Acanthostomum americanum is a digenean trematode found in the intestine of Morelet's crocodile (Crocodylus moreletii) from Yucatan, Mexico. The crocodiles acquire this parasite when they eat fish that are infected with the parasite's encysted larval stages.The early juveniles of these worm are characterized by the lack of spines on the oral sucker, which is likely to be an adaptation which allows it to make a smooth seal with the intestinal wall before suction, which maintains the developing parasite in position between the intestinal villi. As the parasite grows, so do the spines around its oral sucker, which then take over the role of anchoring it firmly in the intestinal mucosa.
Image adapted from:
Moravec, F. 2001. Some helminth parasites from Morelet's crocodile, Crocodylus moreletii, from Yucatan, Mexico. Folia Parasitologica 48: 47-62.
Contributed by Tommy Leung.