MEXICAN LAMPREYS (PETROMYZONTIDAE: LAMPETRA: SUBGENUS TETRAPLEURODON)

Little is known about the population status of the parasitic lamprey Lampetra spadicea and its nonparasitic counterpart L. geminis, relict species endemic to the highlands of central Mexico. We used literature and museum specimen data to delineate the historical distribution of both species and then conducted field surveys to determine current distribution and abundance. Lampetra spadicea was historically found in Lago de Chapala; the lower reaches of the Rio Zula, which enters the Rio Grande de Santiago just below the outlet of Lago de Chapala; the Rio Duero, which enters the Rio Lerma about 20 km above the inlet to Lago de Chapala; and endorheic Lago de Cuitzeo and its tributary Rio Grande de Morelia drainage, which are adjacent to the Rio Lerma drainage. Lampetra spadicea apparently has been eliminated from the Morelia-Cuitzeo basin and persists, in low numbers, at only a few localities in the Lerma-Chapala-Santiago basin. It should be considered endangered. Declines in distribution and abundance were probably caused by environmental degradation. Lampetra geminis was historically known from the upper Rio Duero and Rio Grande de Morelia drainages, and it remains locally common in both. However, the range of the species is small, and pollution and habitat modification threaten several populations. This species should be given "special concern" status.