Variable asymmetry and resonance in the avian vocal tract: a structural basis for individually distinct vocalizations

The social vocalizations of the oilbird (Steatornis caripensis) frequently have their acoustic energy concentrated into 3 prominent formants which appear to arise from the filter properties of their asymmetrical vocal tract with its bronchial syrinx. The frequency of the second and third formants approximate the predicted fundamental resonances of the unequal left and right cranial portions of each primary bronchus, respectively. Reversibly plugging either bronchus eliminates the corresponding formant. The first formant may arise in the trachea. The degree of vocal tract asymmetry varies between individuals, endowing them with different formant frequencies and providing potential acoustic cues by which individuals of this nocturnal, cave dwelling species may recognize each other in their dark, crowded colonies.     

Family-specific chemical profiles provide potential kin recognition cues in the sexually cannibalistic spider Argiope bruennichi

Kin recognition, the ability to detect relatives, is important for cooperation, altruism and also inbreeding avoidance. A large body of research on kin recognition mechanisms exists for vertebrates and insects, while little is known for other arthropod taxa. In spiders, nepotism has been reported in social and solitary species. However, there are very few examples of kin discrimination in a mating context, one coming from the orb-weaver Argiope bruennichi. Owing to effective mating plugs and high rates of sexual cannibalism, both sexes of A. bruennichi are limited to a maximum of two copulations. Males surviving their first copulation can either re-mate with the current female (monopolizing paternity) or leave and search for another. Mating experiments have shown that males readily mate with sisters but are more likely to leave after one short copulation as compared with unrelated females, allowing them to search for another mate. Here, we ask whether the observed behaviour is based on chemical cues. We detected family-specific cuticular profiles that qualify as kin recognition cues. Moreover, correlations in the relative amounts of some of the detected substances between sexes within families indicate that kin recognition is likely based on subsets of cuticular substances, rather than entire profiles.     

Hierarchical auditory perception for species discrimination and individual recognition in the music frog

The ability to discriminate species and recognize individuals is crucial for reproductive success and/or survival in most animals. However, the temporal order and neural localization of these decision-making processes has remained unclear. In this study, event-related potentials (ERPs) were measured in the telencephalon, diencephalon, and mesencephalon of the music frog Nidirana daunchina. These ERPs were elicited by calls from 1 group of heterospecifics (recorded from a sympatric anuran species) and 2 groups of conspecifics that differed in their fundamental frequencies. In terms of the polarity and position within the ERP waveform, auditory ERPs generally consist of 4 main components that link to selective attention (N1), stimulus evaluation (P2), identification (N2), and classification (P3). These occur around 100, 200, 250, and 300 ms after stimulus onset, respectively. Our results show that the N1 amplitudes differed significantly between the heterospecific and conspecific calls, but not between the 2 groups of conspecific calls that differed in fundamental frequency. On the other hand, the N2 amplitudes were significantly different between the 2 groups of conspecific calls, suggesting that the music frogs discriminated the species first, followed by individual identification, since N1 and N2 relate to selective attention and stimuli identification, respectively. Moreover, the P2 amplitudes evoked in females were significantly greater than those in males, indicating the existence of sexual dimorphism in auditory discrimination. In addition, both the N1 amplitudes in the left diencephalon and the P2 amplitudes in the left telencephalon were greater than in other brain areas, suggesting left hemispheric dominance in auditory perception. Taken together, our results support the hypothesis that species discrimination and identification of individual characteristics are accomplished sequentially, and that auditory perception exhibits differences between sexes and in spatial dominance.     

Variability in the mating calls of the Lusitanian toadfish Halobatrachus didactylus: cues for potential individual recognition

The mating sounds (boatwhistles) of nesting batrachoidid Halobatrachus didactylus males were recorded in the Tagus Estuary from piers. Thirteen males with 16 boatwhistles per fish were analysed for 20 acoustic features. All variables showed larger between‐male than within‐male variation and differed significantly among individuals. Discriminant function analyses (DFA) considering seven of these variables assigned 90–100% of boatwhistles to the correct individual, depending on the number of males and number of sounds per male included in the model. The acoustic features that consistently best discriminated individuals were the dominant frequency of the middle tonal segment of the boatwhistle (P₂) and dominant frequency modulation, followed by P₂ pulse period, amplitude modulation and sound duration. These results suggest the possibility of individual recognition based on acoustic cues.     

Solution NMR studies provide structural basis for endotoxin pattern recognition by the innate immune receptor CD14

CD14 functions as a key pattern recognition receptor for a diverse array of Gram-negative and Gram-positive cell-wall components in the host innate immune response by binding to pathogen-associated molecular patterns (PAMPs) at partially overlapping binding site(s). To determine the potential contribution of CD14 residues in this pattern recognition, we have examined using solution NMR spectroscopy, the binding of three different endotoxin ligands, lipopolysaccharide, lipoteichoic acid, and a PGN-derived compound, muramyl dipeptide to a ¹⁵N isotopically labeled 152-residue N-terminal fragment of sCD14 expressed in Pichia pastoris. Mapping of NMR spectral changes upon addition of ligands revealed that the pattern of residues affected by binding of each ligand is partially similar and partially different. This first direct structural observation of the ability of specific residue combinations of CD14 to differentially affect endotoxin binding may help explain the broad specificity of CD14 in ligand recognition and provide a structural basis for pattern recognition. Another interesting finding from the observed spectral changes is that the mode of binding may be dynamically modulated and could provide a mechanism for binding endotoxins with structural diversity through a common binding site.     

A novel multigene family may encode odorant receptors: a molecular basis for odor recognition.

The mammalian olfactory system can recognize and discriminate a large number of different odorant molecules. The detection of chemically distinct odorants presumably results from the association of odorous ligands with specific receptors on olfactory sensory neurons. To address the problem of olfactory perception at a molecular level, we have cloned and characterized 18 different members of an extremely large multigene family that encodes seven transmembrane domain proteins whose expression is restricted to the olfactory epithelium. The members of this novel gene family are likely to encode a diverse family of odorant receptors.     

Diverse sensory cues for individual recognition

To be social, the ability to recognize and discriminate conspecific individuals is indispensable in social animals, including primates, rodents, birds, fish, and social insects which live in societies or groups. Recent studies using molecular biology, genetics, in vivo and in vitro physiology, and behavioral neuroscientific approaches have provided detailed insights into how animals process and recognize the information of individuals. Here, we review the most distinct sensory modalities for individual recognition in animals, namely, olfaction and vision. In the case of rodents, two polymorphic gene complexes have been identified in their urine as the key and essential pheromonal components for individual recognition: the major histocompatibility complex (MHC) and the major urinary protein (MUP). Animals flexibly utilize MHC and/or MUP, which are detected by the main olfactory epithelium (MOE) and/or the vomeronasal organ (VNO) for various types of social recognition, such as strain recognition, kin recognition, and individual recognition. In contrast, primates, including humans, primarily use facial appearance to identify others. Face recognition in humans and other animals is naturally unique from genetic, cognitive, developmental, and functional points of view. Importantly note that nurture effects during growth phase such as social experience and environment can also shape and tune this special cognitive ability, in order to distinguish subtle differences between individuals. In this review, we address such unique nature and nurture mechanisms for individual recognition.     

Domain-swapped dimerization of the second PDZ domain of ZO2 may provide a structural basis for the polymerization of claudins

Zonula occludens proteins (ZOs), including ZO1/2/3, are tight junction-associated proteins. Each of them contains three PDZ domains. It has been demonstrated that ZO1 can form either homodimers or heterodimers with ZO2 or ZO3 through the second PDZ domain. However, the underlying structural basis is not well understood. In this study, the solution structure of the second PDZ domain of ZO2 (ZO2-PDZ2) was determined using NMR spectroscopy. The results revealed a novel dimerization mode for PDZ domains via three-dimensional domain swapping, which can be generalized to homodimers of ZO1-PDZ2 or ZO3-PDZ2 and heterodimers of ZO1-PDZ2/ZO2-PDZ2 or ZO1-PDZ2/ZO3-PDZ2 due to high conservation between PDZ2 domains in ZO proteins. Furthermore, GST pulldown experiments and immunoprecipitation studies demonstrated that interactions between ZO1-PDZ2 and ZO2-PDZ2 and their self-associations indeed exist both in vitro and in vivo. Chemical cross-linking and dynamic laser light scattering experiments revealed that both ZO1-PDZ2 and ZO2-PDZ2 can form oligomers in solution. This PDZ domain-mediated oligomerization of ZOs may provide a structural basis for the polymerization of claudins, namely the formation of tight junctions.     

A review of automatic recognition technology for bird vocalizations in the deep learning era

Birds are considered critical indicators of ecosystem condition. Automatic recording devices have emerged as a trending tool to assist field observations, contributing to biodiversity monitoring on large spatio-temporal scales. However, manually processing huge volumes of recordings is challenging. Consequently, there has been a growing interest in automatic bird vocalization recognition in recent years. Automatic bird vocalization recognition technology has advanced from classical pattern recognition to deep learning (DL), with significantly improved recognition performance. This paper reviews related works on DL-based automatic bird vocalization recognition technology in the last decade. In this review, we present the current state of research in the three key areas of pre-processing, feature extraction and recognition methods involved in automatic bird vocalization recognition. The related datasets, evaluation metrics and software are also summarized. Finally, existing challenges along with opportunities for future work are highlighted. We conclude that, while DL-based automatic bird vocalization recognition has made recent advances in specific species, more robust denoising approaches, larger public datasets, and stronger generalization capabilities of feature extraction and recognition are required to achieve reliable and general bird recognition in the wild. We expect that this review will serve as a firm foundation for new researchers working in the field of DL-based automatic bird vocalization recognition technologies, as well as become an insightful guide for computer science and ecology experts.     

Kin recognition and cannibalism in a subsocial spider

Evolution of cooperation and group living in spiders from subsocial family groups may be constrained by their cannibalistic nature. A tendency to avoid cannibalizing kin may facilitate tolerance among spiders and implies the ability to identify relatives. We investigated whether the subsocial spider Stegodyphus lineatus discriminates kin by recording cannibalism among juveniles in experiments during which amount of food and size difference among spiders in groups were varied. We hypothesized that family groups should be less cannibalistic than groups of mixed‐parental origin. Further, we tested whether food‐stress would influence cannibalism rates differently in kin and nonkin groups and the effect of relatedness on cannibalism within groups of spiders of variable size compared with those of homogenous size. In groups of six spiders, more spiders were cannibalized in nonsib groups than in sib groups under low food conditions. A tendency for nonkin biased cannibalism in starved spider pairs supported that kin recognition in S. lineatus is expressed when food is limited. Size variance of individuals within well‐fed groups of siblings and unrelated spiders had no influence on cannibalism rates. Apparently, both hunger and high density are important promoters of cannibalism. In addition to inclusive fitness benefits, we suggest that an ability to avoid cannibalizing kin will favour the evolution of cooperation and group living in phylogenetically pre‐adapted solitary species.     

Cellular basis for polarized light perception in the spider crab,Libinia

Summary Differential increases in the numbers of pinocytotic vesicles, multivesicular bodies and total complex bodies occurred in the cytoplasm of specific photoreceptor cells in the compound eye of the crab Libinia exposed for six hours to polarized light with various e-vector orientations. These data coupled with previous results on the same species proved that the seven retinular cells in each ommatidium formed two functional groups selectively light adaptable by e-vectors oriented 90° apart. One group (Channel I, comprising Cells 1, 4 and 5) was more affected by horizontal polarization; the other (Channel II, comprising Cells 2, 3, 6 and 7) was more affected by vertical polarization.This confirmed by a quite independent technique the conclusion reached from electrophysiological experiments on the crab Cardisoma that decapod compound eyes have two orthogonal polarization analyzer channels. In addition the present data showed that both channels occur in each ommatidium as hypothesized on previous electron microscopic evidence and that the axes of maximum absoprtion in the two retinal channels were parallel to the long axes of their cells' rhabdom microvilli, horizontal in Channel I and vertical in Channel II. The latter relations in turn supported the hypothesis that the dichroism of rhodopsin was fundamental to the analyzer mechanism.This research has been supported by U. S. Air Force Grant AFOSR 1064 and NASA Grant NGR 07-004-055. The authors wish to thank Professor Joseph G. Gall for generously sharing his electron microscope facilities.     

Validating the use of colouration patterns for individual recognition in the worm pipefish using a novel set of microsatellite markers

In studies of behaviour, ecology and evolution, identification of individual organisms can be an invaluable tool, capable of unravelling otherwise cryptic information regarding group structure, movement patterns, population size and mating strategies. The use of natural markings is arguably the least invasive method for identification. However, to be truly useful natural markings must be sufficiently variable to allow for unique identification, while being stable enough to permit long‐term studies. Non‐invasive marking techniques are especially important in fishes of the Family Syngnathidae (pipefishes, seahorses and seadragons), as many of these taxa are of conservation concern or used extensively in studies of sexual selection. Here, we assessed the reliability of natural markings as a character for individual identification in a wild population of Nerophis lumbriciformis by comparing results from natural markings to individual genetic assignments based on eight novel microsatellite loci. We also established a minimally invasive method based on epithelial cell swabbing to sample DNA. All pipefish used in the validation of natural markings, independently of sex or time between recaptures, were individually recognized through facial colouration patterns. Their identities were verified by the observation of the same multilocus genotype at every sampling event for each individual that was identified on the basis of natural markings. Successful recaptures of previously swabbed pipefish indicated that this process probably did not induce an elevated rate of mortality. Also, the recapture of newly pregnant males showed that swabbing did not affect reproductive behaviour.     

Attachment may be a basis for specialization in oak aphids

ABSTRACT.

• 1 The potential role of tarsal attachment in host selection was studied in the specialist aphids Tuberculoides annulatus Hartig and Myzocallis schreiberi Hille Ris Lambers and Stroyan.
• 2 M.schreiberi could walk freely on its host, Quercus ilex and on Q.robur, whereas T.annulatus could walk freely on its host, Q.robur but had difficulty on Q. ilex.
• 3 Attachment to the rough-textured leaves of Q.robur was achieved by means of the pretarsal claws, and to the smooth upper surface of individual trichomes on the lower surface of Q.ilex using flexible pretarsal empodia.
• 4 Both behavioural and allometric differences can account for the inability of T.annulatus to grip onto Q.ilex.
• 5 The role of attachment by phytophagous insects in host plant resistance and selection is discussed.

     

Structural basis for recognition of S-adenosylhomocysteine by riboswitches

S-adenosyl-(L)-homocysteine (SAH) riboswitches are regulatory elements found in bacterial mRNAs that up-regulate genes involved in the S-adenosyl-(L)-methionine (SAM) regeneration cycle. To understand the structural basis of SAH-dependent regulation by RNA, we have solved the structure of its metabolite-binding domain in complex with SAH. This structure reveals an unusual pseudoknot topology that creates a shallow groove on the surface of the RNA that binds SAH primarily through interactions with the adenine ring and methionine main chain atoms and discriminates against SAM through a steric mechanism. Chemical probing and calorimetric analysis indicate that the unliganded RNA can access bound-like conformations that are significantly stabilized by SAH to direct folding of the downstream regulatory switch. Strikingly, we find that metabolites bearing an adenine ring, including ATP, bind this aptamer with sufficiently high affinity such that normal intracellular concentrations of these compounds may influence regulation of the riboswitch.     

Feeding rate may affect dispersal in the orb-web spider Nephila clavata

Population parameters of the orb-web spider Nephila clavata were estimated at two sites with different spider densities (for 2 successive years at the high density site and 1 year at the low density site), and the relationship between survival rate and feeding conditions was examined. The rate of decrease of population density was almost constant over time and nearly the same at the two sites. Daily survival rate (sum of the effects of mortality and emigration) was low during August to early September and increased markedly thereafter. Daily immigration rate (number of immigrants/number of residents) was high during August to early September. Since there were strong negative correlations between survival and immigration rates, low survival rate seems to be caused by a high rate of emigration. Strong positive correlations were found between survival rate and feeding frequency (mean percent observed feeding). Analysis of covariance revealed that the parameters of the regression between survival rate and feeding frequency did not differ significantly among three occasions. These results suggest that feeding condition has a significant influence on dispersal activity of populations in this spider.     

Early maternal recognition of offspring vocalizations in rhesus macaques (Macaca mulatta)

This study investigated the development of maternal recognition of infant calls in rhesus macaques (Macaca mulatta). Fifteen mothers and their offspring, of age ranging from several hours to 28 days, served as subjects of an experiment in which the offspring's distress vocalizations were recorded and then played back to their mothers simultaneously with those of an age-matched control infant. The proportion of time looking at, but not the proportion of orientations to the speaker playing the offspring's vocalizations increased significantly as a function of infant age. Specifically, mothers of infants older than 1 week of age responded longer to the playback of their own infant's calls than did mothers of younger infants. These findings provide the firt evidence that offspring recognition in macaques develops between the first and second week of the infant's life and are consistent with the hypothesis that mothers need to be exposed to their infants' calls in order to learn their acoustic characteristics.