Types of Amphibian Metamorphosis

Mechanisms of Egg Activation and Polyspermy Block in Amphibians and Comparative Aspects with Fertilization in Other Vertebrates

“…In neoteny, the reproductive system (and germ cells) mature, while the rest of the body remains its juvenile form throughout its life (Lynn, 1961;Dent, 1968;Gould, 1977;Armstrong and Malacinski, 1989;Wakahara, 1996a). The neotenic urodeles have been divided into three categories according to their ability of metamorphosis; permanent or obligate neoteny which cannot metamorphose at all in both natural and experimental conditions (Necturus, Proteus, Siren), "inducible" obligate neoteny which cannot metamorphose in nature but can metamorphose after treatment with THs (axolotl), and facultative neoteny which metamorphoses depending on the environmental conditions (Ambystoma tigrinum, A. gracile) (Frieden, 1981).…”

The ‘male escape hypothesis’: sex-biased metamorphosis in response to climatic drivers in a facultatively paedomorphic amphibian

“…Paedomorphosis is particularly obvious in newts and salamanders where it corresponds to the retention of a larval traits such as gills and gill slits at the adult stage, and, therefore, to an aquatic life instead of the typical biphasic life cycle of a species going through metamorphosis [10,11]. It is a highly complex life-history trait in which exhibition in relation to metamorphosis can depend on many factors, both abiotic and biotic [12,13].…”

Erythropoiesis and Conversion of RBCs and Hemoglobins from Larval to Adult Type during Amphibian Development

“…The direct development is a widespread alternate reproductive mode in living amphibians that is characterized by evolutionary loss of the free-living, aquatic larval stage (Lynn, 1961;Dent, 1968;Wake and Hanken, 1996). The direct developing larvae have no gill slits because respiration in water is not required.…”