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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.

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The effects of environmental quantity (moderate soil moisture vs. low soil moisture) and quality (low soil moisture vs. low temperature) on multilocus heterozygosity (MLH)-growth relationships were tested in the earthworm Eisenia fetida. The control treatment was high soil moisture and high temperature. Fresh weight was measured weekly for 4 weeks; MLH was computed for eight polymorphic loci. Moderate moisture limited growth (change in fresh weight) to 50 per cent of control growth; both low moisture and low temperature limited growth to 25 per cent of control growth. MLH was not correlated with growth at any time in the control treatment. MLH was strongly correlated with growth (P < 0.01) in three out of four weekly intervals in the moderate moisture treatment; MLH was weakly correlated with growth (P < 0.05) in two out of four weekly intervals in the low moisture treatment. MLH was not correlated with growth at any time in the low temperature treatment. Moderate soil moisture produced significantly stronger MLH-growth relationships than high moisture or low temperature. Even though low soil moisture and low temperature depressed growth to the same extent, the former produced MLH-growth relationships whereas the latter did not. Thus both environmental quantity and quality affected the existence and recurrence of MLH-growth relationships.

The heterozygosity of 13 polymorphic loci, encoding 10 enzymes from several pathways in carbohydrate metabolism, was tested for its effect on growth in juvenile manure worms Eisenia foetida (n = 169), raised under stressful (limited food, low moisture) followed by non-stressful (abundant food, high moisture) conditions. The predictive value of heterozygosity on growth was greatly improved by treating each locus separately rather than summing heterozygosity across all loci (multilocus heterozygosity). Under non-stressful conditions, heterozygosity among loci treated separately had no effect on growth rate (F = 1.60; df = 13, 155; NS); whereas under stressful conditions, heterozygosity among loci treated separately had significant and differential effects on growth rate (F = 234; df = 13, 155; P <0.01) with 7 loci contributing to a positive heterozygosity-growth rate correlation (r =0235; P <0.005) and 6 loci contributing to a negative heterozygosity-growth rate correlation (r = -0•202, P <0.01). Implicated loci could not be easily grouped into specific metabolic pathways. The negative contribution by some loci may arise as a consequence of heterozygote inferiority, linkage disequilibria with positively-contributing loci, or strong selection at that locus.