Aquatic Parasite Observatory

Ascocotyle spp.

    • Species Name: Ascocotyle spp.
    • Synonyms: None
    • Taxonomy: Animalia, Platyhelminthes, Trematoda, Echinostomida, Heterophyidae, Ascocotyle spp.
    • Description: “Body thickly spinose. Oral sucker with one or two rows of spines and with a, distinct posterior muscular projection. Prepharynx long, pharynx well developed. Esophagus may or may not be present; intestinal ceca variable in length. Depression on ventral surface of body containing the genital sinus and the aeetabulum. Testes paired posteriorly. Seminal vesicle very prominent and well developed. Ovary pretesticular median or slightly to one side. Seminal receptacle large, behind or on level with ovary. Vitellaria lateral, usually postacetabular. Uterus usually confined to postacetabular region. Eggs large, operculate” (Looss, 1899).
    • Life Cycle: “Their metacercariae encyst in different organs of fish (Scholz et al., 2001; Steele, 2003). The adult worms are non-pathogenic, intestinal parasites of piscivorous, or fish eating birds and mammals (Armitage, 1998). In the intestine, the parasite matures and produces eggs which are passed into the water. Because these organisms are hermaphroditic, one parasite can populate a marsh with eggs. The first intermediate hosts are amnicolid and hydrobiid snails, which take up the eggs while feeding over the bottom surface of the estuary. The eggs develop sporocysts containing many redia or brood stage, and often move from the snail digestive gland to the gonads or hepatopancreas where further development ensues. When mature, these cercariae leave the redia and swim out of the snail towards illuminated areas of the water. The second intermediate hosts are centrarchiid, mugilid, cyprinodontid, and poeciliid fishes, and in at least one instance, anuran tadpoles. Within the gills, Ascocotyle cercariae enter the blood stream by penetration of the vascular tissue and encyst to form metacercariae in the fish host” (Armitage, 1998; Steele, 2003).
    • Sources: Looss, A., 1899. Weitere Beitrage zur Kenntnis der Trematoden-fauna Aegypteus. Zool. Jber. syst. Vol. 12, p. 521-784.
    • Omrani, S.B., Mousavi, E.H., Sharifpour, A.I. 2009. Occurrence and histopathology of Ascocotyle tenuicollis metacercaria in gill of platyfish (Xiphophorus maculatus) imported to Iran. Iranian Journal of Fisheries Sciences, Vol. 9, p.472-477.

      Scholz, T., Aguirre-Macedo, M.L. and Salgado-Maldonado, G., 2001. Trematodes of the family Heterophyidae (Digenea) in Mexico: a review of species and new host and geographical records. Journal of Natural History, Vol. 35, Issue 12, p. 1733-1772.

      Steele, E. and Hicks, T., 2003. Histological effect of Ascocotyle tenuicollis (Digenea: Heterophyidae) metacercarial infection on the heart of fundulus heteroclitus (Teleostei: Cyprinodontidae). Journal of the South Carolina academy of science 18.

      Armitage, M.H. 1998. Complex Life Cycles in Heterophyid Trematodes: Structural and Developmental Design in the Ascocotyle Complex of Species. Fourth International Conference on Creationism. Creation Science Fellowship.

    • APO Parasite Records: (by Life Cycle)

Parasite Images:


  • University of Colorado Boulder