such as mice or rats. Infection occurs in the definitive host when the animal eats an infected rodent. While T. leonina can occur in either dogs or cats, it is far more frequent in cats.
The worm pearlfish is an eel-like fish in the family Carapidae.
Taenia serialis, also known as a canid tapeworm, is found within canines such as foxes and dogs. Adult T. serialis are parasites of carnivores, particularly dogs, with herbivorous lagomorph mammals such as rabbits and hares, serving as intermediate hosts. In definitive hosts, T. serialis is acquired by eating tissues from a variety of intermediate hosts. Accidental infection of humans though, can occur when eggs are ingested from food or water contaminated with dog feces and the human then becomes the T. serialis intermediate host.
Entovalva nhatrangensis is a species of small marine bivalve mollusc in the family Lasaeidae. It was first described in 2010 and its specific name "nhatrangensis" derives from the locality where it was originally found, Nha Trang Bay in Vietnam. It lives inside the oesophagus of certain species of sea cucumbers. It is considered to be an endosymbiont rather than a parasite because it does not harm its host.
Paragordius varius, also known as the nematomorphs or horsehair worm, are known to control their definitive host to jump into a pool of water, thus allowing the adult worm to escape and reproduce. They are similar to nematodes but are much longer and very thin. P. varius is usually found in water or wet areas. These worms definitive hosts consist of grasshoppers, crickets, cockroaches, and some beetles.
Parascaris equorum is a species of ascarid that is the equine roundworm. Amongst horse owners, the parasites are colloquially called "Ascarids". This is a host-specific helminth intestinal parasite that can infect horses, donkeys, and zebras. Horses up to six months of age are the most susceptible to infection. After this time, infection rates begin to decline and is extremely uncommon in horses over twelve months of age. It cannot infect humans or other animals. It is yellow-white in color, and females can become as large as 15 inches (38 cm) in length. Found worldwide, P. equorum is one of the most difficult equine parasites to kill, requiring larger doses of more powerful anthelmintic medications than are needed for other equine parasites.
Baylisascaris shroederi, common name giant panda roundworm, is a roundworm (nematode), found ubiquitously in giant pandas of central China, the definitive hosts. Baylisascaris larvae in paratenic hosts can migrate, causing visceral larva migrans (VLM). It is extremely dangerous to the host due to the ability of the parasite's larvae to migrate into brain tissue and cause damage. Concern for human infection is minimal as there are very few giant pandas living today and most people do not encounter giant pandas in their everyday activities. There is growing recognition that the infection of Baylisascaris shroederi is one of the major causes of death in the species. This is confirmed by a report stating that during the period of 2001 to 2005; about 50% of deaths in wild giant pandas were caused by the parasite infection.
Thyonicola dogieli is a parasitic species of gastropod mollusc in the family Eulimidae. It parasitises sea cucumbers in the northeastern Pacific Ocean.
Eupentacta quinquesemita is a species of sea cucumber, a marine invertebrate with an elongated body, a leathery skin and tentacles surrounding the mouth. It is commonly known as the stiff-footed sea cucumber or white sea cucumber, and occurs on rocky coasts in the northeastern Pacific Ocean.
Contracaecum is genus of parasitic nematodes from the family Anisakidae. These nematodes are parasites of warm-blooded, fish eating animals, i.e. mammals and birds, as sexually mature adults. The eggs and the successive stages of their larvae use invertebrates and increasing size classes of fishes as intermediate hosts. It is the only genus in the family Anisakidae which can infect terrestrial, marine and freshwater animals.
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