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

Shelter selection is an important task in an animal's life. Concerning scorpions, little is known on the evaluation of potential shelters and the importance of chemosensation. To address these issues, we conducted a two-choice shelter test in rectangular open field arenas to identify properties rendering shelters attractive for female scorpions of the species E. italicus and M. eupeus. Shelters varied in size (large, small) and scent (none, conspecific: male or female, attractive: prey, aversive: rosemary oil). Contact with the shelters was video-recorded under red light for 13 h, including the whole night phase. Results revealed a preference for larger shelters, with conspecific scent having minor or no influence. Striking differences occurred with regard to prey and rosemary oil scents. Prey scent was more attractive to M. eupeus, while rosemary oil did not act as a repellent. E. italicus was not very attracted by prey scent, but was repelled by rosemary oil. These findings might reflect the different habitats, semi-arid vs. Mediterranean climates: prey and rosemary are scarce in the semi-arid climate (habitat of M. eupeus), whereas they are abundant in the Mediterranean climate (habitat of E. italicus). We carried out impairment experiments to identify the main sensory organs responsible for the above observations. These are the pectines and pedipalps which function as mechano- and chemosensors. Scorpions could not detect size nor scent properly when either their pectines or pedipalps were impaired.

Zebrafish (Danio rerio), an alternative to rodents, are widely used in neurological, genetic, and toxicology research. The zebrafish larval spinal cord injury model has been used in neural mechanistic analyses owing to its high regenerative capacity and throughput; however, it also had several limitations in imitating rodents. Therefore, we investigated the use of adult zebrafish as an alternative model to rodents for evaluating nerve regeneration. Here, we established a novel spinal cord regeneration evaluation method, which was based on the maximum swimming speed of adult zebrafish in a custom-built hydrodynamic-based aquarium. The spinal cords of adult male zebrafish were crushed using forceps, and maximum swimming speed and histological spinal cord regeneration were evaluated. Spinal cord-injured zebrafish showed a significant decline in motor function, followed by recovery at 3 weeks postoperatively, accompanied by histological regeneration. Spinal cord regeneration can be indirectly assessed by monitoring maximum swimming speed. They were also fed a diet containing fig extract, which can promote peripheral nerve regeneration; they were fed daily starting 1 week before the operation. Maximum swimming speed was measured time-dependently until 3 weeks postoperatively. Fig-consuming fish showed improved recovery of maximum swimming speed compared to the controls, which was consistent with the histological analysis. In summary, we established a spinal cord regeneration assessment system using adult zebrafish in a customized aquarium, which enables researchers to evaluate spinal cord regeneration in adult zebrafish similar to that of rodent experiments, contributing to faster and easier screening of neuroregenerative technology.

In the longstanding discussion of whether insects, especially central place foragers such as bees and ants, use metric representations of their landmark surroundings (so-called "cognitive maps"), the ability to find novel shortcuts between familiar locations has been considered one of the most decisive proofs for the use of such maps. Here we show by channel-based field experiments that desert ants Cataglyphis can travel such shortcuts between locations (defined by memorized goal vectors) just on the basis of path integration. When trained to visit two spatially separated feeders A and B they later travel the hitherto novel route A→B. This behavior may originate from the interaction of goal vectors retrieved from long-term memory and the current vector computed by the continuously running path integrator. Based on former experiments, we further argue that path integration is a necessary requirement also for acquiring landmark information (in form of learned goal-directed views). This emphasizes the paramount importance of path integration in these central place foragers. Finally we hypothesize that the ant's overall system of navigation consists in the optimal combination of path-integration vectors and view-based vectors, and thus handles and uses vectorial information without the need of constructing a "vector map", in which vectors are linked to known places in the environment others than to the origin of all journeys, the nest.

Widespread direct photoentrainment in zebrafish peripheral tissues is linked to diverse non-visual opsins. To explore whether this broadly distributed photosensitivity is specific to zebrafish or is a general teleost feature, we investigated hepatic photosynchronization in goldfish. First, we focused on the opsin 7 family (OPN7, a key peripheral novel opsin in zebrafish), investigating its presence in the goldfish liver. Subsequently, we studied whether light can directly entrain the goldfish liver and retina clocks. Silico analysis revealed seven OPN7 paralogs from four gene families, suggesting expansion through whole-genome and tandem duplications. The paralogs of families OPN7a, OPN7b, and OPN7d were mainly localized in neural tissues, while OPN7c paralogs were more abundant in peripheral tissues-including the liver-suggesting divergent roles. Light (independently of the wavelength employed) directly induced the per2a clock gene in the retina both in vivo and in vitro, confirming expected photoentrainment. However, in the liver, photoinduction of per1a and cry1a only occurred in vivo, not in vitro. These results suggest an indirect light-entrainment mechanism of the goldfish hepatic clock, possibly mediated by other oscillators or photosensitive organs. Our findings challenge the assumption of widespread direct photosensitivity in the peripheral tissues of teleosts. Further research is needed to understand the role of tissue-specific photoentrainment and non-visual opsins in diverse teleost species.

Animals often form organized cooperative foraging groups, where individual members must adhere to specific rules to maintain cohesiveness. These groups face the challenge of managing potential intruders, who may or may not assist in foraging. In semi-liquid food environments, Drosophila larvae learn to synchronize their movements into clusters, which are thought to make feeding more efficient. Individuals who do not synchronize with the group are excluded from the cluster. Whether clustering behavior occurs in wild-caught larvae, and if so, the extent of their selectivity in group membership, remains unknown. Here, we show that clustering occurs across a number of fly species, and the capacity to join different clusters varies both between and within species. We collected and observed a larval cluster from rotting fruit in the field, yielding seven fly species. Subsequent tests for clustering on five lines from this collection and 20 other inbred wild-caught lines revealed that all species, except D. suzukii, exhibit clustering behavior. Each line demonstrates varying capacities to become members of different clusters. This study also indicates that there is high genetic variance in how individual lines cluster with each other that is not explained by cross species features. Additionally, combinations of wild species with lab benchmark strains give varied outcomes in resultant adult fitness. The ability to co-cluster varies between and within species boundaries. However, fly lines that cluster with another tend to impart fitness both to themselves and their host. Our findings demonstrate that multiple species of fly larvae can co-cluster. This behavior tends to confer mutual benefits to cluster members, suggesting significant ecological implications in Drosophila communities.

Sleep replay activity involves the reactivation of brain structures with patterns similar to those observed during waking behavior. In this study, we demonstrate that adult male canaries exhibit spontaneous, song-like peripheral reactivation during night sleep. Our findings include: (1) the presence of activity in respiratory muscles, leading to song-like air sac pressure patterns of low amplitude, (2) the simultaneous occurrence of respiratory replay events and reactivation of syringeal muscles, and (3) the reactivation of syringeal muscles without concurrent respiratory system activity. This song-like reactivation of peripheral motor systems enables the identification of specific motor patterns, with replay events preserving individual morphological and temporal properties. The activation of peripheral motor systems in songbirds and the differences in activation patterns between species give unique insights into the fictive behavioral output of activation of a complex learned motor behavior during sleep, shedding light on the neural control mechanisms and potential functions.

Monarch butterflies (Danaus plexippus) undertake one of the most remarkable long-distance insect migrations, travelling thousands of kilometres to overwinter in the central trans-volcanic belt of Mexico. This study explored how monarch butterflies use essential fatty acids (EFA) and nonessential fatty acids (NFA) during overwintering. We collected 150 (male/female) butterflies from the Sierra Chincua wintering colony from the time of arrival (December 2022) to before departure (February 2023) and analysed their lipid content. Our findings revealed that although females have a higher mass fraction of lipids, male and female monarch butterflies depleted their lipids similarly over time, resulting in low abdominal lipid mass fractions by late February. NFA, including oleic and palmitic acid, were predominantly used for energy during overwintering by male and female butterflies. In contrast, the EFA alpha-linolenic and linoleic acids, critical for reproductive success and cellular functions, were conserved in both sexes. Males began the overwintering period with a higher mass fraction of EFA in the polar components of the head and thorax, which may impact the degree of cold acclimation of these tissues during this period. Strategic lipid utilisation, prioritising the preservation of EFA over NFA and optimizing overwintering survival probably enhance readiness for spring remigration and reproduction. This differential fatty acid use underscores the delicate balance monarch butterflies maintain to survive overwintering and highlights the potential impacts of environmental changes on their lipid dynamics and survival.

To sense light, animals often utilize mechanisms that rely on visual pigments composed of opsin and retinal. The photon-induced isomerization of 11-cis-retinal to the all-trans configuration triggers phototransduction cascades, resulting in a change in the membrane potential of the photoreceptor. In mollusks, the most abundant opsin in the eye is Gq-coupled rhodopsin (Gq-rhodopsin). The Gq-rhodopsin-based visual pigment is bistable, with the regeneration of 11-cis-retinal occurring in a light-dependent manner without leaving the opsin moiety. 11-cis-retinal is also regenerated by the action of retinochrome in the cell bodies. Retinal binding protein (RALBP) mediates retinal transport between Gq-rhodopsin and retinochrome in the cytoplasm. However, recent studies have identified additional bistable opsins in mollusks, including Opn5 and xenopsin. It is unknown whether these bistable opsins require RALBP and retinochrome for the continuous regeneration of 11-cis-retinal. In the present study, we examined the expression of RALBP and retinochrome in the photoreceptors expressing Opn5 or Xenopsin in the heterobranch gastropods Limax and Peronia. Our findings revealed that retinochrome, but not RALBP, was present in some of the Opn5A-positive brain photosensory neurons of Limax. The ciliary cells in the dorsal eye of Peronia, which express Xenopsin2, lacked both retinochrome and RALBP. Therefore, bistable opsins do not necessarily depend on the RALBP-retinochrome system in a cell. We also examined the expression of other proteins that support visual function, such as β-arrestin, Gq, and Go, in all types of photoreceptors in these animals, and uncovered differences in the molecular composition among the photoreceptors.

The acquisition of an acoustic template is a fundamental component of vocal imitation learning, which is used to refine innate vocalizations and develop a species-specific song. In the absence of a model, birds fail to develop species typical songs. In zebra finches (Taeniopygia guttata), tutored birds produce songs with a stereotyped sequence of distinct acoustic elements, or notes, which form the song motif. Songs of untutored individuals feature atypical acoustic and temporal structure. Here we studied songs and associated respiratory patterns of tutored and untutored male zebra finches to investigate whether similar acoustic notes influence the sequence of song elements. A subgroup of animals developed songs with multiple acoustically similar notes that are produced with alike respiratory motor gestures. These birds also showed increased syntactic variability in their adult motif. Sequence variability tended to occur near song elements which showed high similarity in acoustic structure and underlying respiratory motor gestures. The duration and depth of the inspirations preceding the syllables where syntactic variation occurred did not allow prediction of the following sequence of notes, suggesting that the varying duration and air requirement of the following expiratory pulse is not predictively encoded in the motor program. This study provides a novel method for calculation of motor/acoustic similarity, and the results of this study suggest that the note is a fundamental acoustic unit in the organization of the motif and could play a role in the neural code for song syntax.

Little is known about the chemosensory system of gustation in sea lampreys, basal jawless vertebrates that feed voraciously on live prey. The objective of this study was to investigate taste bud distribution and chemosensory responses along the length of the pharynx in the sea lamprey. Scanning electron microscopy and immunocytochemistry revealed taste buds and associated axons at all six lateral pharyngeal locations between the seven pairs of internal gill pores. The most rostral pharyngeal region contained more and larger taste buds than the most caudal region. Taste receptor cell responses were recorded to sweet, bitter, amino acids and the bile acid taurocholic acid, as well as to adenosine triphosphate. Similar chemosensory responses were observed at all six pharyngeal locations with taste buds. Overall, this study shows prominent taste buds and taste receptor cell activity in the seven pharyngeal regions of the sea lamprey.