Opisthorchiida

flatworm order

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Last updated

July 1, 2026

Quick Summary

The Opisthorchiida are an order of flatworms, specifically within the Class Trematoda. These organisms are typically endoparasites, meaning they live inside a host organism, and their life cycles generally involve at least one intermediate host. A characteristic of the Opisthorchiida order is that their cercaria, an immature form, is never armed, and their excretory pores open on the margins of the tail. There are approximately 700 species within this order. The term "opisthorchiid" can also refer to a trematode belonging to the family Opisthorchiidae.12

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flatworm
Annotated classification
Order Opisthorchiida Cercaria never armed; excretory pores open on margins of tail; about 700 species. There is disagreement on many aspects of the taxonomy of Platyhelminthes, especially regarding class divisions. For example, some authorities consider Monogenea to be a subclass within the class Trematoda.
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Order Opisthorchiida Cercaria never armed; excretory pores open on margins of tail; about 700 species. There is disagreement on many aspects of the taxonomy of Platyhelminthes, especially regarding class divisions. For example, some authorities consider Monogenea to be a subclass within the class Trematoda.
Read More