What are the developmental stages of trematodes?
What are the developmental stages of trematodes?
There are three distinct larval stages involved in all digenetic trematode life cycles: the miracidium, sporocyst, and cercaria. Some taxa also produce rediae and/or encysted metacercariae. All of these life stages except for the miracidium can be found in first intermediate hosts.
What are the larval stages in flukes?
platyhelminthes • All digenetic trematodes have indirect life cycles. host & under suitable conditions miracidium hatches. Hatching is controlled by light temperature & salinity. Five larval stage are miracidium, sporocyst, rediae, cereariae & metacercariae.
Which trematode Redia stage is absent?
Different species of trematode will undergo different patterns of larval development, although once sporocysts produce daughter sporocysts, rediae do not develop. In the schistosomes there are two generations of sporocyst in the snail host, but the redia stage is absent.
What are the 4 species of Heterophyids?
Species in the trematode family Heterophyidae infecting humans include Centrocestus formosanus, Haplorchis pumilio, H. taichui, H. yokogawai, Procerovum varium and Stellantchasmus falcatus.
What is intermediate parasite?
1 : a host which is normally used by a parasite in the course of its life cycle and in which it may multiply asexually but not sexually — compare definitive host.
How are trematodes transmitted?
These parasitic flukes have a complex life cycle involving diverse definitive hosts and one or two intermediate hosts. Foodborne trematodes cause infection in humans via the consumption of contaminated food (raw fish, crustaceans or vegetables).
How do the larval forms of the trematodes and the Cestodes differ?
Cestodes are tape-like and segmented in shape, have a head with suckers and possibly hooks, and lack a digestive tract. Trematodes are leaf-like and unsegmented, lack hooks entirely, and have an incomplete digestive tract.
What is Hexacanth and oncosphere?
Hexacanth – a six-hooked larva derived from micromeres, which is the definitive product of embryogenesis. of a cestode, and that invades the first or sole intermediate host. Oncosphere – a hexacanth enclosed by one or two embryonic envelopes.
What are trematode worms?
Trematodes, or flukes, are parasitic flatworms with unique life cycles involving sexual reproduction in mammalian and other vertebrate definitive hosts and asexual reproduction in snail intermediate hosts.
What is the difference between Cercariae and Metacercariae?
At this stage, the cercaria is released from the snail and seeks out a second intermediate host to infect. Metacercaria: It is in this stage that the parasite infects the definitive human host via ingestion of the snail or other second intermediate host.
What is the infective stage of Heterophyes Heterophyes?
Life Cycles of Intestinal Trematodes The infective stage (metacercaria) can be found in a wide variety of freshwater and brackish water fishes. Perhaps most important are Haplorchis spp., Heterophyes heterophyes, and Metagonimus yokogawai.
How does a trematode infect a vertebrate host?
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 through the rejected host’s faeces or urine.
Where does the larval form of a trematode develop?
The larval form of the parasite develops within the germinal cells of the sporocyst or redia. A cercaria has a tapering head with large penetration glands. It may or may not have a long swimming “tail”, depending on the species.
Which is the largest group of parasitic trematodes?
Digenean Trematodes The sub-class Digenea is the largest group of parasitic Platyhelminthes. Like many of the other platyhelminths, digeneans are endoparasites and thus found inside the body of the host.
What kind of life cycle does a digenean trematode have?
While Digenean trematodes are parasitic in nature, studies have them to be free-living in two stages of their life cycle. These include the miracidium and cercaria larval stages. Morphologically, Digenea is characterized by an oval, dorso-ventrally flattened body. They also have a smooth surface with spines as well as anterior and ventral suckers.
