The Herpetological Journal

pp.37-42

Authors: Michael B. Thompson And Kylie J. Russell

Abstract: We measured water contents, gro wth of embryos and metaboli c rates in hard-shelled eggs of the Australian gecko, Phyllodactylus marmoratus, throughout incubation to make comparisons between (I) the proportional water content at oviposition of eggs of P. marmoratus and flexible-shelled eggs of lizards; and (2) the dry-mass specific energy consumption during development in P. marmoratus and lizards with flexible-shelled eggs. Egg contents (i.e. excluding eggshell) contained nearly 80% water, higher than reported for any other squamate reptile. Eggs were laid at embryonic stages 26/27-29, which is slightly earlier than for most other lizards. Incubation lasted 79-84 days at 25 °C and net water loss averaged just under 3 mg. Metabolism reflected the size of embryos, with little growth and lo w rates of oxygen consumption during the first third of incubation. Thereafter, growth and oxygen consumption in creased, with oxygen consumption slowing after day 70. This pattern is similar to that of other species of lizard. Water content of embryos fell from above 90% early in incubation to around 70% at hatching. Thus, the embryonic metabolic scaling factor was different when based on embryonic wet and dry mass. The dry-mass specific energetic cost of development in P. marmoratus was lower than other lizards, but this result was not related to having a hard-shelled egg. The respiratory exchange ratio suggests that embryonic metabolism is based on mixed protein and lipid, a pattern similar to that in flexible-shelled eggs of lizards, but different from birds.

Keywords: Phyllodactylus, gecko, embryonic development.