Embryogenesis in Myrmicinae Ants exhibits features of short/intermediate germ-band development
Chi-Chun Fang, Chi-Chun Fang , Arjuna Rajakumar , Ehab Abouheif , Ulrich Mueller , David Stein
Department of Integrative Biology, The University of Texas at Austin, Texas, USA; Department of Integrative Biology, The University of Texas at Austin, Texas, USA ; Department of Biology, McGill University, Montreal, Quebec Canada ; Department of Biology, McGill University, Montreal, Quebec Canada ; Department of Integrative Biology, The University of Texas at Austin, Texas, USA ; Department of Molecular Biosciences, The University of Texas at Austin, Texas, USA
Ants (Formicidae, Hymenoptera) are useful model systems for studying caste determination and division of labor because of their diverse morphology, behavior, and life history traits. We have been interested in the questions of whether events that occur during embryogenesis might influence caste determination. However, before addressing that question, it is essential to more completely characterize the process of embryogenesis in ants. The best studied insect developmental system is Drosophila melanogaster. Drosophila embryos undergo a long germ-band mode of development, in which the entire segmented anterior-posterior axis is established simultaneously, and in which the developing embryo fills the egg, with little or no growth occurring during embryogenesis. More basal insect species undergo short or intermediate germ-band development, in which the developing embryo occupies a smaller portion of the egg, with more posterior segments forming progressively over the course of embryogenesis and in which the embryos grow to fill the egg. Like Drosophila, other Hymenopteran species (Apis, Nasonia) whose embryogenesis had been characterized, undergo long germ-band development. We have begun to characterize embryonic development of three myrmicine ants, Solenopsis invicta (fire ant), Mycocepurus smithii and Atta texana (fungus-gardening ants). Surprisingly, we observe several characteristics of short/intermediate germ-band development. At early stages, the embryo occupies a small portion of the egg and over the course of embryogenesis undergo considerable growth. In continuing experiments, we are examining the expression of the segment polarity gene wingless (wg), whose characterization will provide additional insight into the mode of development of myrmicine ants. Through these studies we hope to encourage further embryonic studies that may lead to an integrative picture of ant development.