It remains an enigma how the nervous system of different animal species produces different behaviors. We studied the neural circuitry for mating behavior in , a species that displays unique courtship actions not shared by other members of the genera including the genetic model, in which the core courtship circuitry has been identified. We disrupted the () gene, a master regulator for the courtship circuitry formation in , resulting in complete loss of mating behavior. We also generated , which expresses the optogenetic activator Chrimson fused with a fluorescent marker under the native promoter. The-labeled circuitry in visualized by revealed differences between females and males, optogenetic activation of which in males induced mating behavior including attempted copulation. These findings provide a substrate for neurogenetic dissection and manipulation of behavior in non-model animals, and will help to elucidate the neural basis for behavioral diversification. How did behavioral specificity arise during evolution? Here we attempted to address this question by comparing the parallel genetically definable neural circuits controlling the courtship behavior of , a genetic model, and its relative,, which exhibits a courtship behavioral pattern unique to it, including nuptial gift transfer. We found that the circuit, which is required for male courtship behavior, was slightly but clearly different from its counterpart, and that optogenetic activation of this circuit induced -specific behavior, i.e., regurgitating crop contents, a key element of transfer of nuptial gift. Our study will pave the way for determining how and which distinctive cellular elements within the circuit determine the species-specific differences in courtship behavior.

Although genetic diversity within a population is suggested to improve population-level fitness and productivity, the existence of these effects is controversial because empirical evidence for an ecological effect of genetic diversity and the underlying mechanisms is scarce and incomplete. Here, we show that the natural single-gene behavioural polymorphism ( and ) in has a positive effect on population fitness. Our simple numerical model predicted that the fitness of a polymorphic population would be higher than that expected with two monomorphic populations, but only under balancing selection. Moreover, this positive diversity effect of genetic polymorphism was attributable to a complementarity effect, rather than to a selection effect. Our empirical tests using the behavioural polymorphism in clearly supported the model predictions. These results provide direct evidence for an ecological effect of genetic diversity on population fitness and its condition dependence.

The solubilization of two water-insoluble dyes, o-(2-amino-1-naphthylazo)toluene (OY) and 1-pyrenecalbaldehyde (PyA), by complexes of anionic polyelectrolyte and alkyltrimethylammonium bromide (C12TAB, C14TAB, C16TAB) was examined using sodium poly(vinyl sulfate) (PVS) with different charge densities at 298.2 K. The change in the Gibbs function was estimated for this solubilization equilibrium. These complexes showed a larger solubilizing capacity for OY than for PyA. Their capacity for OY was larger than that of the corresponding surfactant micelles. The charge density of PVS influenced the solubilizing capacity in C12TAB and C14TAB solutions but had little effect in C16TAB solutions. PVS with a 40% charge density had the lowest solubilizing capacity. Bound short-chain surfactants are expected to have a smaller lateral interaction with neighboring surfactants bound to PVS with a lower charge density, thus forming a less hydrophobic complex with a lower solubilization capacity. The observed weak solubilization by PVS with a low charge density was ascribed to this less hydrophobic complex.

Behavior is a readout of neural function. Therefore, any difference in behavior among different species is, in theory, an outcome of interspecies diversification in the structure and/or function of the nervous system. However, the neural diversity underlying the species-specificity in behavioral traits and its genetic basis have been poorly understood. In this article, we discuss potential neural substrates for species differences in the courtship pulse song frequency and mating partner choice in the Drosophila melanogaster subgroup. We also discuss possible neurogenetic mechanisms whereby a novel behavioral repertoire emerges based on the study of nuptial gift transfer, a trait unique to D. subobscura in the genus Drosophila. We found that the conserved central circuit composed primarily of fruitless-expressing neurons (the fru-circuit) serves for the execution of courtship behavior, whereas the sensory pathways impinging onto the fru-circuit or the motor pathways downstream of the fru-circuit are susceptible to changes associated with behavioral species differences.

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