Divergence of behavioral traits with adaptation to changes in the environment has been well documented in many animals and is often accompanied by divergence in sensory systems. Shifts in insect host plant preference behavior, in particular, are often associated with changes to the olfactory system, including differences in the sensitivity, specificity, or abundance of olfactory sensory neurons (OSNs). Here, we examine 12 species from the cactophilic Drosophila repleta group that represent three broad host-use categories: Opuntia specialists, columnar cactus specialists, and polymorphic species that use both host types. We recorded odor-evoked responses from all six maxillary palp OSN classes using single sensillum recordings and used electropalpograms to further evaluate species in which a pb2B-like class was not detected by single sensillum recordings (SSRs). The B-neuron classes clustered largely by OSN identity across species, retaining characteristic class-specific response profiles. The A-neuron classes were less clearly separated because of weak or overlapping response profiles. Despite these shared class-specific responses, species differed substantially in response magnitude and sensitivity to odorants. A pb2B-like class was not detected by SSR in D. mulleri, D. aldrichi, and D. straubae. Electropalpograms supported the absence or strong reduction of a phenol-responsive palpal signal in D. mulleri and D. straubae, while D. aldrichi retained a strong response. Principal component and phylogenetic principal component analyses did not reveal consistent clustering by host-use category. These results suggest that maxillary palp olfaction has evolved in a species- or lineage-specific manner rather than through a repeated host-category-specific shift in peripheral sensitivity.
Oscine songbirds show remarkable diversity in song organization spanning from long songs composed of many different syllables to short single songs. All of these likely arose through sexual selective forces and therefore are thought to reflect a singer’s skill, often described as vocal performance. It is therefore important to gain insight into the song production mechanisms in species that sing a single, short song. Here we investigated the physiological control underlying learned song and other song-like vocalizations in the white-crowned sparrow (Zonotrichia leucophrys) by recording air sac pressure, tracheal and bronchial airflow and sound during spontaneously generated vocal behavior in 19 males (11 tutored, 8 untutored). The left side of the syrinx tends to produce more contributions to most song syllables than the right side, while both sides generate similar and overlapping frequency ranges and interact in the production of buzzy syllables. Two other song-like vocalizations, trills and twitter song also require sophisticated respiratory and syringeal movements. Trills display the most rapid temporal pattern with mini-breath rates of > 20 Hz. This illustrates that vocalizations other than typical song can also inform us about vocal performance. The basic production mechanism and syringeal lateralization was consistent between tutored and untutored birds, as well as across the different vocalizations studied here, suggesting innate development of the respective contributions of the two sound sources.
The magnetic compass has been shown in several classes of vertebrates, including anuran amphibians. Frogs obtain information from the magnetic field (MF) to follow migratory directions during their movements between wintering and breeding sites. In birds that are most studied in this respect, the magnetic compass sensor is thought to be located in the retina, and we explored this possibility in anurans. We previously reported the effect of the MF on the avian retina by electrophysiological methods; in the present study, we performed similar research in amphibians. Marsh frogs were captured in southern Russia in early autumn, and subsequently induced into a breeding migratory state through exposure to a spring-like photoperiod and temperature. Electroretinograms (ERGs) were recorded from isolated retinas that were carefully oriented in the sample holder to ensure consistent application of the MF. ERGs in response to red, blue, and ultraviolet light flashes were recorded under different MF directions: baseline (field passing through the eye during eastward migration, the predominant migratory direction for this frog population) and inverted inclination. Data were also examined by MF orientation relative to the retinal preparation (near‑perpendicular/near‑parallel). Our analysis revealed no significant effect of MF direction on the amplitudes of the a‑ or b‑waves of the ERG in response to light of any wavelength. This suggests that the sensory mechanism of the magnetic compass in frogs is either not located in the retina or that the reaction is so subtle that it cannot be recorded using the total ERG from the entire retina.
More than half a century ago, Buchner (1971) evaluated the visual axes of the ommatidia in a Drosophila’s neural superposition eyes, using the pseudopupil method. The spatial distribution of the visual axes was reported in a stereographic projection chart. Analysis of this chart shows that the ommatidial lattice is well described by a horizontal-vertical (H-V)-coordinate system, which allows assessment of the partial interommatidial angles between the vertical columns and horizontal rows of ommatidia, Δφh and Δφv, respectively. Their angular ratio ρa = Δφh/Δφv is expected in an ideal neural superposition eye to be √3, but this appears to hold only in a central band of the eye. Dorsally and ventrally ρa is much smaller, while posteriorly it is much larger. The quite different gradients of Δφh and Δφv over the eye cause distinct regional deviations from ideal neural superposition. Instead of the interommatidial angle Δφ, considered to be the central factor determining the eyes’ spatial resolving power, the local values of Δφh and Δφv will presumably be the important determinants for the spatial resolving power, at least for the vertical and horizontal motion-sensitive neurons in the fly brain. Various ways to chart the visual space of a compound eye are demonstrated and discussed.
Social context is a key modulator of behaviour and cognition across taxa, yet the effects of social isolation (SI) and subsequent recovery remain poorly characterised in invertebrate systems. Here, we developed a longitudinal behavioural procedure to examine how SI and social reintroduction (SR) influence feeding, exploration, and operant conditioning behavioural assays in the pond snail Lymnaea stagnalis. To capture biologically relevant variation, we compared two populations with differing environmental backgrounds: a long-established laboratory strain (W) and a “wild” population (TC1). Isolation was associated with reproducible changes across multiple behavioural domains, including reduced feeding and impaired memory performance in an operant conditioning assay. These effects emerged more rapidly in laboratory-inbred snails, whereas the “wild” ones required a longer isolation period to exhibit comparable behavioural alterations, indicating differences in response dynamics between populations with distinct environmental backgrounds. Following SR, behavioural recovery was modulated by social context. In W snails, social reintroduction with familiar conspecifics was associated with substantial recovery, whereas social reintroduction with unfamiliar conspecifics produced more limited improvement. In contrast, TC1 snails showed a delayed onset of behavioural disruption and less complete recovery after social reintroduction within the tested Timeframe, irrespective of conspecific familiarity. Together, these findings demonstrate that responses to social isolation in L. stagnalis are strongly influenced by population background and the social environment during recovery. By integrating laboratory-reared and “wild” populations within a multi-behavioural approach, this study establishes a tractable framework for future investigations linking social context to the neural and molecular mechanisms underlying behaviour and learning.
