Sex differences in Drosophila behavior: Qualitative and Quantitative Dimorphism

Abstract

The importance of sex as a biological variable is being recognized by more and more researchers, including those using Drosophila melanogaster as a model organism. Differences between the two sexes are not confined to well-known reproductive behaviors, but include other behaviors and physiological characteristics that are considered "common" to both sexes. It is possible to categorize sexual dimorphisms into "qualitative" and "quantitative" differences, and this review focuses on recent advances in elucidating genetic and neurophysiological basis of both qualitative and quantitative sex differences in Drosophila behavior. While sex-specific behaviors are often mediated by sexually dimorphic neural circuits, quantitative sexual dimorphism is caused by sex-specific modulation of a common neuronal substrate.

Figure 1. Cell types specified by dsx and fru

A. dsx and fru expression are partially overlapping, creating three “cell types”. Since both fru and dsx produce sex-specific transcripts (fruM and fruF for fru, dsxM and dsxF for dsx), class A, class B, and class C neurons in both sexes express a unique combination of sex-specific transcripts. B. Summary of behaviors influenced by the manipulation of class A, class B, or class C neurons in “P1/pC1” (fru-expressing (P1) neurons are also referred to as pMP-e [23] or pMP4 [22])”, “TN1”, or “Abg” clusters (see text for details). Colors of dots correspond to cell types in A. Motoneurons near the TN1 cluster do not express dsx (see text for details), but are shown here in a broken line box as relevant neurons. Neurotransmitter and/or neuromodulator expression is omitted for clarity, but these details often provide further information concerning the identity of neurons.

Figure 2. Sex-specific modulations of sleep

Purple arrows indicate female-specific, mating-dependent modulations of sleep, and brown arrows indicate male-specific sleep modulations in response to the presence of female cues. Gray italic letters indicate neuronal names. Solid arrows represent established neuronal connections (but do not necessarily represent monosynaptic connections); dotted arrows represent uncharacterized but potential neuronal connections. Data sources: [31, 56, 64, 65, 68, 71, 72].

Figure 3. Sex-specific modulations of chemosensory-guided behaviors

Purple arrows indicate female-specific, mating-dependent modulations of chemosensory-guided behaviors, and brown arrows indicate male-specific, age-dependent modulations. Gray italic letters indicate neuronal names. Ir76b subclasses can be further divided by the co-expression of receptors, which are omitted in this panel for clarify. Data sources: [85, 87, 88, 95]. JH: juvenile hormone.