Meeting Abstract

56.2  Saturday, Jan. 5  Allometric engineering of salamanders LANDBERG, T; University of Connecticut, Storrs tobias.landberg@uconn.edu

Egg size is a key life-history trait of amphibians that varies at every level: within clutches, between individuals, across species and among habitats. Egg size variation may mediate competitive and predatory interactions through links with growth and developmental rates. Unfortunately, we have previously had no direct experimental means of assessing the developmental effects of egg size variation. Instead we have had to rely on natural variation that may be confounded by several other genetic and/or maternally derived factors. Yolk removal experiments can help disentangle the effects of egg size from other influences on the phenotype. The surgical technique described here involves the removal of yolk from embryonic salamanders. Mortality rates (of ~50%) prior to hatching did not differ among the treatment groups, however there was an optimum developmental stage for the surgery with highest survival between Harrison stages 29 and 34. Preliminary results show that embryos in the yolk-reduced treatments hatch at the same time as their control and sham treated siblings, but at a smaller body size. Survival after hatching and after the yolk has been resorbed was lowest in the yolk-reduced groups indicating a strong fitness advantage to larger egg size. Early egg size (dis)advantages in growth, development and survival are expected to cascade through larval ontogeny and metamorphosis. The functional implications of egg size variation in amphibian life-history evolution and ecology are potentially vast. The phenotypic manipulation technique developed here offers to help test a few hypotheses.