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Metacercariae
Trematodes are parasitic flatworms of the class ''Trematoda'', specifically parasitic flukes with two Sucker (zoology), suckers: one ventral and the other Mouth, oral. Trematodes are covered by a Tegument (helminth), tegument, that protects the organism from the environment by providing secretory and absorptive functions. The life cycle of a typical trematode begins with an egg. Some trematode eggs hatch directly in the environment (water), while others are eaten and hatched within a host, typically a mollusc. The hatchling is called a ''miracidium,'' a free-swimming, ciliated larva. Miracidia will then grow and develop within the intermediate host into a sac-like structure known as a sporocyst or into rediae, either of which may give rise to free-swimming, motile cercariae larvae. The cercariae then could either infect a vertebrate host or a second intermediate host. Adult metacercariae or mesocercariae, depending on the individual trematode's life cycle, will then infect the ve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trematode Lifecycle Stages
Trematodes are parasitic flatworms of the class ''Trematoda'', specifically parasitic flukes with two suckers: one ventral and the other oral. Trematodes are covered by a tegument, that protects the organism from the environment by providing secretory and absorptive functions. The life cycle of a typical trematode begins with an egg. Some trematode eggs hatch directly in the environment (water), while others are eaten and hatched within a host, typically a mollusc. The hatchling is called a ''miracidium,'' a free-swimming, ciliated larva. Miracidia will then grow and develop within the intermediate host into a sac-like structure known as a sporocyst or into rediae, either of which may give rise to free-swimming, motile cercariae larvae. The cercariae then could either infect a vertebrate host or a second intermediate host. Adult metacercariae or mesocercariae, depending on the individual trematode's life cycle, will then infect the vertebrate host or be rejected and excreted th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trematode Infection
Trematoda is a class of flatworms known as trematodes, and commonly as flukes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is a mollusk, usually a snail. The definitive host, where the flukes sexually reproduce, is a vertebrate. Infection by trematodes can cause disease in all five vertebrate classes: mammals, birds, amphibians, reptiles, and fish. Etymology Trematodes are commonly referred to as flukes. This term can be traced back to the Old English name for flounder, and refers to the flattened, rhomboidal shape of the organisms. The etymology of trematode stems from the Greek word ''trēmatṓdēs'', which means "pierced with holes", and refers to the worm's sucker, which pierces a hole in the host while the worm is attached and feeding. Taxonomy There are 18,000 to 24,000 known species of trematodes, divided into two subclasses — the Aspidogastrea and the Digen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trematodes
Trematoda is a class of flatworms known as trematodes, and commonly as flukes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is a mollusk, usually a snail. The definitive host, where the flukes sexually reproduce, is a vertebrate. Infection by trematodes can cause disease in all five vertebrate classes: mammals, birds, amphibians, reptiles, and fish. Etymology Trematodes are commonly referred to as flukes. This term can be traced back to the Old English name for flounder, and refers to the flattened, rhomboidal shape of the organisms. The etymology of trematode stems from the Greek word ''trēmatṓdēs'', which means "pierced with holes", and refers to the worm's sucker, which pierces a hole in the host while the worm is attached and feeding. Taxonomy There are 18,000 to 24,000 known species of trematodes, divided into two subclasses — the Aspidogastrea and the D ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bucephalus Polymorphus
''Bucephalus polymorphus'' is a type of flatworm. This species is within the Bucephalidae family of Digenea, which in turn is a subclass of Trematodes within the phylum Platyhelminthes (i.e. flatworm). It is characterized by having a mouth near the middle of its body, along with a sac-like gut. The mouth opening is located in the centre of the ventral surface. This is a specific body type of cecaria known as a gastrostome. The adults occur in the gut of marine and fresh-water fish. The metacercariae encyst in smaller fish, sometimes in the nervous system. These parasitic flatworms are dorso-ventrally flattened animals characterized by a bilaterally symmetrical body enclosed within a syncytial tegument. They have a distal, anucleate later (distal cytoplasm). The distal cytoplasm contains vesicular inclusions that are Golgi derived. The adults of these acoelomate worms are common in the digestive tract, but are also found in other organs of vertebrates. The adult parasite attaches ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribeiroia
''Ribeiroia'' () is a genus of trematode parasites that sequentially infect freshwater snails in the family Planorbidae (ramshorn snails) as first intermediate hosts, fish and larval amphibians as second intermediate hosts, and birds and mammals as definitive hosts (see ). In North America, infection by ''Ribeiroia'' has been linked to amphibians with limb malformations. The connection between parasitic infection and limb malformations has generated questions about (a) whether parasite-induced malformations in amphibians are increasing (see ), and (b) the consequences of such abnormalities for amphibian population conservation (see ). Taxonomy ''Ribeiroia'' is a genus of parasites in the class Trematoda, phylum Platyhelminthes. Currently three species and one subspecies of ''Ribeiroia'' are recognized: '' R. ondatrae'' in North America, ''R. marini'' in the Caribbean, ''R. m. guadeloupensis'' on the Caribbean island of Guadeloupe, and ''R. congolensis'' in Africa (Johnson et a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Krill
Krill ''(Euphausiids)'' (: krill) are small and exclusively marine crustaceans of the order (biology), order Euphausiacea, found in all of the world's oceans. The name "krill" comes from the Norwegian language, Norwegian word ', meaning "small Fry (biology), fry of fish", which is also often attributed to species of fish. Krill are considered an important trophic level connection near the bottom of the food chain. They feed on phytoplankton and, to a lesser extent, zooplankton, and are also the main source of food for many larger animals. In the Southern Ocean, one species, the Antarctic krill, makes up an estimated biomass (ecology), biomass of around 379 million tonnes, making it among the species with the largest total biomass. Over half of this biomass is eaten by whales, Pinniped, seals, penguins, seabirds, squid, and fish each year. Most krill species display large diel vertical migration, daily vertical migrations, providing food for predators near the surface at night an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dioecious
Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is biparental reproduction. Dioecy has costs, since only the female part of the population directly produces offspring. It is one method for excluding self-fertilization and promoting allogamy (outcrossing), and thus tends to reduce the expression of recessive deleterious mutations present in a population. Plants have several other methods of preventing self-fertilization including, for example, dichogamy, herkogamy, and self-incompatibility. In zoology In zoology, dioecy means that an animal is either male or female, in which case the synonym gonochory is more often used. Most animal species are gonochoric, almost all vertebrate species are gonochoric, and all bird and mammal species are gonochoric. Dioecy may also describe colonies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schistosomatidae
Schistosomatidae is a family of digenetic trematodes with complex parasitic life cycles. Immature developmental stages of schistosomes are found in molluscs and adults occur in vertebrates. The best studied group, the blood flukes of the genus ''Schistosoma'', infect and cause disease in humans. Other genera which are infective to non-human vertebrates can cause mild rashes in humans. Schistosomatids are dioecious (individuals are of separate sexes) which is exceptional with regards to their phylum, Platyhelminthes, in which most species are hermaphroditic (individuals possess both male and female reproductive systems). History The eggs of these parasites were first described by Theodor Bilharz, a German pathologist working in Egypt in 1851 who found the eggs during the course of an autopsy. He wrote two letters to his former teacher Karl Theodor Ernst von Siebold in May and August 1851 describing his findings. von Siebold wrote a paper (published in 1852) summarizing Bil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hermaphroditic
A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many taxonomic groups of animals, primarily invertebrates, are hermaphrodites, capable of producing viable gametes of both sexes. In the great majority of tunicates, mollusks, and earthworms, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which either partner can act as the female or male. Hermaphroditism is also found in some fish species, but is rare in other vertebrate groups. Most hermaphroditic species exhibit some degree of self-fertilization. The distribution of self-fertilization rates among animals is similar to that of plants, suggesting that similar pressures are operating to direct the evolution of selfing in animals and plants. A rough estimate of the number of hermaphroditic animal species is 6 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Encyst
A microbial cyst is a resting or dormant stage of a microorganism, that can be thought of as a state of suspended animation in which the metabolic processes of the cell are slowed and the cell ceases all activities like feeding and locomotion. Many groups of single-celled, microscopic organisms, or microbes, possess the ability to enter this dormant state. Encystment, the process of cyst formation, can function as a method for dispersal and as a way for an organism to survive in unfavorable environmental conditions. These two functions can be combined when a microbe needs to be able to survive harsh conditions between habitable environments (such as between hosts) in order to disperse. Cysts can also be sites for nuclear reorganization and cell division, and in parasitic species they are often the infectious stage between hosts. When the encysted microbe reaches an environment favorable to its growth and survival, the cyst wall breaks down by a process known as excystation. En ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
