Aquatic Parasite Observatory

Alaria spp. (Schrank, 1788)

    • Species Name: Alaria spp. (Schrank, 1788)
    • Synonyms: None
    • Taxonomy: (Schrank, 1788) Animalia, Platyhelminthes, Trematoda, Strigeidida, Diplostomatidae, Alaria spp.
    • Description: "Body indistinctly bipartite; forebody linguiform, concave; hindbody cylindrical, usually shorter than forebody. Pseudosuckers present, forming ear-like projections. Oral and ventral suckers rather small; pharynx relatively large. Holdfast organ round to elongate, variable in length; anterior margin may reach pharynx. Testes of different size and form, multi- or bilobed, tandem; anterior asymmetrical, opposite ootype; posterior symmetrical, larger. Ovary oval, median, pretesticular, at junction of fore- and hindbody. Vitellarium mainly in forebody, may penetrate holdfast organ and extend into hindbody. Seminal vesicle with either ejactulatory pouch or ejactulatory duct with muscular region. Copulatory bursa small, with subterminal dorsal pore. Hermaphroditic duct opens at tip of small papilla. In Carnivora. Eurasia and tropical North America. Mesocercariae in anurans. Paratenic hosts of mesocercariae are included in life cycle. Cercariae with two pairs of pre-acetabular penetration glands; flame-cell formula 2[(2+2+2)+(2+2+2)]=24 Metacercariae of 'diplostomulum' type, develop during trans-entero-pulmonary migration in final host. Type species A. alata (Goeze, 1782) Krause, 1914" (Bray et al., 2002).
    • Life Cycle: Species of Alaria have indirect lifecycles utilizing up to 4 different hosts. Eggs embryonate and hatch into miricidium which infect a snail host (typically Helisoma). The miracidiae then develop into sporocycsts that produce cercariae. Cercariae swim freely through the water column until they find a tadpole host. Inside the tadpole, they develop into mesocercariae, which can survive the metamorphosis of the frog. If the frog is eaten by a canid, the parasite will develop into an adult and reside in the intestine. If the tadpole is eaten by a non-canid, the parasite can remain a mesocercariea in the new, paratenic host until transmission into a canid can occur. Eggs are expelled through the feces (University of Alberta).
    • Sources: Bray, R.A., Gibson D.I., and Jones, A. 2002. Keys to the Trematoda, Vol. 1, p. 184.
    • University of Alberta
    • APO Parasite Records: (by Life Cycle)

Parasite Images:

Distribution Map:

  • University of Colorado Boulder