Mexican Lamprey Identification Guide

Key identification features

• Moderate-sized lamprey with a well-developed, rounded oral sucker disc
• Four distinct rows of posterior teeth on the disc, an unusual trait that helps define its genus
• Brownish body coloration, fairly uniform along the flanks
• Two dorsal fins set toward the rear half of the body
• Slender, scaleless, cylindrical build typical of lampreys
• Eyes functional and visible in the transformed adult stage

Common look-alikes

• A closely related highland lamprey shares much of the same range but differs in fine details of tooth counts and disc structure, so precise locality helps confirm identification.
• Small non-parasitic brook lampreys elsewhere in Mexico have weaker, less developed teeth and a noticeably smaller oral disc.
• Eels and other elongated freshwater fish share the general body shape but have jaws, paired fins, and scales the Mexican Lamprey lacks.

Where you'll see one

This lamprey is restricted to high-elevation streams and lakes of the central Mexican plateau, including waters of the Lerma-Santiago system and the Lake Pátzcuaro basin, where it spends its entire life cycle in fresh water.