Meeting Abstract

S8.1  Thursday, Jan. 6  Introduction to the Symposium – Eggs as organisms: environmentally cued hatching and adaptive embryo responses to risk and opportunity WARKENTIN, K.M.; Boston University, MA kwarken@bu.edu

Most animals begin life as eggs, protected and constrained by a capsule, shell, or other barrier. As embryos develop, their needs and abilities change, and at some point the costs of encapsulation outweigh the benefits. Adaptive hatching timing evolves in this context. However, many environmental variables affect the optimal timing of hatching so there is often no consistent best time. Across a broad range of animals, from flatworms and snails to frogs and birds, embryos hatch at different times or developmental stages in response to changing risks or opportunities. Parents also manipulate hatching timing. Embryos respond to many cue types, in different sensory modalities. Some responses appear simple. Others are surprisingly complex and sophisticated. Given the number and breadth of examples of environmentally cued hatching, we now need some general theory to structure comparisons across diverse taxa, facilitate integration of case studies into a larger picture, and identify critical gaps in our understanding. Useful starting points are: (1) the concept of heterokairy — individual, plastic variation in the rate, timing, or sequence of developmental events and processes — as a general framework to compare mechanisms and patterns of hatching timing; and (2) evolutionary theory on plasticity which directs our attention to fitness trade-offs, the extent and nature of environmental variation, and the availability and reliability of cues, to understand the evolved diversity of plastic and constitutive hatching timing. Combining mechanistic and evolutionary perspectives is necessary because development changes organismal interactions with the environment. Integrative and comparative studies of hatching timing will improve our understanding of eggs as both evolving and developing organisms.