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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 trematode Hirudinella ventricosa releases eggs in strings. Each egg contains a single miracidium, while the string contains living spermatozoa . Miracidia have cilia that are only present in the upper portion of the body near an apical gland with 12 hook-like spines in the opening.
Eggs are then sequestered within the portal system (or perivesicular plexus in some species) of homeotherms which restricts egg dispersal but limits the resulting pathology to less sensitive organs. A significant number of eggs may escape into the external environment before a heavily infected host is incapacitated by, or dies from, the infection.
Alaria is a genus of flatworms, or trematodes, in the family Diplostomidae. Alaria is a genus of small parasitic worm about 2–6 mm long and approximately 2 mm wide. It is usually found in the small intestine of dogs, cats, or wild carnivores. It is most commonly found in Europe, Asia, and the Americas.
Sexual maturation is attained after 4–6 weeks of initial infection. A female generally lays 500–1,000 eggs in a day. [27] The female only leaves the male briefly for laying eggs. It has to because only it can enter the small and narrow peripheral venule in the submucosa so that the eggs can be released into the bladder.
Schistosoma is a genus of trematodes, commonly known as blood flukes.They are parasitic flatworms responsible for a highly significant group of infections in humans termed schistosomiasis, which is considered by the World Health Organization to be the second-most socioeconomically devastating parasitic disease (after malaria), infecting millions worldwide.
Digenea (Gr. Dis – double, Genos – race) is a class of trematodes in the Platyhelminthes phylum, consisting of parasitic flatworms (known as flukes) with a syncytial tegument and, usually, two suckers, one ventral and one oral.
In the mouse, by days 6.25 to 7.25 after fertilization of an egg by a sperm, cells in the embryo are set aside as primordial germ cells (PGCs). These PGCs will later give rise to germline sperm cells or egg cells. At this point the PGCs have high typical levels of methylation.