Date Written

Spring 2012

Document Type

Distinction Paper

Degree Name

Biology-BS

Department

Biology & Earth Science

Advisor

Dr. Sarah Bouchard, Ph.D.

First Committee Member

Dr. Jeffrey Lehman, Ph.D.

Second Committee Member

Dr. Carrie Scheckelhoff, Ph.D.

Keywords

amphibians, morphological changes, ontogenetic diet shifts, red-eyed tree frog, Central America

Subject Categories

Biology | Other Ecology and Evolutionary Biology

Abstract

Larval environment has a profound effect on post-metamorphic nutrition in red-eyed treefrogs. Small froglets emerging from high density larval environments feed sooner and grow at a faster rate than large froglets from low density environments. Additionally, insect intake by froglets does not scale with body size despite large differences in froglet mass. These patterns could be attributed to effects of larval plasticity that carry over post-metamorphosis. It was hypothesized that larvae from high densities would increase gut length (increasing digestive efficiency) and reduce liver size (fat storage) in response to lower per capita food resources. We reared larvae at three densities (5, 25 and 45 individuals per 400 L tank), and euthanized 10 size-matched larvae and 10 froglets from each density. Guts, livers, and fat bodies of all individuals were dissected and weighed. Guts were uncoiled and photographed, and gut length and area were assessed using ImageJ software. Diet transit time was assessed in both larvae and froglets to determine if any differences in gut length related to differences in diet processing. As predicted, guts of high- and medium-density larvae were 23% longer than that of low-density larvae, and livers and fat bodies were significantly smaller. Low-density froglets were three times heavier than high-density froglets (0.93 vs. 0.39 g). Despite this extreme size difference, gut length did not vary with density, although high- and medium-density guts were lighter and thinner than low-density guts. High- and medium-density froglets also had proportionately smaller livers and fat bodies than low-density froglets. Differences in gut anatomy were correlated with diet processing time. These results confirm carryover effects of larval plasticity post-metamorphosis.

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