The relationship of neonate mass and incubation temperature to embryonic development time in a range of animal taxa

Embryonic development time has been of long-standing interest to physiologi sts and ecologists because of its importance in understanding the behaviour and ecology of reproduction, and the evolution of reproductive strategics ill animals. Yet, the relationship of embryonic development time to both ne onate mass and incubation temperature remains poorly understood for most ta xonomic groups. Here we define the relationship of embryonic development ti me to neonate mass (embryo mass at birth) and incubation temperature for a broad range of animals, ectothermic and endothermic, invertebrate and verte brate, microscopic and gigantic. We begin by establishing the relationship of embryonic development time to neonate mass for a broad array of zooplank ton, fishes and amphibians for temperatures from 5 to 20 degrees C. Next, w e compare the relationships of embryonic development time to neonate mass i n these aquatic ectotherms to those for terrestrial ectotherms (reptiles) a nd endotherms (birds and mammals) in terms of degree-days. The similar natu re of these relationships allows us to define embryonic development time as a function of neonate mass for many of the species considered here with a single equation in terms of degree-days for incubation temperatures ranging from 5 to 38 degrees C. This relationship establishes a basis by which to compare differences in embryonic development time among species.