GENERIC KEY AND SYNOPSES FOR FREE-LIVING LARVAE AND TADPOLES OF MEXICAN AMPHIBIANS RONALD ALTIG Department of Zoologij, Mississippi State University, State College, Mississippi 39762 and RONALD A. BRANDON Department of Zoology, Southern Illinois University, Carbondale, Illinois 62901 Abstract A key to the genera of free-living larvae and tadpoles of Mexican amphibians, ac-companied by generic synopses and a bibliography, is presented. The salamander key applies to posthatching specimens with front digits fully formed ( ca. 20 mm snout-vent length), while the tadpole key applies to premetamorphic and prometamorphic specimens. Knowledge of Mexican amphibians has increased rapidly during the last 20 years. Although comprehensive reviews can now be made of some groups (e.g., Tihen, 1958; Duellman, 1963; Duellman and Trueb. 1966), investigation of larval forms has lagged. Once larval taxonomy is stabilized, ecological and behavioral studies of the im-mature forms can be undertaken. The present key and synopses summarize the characteris-tics of the genera of free-living larval am-phibians of Mexico. Data from the literature are combined with new information. Expla-nation of new terminology and pertinent figures appear in Altig (1970). Free-living larval salamanders of 19 species in 4 genera and 3 families inhabit Mexico. At least two species, Siren intermedia and A?nbystoma dumerilii, are paedogenetic. In several species of Ambystoma and Rhyaco-siredon, some or all specimens in some populations breed while retaining larval form and external gills; Ambystoma mexicanum usually does. Life histories of many other species are poorly known. Although Taricha is unknown in Mexico, it is included here because T. torosa possibly occurs in Baja Cal-ifornia. Species of Bolitoglossa, Chiropterotriton, Lineatriton, Parvimolge, Pseudoeurycea, and Thorius ( Family Plethodontidae ) , compris-ing over two-thirds of the Mexican salaman-der fauna, have terrestrial eggs and direct development; gills and other larval features are lost before hatching. Free-living tadpoles of 127 species in 21 genera and 8 families inhabit Mexico. Over half of the species are hylids, with the major-ity of the remainder being bufonids and ranids. All the eggs are aquatic, except for those of P achy medusa, Agalychnis, Centro-lenella, and Leptodactylus. The first three-lay arboreal eggs and the latter lays eggs in a foam nest in a terrestrial burrow; Physa-laemus has a floating foam nest. Due to the incomplete data on tadpoles, future revision of some couplets is inevitable. About 787o of the tadpoles have some descriptive data available. Rana, Bufo, and certain groups of hylids need special attention. Species of Eleutherodactylus, Hylactophryne, Syrrho-phus, and Tomodactyh/s (Family Leptodac-tylidae) have terrestrial eggs, direct develop-ment, and lack a free-living tadpole. Key 1. Salamander larva or paedogenetic or neotenic adult; external gills present; body form similar to transformed adult 2 Anuran tadpole; external gills ab-sent; body globular 5 2. Costal grooves absent Notophthalmus (east coast), Taricha (west coast) Costal grooves present 3 Editorial Committee for this Paper: Kenneth L. Gosner, Curator of Zoology, The Newark Museum, 43-49 Washington Street, Newark, New Jersey Dr. Priscilla Starrett, Lecturer, Department of Biological Sciences, University of Southern California, Los Angeles, California 10
BioStor
