The influence of thermal and hydric environments on embryonic use of energy and nutrients, and hatchling traits, in the wall lizards (Podarcis muralis)

Among (different) clutch variation in egg composition, influence of thermal and hydric environments on incubating eggs, embryonic use of energy and nu trients, and hatchling traits were studied in the wall lizard Podarcis mura lis from a lowland population of Northern Spain. When initial egg mass was kept constant, we found that some measured egg variables such as water, lip id-free organic material, ash, calcium and magnesium in egg contents, and a sh and magnesium in eggshell, remained remarkably constant, whereas other v ariables differed considerably among clutches. All viable eggs increased in mass over the course of incubation due to absorption of water, and mass ga in during incubation was dependent on initial egg mass, temperature and sub strate water potential. Variations in the wet mass of hatchlings among trea tments stemmed mainly from variations in water content. Hatching success, e mbryonic use of energy and nutrients, and sex, size and mass of hatchlings were unaffected over a wide range of substrate moisture. The incubation len gth decreased as temperature increased. However, the effect of substrate mo isture on duration of incubation varied with temperature. The influence of incubation temperature on the snout-vent length of hatchlings, if present, was very weak. Incubation temperatures did not affect the sex ratio and car cass dry mass of hatchlings, but significantly affected the tail length of hatchlings, with individuals from the highest temperature having the shorte st tails. The energy expenditure of embryogenesis during incubation remaine d remarkably constant among treatments, and energy reserves in the hatchlin g were largely dependent on allocation of energy materials in eggs. A high incidence of dead-in-shell embryos occurred in eggs that were laid in June and, thereafter, when ambient temperatures were high. Deformed hatchlings w ere distributed nearly equally among treatments. (C) 1999 Elsevier Science Inc. All rights reserved.