Food deprivation during different periods of tadpole (Hyla chrysoscelis) ontogeny affects metamorphic performance differently

Abstract

Tadpoles in small, ephemeral pools whose duration and food content are unpredictable can potentially encounter substantial variation in diet composition and availability. We compared the effects of 10 days of food deprivation occurring early, midway and late in ontogeny on the metamorphic size and bioenergetic properties of Hyla chrysoscelis tadpoles. Tadpoles fed throughout ontogeny were controls. Metamorphs from tadpoles starved early and midway in ontogeny had the same snout-vent length and dry mass as controls, but the time to metamorphosis was extended by 8 and 19% respectively. Metamorphs of tadpoles starved late in development attained 85% of the length and 55% of the mass of controls, metamorphosed at the same time as controls, and suffered mortality 15 times greater than other treatments, perhaps because they were near the absolute minimum necessary level of energy reserves. There were no significant differences in percent organic matter, percent tissue water, condition index, and protein or glycogen concentrations between any experimental and control treatments. If food deprivation occurred early in development, the tadpoles caught up to the size of controls, but an extended developmental time would increase the risk of predation or habitat loss. If food reductions occur late in development, perhaps magnified by pond desiccation, tadpoles are stimulated to metamorphose at the same time as controls but at a smaller size. The bioenergetic composition of tadpoles at metamorphosis is unaffected by time of food deprivation.

Ecological constraints on amphibian metamorphosis: interactions of temperature and larval density with responses to changing food level

“…However, experiments employing constant resource levels do not directly test the predicted relationship between growth history and metamorphosis. Several experiments have tested the prediction that growth history aects size at and timing of metamorphosis (Alford and Harris 1988;Audo et al 1995;Hensley 1993;Leips and Travis 1994;Newman 1994a;Tejedo and Reques 1994a;Travis 1984, and see Twombly 1996 for a similar study on a copepod). These studies examined a variety of species and, although growth history has been seen to in¯uence metamorphosis, the predicted adaptive response to decreasing food level has not been observed in most studies.…”

Differential Morphology and Jumping Performance of Newly Metamorphosed Frogs of the Hybridogenetic Rana esculenta Complex

“…Larval growth history may also determine variability in locomotor response, independent of size, by affecting relative muscular mass, energetic reserves, and metabolic rate. However, food deprivation and its timing did not affect energetic reserves or metabolism in an anuran species (Audo et al, 1995), thus suggesting that effects of larval history on locomotor performance would occur only through differential size and shape. Performance in anurans is also highly dependent on.…”

Models of metamorphic timing: an experimental evaluation with the pond-dwelling salamander Hemidactylium scutatum (Caudata: Plethodontidae)

“…Studies with amphibians (Alford and Harris 1988;Tejedo and Reques 1994;Audo et al 1995;Beck 1997;Denver et al 1998;Morey and Reznick in press) have supported the general conclusions of the WCH model, i.e., there is a threshold body size below which metamorphosis will not occur (e.g., Morey and Reznick, in press), larvae will respond to changes in growth rate by altering developmental rate (e.g., Alford and Harris 1988), and there is a developmental stage at which metamorphosis is initiated and developmental rate becomes fixed (e.g., Hensley 1993). Studies with other groups, such as plants (Lacey 1986), fish (Reznick 1990) and arthropods (Bradshaw and Johnson 1995;Twombly 1997) also show some support for the WCH model.…”