This is a summary of Drosophila melanogaster anatomy. Many studies using drosophila as a model system have focused on the understanding on how fly structures are formed (developmental biology), how they work (neurobiology), and how organs grow as the animal grows.

A collection of images and drawings of the fly anatomy can be found at Flybase [5]. The following link to an anatomical atlas allows to easily identify adult Drosophila structures [6]: http://www.ento.csiro.au/biology/drosophila/melanogaster.html

Some examples of well-studied structures or organs are:

• Compound Eye (3 on the image): it is composed by thousands of cells, with differentiated functions (from photoreception to non-neuronal cells). Multiple studies on patterning and morphogenesis and cell-cell communication have allowed to understand eye function and development [7]

• Antennae (1 and 2 on the image): this is a pair of sensory elements on the head part of the fly. In the second antennal segment (2 in the image) stands a mass of receptor cells, called the Johnston organ. The Johnston organ is the hearing organ of the fruit fly, and it allows flies to sense different mechanosensory stimuli like sound (for instance during courtship) but also wind and gravity. Neuronal signalling from the antenna to the brain allows for behavioural responses to these stimuli [8].

• Proboscis (mouthpart): the mouth part of the fly has an important role in detecting non- volatile compounds, with functions in feeding or detection of toxic compounds, mating (non-volatile pheromones), and egg laying. These receptors though, are not restricted to the mouth and are distributed all along the fly body through hairlike structures. Many studies have focused on gustatory receptors and chemosensation [9].

• Bristles (6 on the image). They are one more component of the Drosophila peripheral nervous system. They are sensory organs placed across the surface of the adult fly. They are mechanoreceptors composed of 4 specialized cells, one of them a neuron. The development of bristles occurs at the late larva and early pupa stages [10]. Bristles are generated from a single cell SOP (sensory organ precursor), what makes them a model structure to understand asymmetric cell division and cell differentiation.

• Ovaries: In the adult female, the largest organ is the ovary. Each ovary contains around 18 ovarioles, where eggs are generated. Oogenesis in the female fly is the process of development of a mature egg (oocyte) from a stem cell. Oogenesis takes place in the ovaries, during about one week. It starts with the budding of the egg chambers (follicles) from the germinarium in the ovary and finishes with the formation of a mature oocyte. Egg chambers are comprised of multiple cells (somatic and germ line) and give rise to a single mature egg. Assymetric cell division and cell fate determinants, together with cell migration, are required for oogenesis [4].