title: Alternative competition-induced digestive strategies yield equal growth, but constrain compensatory growth in red-eyed treefrog larvae.
abstract: Compensatory growth is well documented across taxa and provides a fitness advantage to animals who would otherwise reach a smaller reproductive size. We investigated the role of competition-induced gut plasticity in facilitating a compensatory response in red-eyed treefrog larvae. We reared larvae at low, medium, and high densities with different per capita resources, environments known to produce individuals with long and short guts. We then transferred larvae to competitively equal environments to determine if longer guts provided an advantage when resources became available. We predicted that larvae from higher densities with longer guts would exhibit hyperphagia and compensatory growth. We measured growth over 1-week, as well as the time to and size at metamorphosis. To assess mechanisms underlying the growth response, we measured diet transit time and intake. Growth, development, and metamorph snout-vent length did not differ between larvae with long and short guts. Instead, different gut lengths were associated with dramatically different feeding strategies. Medium- and high-density larvae fed at rates far below what their guts could accommodate. However, the combination of low intake and longer guts extended diet transit times, presumably increasing digestibility. This unexpected strategy achieved the same results as that of low-density larvae, which ate twice as much food, but passed it more quickly through a shorter gut. The lack of a compensatory response may be attributed to the costs of accelerated growth and weak seasonal time constraints in the tropics. This suggests that although compensatory growth is widespread among animals, expression of the response may vary with environmental context. J. Exp. Zool. 323A: 778-788, 2015. © 2015 Wiley Periodicals, Inc.
authors.affiliation: Department of Biology and Earth Science, Otterbein University, Westerville, Ohio.
authors.forename: Sarah S
authors.initials: SS
authors.lastname: Bouchard
authors.affiliation: Department of Biology and Earth Science, Otterbein University, Westerville, Ohio.
authors.forename: Chelsea J
authors.initials: CJ
authors.lastname: O'Leary
authors.affiliation: Department of Biology and Earth Science, Otterbein University, Westerville, Ohio.
authors.forename: Lindsay J
authors.initials: LJ
authors.lastname: Wargelin
authors.affiliation: Department of Biology and Earth Science, Otterbein University, Westerville, Ohio.
authors.forename: Whitney B
authors.initials: WB
authors.lastname: Rodriguez
authors.affiliation: Department of Biology and Earth Science, Otterbein University, Westerville, Ohio.
authors.forename: Kadeen X
authors.initials: KX
authors.lastname: Jennings
authors.affiliation: Department of Biology, Boston University, Boston, Massachusetts.|Smithsonian Tropical Research Institute, Balboa, Ancon, Republic of Panama.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Warkentin