Aliens among us: nestmate recognition in the social huntsman spider, Delena cancerides

Unlike all other social spiders, the social huntsman spider, Delena cancerides, has been reported to rapidly respond to non-nestmates with lethal aggression, similar to the behavior of some eusocial insects. We tested for the presence of nestmate recognition in D. cancerides under laboratory conditions by introducing 105 unrelated alien conspecifics into foreign colonies and comparing their behavior to 60 control spiders removed and returned to their natal colony. Spiders demonstrated nestmate recognition by investigating alien spiders far more than nestmates and by resting closer to nestmates than to aliens. Serious attacks or deaths occurred in 23% of all trials; however, aggression was not directed significantly more toward aliens than to nestmates. Most notably, aggression was largely mediated by the adult females (resident or alien), who were most likely to attack or kill other subadult or mature individuals. Young individuals (resident or alien) were largely immune from serious aggression. Spiders recently collected from the field tended to be more aggressive than spiders born and raised in the laboratory, possibly due to blurring of recognition cues related to laboratory husbandry. Our findings support the prediction that nestmate recognition should evolve when there is a benefit to discriminating against non-kin, as in this social spider system where foraging individuals may enter a foreign colony and the colony retreat is a limited resource.     

Intraspecific nestmate recognition in two parabiotic ant species: acquired recognition cues and low inter-colony discrimination

Parabiotic ants—ants that share their nest with another ant species—need to tolerate not only conspecific nestmates, but also nestmates of a foreign species. The parabiotic ants Camponotus rufifemur and Crematogaster modiglianii display high interspecific tolerance, which exceeds their respective partner colony and extends to alien colonies of the partner species. The tolerance appears to be related to unusual cuticular substances in both species. Both species possess hydrocarbons of unusually high chain lengths. In addition, Cr. modiglianii carries high quantities of hereto unknown compounds on its cuticle. These unusual features of the cuticular profiles may affect nestmate recognition within both respective species as well. In the present study, we therefore examined inter-colony discrimination within the two parabiotic species in relation to chemical differentiation. Cr. modiglianii was highly aggressive against workers from alien conspecific colonies in experimental confrontations. In spite of high inter-colony variation in the unknown compounds, however, Cr. modiglianii failed to differentiate between intracolonial and allocolonial unknown compounds. Instead, the cuticular hydrocarbons functioned as recognition cues despite low variation across colonies. Moreover, inter-colony aggression within Cr. modiglianii was significantly influenced by the presence of two methylbranched alkenes acquired from its Ca. rufifemur partner. Ca. rufifemur occurs in two varieties (‘red’ and ‘black’) with almost no overlap in their cuticular hydrocarbons. Workers of this species showed low aggression against conspecifics from foreign colonies of the same variety, but attacked workers from the respective other variety. The low inter-colony discrimination within a variety may be related to low chemical differentiation between the colonies. Ca. rufifemur majors elicited significantly more inter-colony aggression than medium-sized workers. This may be explained by the density of recognition cues: majors carried significantly higher quantities of cuticular hydrocarbons per body surface.     

A new ethological test to study nestmate recognition in adult ants

Summary An ethological test was designed to investigate nestmate recognition in adult ants. Contrary to classic dyadic tests, it consisted of a choice situation where a tested-worker was faced with nestmate and non-nestmate workers. These were kept alive, tied down, and thus immobilised in the neutral arena to record the tested-worker's reactions independently of the behaviour of the others. Such tests, applied to the ponerine ant,Ectatomma tuberculatum, enabled us to record various measures of discrimination and to limit aggressive behaviours between alien ants, which often leads to serious injury in dyadic tests. They also demonstrated the influence of age on discrimination behaviour in this species.     

Cuticular hydrocarbon dynamics in young adult Polistes dominulus (Hymenoptera: Vespidae) and the role of linear hydrocarbons in nestmate recognition systems

In social insects, cuticular hydrocarbons (CHCs) play an important role in nestmate discrimination processes, but young individuals are usually not discriminated. We studied CHC changes in young workers of the social wasp Polistes dominulus. A quantitative estimation demonstrated that total quantities of CHCs increased after emergence, with branched alkanes increasing drastically when compared with other classes of hydrocarbons. The relative quantity of longer-chain compounds increased with respect to shorter ones; unsaturated compounds decreased. These changes might reduce the capacity of the cuticle to acquire compounds of environmental origin. We then tested whether individuals acquire hydrocarbons from the environment, and whether this capability equally characterises newly emerged and mature wasps. We exposed wasps of two age classes (adults younger or older than 24 h) to four linear hydrocarbons in turn, and observed how nestmates reacted to their re-introduction into the natal colony. Exposed young wasps elicited significantly more aggressive responses than control sisters; but treated wasps older than 24 h were generally accepted by nestmates. Chemical assays showed that exposed young wasps readily absorbed hydrocarbons; older ones did not incorporate hydrocarbons, suggesting that the chemical profiles of mature wasps are less prone to chemical shifts than those of newly emerged wasps.     

Absence of aggression but not nestmate recognition in an Australian population of the Argentine ant Linepithema humile

Intraspecific aggression is rare within introduced populations of the Argentine ant Linepithema humile, and colonies exhibit a structure known as unicoloniality, in which aggression among nests is atypical. We document a similar form of colony structure in an introduced population of Argentine ants in Victoria, Australia, in which aggression is extremely rare among nests ranging over hundreds of kilometres. However, using a highly sensitive behavioural bioassay we found that workers display subtle differences in their behaviour towards non-nestmates and nestmates. In particular, non-nestmates consistently engage in antennating behaviour with greater frequency than nestmates, perhaps providing a mechanism for homogenization of nest odour. Further, we found that non-nestmates at seaport sites (where populations may derive from multiple introductions) antennate each other with greater frequency than their counterparts from non-seaport sites. These data suggest that the Victorian population of L. humile may comprise multiple independent introductions. Received 4 July 2007; revised 15 January and 4 March 2008; accepted 4 March 2008.     

The role of cuticular hydrocarbons as chemical cues for nestmate recognition in the invasive Argentine ant (<Emphasis Type="Italic">Linepithema humile</Emphasis>)

Argentine ants (Linepithema humile) in their native South American range, like most other ant species, form spatially restricted colonies that display high levels of aggression toward other such colonies. In their introduced range, Argentine ants are unicolonial and form massive supercolonies composed of numerous nests among which territorial boundaries are absent. Here we examine the role of cuticular hydrocarbons (CHCs) in nestmate recognition of this highly damaging invasive ant using three supercolonies from its introduced range. We conducted behavioral assays to test the response of Argentine ants to workers treated with colonymate or non-colonymate CHCs. Additionally, we quantified the amount of hydrocarbons transferred to individual ants and performed gas chromatography-mass spectrometry (GC/MS) to qualitatively characterize our manipulation of CHC profiles. The GC/MS data revealed marked differences in the hydrocarbon profiles across supercolonies and indicated that our treatment effectively masked the original chemical profile of the treated ants with the profile belonging to the foreign individuals. We found that individual workers treated with foreign CHCs were aggressively rejected by their colonymates and this behavior appears to be concentration-dependent: larger quantities of foreign CHCs triggered higher levels of aggression. Moreover, this response was not simply due to an increase in the amount of CHCs applied to the cuticle since treatment with high concentrations of nestmate CHCs did not trigger aggression.The results of this study bolster the findings of previous studies on social insects that have implicated CHCs as nestmate recognition cues and provide insight into the mechanisms of nestmate recognition in the invasive Argentine ant. Received 6 February 2007; revised 31 May and 27 July 2007; accepted 16 August 2007.     

Nest surface hydrocarbons facilitate nestmate recognition for the social wasp,Polistes metricus Say (Hymenoptera: Vespidae)

Nestmate recognition was observed inPolistes metricus Say workers only if the workers were exposed to their nest surface hydrocarbons after eclosion. If the newly emerged workers were never exposed to the nest hydrocarbons as adults, they showed no discrimination between nestmates and nonnestmates. Furthermore, the newly emerged workers were accepted more readily by their experienced nestmates than by experienced nonnestmates only if the newly emerged wasps had been exposed to the nest surface hydrocarbons. This reciprocal recognition implies that the nest recognition cues are nest surface hydrocarbons that are learned and that may be acquired byP. metricus workers as adults on the natal nest.     

A T cell clone expresses two T cell receptor alpha genes but uses one alpha beta heterodimer for allorecognition and self MHC-restricted antigen recognition

All of the T cell receptor alpha- and beta-chain rearrangements present in a dual reactive T cell clone were characterized. This clone exhibits allelic exclusion of its beta-chain genes in that only one of the two alleles is productively rearranged. Unexpectedly, it displays two productive V alpha-gene rearrangements, which are both transcribed into 1.5 kb mRNA. The contribution of each of the two productive alpha genes to the dual recognition was analyzed by gene transfer. To this end, each of the two alpha genes was separately transfected with the single productively rearranged beta gene. Transfer of only one of the two alpha beta combinations restored both allogeneic MHC recognition and self MHC-restricted antigen recognition. Thus, T cell dual recognition results from the cross-reactive recognition of an allo-MHC product by a single antigen-specific and MHC-restricted alpha beta T cell receptor. Furthermore, the presence of two productively rearranged alpha-chain genes in a T cell clone raises questions concerning the level at which allelic exclusion operates in T cells.     

A new electrochemical biosensor for DNA detection based on molecular recognition and lead sulfide nanoparticles

In this paper, we constructed a new electrochemical biosensor for DNA detection based on a molecule recognition technique. In this sensing protocol, a novel dual-labeled DNA probe (DLP) in a stem–loop structure was employed, which was designed with dabcyl labeled at the 3′ end as a guest molecule, and with a Pb nanoparticle labeled at the 5′ end as electrochemical tag to indicate hybridization. One α-cyclodextrin-modified electrode (α-CD/MCNT/GCE) was used for capturing the DNA hybridization. Initially, the DLP was in the “closed” state in the absence of the target, which shielded dabcyl from the bulky α-CD/MCNT/GCE conjugate due to a steric effect. After hybridization, the loop sequence (16 bases) formed a rigid duplex with the target, breaking the relatively shorter stem duplex (6 bases). Consequently, dabcyl was forced away from the Pb nanoparticle and became accessible by the electrode. Therefore, the target hybridization event can be sensitively transduced via detecting the electrochemical reduction current signal of Pb. Using this method, as low as 7.1 × 10⁻¹⁰ M DNA target had been detected with excellent differentiation ability for even a single mismatch.     

A general criterion for molecular recognition: implications for chiral interactions

A general criterion is formulated for molecular recognition. The criterion for recognition is the inequality of the distance matrices of complexes of different compounds with a resolving agent under ambient experimental conditions. It is shown how this criterion provides for an objective, well-defined, and simple explanation for recognition of chiral compounds. This approach may be used to explain models (e.g., three-point of attachment) and relationships for chiral recognition. It is also shown how one-, two-, or three-point mechanisms are equivalent in this formalism and could result in chiral recognition. Examples are used to illustrate how the so called one- or two-point mechanisms may be operative in many experimental findings. Symmetry requirements of resolving agents may also be derived from considerations of distance matrices. Finally, the reciprocal relationship of chiral resolving agents is easily derived from the present method of analysis.     

The role of pattern recognition in creative problem solving: A case study in search of new mathematics for biology

Rosen classified sciences into two categories: formalizable and unformalizable. Whereas formalizable sciences expressed in terms of mathematical theories were highly valued by Rutherford, Hutchins pointed out that unformalizable parts of soft sciences are of genuine interest and importance. Attempts to build mathematical theories for biology in the past century was met with modest and sporadic successes, and only in simple systems. In this article, a qualitative model of humans' high creativity is presented as a starting point to consider whether the gap between soft and hard sciences is bridgeable. Simonton's chance-configuration theory, which mimics the process of evolution, was modified and improved. By treating problem solving as a process of pattern recognition, the known dichotomy of visual thinking vs. verbal thinking can be recast in terms of analog pattern recognition (non-algorithmic process) and digital pattern recognition (algorithmic process), respectively. Additional concepts commonly encountered in computer science, operations research and artificial intelligence were also invoked: heuristic searching, parallel and sequential processing. The refurbished chance-configuration model is now capable of explaining several long-standing puzzles in human cognition: a) why novel discoveries often came without prior warning, b) why some creators had no ideas about the source of inspiration even after the fact, c) why some creators were consistently luckier than others, and, last but not least, d) why it was so difficult to explain what intuition, inspiration, insight, hunch, serendipity, etc. are all about. The predictive power of the present model was tested by means of resolving Zeno's paradox of Achilles and the Tortoise after one deliberately invoked visual thinking. Additional evidence of its predictive power must await future large-scale field studies. The analysis was further generalized to constructions of scientific theories in general. This approach is in line with Campbell's evolutionary epistemology. Instead of treating science as immutable Natural Laws, which already existed and which were just waiting to be discovered, scientific theories are regarded as humans' mental constructs, which must be invented to reconcile with observed natural phenomena. In this way, the pursuit of science is shifted from diligent and systematic (or random) searching for existing Natural Laws to firing up humans' imagination to comprehend Nature's behavioral pattern. The insights gained in understanding human creativity indicated that new mathematics that is capable of handling effectively parallel processing and human subjectivity is sorely needed. The past classification of formalizability vs. non-formalizability was made in reference to contemporary mathematics. Rosen's conclusion did not preclude future inventions of new biology-friendly mathematics.     

A new model for Schizosaccharomyces pombe telomere recognition: the telomeric single-stranded DNA-binding activity of Pot11-389

The protection of telomeres 1 (Pot1) proteins specifically recognize the single-stranded 3' end of the telomere, an activity essential for sustained cellular viability and proliferation. The current model for the telomeric single-stranded DNA (ssDNA) binding activity of Schizosaccharomyces pombe Pot1 is based on a 20 kDa fragment, Pot1pN. Recent biochemical studies suggest that SpPot1 contains a larger ssDNA-binding domain and we have identified a novel ssDNA-binding domain similar in size to the human Pot1 domain. This domain, Pot1(1-389), binds extremely tightly to an oligonucleotide consisting of two conserved hexameric S. pombe telomere repeats, d(GGTTACGGTTAC), with an affinity approximately 4000-fold tighter than Pot1pN binds its cognate ssDNA. The Pot1(1-389)/ssDNA complex exhibits a half-life of 53 min, consistent with that estimated for full-length SpPot1 and significantly longer than that of Pot1pN. Single nucleotide substitutions reveal that, in contrast to Pot1pN, tandem trinucleotide repeats (GTT) within d(GGTTACGGTTAC) are specifically recognized by Pot1(1-389). Interestingly, certain single nucleotide substitutions that impacted Pot1pN binding exhibited no effect on binding affinity by Pot1(1-389). However, these substitutions reduced binding affinity when simultaneously substituted in each hexameric repeat. The non-additive nature of these substitutions suggests that certain nucleotides are coupled through the ability of the flexible ssDNA oligonucleotide to adopt alternate, thermodynamically equivalent conformations. The biochemical behavior of Pot1(1-389) is more similar to that of the full-length SpPot1 protein than to that of Pot1pN, making Pot1(1-389) a valuable domain for the future study of how full-length SpPot1 interacts with telomeric ssDNA.     

A comparative study in birds: call-type-independent species and individual recognition using four machine-learning methods and two acoustic features

Species- and individual-specific animal calls can be used in identification as verified in playback experiments and analyses of features extracted from these signals. The use of machine-learning methods and acoustic features borrowed from human speech recognition to identify animals at the species and individual level has increased recently. To date there have been few studies comparing the performances of these methods and features used for call-type-independent species and individual identification. We compared the performance of four machine-learning classifiers in the identification of ten passerine species, and individual identification for three passerines using two acoustic features. The methods did not require us to pre-categorize the component syllables in call-type-independent species and individual identification systems. The results of our experiment indicated that support vector machines (SVM) performed best generally, regardless of which acoustic feature was used, linear predictive coefficients (LPCs) increased the recognition accuracies of hidden Markov models (HMM) greatly, and the most appropriate classifiers for LPCs and Mel-frequency cepstral coefficients (MFCCs) were HMM and SVM respectively. This study will assist researchers in selecting classifiers and features to use in future species and individual recognition studies.     

Gaussian neighborhood: A new measure of accessibility for residues of protein molecules

We introduce a new method for assessing the extent of residue exposure in proteins. For each atom of every residue a Gaussian-weighted atomic surroundings value (the G-neighborhood) is calculated. A normalized sum of G-neighborhood values over all the atoms of a residue is complementary to conventional surface accessibility characteristics. The G-0neighborhood value of a residue is a sensitive indicator of its location, strongly dependent on the 3D structure of a the protein. Correlations between secondary structures and patterns of G-neighborhood values for six different protein molecules are discussed. Comparison of the distribution of hydrophobic and charged residues in the 3D structure for the alcohol-soluble protein crambin and that of five water-soluble proteins (cytochrome c, flavodoxin, myoglobin, rhodanese, and Bence–Jones protein) shows striking differences in their G-neighborhood patterns. Contacts between the prosthetic group and the peptide portion of a protein as well as protein interdomain contacts and monomer–monomer contacts are characterized. © 1993 Wiley-Liss, Inc.     

A new kinetic model for biochemical oscillations: Graph-theoretical analysis

A graphical analysis demonstrates the ability of slow substrate activation and certain types of cooperativity between the two enzyme active sites to generate sustained oscillations. The analysis allows us to estimate kinetic parameter values for which oscillations exist. The scheme analyzed can explain the cyclical changes in functioning of various motor enzymes. Moreover, this scheme does not generate bistability for any parameter values. The graphical analysis presented is simple and visually clarifies the regulatory role of the details in the kinetic schemes.     

Lymphocyte attachment to high endothelial venules during recirculation: A possible role for carbohydrates as recognition determinants

During the course of their recirculation through the body, blood-borne lymphocytes specifically adhere to high endothelial venules (HEV) within secondary lymphoid organs such as peripheral lymph nodes (PN) and gut-associated Peyer's patches (PP). This adherence event, which initiates the extravasation of the lymphocyte, is highly specific in terms of the class of lymphocyte and the anatomic location of the HEV. We review evidence that the lymphocyte adhesive molecule (homing receptor) involved in attachment to PN HEV is a carbohydrate-binding receptor (lectin-like) with specificity for mannose-6-phosphate (M6P)-like ligands. We describe the use of a novel cytochemical probe for the detection and characterization of cell surface carbohydrate-binding receptors. Using a M6P-based probe, we show that the carbohydrate-binding receptor on lymphocytes is closely-related or identical to the MEL-14 antigen, a putative homing receptor identified by a monoclonal antibody. Evidence is presented that the lymphocyte attachment sites on both PN and PP HEV are inactivated by mild periodate oxidation and hence are probably carbohydrate in nature. Yet, the sites are biochemically distinguishable in that one class (PN) requires sialidase-sensitive structures whereas the other (PP) does not. We raise the possibility that diversity in the carbohydrate-based recognition determinants on HEV may underlie the adhesive specificities in this system.