Dicrocoelium dendriticum
4045978
224724124
2008-07-10T03:34:43Z
Jondel
32267
/* Ecological role */ avoid=>kept away from
{{Taxobox
| name =Lancet liver fluke
| image= Dicrocoelium dendriticum2.jpg
| regnum = [[Animal]]ia
| phylum = [[Platyhelminthes]]
| classis = [[Trematoda]]
| ordo = [[Plagiorchiida]]
| familia =[[Dicrocoeliidae]]
| genus = ''[[Dicrocoelium]]''
| species = '''''D. dendriticum'''''
| binomial = ''Dicrocoelium dendriticum''
| binomial_authority = ([[Karl Rudolphi|Rudolphi]], 1819)
}}
The '''Lancet liver fluke''' (''Dicrocoelium dendriticum'') is a [[parasite]] [[Trematoda|fluke]] that tends to live in [[cattle]] or other grazing mammals.<ref>{{cite web|url=http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/22705.htm|title=The Merckt Veterinary Manual|date=2008|publisher=Merck & Co., Inc.|accessdate=2008-07-03}}</ref>
== Life cycle ==
''D. dendriticum'' spends its adult [[Biological life cycle|life]] inside the [[liver]] of its [[host (biology)|host]]. After mating, the eggs are excreted in the [[feces]]. The first intermediate host, the terrestrial [[snail]] (''Cionella lubrica'' in the United States), eats the feces, and becomes infected by the [[larva]]l parasites. The larvae (or [[Miracidium|cercariae]]) drill through the wall of the gut and settle in its digestive tract, where they develop into a juvenile stage. The snail tries to defend itself by walling the parasites off in cysts, which it then excretes and leaves behind in the grass. The second intermediate host, an [[ant]] (''[[Formica fusca]]'' in the United States), uses the trail of slime as a source of moisture. The ant then swallows a cyst loaded with hundreds of juvenile lancet flukes. The parasites enter the gut and then drift through its body. Most of the cercariae encyst in the haemocoel of the ant and mature into [[Miracidium|metacercariae]], but one moves to the sub-esophageal [[ganglion]] (a cluster of [[nerve cell]]s underneath the [[esophagus]]). There, the fluke takes control of the ant's actions by manipulating these nerves. As evening approaches and the air cools, the infested ant is drawn away from other members of the colony and upward to the top of a blade of grass. Once there, it clamps its [[mandible (arthropod)|mandible]]s onto the top of the blade and stays there until dawn. Afterward, it goes back to its normal activity at the ant colony. If the host ant were to be subjected to the heat of the direct sun, it would die along with the parasite. Night after night, the ant goes back to the top of a blade of grass until a grazing animal comes along and eats the blade, upon which the lancet flukes will be back inside their host. They live out their adult lives inside the animal, reproduce, and the cycle continues.<ref>{{cite news|url=http://www.exile.ru/articles/detail.php?ARTICLE_ID=7145&IBLOCK_ID=35|title=Dicrocoelium Dendriticum, the Liver Fluke|date=December 12th, 2003|publisher=The Exile|language=English|accessdate=2008-07-03}}</ref><ref>{{cite news|url=http://www.em-news.com/pt/re/emmednews/pdfhandler.00132981-200211000-00034.pdf;jsessionid=Lt8Q13cFbyTBm7WS2T3vqwtZF05Tj8HMS7Mq0ynCh21p0yJLkhFL!1798224314!181195629!8091!-1|title=Infectious Madness: Disease with a Past and a Purpose: Mental illness may not be just craziness, but have a parasitic, fungal, or viral etiology|last=Callahan|first=Gerald N.|date=November 24th, 2002|publisher=Emergency Medicine News|language=English|accessdate=2008-07-03}}</ref><ref>{{cite news|url=http://www.newscientist.com/article/mg14018983.500-evolutions-neglected-superstars-there-is-nothing-glamorousabout-fleas-flukes-or-intestinal--worms-so-why-are-they-suddenlyattracting-so-much-attention-.html|title=Evolution's neglected superstars: There is nothing glamorous about fleas, flukes or intestinal worms. So why are they suddenly attracting so much attention?|last=Holmes|first=Bob|date=November 6th, 1993|publisher=NewScientist|language=English|accessdate=2008-07-03}}</ref>
== Ecological role ==
{{OR-section|date=July 2008}}
The lancet flukes are important to [[grassland]]s. To prevent infestation, cattle are kept away from patches of the greenest grass, which has been fertilized by [[manure]]. The danger for them is not the feces itself, but rather the possibility that tiny ants might be at the tops of the blades, carrying the parasite. Therefore, those patches grow undisturbed as cows feed on the remaining grass, which is not enough for all of them. The cows are then forced to eat the green grass, and for a while the cow population rises. Eventually, the parasites infect the cows. Infected cows eat less and fail to reproduce as frequently. The cow population drops, allowing the grass to regrow. The cow population eventually recovers and returns to being wary of the greenest grass, completing the cycle.
==References==
{{reflist}}
==External links==
*[http://www.weichtiere.at/Mollusks/Schnecken/parasitismus/dicrocoelium.html Lancet Fluke (Dicrocoelium lanceolatum) at The Living World of Molluscs]
[[Category:Bovine diseases]]
[[Category:Platyhelminthes]]
[[Category:Parasites]]
[[Category:Suicide-inducing parasitism]]
[[Category:Veterinary helminthology]]
[[cs:Motolice kopinatá]]
[[de:Kleiner Leberegel]]
[[fr:Dicrocoelium dendriticum]]
[[pl:Motyliczka wątrobowa]]
[[sv:Dicrocoelium dendriticum]]