Biology Reference
In-Depth Information
Figure 8.3 Ambystoma dumerilii is a paedomorph that has secondarily evolved
webbed-feet and extra filaments that develop on the dorsal surfaces of each gill. The
bottom panel is a magnified image of the dorsal gill surface. The arrow indicates dorsal
filaments (
<
1.0 mm in length) that are sprouting on the gill surface. These extra fibers
form late in the larval period, at the time metamorphosis normally occurs in related
metamorphic species. The A. dumerilii picture was taken by Brad Shaffer.
Salamandridae and Ambystomatidae. Studies of paedomorphic and facult-
ative species within these families have better elucidated environmental and
broad-sense genetic correlates of metamorph and paedomorph expression,
and these species continue to provide exceptional models for investigating
ecological aspects of life history evolution (
Denoel, Ivanovic, Dzukic, &
Kalezic, 2009; Denoel et al., 2005; Doyle & Whitemann, 2008; Takahashi
& Parris, 2008; Whiteman et al., 2012
).
3. HORMONAL BASIS OF SALAMANDER
METAMORPHOSIS
Biphasic, paedomorphic, and facultative life histories begin the same
way, with embryonic and larval development occurring in an aquatic hab-
itat. The primary difference is when and if metamorphosis occurs. Although