Trematoda Rudolphi

Santos, Cláudia Portes & Gibson, David I., 2015, Checklist of the Helminth Parasites of South American Bats, Zootaxa 3937 (3), pp. 471-499 : 477-478

Class Trematoda Rudolphi

The Trematoda is a large class of 15,000–20,000 parasitic species which utilize all of the major vertebrate groups as hosts. The vast majority belong to the subclass Digenea, the members of which are characterised by having multiple generations (usually three) within their life-cycle, i.e. two asexual generations which mature in a molluscan host and one sexual generation which occurs within a vertebrate host. In terms of morphology, life-cycle and site, the group is very plastic, although this is not the case for individual lower taxa. Digeneans are usually parasites of the alimentary canal of their host, usually have a blind intestine and usually attach to the host using two (sometimes one) suckers. Transmission to the vertebrate host is usually by the direct penetration of a larval stage (the cercariae) or, more often, by the ingestion of an encysted larval stage (the metacercaria) with the host’s food, e.g. within an intermediate host.

Key to Families

1. Alimentary canal absent................................................................. Anenterotrematidae

- Alimentary canal present................................................................................2

2. Body bipartite, with spatulate anterior and oval posterior regions..................................... Diplostomidae

- Body not bipartite..................................................................................... 3

3. Anterior body bears proboscis with hooks......................................................... Rhopaliidae

- Anterior region of body without proboscis..................................................................4

4. Intestinal caeca short to medium, may be restricted to anterior region of body; vitelline fields limited in distribution, often with limited number of follicles, often restricted to forebody....................................................... 5

- Intestinal caeca medium to long; vitelline fields usually extensive, with many follicles, entirely or mainly in hindbody..... 6

5. True cirrus-sac absent; pseudocirrus-sac usually present; genital pore usually median or submedian in forebody.................................................................................................. Lecithodendriidae

- True cirrus-sac present; genital pore usually sublateral to lateral at level of ventral sucker................ Phaneropsolidae

6. Genital pore in posterior region of body.................................................................... 7

- Genital pore in anterior region of body..................................................................... 8

7. Ventral sucker absent........................................................................ Nudacotylidae

- Ventral sucker present....................................................................... Urotrematidae

8. Ovary between testes (in forms from the Americas)................................................. Hasstilesiidae

- Ovary anterior or posterior to testes...................................................................... 9

9. Ovary post-testicular........................................................................ Dicrocoeliidae

- Ovary pre-testicular......................................................................... Plagiorchiidae