Changes in the cellular makeup of motor patterning circuits drive courtship song evolution in Drosophila.

How evolutionary changes in genes and neurons encode species variation in complex motor behaviors is largely unknown. Here, we develop genetic tools that permit a neural circuit comparison between the model species Drosophila melanogaster and the closely related species D. yakuba, which has undergone a lineage-specific loss of sine song, one of the two major types of male courtship song in Drosophila. Neuroanatomical comparison of song-patterning neurons called TN1 across the phylogeny demonstrates a link between the loss of sine song and a reduction both in the number of TN1 neurons and the neurites supporting the sine circuit connectivity. Optogenetic activation confirms that TN1 neurons in D. yakuba have lost the ability to drive sine song, although they have maintained the ability to drive the singing wing posture. Single-cell transcriptomic comparison shows that D. yakuba specifically lacks a cell type corresponding to TN1A neurons, the TN1 subtype that is essential for sine song. Genetic and developmental manipulation reveals a functional divergence of the sex determination gene doublesex in D. yakuba to reduce TN1 number by promoting apoptosis. Our work illustrates the contribution of motor patterning circuits and cell type changes in behavioral evolution and uncovers the evolutionary lability of sex determination genes to reconfigure the cellular makeup of neural circuits.

Changes in the cellular makeup of motor patterning circuits drive courtship song evolution in Drosophila.

How evolutionary changes in genes and neurons encode species variation in complex motor behaviors are largely unknown. Here, we develop genetic tools that permit a neural circuit comparison between the model species Drosophila melanogaster and the closely-related species D. yakuba, who has undergone a lineage-specific loss of sine song, one of the two major types of male courtship song in Drosophila. Neuroanatomical comparison of song patterning neurons called TN1 across the phylogeny demonstrates a link between the loss of sine song and a reduction both in the number of TN1 neurons and the neurites serving the sine circuit connectivity. Optogenetic activation confirms that TN1 neurons in D. yakuba have lost the ability to drive sine song, while maintaining the ability to drive the singing wing posture. Single-cell transcriptomic comparison shows that D. yakuba specifically lacks a cell type corresponding to TN1A neurons, the TN1 subtype that is essential for sine song. Genetic and developmental manipulation reveals a functional divergence of the sex determination gene doublesex in D. yakuba to reduce TN1 number by promoting apoptosis. Our work illustrates the contribution of motor patterning circuits and cell type changes in behavioral evolution, and uncovers the evolutionary lability of sex determination genes to reconfigure the cellular makeup of neural circuits.

The evolution of red color vision is linked to coordinated rhodopsin tuning in lycaenid butterflies.

Color vision has evolved multiple times in both vertebrates and invertebrates and is largely determined by the number and variation in spectral sensitivities of distinct opsin subclasses. However, because of the difficulty of expressing long-wavelength (LW) invertebrate opsins in vitro, our understanding of the molecular basis of functional shifts in opsin spectral sensitivities has been biased toward research primarily in vertebrates. This has restricted our ability to address whether invertebrate Gq protein-coupled opsins function in a novel or convergent way compared to vertebrate Gt opsins. Here we develop a robust heterologous expression system to purify invertebrate rhodopsins, identify specific amino acid changes responsible for adaptive spectral tuning, and pinpoint how molecular variation in invertebrate opsins underlie wavelength sensitivity shifts that enhance visual perception. By combining functional and optophysiological approaches, we disentangle the relative contributions of lateral filtering pigments from red-shifted LW and blue short-wavelength opsins expressed in distinct photoreceptor cells of individual ommatidia. We use in situ hybridization to visualize six ommatidial classes in the compound eye of a lycaenid butterfly with a four-opsin visual system. We show experimentally that certain key tuning residues underlying green spectral shifts in blue opsin paralogs have evolved repeatedly among short-wavelength opsin lineages. Taken together, our results demonstrate the interplay between regulatory and adaptive evolution at multiple Gq opsin loci, as well as how coordinated spectral shifts in LW and blue opsins can act together to enhance insect spectral sensitivity at blue and red wavelengths for visual performance adaptation.

Effects of Abdominal Rotation on Jump Performance in the Ant Gigantiops destructor (Hymenoptera, Formicidae).

Jumping is an important form of locomotion, and animals employ a variety of mechanisms to increase jump performance. While jumping is common in insects generally, the ability to jump is rare among ants. An exception is the Neotropical ant Gigantiops destructor (Fabricius 1804) which is well known for jumping to capture prey or escape threats. Notably, this ant begins a jump by rotating its abdomen forward as it takes off from the ground. We tested the hypotheses that abdominal rotation is used to either provide thrust during takeoff or to stabilize rotational momentum during the initial airborne phase of the jump. We used high speed videography to characterize jumping performance of G. destructor workers jumping between two platforms. We then anesthetized the ants and used glue to prevent their abdomens from rotating during subsequent jumps, again characterizing jump performance after restraining the abdomen in this manner. Our results support the hypothesis that abdominal rotation provides additional thrust as the maximum distance, maximum height, and takeoff velocity of jumps were reduced by restricting the movement of the abdomen compared with the jumps of unmanipulated and control treatment ants. In contrast, the rotational stability of the ants while airborne did not appear to be affected. Changes in leg movements of restrained ants while airborne suggest that stability may be retained by using the legs to compensate for changes in the distribution of mass during jumps. This hypothesis warrants investigation in future studies on the jump kinematics of ants or other insects.

Spanish: Efectos de la rotación abdominal en el desempeño del salto de la hormiga Gigantiops destructor (Hymenoptera, Formicidae) El salto es una forma importante de locomoción y muchos animales utilizan diversidad de mecanismos al saltar para mejorar su desempeño. A pesar de que el salto es común en insectos, en general, las hormigas presentan una habilidad limitada. La hormiga neotropical Gigantiops destructor (Fabricius 1804) es una excepción, y utiliza el salto para capturar presas o escapar de potenciales amenazas. Esta especie empieza el salto rotando el abdomen anteriormente al impulsarse desde el suelo. Se evaluaron las hipótesis que la rotación abdominal se usa tanto para la proporción de empuje durante el impulso, así como en la estabilización de la cantidad de movimiento rotacional durante la fase inicial del salto mientras se encuentra en el aire. Se usó videografía de alta velocidad para caracterizar el desempeño del salto entre dos plataformas. Posteriormente, un grupo de hormigas fueron anestesiadas, y con el uso de pegamento, se restringió el movimiento del abdomen para evitar la rotación de éstos en la subsecuente caracterización del desempeño al saltar. Los resultados apoyan la hipótesis que la rotación abdominal proporciona impulso adicional. La distancia máxima, el peso máximo y la velocidad del impulso durante el salto fueron reducidos cuando el abdomen está fijo comparados con los saltos de las hormigas que no sufrieron manipulación y las que se usaron en el tratamiento control. En contraste, no hubo evidencia que la estabilidad de rotación de las hormigas mientras se encontraban en el aire fuera afectada. Las hormigas con abdómenes fijos presentaron cambios en el movimiento de las patas que sugieren que la estabilidad se puede mantener al usar las patas y compensar la distribución de la masa durante el salto. Esta hipótesis justifica futuros estudios evaluando la cinemática del salto en hormigas y otros grupos de insectos. Translated to Spanish by Rafael Achury (rafaelachury@gmail.com).

French: Effet de la rotation abdominal sur les performances du saut chez la fourmi Gigantiops destructor (Hymenoptera, Formicidae) Sauter est une importante forme de locomotion, et les animaux utilisent une diversité de mécanismes pour améliorer les performances de leurs sauts. Meme si sauter est commun chez les insectes en général, la capacité de sauter est rare chez les fourmis. La fourmi néotropicale Gigantiops destructor (Fabricius 1804) est une exception, elle est reconnue pour sauter sur ces proies ou pour s'échapper des menaces. Singulièrement, cette fourmi commence un saut par une rotation de son abdomen vers l'avant au moment de décoller du sol. Nous avons testé l'hypothèse que la rotation abdominale est utilisée pour soit générer une poussée au décollage, soit stabiliser l'élan rotatif pendant la phase aérienne initiale du saut. Nous avons utilisé l'enregistrement vidéo de grande vitesse pour caractériser la performance du saut des ouvrières G. destructor entre deux plateformes. Ensuite, nous avons anesthesié les fourmis et utilisé de la colle pour empêcher leurs abdomens de pivoter durant les prochains sauts, pour de nouveau caractériser la performance du saut suite à la restriction dudit abdomen de cette manière. Nos résultats soutiennent l'hypothèse que la rotation de l'abdomen entraine une poussée supplementaire vu que la distance maximale, la hauteur maximale et la vitesse de décollage des sauts sont réduites par la restriction du mouvement de l'abodmen comparer aux sauts des fourmis non manipulées du groupe témoin. Au contraire, la stabilité rotative des fourmis en phase aérienne ne semble pas être affectée. Les changements dans le mouvement des pattes des fourmis restraintes suggèrent que la stabilité peut être conservée en utilisant les pattes pour compenser les variations de la distribution de la masse pendant le saut. Cette hypothèse garantie, dans de futures études, l'exploration la cinématique du saut chez les fourmis et autres insectes. Translated to French by Jules Chabain (chabain2@illinois.edu).

Portuguese: Efeitos de Rotação Abdominal no Desempenho de Salto na Formiga Gigantiops destructor (Hymenoptera, Formicidae) O salto é uma forma importante de locomoção, e os animais empregam uma variedade de mecanismos para aumentar a performance de salto. Embora o salto seja comum nos insetos em geral, a capacidade de saltar é rara entre as formigas. Uma exceção é a formiga neotropical Gigantiops destructor (Fabricius 1804), conhecido por saltar para capturar presas ou escapar de ameaças. Notavelmente, essa formiga começa um salto girando seu abdômen para a frente enquanto sai do chão. Testamos as hipóteses de que a rotação abdominal é usada para fornecer impulso durante a saída do chão ou para estabilizar o momento de rotação durante a fase inicial do salto no ar. Utilizamos videografia de alta velocidade para caracterizar o desempenho de saltos de formigas operárias de G. destructor saltando entre duas plataformas. Em seguida, anestesiamos as formigas e aplicamos cola para impedir que o abdômen gire durante os saltos subsequentes, caracterizando novamente o desempenho do salto após restringir o abdômen dessa maneira. Nossos resultados suportam a hipótese de que a rotação abdominal fornece impulso adicional, pois a distância máxima, a altura máxima e a velocidade de saída dos saltos foram reduzidas pela restrição do movimento do abdômen, em comparação aos saltos das formigas não manipuladas e de controle. Em contraste, a estabilidade rotacional das formigas no ar não pareceu ser afetada. Alterações nos movimentos das pernas no ar das formigas restringidas sugerem que a estabilidade pode ser mantida usando as pernas para compensar as mudanças na distribuição da massa durante os saltos. Essa hipótese merece investigação em estudos futuros sobre a cinemática do salto de formigas ou outros insetos.Translated to Portuguese by Diego Vaz (dbistonvaz@vims.edu).