Journal of Comparative Physiology A-Neuroethology Sensory Neural and Behavioral Physiology最新文献

The antennae are the primary olfactory organs of insects, though other appendages, such as mouthparts and the female ovipositor, can also detect odors. A prerequisite for the olfactory function of an appendage is the presence of sensilla with porous walls and the expression of chemosensory receptors by sensory neurons housed in these sensilla. In the tobacco hawkmoth, Manduca sexta, we demonstrate that the epiphysis, a small process on the tibia of the forelegs that is used to clean the antennae, is an olfactory organ. The epiphysis carries approximately 150 sensilla with wall pores, suggesting an olfactory function. Additionally, the epiphysis expresses a variety of chemosensory receptor genes. We identified the expression of ORCo, the obligate co-receptor of odorant receptors (ORs), as well as 54 tuning ORs. Moreover, the epiphysis expresses 22 ionotropic receptors (IRs), including the co-receptors IR8a, IR25a, and IR76b, and 33 gustatory receptors (GRs). Several of these IRs and GRs had not previously been found in the antennae or other appendages. Electrophysiological recordings from isolated epiphyses revealed responses to odorants from several chemical classes, host plant leaves, and the female pheromone gland. The strongest responses were elicited by acids and the amine pyrrolidine. Epiphysectomy did not affect courtship or foraging behavior; however, epiphysectomized females were less likely to reach a host plant than controls. Our study reveals the epiphysis of M. sexta to be a previously unknown olfactory appendage with a broad and partly unique chemosensory repertoire. Because the epiphysis is a constitutive feature of lepidopteran insects, its olfactory function may be present in most moths and butterflies.

Butterflies have evolved a remarkable diversity in eye organization to support a range of vision-based behaviors including courtship, oviposition, and foraging. This diversity has been surveyed extensively across the butterfly phylogeny, but variation across closely related species remains less clear. We compared eye organization in Heliconius cydno, a clade of mimetic, Neotropical butterflies that have been studied in the context of wing coloration and courtship. Using a combination of eyeshine and opsin immunohistochemistry, we identified several sexually dimorphic features of eye organization where male eyes varied with species and female eyes did not. These features included the distribution of a red screening pigment across the eye, co-expression of the two UV opsins within single photoreceptors, and the relative distribution of UV and blue opsin expression in R1/R2 photoreceptors. Together, this suggests a shift in H. cydno males from an ancestor strongly biased towards the expanded Nymphalid mosaic characterized by blue and long wavelength opsin co-expression, red screening pigment, and green vs. red inter-photoreceptor opponency to one biased towards the basic mosaic consisting of UV-UV, Blue-Blue, and UV-Blue ommatidia. We hypothesize that this sex-limited variability may function to adapt these butterflies to sexually dimorphic behaviors like courtship and oviposition in the context of the natural light environment.

Insect compound eyes adapt in response to average stimulus intensity, but the adaptation is mediated also by intrinsic circadian rhythms and abiotic factors like temperature, which are indirectly related to the stimulus. We studied the effect of light, circadian rhythm, temperature and body size on light adaptation in Grapholita molesta (GM), Lobesia botrana (LB) and Cydia pomonella (CP) (Lepidoptera: Tortricidae). These moths have superposition compound eyes with identical trichromatic photoreceptor sets and temporal resolution; however, the adults are sexually active before (GM), during (LB) or after (CP) sunset, and experience very different light intensity and temperature variations during their activity period. Their eyes were examined with infrared pupillometry, light microscopy and micro-CT. The compound eyes are very small to medium-sized, with a clearly visible superposition pupil. The pupil reflectance of adults entrained to a 12/12 h light/dark cycle for 2 days maintained the entrained rhythm for days, closing and opening during the subjective day and night, respectively. Circadian rhythm was the most robust in CP. A fully open pupil was forced to close with a light pulse, and pupil brightness changes were monitored at 15 and 22 °C. The experiment revealed complex and different pupil dynamics among species at both temperatures. GM, the smallest species, was most affected by the lower temperature. The experimental paradigm can be used for high-throughput, non-invasive monitoring of multiple species' response to climate change, and to chemical and light pollution.

Compound eyes deliver a vast stream of information to the tiny insect brains. To maximize the information content and minimize the redundancy of neural signals, insect eyes are built so to encode the relevant and filter out the unimportant elements of the visual environment. Terrestrial habitats have a predictable spatio-spectral structure, which can be matched by the distribution of photoreceptors with different spectral sensitivities across the retina. Here, we investigate the retinal organization of the nymphalid butterfly Heliconius melpomene using single-cell recordings, immunohistochemistry and eye shine imaging. The ventral retina is enriched with ommatidia, which contain red screening pigments that shape the spectral sensitivity of basal red receptors R9, while their long visual fibre photoreceptors R1&2, expressing a long-wavelength (L) opsin, are synaptically inhibited by R9 and directly participate in colour vision. These G + R- receptors frequently co-express the L opsin with the blue (B) or ultraviolet (U) opsin. U&L opsin-co-expressing R1&2 are scarce, while B&L co-expression is frequent in the ventral ommatidia and gradually diminishes towards the eye equator, where G + R- receptors express the L opsin only. In this region, G + R- receptors are further inhibited by blue-sensitive receptors. With electrophysiology matching immunohistochemistry, we reveal the fine tuning of spectral sensitivity of a single photoreceptor class across the dorso-ventral axis of the butterfly compound eye. Similar tuning is found in other nymphalid butterflies across the phylogeny, suggesting that this adaptation is ancestral and confers an advantage to those diurnal nymphalids, equipped with the cellular toolkit for colour vision in the red.

Lepidoptera, having co-diversified with flowering plants and adapted to various diel niches, present a remarkable system for studying compound eye cell type diversity. Here we synthesize the latest research regarding Lepidopteran eye evolution across different timescales, from species-level variation to family-level changes, and mechanistic levels, from broad anatomical variation to molecular mechanisms responsible for spectral tuning. Opsin duplication, differential expression, and co-expression, combined with lateral filtering pigments, generate diverse spectral sensitivities in photoreceptors. Lateral filtering is particularly important for the convergent evolution of red vision. These diverse photoreceptors combine to form a handful of ommatidial types distributed differentially across eye regions, potentially specializing for distinct behavioral tasks. The coordinated development of these complex retinal mosaics requires precise regulatory mechanisms that we are only beginning to understand. Notably, only a subset of these ommatidial types contribute to color vision, highlighting the need for more research on their roles in motion and polarization vision. We also review support cells providing essential functions such as light insulation or reflection. Future research should focus on identifying ecological pressures driving visual system evolution, genetic bases of diverse retinal mosaics, and neural integration of visual information in Lepidoptera.

Masashi Kawasaki tragically died in a car accident on May 18, 2025. A dedicated neuroethologist and beloved faculty member at the University of Virginia, Charlottesville, he spent over four decades exploring neural mechanisms underlying echolocation in bats and electric behavior in weakly electric fish. He will be remembered for his expertise in carrying out challenging electrophysiological experiments in whole animals where others failed. His success was grounded on his mastery in combining a deep knowledge in neurophysiology with an excellent skill set for designing and building sophisticated experimental apparatus. Through his seminal research contributions and his generosity in sharing his knowledge with others, he left footprints in the minds and hearts of many.

The Garcia-effect is a unique form of conditioned taste aversion for two main reasons: the first is that the taste must be a novel one; the second is the requirement of a sickness state that can occur hours after experiencing the novel taste. The Garcia-effect has been shown in the pond snail Lymnaea stagnalis. Here we use the requirement of novelty to determine the ability of the snails to differentiate between different food substances (carrot and beet) as well as a mixture of the two (called the Mélange). We hypothesized that L. stagnalis's tasting abilities as well as their memory are competent to discriminate between individual and mixed foods and remember different foods, without associating the mixture with its component ingredients. Thus, for example, a Garcia-effect for the Mélange taste, does not alter the hedonic value of either carrot or beet taste and vice-versa.

The homing pigeon (Columba livia) is one of the best examples of human selection for behaviour among domesticated animals. Several brain regions purportedly differ in size between homing and other pigeons as a result of this selection, one of which is the olfactory bulbs. Olfaction is considered by many to be one of the sensory cues homing pigeons use to orient home. The intense selection for homing could therefore have driven anatomical changes in the olfactory bulbs, the first site of olfactory processing in the brain, in homing pigeons. Here, we compared the size of the olfactory bulbs, as well as size and number of mitral cells, among homing pigeons, feral pigeons, and several sporting and show breeds. Homing pigeons did not differ in absolute of relative olfactory bulb size from wild, feral, or most other pigeon breeds. Only a small show breed (figurita frill) and a meat/show breed (king) differed in absolute and relative olfactory bulb sizes from other pigeon breeds. Similarly, there were no significant differences among breeds in the absolute or relative number of mitral cells or mitral cell soma size. The lack of significant differences among most of the pigeon breeds sampled suggests neither experience nor selection for different behavioural or physical traits affects olfactory bulb size or the number and size of mitral cells. Although the results might indicate that there is not anything special about the olfactory abilities of homing pigeons, we lack data on other aspects of olfactory bulb anatomy and the acuity and sensitivity of the olfactory system across pigeon breeds. The latter knowledge gap could be addressed through genomic and transcriptomic techniques, which would provide new insights to the ongoing debate surrounding the use of olfactory cues in homing.