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Posted by Marla on May 14, 2003 at 00:32:36:
In Reply to: Question about Neoteny posted by MCBond on May 01, 2003 at 22:59:09:
i just wrote my undergrad thesis on axolotls, so i think i can address your question pretty well. neoteny has three 'sub-types.' firstly, obligate neoteny is when all animals in a species never metamophose, and cannot be induced to do so under laboratory conditions (ex- sirens and necturus species). obligate-inducible neoteny is what the axolotl has, it means that the species can be induced to undergo metamorphosis using hormones and such in the lab. i know nothing about the kind of salamander you mentioned, but from your description, it sounds like that species manifests facultative neoteny, which is the third type of neoteny. facultatively neotenous species metamorphose or remain branchiates based on environmental cues. here, genetics may cause a predisposition, but environmental stimuli is much more important (insofar as i know forthe tiger salamander, anyways...). so, if your salamanders are in a species that is capable of metamorphosing, and they haven't, their species is facultatively neotenous. and, if they are adults, you don't want to induce them to metamorphose, though it's possible. metamorphosis is set at a certain time in the ontogeny of a salamander. when the time comes, it's body responds to the environment, and either metamorphoses or not (in a facultatively neotenous species). after that, it's more commited. it's body adjusts and matures in the form it's taken. while adult, neotenous animals can undergo 'spontaneous metamorphosis,' they usually significantly reduce their lifespan, are highly suceptible to illness, etc. so- my recommends- just be happy with your sally the way they are, and provide a fully aquatic environment.
o- and about neoteny being caused by a lack of iodine in cold environments- that's just a hypothesis, and is likely just a correlation, not a causal factor. it's more liely due to heterochrony, or the rate at which different parts of the body develop, and evolution selecting for neoteny. for example, in environments that have harsh terrestrial conditions, neoteny is favored, because it (to put it briefly) sucks to metamorphose. in ephemeral environments, where ponds dry up, it's better to metamorphose quickly, as neotenous individuals will dessicate and die.
