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Miracidium

The miracidium is the second stage in the life cycle of trematodes. When trematode eggs are laid and come into contact with fresh water, they hatch and release miracidium. In this phase, miracidia are ciliated and free-swimming. This stage is completed upon coming in contact with, and entering into, a suitable intermediate host for the purposes of asexual reproduction.[1] Many different species of Trematoda exist, expressing some variation in the physiology and appearance of the miracidia. The various trematode species implement similar strategies to increase their chances of locating and colonizing a new host.

Anatomy edit

Hirundinella ventricosa edit

The trematode Hirundinella 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]

Echinostoma paraensei edit

Miracidia usually need to enter a Mollusca host before they can start growing and begin reproduction, however certain species can use other animals as intermediate or main hosts. Echinostoma paraensei miracidia have 18 plates along the outside of their body.[3]

Even when about to hatch, their eggs show no signs of specialization such as projection or spine-like structure. They have elongated bodies with one intraepidermal ridge in the anterior row. They display a single "excretory vesicle".[4]

The miracidia are oval-shaped and their body is almost entirely covered in cilia except for the most anterior portions, taken up by "apical papilla". The miracidia have four papillae on each side, which contain sensory hairs. They each have an apical gland that leads to the apical papilla. They have four rows of epidermal plates, with row two made up of eight plates, while the other three rows each have six. Their eyespots are dark brown and shaped like an inverted capital letter L, located between the first and second row of plates. A single "large cephalic ganglion" along with several smaller nuclei, make up the nervous system.[5]

Physiology edit

Miracidia do not feed. Their sole purpose is to locate and colonize a host. The ability and efficiency of miracidia to find a host is a crucial factor in the growth and success of later life stages.

Schistosome miracidia follow a three-phase process when searching for a host. In phase one, the miracidia use light gravity stimuli to concentrate in areas that are likely attractive to snail hosts. The second phase consists of randomly moving around. In phase three miracidia begin approaching their host target and preparing to penetrate it.[6]

Chemosensitivity plays a large role in the search for a host, but it is not specific enough to find only those species that are suitable hosts.[6] Carbohydrates along the surface of the miracidia interact with the lectins produced by gastropods. The organization and number of these carbohydrates shift as the miracidia begin their transition to the next step in their development. Certain carbohydrates are bound all over the body of the sporocyst stage but have only been found to be present on the "intercellular ridges" of the miracidia.[7]

Three glands assist them in this process. They use glandular secretions that collect in an indented area of the papilla, as a means of both sticking to the host they are attempting to invade, and breaking down the cells on the outside of the host organism to gain entry into it.

Once inside a host, germ cells begin to form and then replicate into germ balls. Each of the germ balls grows and eventually becomes the next step in the life cycle, the sporocyst.[8]

References edit

  1. ^ Nikander, Sven; Näreaho, Anu; Saari, Seppo (2019). Canine Parasites and Parasitic Diseases. Academic Press. pp. 34–35. ISBN 9780128141120. Retrieved 25 May 2021.
  2. ^ Meenakshi, Murugesh; Madhavi, R. (1990). "Egg and Miracidium of Hirudinella Ventricosa (Trematoda: Hirudinellidae)". The Journal of Parasitology. 76 (5): 748–749. doi:10.2307/3282998. JSTOR 3282998. PMID 2213424. Retrieved 14 March 2021.
  3. ^ Pinheiro, Jairo; Maldonado, Arnaldo (2004). "Light and scanning electron microscopy of the miracidium of Echinostoma paraensei (Trematoda, Echinostomatidae)". Veterinary Parasitology. 121 (3–4): 265–275. doi:10.1016/j.vetpar.2004.02.019. PMID 15135866. Retrieved 14 March 2021.
  4. ^ Pinheiro, J.; Franco-Acuña, D.; Oliveira-Menezes, A.; Brandolini, S.V.P.B.; Adnet, F.A.O.; Lopes Torres, E.J.; Miranda, F.J.B.; Souza, W. De.; Damatta, R.A. (2015-09-01). "Additional study of the morphology of eggs and miracidia of Eurytrema coelomaticum (Trematoda)". Helminthologia. 52 (3): 244–251. doi:10.1515/helmin-2015-0039. S2CID 90946928. Retrieved 3 March 2021.
  5. ^ Diaz, M.T.; Hernández, L.E.; Bashirullah, A.K. (June 2002). "Experimental life cycle of Philophthalmus gralli (Thematoda: Philophthalmidae) in Venezuela". Revista de Biología Tropical. 50 (2): 629–641. PMID 12298291. Retrieved 3 March 2021.
  6. ^ a b Christensen, N (December 1980). "A review of the influence of host- and parasite-related factors and environmental conditions on the host-finding capacity of the trematode miracidium". Acta Tropica. 37 (4): 303–318. doi:10.5169/seals-312667. PMID 6110321. Retrieved 2 March 2021.
  7. ^ Georgieva, Katya; Georgieva, Simona; Mizinska, Yana; Stoitsova, Stoyanka (March 2012). "Fasciola hepatica miracidia: Lectin binding and stimulation of in vitro miracidium-to-sporocyst transformation". Acta Parasitologica. 57 (1): 46–52. doi:10.2478/s11686-012-0007-8. PMID 22807013. S2CID 255346391. Retrieved 2 March 2021.
  8. ^ Bogitsh, Burton; Carter, Clint; Oeltmann, Thomas (July 11, 2018). Human Parasitology (Fifth ed.). Academic Press. pp. 149–174. ISBN 978-0-12-813712-3. Retrieved 2 March 2021.

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The miracidium is the second stage in the life cycle of trematodes When trematode eggs are laid and come into contact with fresh water they hatch and release miracidium In this phase miracidia are ciliated and free swimming This stage is completed upon coming in contact with and entering into a suitable intermediate host for the purposes of asexual reproduction 1 Many different species of Trematoda exist expressing some variation in the physiology and appearance of the miracidia The various trematode species implement similar strategies to increase their chances of locating and colonizing a new host Contents 1 Anatomy 1 1 Hirundinella ventricosa 1 2 Echinostoma paraensei 2 Physiology 3 ReferencesAnatomy editThis section needs additional citations for verification Please help improve this article by adding citations to reliable sources in this section Unsourced material may be challenged and removed May 2021 Learn how and when to remove this message Hirundinella ventricosa edit The trematode Hirundinella 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 Echinostoma paraensei edit Miracidia usually need to enter a Mollusca host before they can start growing and begin reproduction however certain species can use other animals as intermediate or main hosts Echinostoma paraensei miracidia have 18 plates along the outside of their body 3 Even when about to hatch their eggs show no signs of specialization such as projection or spine like structure They have elongated bodies with one intraepidermal ridge in the anterior row They display a single excretory vesicle 4 The miracidia are oval shaped and their body is almost entirely covered in cilia except for the most anterior portions taken up by apical papilla The miracidia have four papillae on each side which contain sensory hairs They each have an apical gland that leads to the apical papilla They have four rows of epidermal plates with row two made up of eight plates while the other three rows each have six Their eyespots are dark brown and shaped like an inverted capital letter L located between the first and second row of plates A single large cephalic ganglion along with several smaller nuclei make up the nervous system 5 Physiology editMain article Trematode life cycle stages Miracidia do not feed Their sole purpose is to locate and colonize a host The ability and efficiency of miracidia to find a host is a crucial factor in the growth and success of later life stages Schistosome miracidia follow a three phase process when searching for a host In phase one the miracidia use light gravity stimuli to concentrate in areas that are likely attractive to snail hosts The second phase consists of randomly moving around In phase three miracidia begin approaching their host target and preparing to penetrate it 6 Chemosensitivity plays a large role in the search for a host but it is not specific enough to find only those species that are suitable hosts 6 Carbohydrates along the surface of the miracidia interact with the lectins produced by gastropods The organization and number of these carbohydrates shift as the miracidia begin their transition to the next step in their development Certain carbohydrates are bound all over the body of the sporocyst stage but have only been found to be present on the intercellular ridges of the miracidia 7 Three glands assist them in this process They use glandular secretions that collect in an indented area of the papilla as a means of both sticking to the host they are attempting to invade and breaking down the cells on the outside of the host organism to gain entry into it Once inside a host germ cells begin to form and then replicate into germ balls Each of the germ balls grows and eventually becomes the next step in the life cycle the sporocyst 8 References edit Nikander Sven Nareaho Anu Saari Seppo 2019 Canine Parasites and Parasitic Diseases Academic Press pp 34 35 ISBN 9780128141120 Retrieved 25 May 2021 Meenakshi Murugesh Madhavi R 1990 Egg and Miracidium of Hirudinella Ventricosa Trematoda Hirudinellidae The Journal of Parasitology 76 5 748 749 doi 10 2307 3282998 JSTOR 3282998 PMID 2213424 Retrieved 14 March 2021 Pinheiro Jairo Maldonado Arnaldo 2004 Light and scanning electron microscopy of the miracidium of Echinostoma paraensei Trematoda Echinostomatidae Veterinary Parasitology 121 3 4 265 275 doi 10 1016 j vetpar 2004 02 019 PMID 15135866 Retrieved 14 March 2021 Pinheiro J Franco Acuna D Oliveira Menezes A Brandolini S V P B Adnet F A O Lopes Torres E J Miranda F J B Souza W De Damatta R A 2015 09 01 Additional study of the morphology of eggs and miracidia of Eurytrema coelomaticum Trematoda Helminthologia 52 3 244 251 doi 10 1515 helmin 2015 0039 S2CID 90946928 Retrieved 3 March 2021 Diaz M T Hernandez L E Bashirullah A K June 2002 Experimental life cycle of Philophthalmus gralli Thematoda Philophthalmidae in Venezuela Revista de Biologia Tropical 50 2 629 641 PMID 12298291 Retrieved 3 March 2021 a b Christensen N December 1980 A review of the influence of host and parasite related factors and environmental conditions on the host finding capacity of the trematode miracidium Acta Tropica 37 4 303 318 doi 10 5169 seals 312667 PMID 6110321 Retrieved 2 March 2021 Georgieva Katya Georgieva Simona Mizinska Yana Stoitsova Stoyanka March 2012 Fasciola hepatica miracidia Lectin binding and stimulation of in vitro miracidium to sporocyst transformation Acta Parasitologica 57 1 46 52 doi 10 2478 s11686 012 0007 8 PMID 22807013 S2CID 255346391 Retrieved 2 March 2021 Bogitsh Burton Carter Clint Oeltmann Thomas July 11 2018 Human Parasitology Fifth ed Academic Press pp 149 174 ISBN 978 0 12 813712 3 Retrieved 2 March 2021 Retrieved from https en wikipedia org w index php title Miracidium amp oldid 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