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The egg is found in the faeces, sputum, or urine of the definitive host. Depending on the species, it will either be non-embryonated (immature) or embryonated (ready to hatch). The eggs of all trematodes (except schistosomes) are operculated. Some eggs are eaten by the intermediate host (snail) or they are hatched in their habitat (water).
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. [2]
Egg of S. haematobium. Note the pointed spine on the left tip. Normal infection of adults does not produce symptoms. When eggs are released, they sometimes become permanently stuck in the bladder and cause pathological symptoms. The eggs are initially deposited in the muscularis propria which leads to
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.
An egg-making organ, the vitelline gland, does not develop in females in the absence of a male. [16] Male gametes, spermatozoa, are present in the oviduct. [17] In males, there are rudimentary ovaries, oviduct, and oocytes (developing female gametes), [18] as well as vitelline cells. [19] Males also possess the genes for hermaphroditism in ...
An oocyte (/ ˈ oʊ ə s aɪ t /, oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell (PGC), which then undergoes mitosis ...
The eggs of some digeneans, for example, are (passively) eaten by snails (or, rarely, by an annelid worm), [2] in which they proceed to hatch. Alternatively, eggs may hatch in water to release an actively swimming, ciliated larva, the miracidium , which must locate and penetrate the body wall of the snail host.
In helminthology, the state of development of an egg is often relevant to particular phases of the life cycle; commonly the visible presence of an embryo is an important criterion for egg "maturity". Use of this definition of embryonated is common in certain scientific literature.