Amphibian larvae, Cannibal morphs, Ontogeny, Aquatic ecology, Competition, Predation
Salamander larvae of the species Ambystoma tigrinum are dimorphic in northwestern Iowa. In addition to common typical morphs, there exist rare, specialized cannibal morphs, which are induced environmentally by crowding. Cannibal morph phenotypes are characterized morphologically by their large size, proportionately large heads and hypertrophied vomerine teeth, and behaviorally by facultative cannibalism. During metamorphosis amphibians are particularly sensitive to predation. To help understand why cannibal morphs are uncommon, we have raised cannibal and typical morphs in isolation and under crowded conditions to compare the timing and duration of metamorphosis between these morphs. Results show that larger larvae, most of which exhibit characteristics intermediate between cannibal and typical morphs, and three true cannibal morphs, do not exhibit a discrete time to metamorphosis; they are among the first, but not the first animals to metamorphose. Therefore cannibal morphs may be no more vulnerable to predation than typical morphs during this critical period, and we do not consider that our "metamorphic bottleneck" hypothesis is supported. Overall, crowded larvae metamorphosed an average of three to four days earlier than isolates and were an average of 6 mm smaller at metamorphosis.
Journal of the Iowa Academy of Science
© Copyright 1990 by the Iowa Academy of Science, Inc.
Lannoo, Michael J.; Sweet, Michael P.; Ladehoff, Nancy M.; Fangman, Edmund S.; and Collins, William B.
"Time to Metamorphosis as a Function of Larval Size in a Population of Ambystoma tigrinum Salamanders Consisting of Cannibal and Typical Morph Phenotypes,"
The Journal of the Iowa Academy of Science: JIAS: Vol. 97:
, Article 7.
Available at: http://scholarworks.uni.edu/jias/vol97/iss4/7