For animals with complex life cycles, conditions in the larval environment can have important effects that persist after metamorphosis. These carry-over effects may influence juvenile growth plasticity and have important fitness consequences. Small juvenile red-eyed treefrogs, Agalychnis callidryas, grow faster than larger ones. We examined to what extent this growth pattern is due to carry-over effects of intraspecific larval competition. In particular, we assessed larval gut plasticity and determined whether carry-over effects could persist given the extensive gut remodelling that occurs when herbivorous larvae transition to carnivorous juveniles. We reared larvae in mesocosms at low, medium and high densities and measured the size of both larval and juvenile guts, livers and fat bodies. We also monitored the timing of the onset of juvenile feeding post-metamorphosis and, after the onset of feeding, we measured intake rate and mean diet retention time. Finally, we measured juvenile metabolic rates to determine whether any organ size plasticity contributed to metabolic carry-over effects. Larval density had strong effects on larval morphology with higher densities increasing gut length and decreasing liver and fat body sizes. The effects of this plasticity carried over post-metamorphosis. High larval densities produced smaller juveniles with proportionately longer guts and extremely small livers and fat bodies. There were no apparent carry-over effects on size-specific metabolic rate. Differences in larval density were also associated with differences in post-metamorphic feeding. Small juveniles from high larval densities began feeding even before metamorphosis was complete, whereas large juveniles from low larval densities experienced a significant 2-week delay. Although juvenile body mass varied over threefold across treatments, once feeding was initiated, neither intake nor mean diet retention time scaled with body size. Overall, high larval densities produced small juveniles with very low lipid reserves that may have stimulated hyperphagia relative to larger juveniles. Longer guts carried over from the larval stage could facilitate this by allowing small juveniles to elevate intake without sacrificing diet retention time. Patterns of intake coupled with differences in the onset of feeding explain the size-dependent growth pattern previously reported in this and other species.
Larval Dissections
This file contains the dissection data for Agalychnis callidryas larvae reared at 5, 25, or 45 individuals per mesocosm at the Smithsonian Tropical Research Institute in Gamboa, Panama. The file provides the density, tank number and larval ID for each individual. There are total body lengths and body masses for each individual, as well as liver masses, fat body masses, and total gut masses. There are also measures of length and projected area for each section of the gut including the manicotto, small intestine, and large intestine. These values were obtained by photographing the gut and a ruler from above and analyzing the photo using ImageJ software from the National Institute of Health. The area represents the area of each gut section as seen in the photo, not the surface area of the gut.
Metamorph external morphology
This file contains morphometric data for Agalychnis callidryas metamorphs on the day they emerged from the mesocosm in which they were reared as larvae. They were reared at either 5, 25, or 50 individuals per mesocosm. The file contains the date of emergence, the tank (mesocosm) number, rearing density, and metamorph ID for each individual. The measurements include snout-vent length, belly width and tail length, as well as body mass. The linear measurements were made when the metamorph was asleep in its water conservation posture on the side of a small, clear cup. We used dial calipers to make each measurement through the cup wall. Snout vent length was the distance from the tip of the snout on the most anterior end of the animal to the vent (cloaca). The belly was measured at its widest part, and the tail was measured from its base to its tip.
Metamorph morphology.csv
Froglet dissections
This file contains the dissection data for Agalychnis callidryas froglets reared as larvae at 5, 25, or 45 individuals per mesocosm at the Smithsonian Tropical Research Institute in Gamboa, Panama. We dissected froglets one after they had completed tail resorption. The file provides the rearing density, tank number and froglet ID for each individual. There are snout vent lengths and body masses for each individual, as well as liver masses, fat body masses, and total gut masses. There are also measures of length and projected area for each section of the gut including the stomach, small intestine, and large intestine. These values were obtained by photographing the gut and a ruler from above and analyzing the photo using ImageJ software from the National Institute of Health. The area represents the area of each gut section as seen in the photo, not the surface area of the gut.
Froglet Dissections.csv
Onset of metamorph feeding
This file contains information on the rate at which Agalychnis callidryas metamorphs initiated feeding upon emergence from mesocosms where they were reared at different larval densities. Data include size at emergence and the time required for tail resorption and the production of the first fecal pellet. The file also contains the number of insect heads egested in each fecal pellet for varying periods of time post-metamorphosis.
Froglet Mean Retention Time
This file contains data for mean retention time for Agalychnis callidryas froglets reared at different larval densities. The data include froglet ID, tank number, rearing density, and froglet size. We maintained froglets on a fruit fly (Drosophila sp.) diet and inserted a single meal of leafhopper insects (Cicadellidae) followed by additional fruit flies. We used the leafhoppers as a diet marker and counted the number of leafhopper and fruit fly heads egested each day to determine mean diet retention time.
Froglet metabolic rates
This file contains metabolic rates of Agalychnis callidryas froglets that were reared as larvae in mesocosms at different densities. The data include metamorph ID, tank (mesocosm) number, body size, and rates of oxygen consumption.