The genome in its ecological context: philosophical perspectives on interspecies epigenesis

Epigenesis concerns the interactions through which the inherited potentials of the genome become actualized into an adult organism. In addition to epigenetic interactions occurring within the developing embryo, there are also critical epigenetic interactions occurring between the embryo and its environment. These interactions can determine the sex of the embryo, increase its fitness, or even be involved in the formation of particular organs. This essay will outline the history of environmental concerns in developmental biology and provide some reasons for the decline and resurgence of these ideas, and it will then focus on two areas that have recently gained much attention: predator-induced polyphenisms and developmental symbioses. Research in these two areas of interspecies cooperation in morphogenesis has profound implications for what we consider to be normal development and how we proceed to study it. Studies of predator-induced polyphenism have shown that soluble factors from predators can change the development of prey in specific ways. Prey has evolved mechanisms to sense compounds released from their predators and to use these chemical cues to change their development in ways that prevent predation. New techniques in molecular biology, especially polymerase chain reaction and microarray analysis, have shown that symbioses between embryos and bacteria are widespread and that animals may use bacterial cues to complete their development.