This chapter deals with the ovarioles, an egg-producing tubules that are the fundamental units of ovaries in female insects. Each ovariole is a tube in which oocytes form at one end and complete development as they reach the other. The terminal filament and the germarium, which contains germ cells, are at the distal end. Ovarioles may have one of several topological arrangements within an ovary. In some species, ovarioles join the end of an oviduct radially around a central point. In others, ovarioles arise in single file off the oviduct, like teeth on a comb. The period during which ovarioles form varies widely in insects, ranging from embryonic development in aphids to the pupal stage in flies. In some taxa, the number of ovarioles can be adjusted on the basis of environmental factors. In Drosophila, for example, ovarioles form during the pupal period. This timing provides the opportunity for the number of ovarioles constructed to be adjusted on the basis of previous diet and temperature. In honeybees, however, ovarioles form in early larval development. The number of ovarioles formed is at first the same in future queens and workers. In workers, however, most ovarioles undergo cell death, whereas those in developing queens persist. Ovariole architecture is related to both phylogeny and life history. Both panoistic and meroistic ovarioles can support very rapid egg production as illustrated by the more than 40,000 eggs/day produced by both the panoistic ovarioles of the most fecund termite queens and the polytrophic ovarioles of the most fecund ants.
|Original language||English (US)|
|Title of host publication||Encyclopedia of Insects|
|Number of pages||2|
|State||Published - Dec 1 2009|
ASJC Scopus subject areas
- Agricultural and Biological Sciences(all)