Digenean Flatworms are parasitic Helminth Flatworms that typically have two or more hosts in their life-cycle. Their primary host is usually a Vertebrate, where the Flatworms reproduce sexualy with eggs being released in excreta. These eggs are then consumed by the secondary (or intermediate) host, most commonly a Gastropod, where the Flatworms undergo a generation of asexual reproduction, producing a large number of ciliated larvae that leave the secondary host's body and actively swim through waters to seek out the primary host and invade its tissues. Variants of this life-cycle exist in which the eggs hatch in water producing larvae that seek out the secondary host, in which the secondary host is an Annelid Worm or non-Gastropod Mollusc, or where a third host exists, typically an animal consumed by the primary host, which the ciliated larvae invade, forming cysts within its tissue while they wait for it to be consumed by the primary host. These worms are variously known as Liver Flukes, Blood Flukes, Lung Flukes and Intestinal Flukes depending on which tissues they invade.
In a paper published in the journal Zootaxa on 16 June 2014 Norman Dronen of the Laboratory of Parasitology at the Department of Wildlife and Fisheries Sciences at Texas A&M University describes a new species of Liver Fluke from Clapper Rails (Rallus longirostris) from Galveston in Texas.
The new species is placed in the genus Athesmia, members of which have previously been found infecting Birds and occasionally Mammals (one species of Bat and one species of Monkey) in Europe, North and South America, the Caribbean and the Galapagos Islands, and is given the specific name ralli, which derives from the host’s genus name (Rallus). Athesmia ralli is large for a Liver Fluke (specimens examined were 8,978–11,150 μm or 8.798-11.150 mm).
Athesmia ralli from the Clapper Rail, Rallus longirostris (Gruiformes: Rallidae), from Texas. (1) Ventral view of fully mature adult. (2) Composite drawing of cirrus sac and seminal vesicle showing and cirrus and location of the genital pore, ventral view. 3. Composite drawing of female genital complex, ventral view. Abbeviations: AT, anterior testis; B, body wall; C, cecum; GP, genital pore; L, Laurer’s canal; M, Mehlis’ glands; OD, oviduct; OV, ovary; PT, posterior testis; R, vitelline reservoir; SR, seminal receptacle; SV, seminal vesicle; U, uterus; V, vitelline field; VS, ventral sucker. Dronen (2014).
A Clapper Rail, Rallus longirostris, in Citrus County Florida. Barbara Bowen/Wikimedia Commons.
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