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

Seasonal cycles in breeding, often orchestrated by annual changes in photoperiod, are common in nature. Here, we studied how change in photoperiod affects DNA methylation in the testes of a highly seasonal breeder: the Siberian hamster (Phodopus sungorus). We hypothesized that DNA methylation in promoter regions associated with key reproductive genes such as follicle-stimulating hormone receptor in the testes is linked to breeding and non-breeding states. Using Oxford Nanopore sequencing, we identified more than 10 million (10,151,742) differentially methylated cytosine-guanine (CpG) sites in the genome between breeding long photoperiod and non-breeding short photoperiod conditions. ShinyGo enrichment analyses identified biological pathways consisting of reproductive system, hormone-mediated signalling and gonad development. We found that short photoperiod induced DNA methylation in the promoter regions for androgen receptor (Ar), estrogen receptors (Esr1, Esr2), kisspeptin1 receptor (kiss1r) and follicle-stimulating hormone receptor (Fshr). Long photoperiods were observed to have higher DNA methylation in promoters for basic helix-loop-helix ARNT-like 1 (Bmal1), progesterone receptor (Pgr) and thyroid-stimulating hormone receptor (Tshr). Our findings provide insights into the epigenetic mechanisms underlying seasonal adaptations in timing reproduction in Siberian hamsters and could be informative for understanding male fertility and reproductive disorders in mammals.

Since the EU banned classic neonicotinoids like imidacloprid and clothianidin, they may be replaced by more recently marketed insecticides such as flupyradifurone. However, they all operate on the same neuropharmacological principle as selective agonists at the insect's nicotinic acetylcholine receptors. Here we investigated the impact of flupyradifurone, imidacloprid and clothianidin on the neuronal processing in the auditory pathway of the desert locust Schistocerca gregaria. While stepwise increasing the insecticide concentration in the haemolymph, we extracellularly recorded the spike responses of auditory afferents in the tympanal nerve and of auditory interneurons in the neck connectives. All three insecticides showed a very similar dose-dependent suppression of spike responses in the auditory interneurons ascending towards the brain, whereas the spike responses in the sensory neurons of the ears appeared unaffected. Furthermore, by systematic injection experiments we demonstrate that insecticide dosages which already supress the information transfer in the auditory pathway are by far too low to induce the typical poisoning symptoms like trembling, spasms, and paralysis. We discuss how sublethal intoxication with classical neonicotinoids or functionally related insecticides like flupyradifurone may disrupt the postsynaptic balance between excitation and inhibition in the auditory pathway of locusts and other orthopteran insects.

Monoaminergic neurotransmitters are essential for a multitude of physiological and behavioral functions including territoriality and parental care. The Puerto Rican coquí frog, Eleutherodactylus coqui, possesses an intriguing multi-modal male behavioral organization whereby males can be territorial, paternal, and silent (non-calling). The objective of this study was to quantify central monoamines in the three male modes and integrate this neurochemistry with data from microhabitat shelter selection and male social structure. Males were assessed for monoamines and metabolites using high performance liquid chromatography with electrochemical detection. Results indicated that there are distinct and significant differences among the three male behavioral modes based on male social structure, microhabitat shelter selection, and neurochemistry. Silent males are non-combative, quiescent, occur nocturnally in relatively open locations with sparser vegetation, and are characterized by high levels of epinephrine and norepinephrine in several forebrain nuclei. Territorial males emit vocalizations, are typically surrounded by more vegetation than silent males, may have a silent male within their territory, and are denoted by significantly higher levels of norepinephrine in the preoptic area and ventral hypothalamus and dopamine in the amygdala responsible male territorial behaviors. Paternal males brood and guard developing embryos in secluded nest sites that are surrounded by vegetation, not within territories of residential males, and typically not in close proximity of silent males. Paternal brains have significantly higher levels epinephrine and serotonin in the raphe and reticular nuclei indicating the necessity to regulate metabolic processes and stress during the period of prolong paternal care.

A fundamental understanding of animal sensory systems is crucial for comprehending their interactions with the environment and with other conspecifics. However, knowledge gaps persist, particularly in arachnids like the order Solifugae. While certain solifuge setae and palpal papillae have been studied structurally and electrophysiologically, providing evidence of chemoreception and mechanoreception, the sensilla on their walking legs remain unexplored. Notably, elongated sensilla on the femur and tibia of the 4th walking legs resemble trichobothria in other arachnid orders yet their function remains unknown. Thus, this study investigates whether these sensilla serve a mechanosensory function. Using electrophysiological and behavioral assays on Eremobates pallipes (Eremobatidae), we assessed the response of the elongated 4th leg sensilla to- (i) air particle movement and- (ii) air pressure changes. Air particle movement stimuli were generated using a speaker placed in the near field of the elongated sensilla that emitted low-frequency pure tones (10-1000 Hz). Air pressure stimuli involved forceful blowing on the sensilla. No response to air particle movement was observed, but a mechanosensory response to air pressure stimuli was detected. Electrophysiological data identified a fast-adapting and fast-recovering cell, and behavioral observations revealed a startle response. Our electrophysiology results suggest a mechanosensory role of elongated sensilla on the 4th walking legs of solifuge, indicating that although they are not sensitive enough to detect air particle movement stimuli, they can receive and respond to air pressure stimuli. Our behavioral experiments similarly show that these sensilla are not sensitive enough to detect air particle movement but respond to more forceful mechanosensory stimuli.

Larvae of the flesh fly, Sarcophaga similis exhibit photoperiodic responses to control pupal diapause. Although the external coincidence model is applicable to S. similis photoperiodism, it remains unknown how the circadian clock system integrates day-length information. To explore the mechanisms, we examined the neural circuitry involving circadian clock lateral neurons (LNs) and prothoracicotropic hormone (PTTH) neurons. We also examined the photoperiodic effects on LN-fiber patterns in third-instar S. similis larvae. Immunohistochemistry showed that the clock protein PERIOD and the neuropeptide pigment-dispersing factor (PDF) were co-localized in four cells per brain hemisphere, and we named these PDF-LNs of S. similis. Single-cell polymerase chain reaction of backfilled neurons from the ring gland showed that two pairs of pars lateralis neurons with contralateral axons (PL-c neurons) to the ring gland expressed ptth. Double labeling with immunohistochemistry and backfills revealed that PDF-immunoreactive varicose fibers projected close to fibers from PL-c neurons. short neuropeptide f (snpf) receptor and glutamate-gated chloride channel but not pdf receptor were expressed in PL-c neurons. sNPF and L-glutamate but not PDF acutely inhibited the spontaneous firing activity of PL-c neurons. The number of PDF-immunoreactive varicosities of PDF-LNs in the dorsal protocerebrum was significantly higher under short-day than that under long-day conditions in a time-dependent manner. These results suggest that sNPF and/or glutamate signaling to PTTH neurons and PDF-LNs form a potential neural circuity for the photoperiodic control of pupal diapause and that photoperiod modifies the connectivity strength between PDF-LNs and their post- or pre-neurons in the circuitry.

Terrestrial molluscs living in temperate and polar environments must contend with cold winter temperatures. However, the physiological mechanisms underlying the survival of terrestrial molluscs in cold environments and the strategies employed by them are poorly understood. Here we investigated the cold tolerance of Ambigolimax valentianus, an invasive, terrestrial slug that has established populations in Japan, Canada, and Europe. To do this, we acclimated A. valentianus to different environmental conditions (differing day lengths and temperatures), then exposed them to sub-zero temperatures and measured overall survival. Then, we measured low molecular weight metabolites using ¹H NMR to see if they play a role in their cold tolerance as they do in other invertebrate species. We found that A. valentianus is not strongly freeze tolerant but does become more cold-hardy after acclimation to shorter day lengths. We also found that no metabolites were strongly upregulated in response to winter conditions despite the change in cold hardiness, and instead saw evidence of metabolic suppression leading up to winter such as formate and L-glutamine being suppressed in winter conditions.

During copulation male insects transfer sperm and seminal fluids, including accessory gland proteins (Acps) to females, produced in the accessory glands (AGs). These Acps influence female behavior and physiology, inhibiting sexual receptivity, promoting ovulation and/or oviposition. The theory of ejaculate allocation postulates that production is costly; therefore, males strategically allocate ejaculates based on perception of sperm competition and quality and availability of females. The objective of this study was to determine in the South American fruit fly Anastrepha fraterculus whether there is differential allocation of Acps by males under different social contexts: (i) presence or absence of males in the mating arena (male social context), (ii) presence/absence of females in the mating arena (female social context), and (iii) female condition (sugar-fed/protein-fed). This was inferred through female behavior (fecundity, fertility and remating) and the dynamics of the reduction in male AGs size and protein content after copulation. No effect was observed from the various social contexts perceived by males on female's fecundity, fertility, or remating. Mated males had less protein in their AGs compared to unmated males. Male social context affected AG size after copulation: there was a marked decrease in AG size in males which mated in the presence of rival males; moreover, males mated under competition had lower protein content in their AGs than males mating without competition, suggesting that males can adjust seminal fluid quantity depending on social-mating context, although this difference did not impact the physiology and behavior of females after copulation. Our results also indicate that AG size and protein content are correlated.

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.

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 weakly electric brown ghost knifefish (Apteronotus leptorhynchus) exhibits a pronounced sexual dimorphism in its electric behavior-males discharge at higher frequencies than females, with little overlap between the sexes. The frequency of these electric organ discharges is controlled by the frequency of the synchronized oscillations of the medullary pacemaker nucleus. Previous studies have suggested that sex-specific differences in the morphology and gene expression pattern of the astrocytic syncytium that envelopes the pacemaking neural network cause differences in its capacity to buffer the extracellular concentration of K⁺. This change in the K⁺ buffering capacity affects the K⁺ equilibrium potential of the neurons constituting the neural network, which in turn modulates the frequency of the pacemaker nucleus. In the present study, we have tested a critical element of this hypothesis by examining whether, and how, changes in the extracellular K⁺ concentration influence the frequency of the pacemaker nucleus oscillations. By using an in vitro preparation of the pacemaker nucleus, the results of this investigation demonstrate that exposure of this nucleus to acutely increased/decreased concentrations of K⁺ in the perfusate (while maintaining osmolarity) leads to concentration-dependent increases/decreases in the frequency of the synchronized oscillations generated by the pacemaker nucleus.