Complementary left and right eye use during predator inspection and shoal-mate scrutiny in minnows

Minnows Phoxinus phoxinus did not show any difference in the average distance from a predator associated with the left or right position of a shoal-mate. While inspection behaviour of fish tested with a mirror on their left side was indistinguishable from the behaviour of controls tested without a mirror, inspection behaviour of fish tested with the mirror on their right side appeared to be changed and incoherent in both temporal and spatial parameters. These results suggest that, as in mosquitofish Gambusia holbrooki , the condition with the mirror on the left provided the best arrangement of monocular lateral stimulation in which each stimulus fell into the correct lateral visual field. Minnows showed a significant left eye preference during scrutiny of their mirror image when tested in the absence of any predator and a significant right eye preference while monitoring a live predator in the absence of a social partner.     

Morphological determinants of signal carrier frequency in katydids (Orthoptera): a comparative analysis using biophysical evidence of wing vibration

Male katydids produce mating calls by stridulation using specialized structures on the forewings. The right wing (RW) bears a scraper connected to a drum‐like cell known as the mirror and a left wing (LW) that overlaps the RW and bears a serrated vein on the ventral side, the stridulatory file. Sound is generated with the scraper sweeping across the file, producing vibrations that are amplified by the mirror. Using this sound generator, katydids exploit a range of song carrier frequencies (CF) unsurpassed by any other insect group, with species singing as low as 600 Hz and others as high as 150 kHz. Sound generator size has been shown to scale negatively with CF, but such observations derive from studies based on few species, without phylogenetic control, and/or using only the RW mirror length. We carried out a phylogenetic comparative analysis involving 94 species of katydids to study the relationship between LW and RW components of the sound generator and the CF of the male's mating call, while taking into account body size and phylogenetic relationships. The results showed that CF negatively scaled with all morphological measures, but was most strongly related to components of the sound generation system (file, LW and RW mirrors). Interestingly, the LW mirror (reduced and nonfunctional) predicted CF more accurately than the RW mirror, and body size is not a reliable CF predictor. Mathematical models were verified on known species for predicting CF in species for which sound is unknown (e.g. fossils or museum specimens).     

Phylogenetic autocorrelation and heritability of geographic range size,shape and position of fiddler crabs,genus Uca (Crustacea,Decapoda)

The aim of this study was to evaluate the levels of phylogenetic heritability of the geographical range size, shape and position for 88 species of fiddler crabs of the world, using phylogenetic comparative methods and simulation procedures to evaluate their fit to the neutral model of Brownian motion. The geographical range maps were compiled from literature, and range size was based on the entire length of coastline occupied by each species, and the position of each range was calculated as its latitudinal and longitudinal midpoint. The range shape of each species was based in fractal dimension (box‐counting technique). The evolutionary patterns in the geographical range metrics were explored by phylogenetic correlograms using Moran’s I autocorrelation coefficients, autoregressive method (ARM) and phylogenetic eigenvector regression (PVR). The correlograms were compared with those obtained by simulations of Brownian motion processes across phylogenies. The distribution of geographical range size of fiddler crabs is right‐skewed and weak phylogenetic autocorrelation was observed. On the other hand, there was a strong phylogenetic pattern in the position of the range (mainly along longitudinal axis). Indeed, the ARM and PVR evidenced, respectively, that ca. 86% and 91% of the longitudinal midpoint could be explained by phylogenetic relationships among the species. The strong longitudinal phylogenetic pattern may be due to vicariant allopatric speciation and geographically structured cladogenesis in the group. The traits analysed (geographical range size and position) did not follow a Brownian motion process, thus suggesting that both adaptive ecological and evolutionary processes must be invoked to explain their dynamics, not following a simple neutral inheritance in the fiddler‐crab evolution.     

Laterality Influences Schooling Position in Rainbowfish,Melanotaenia spp

Cerebral lateralization is a widespread trait among animals, is often manifested as side biases in behaviour (laterality) and has been suggested to provide fitness benefits. Here we examined the influence of laterality on the organisation of fish schools using rainbowfish (Melanotaenia spp) as model species. The pattern and strength of laterality for each individual was determined by examining eye preferences whilst examining their reflection in a mirror. Schools of four fish of known laterality were then created and the preferred position for each fish within the school was repeatedly observed in a flume. Fish which showed right eye preferences in the mirror test preferentially adopted a position on the left side of the school. Conversely, fish that showed left eye preferences in the mirror test or where non-lateralised preferentially adopted a position slightly to the right side of the school. However, this general pattern varied depending on the species and sex of the school. Our results strongly implicate individual laterality in the geometry of school formation.     

Specification of polarity of teloblastogenesis in the oligochaete annelid Tubifex: cellular basis for bilateral symmetry in the ectoderm

Ectodermal teloblastogenesis in the oligochaete annelid Tubifex is a spatiotemporally regulated process that gives rise to four bilateral pairs of ectoteloblasts (N, O, P, and Q) that assume distinct fates. Ectoteloblasts on either side of the embryo arise from an invariable sequence of asymmetric cell divisions of a proteloblast, NOPQ, which occur with a defined orientation with respect to the embryonic axes: the N teloblast is generated first and located ventralmost, and the Q teloblast, which is generated next, is located dorsalmost; finally, the O and P teloblasts are generated by almost equal division of their precursor cell, OP. Polarity of teloblastogenesis on one side of the embryo is a mirror image of the other; this mirror symmetry of ectoteloblasts about the embryo's midline gives rise to the bilaterally symmetric organization of the ectoderm. In this study, we examined whether cellular interactions are involved in specification of polarity of asymmetric cell divisions in NOPQ cells. A set of cell transplantation experiments demonstrated that NOPQ cells are initially uncommitted in terms of division pattern and cell fates: If a left NOPQ cell is transplanted to the right side of a host embryo, it exhibits a polarity comparable to that of right NOPQ cells. The results of another set of cell transplantation experiments suggest that contact between NOPQ cells serves as an external cue for their polarization, irrespective of their position in the embryo, and that in the absence of host NOPQ cells, transplanted NOPQ cells can be polarized according to positional information residing in the host embryo. The competence of NOPQ cells to respond to external cues tapers down before their division into N and OPQ. A set of cell ablation experiments demonstrated that neighboring cells such as posteriorly located M teloblasts and anterolaterally located micromeres play a role in controlling spatial aspects of NOPQ's behavior that gives rise to their division along the dorsoventral axis. These results suggest that NOPQ cells, which do not initially have a rigidly fixed polarity, become polarized through external cues. Possible sources of signals for this polarizing induction are discussed in the light of the present results.     

Effects of social isolation on aggressiveness in fish with special reference to the swordtail (Xiphophorus helleri)

The attack readiness of socially isolated male swordtails ($\text{Xiphophorus helleri}$) was measured in two different aggression tests: (a) In the standard–opponent test the aggressive responses to a small, rather passive opponent swimming in a small adjacent compartment of the test aquarium were counted. (b) In the mirror test the subjects were confronted with their own mirror image. Social isolation for 4 weeks resulted in a decrease of attack readiness in both test situations. It is concluded that -- similar to cichlids -- external stimuli from conspecifics are essential for maintaining the level of aggression readiness characteristic for socially living males. There are good reasons to propose that the effect of external stimuli is mediated by the pituitary-gonadal axis. On the other hand, it is well known from previous studies that, in escalated encounters between freely swimming males, isolated males fight longer and at higher intensities for rank-order position than non-isolated males. The hypothesis is proposed that the high fighting intensity of previously isolated males could be due to an experience levelling effect of social isolation, i.e. the influence of different agonistic experience is reduced by isolation.A critical review of the literature on isolation-induced decremental and incremental effects on aggression in teleosts is presented. Often it is extremely difficult to compare the results of different authors because the methods of behavioural measurement differ to a large extent. However, it is a striking fact that social isolation of immature fish in all known cases has resulted in an increase of aggressiveness. Probably in mature males, depending on species and circumstances, either an incremental or a decremental effect of social isolation may be adaptive. On the one hand, a spontaneous increase of attack readiness may be advantageous for defence of a territory or a position in the social hierarchy and improves the ability of a single individual to join a group of strange conspecifics. On the other hand, it may be economic to lower the level of androgenic hormones to some extent in the absence of conspecifics, and this could lead to a reduction of the aggression level.     

Reversal of peptide backbone direction may result in the mirroring of protein structure

In linear polypeptides, inversion of amino acid chirality (all- to all- ) achieves a mirroring of side chain positions and interactions in conformational space. A similar mirroring of side chain positions is independently achieved by a reversal of the direction of the peptide backbone (retro modification). Thus, while an all- chain could be expected to adopt a perfect ‘mirror image’ of the three-dimensional structure of its parent all- protein, the retro-all- chain could be expected to adopt a topological equivalent of such a mirror image, through the symmetry transformations of side chain interactions. These notions, supported by sequence analyses, modelling studies, and evidence relating to the activity of ‘retro-inverso’ peptides, are extended towards the proposal, that the backbone reversed chain of a large globular protein might recognize the chiral opposite of the parent protein's substrate(s).     

Mirrors,monkeys, and group dynamics

When presented with his/her own reflection in a mirror (within an environment that is natural for that particular group of primates) the position that animal holds within the group affects his/her interpretation of that image. Each individual perceives the animal in the mirror to be another animal of equal circumstances as him/herself. An alpha animal sees a potential alpha animal attempting to take over the troop. A beta or lesser animal sees another non-alpha animal attempting to enter the troop through affiliation. In this study a group of zoo raised Japanese macaques were challenged with their own reflection in a mirror. Incidents of aggressive behavior rose in the alpha animals while all affiliative behavior ceased between members of the group. The lesser animals vied for time with the mirror, each attempting to be near the perceived con-specific.     

The position of cleavage furrow in cultured <Emphasis Type="Italic">L-929</Emphasis> and <Emphasis Type="Italic">CHO</Emphasis> cells

The position of the cleavage furrow (random or otherwise) was studied on cultured L-929 (NCTC, clone 929) and CHO cells. CHO cells were seeded uniformly on the surface of Petri dishes; L-929 cells were grown as colonies so that migrating cells could be watched. Cell behavior was registered by time-lapse imaging. Two parameters were analyzed on captured images: the angle between the cell polarization axis and cleavage furrow and the angle between the cell polarization axis or cleavage furrow and the horizontal axis of the image field. It was shown that the position of CHO cells in the dish plane and the value of the angle between the cell polarization axis and the cleavage furrow were random. The L-929 cells migrating from the colony were orientated such that their polarization axis was directed to the colony center and the cleavage furrow was perpendicular to this axis. The nonrandom position of cultivated cells during mitosis and their cleavage furrow during the telophase are discussed.     

Asymmetric activation of the primary motor cortex during observation of a mirror reflection of a hand

Mirror therapy is an effective technique for pain relief and motor function recovery. It has been demonstrated that magnetic 20-Hz activity is induced in the primary motor cortex (M1) after median nerve stimulation and that the amount of the stimulus-induced 20-Hz activity is decreased when the M1 is activated. In the present study, we investigated how the image or the mirror reflection of a hand holding a pencil modulates the stimulus-induced 20-Hz activity in the M1. Neuromagnetic brain activity was recorded from 13 healthy right-handed subjects while they were either viewing directly their hand holding a pencil or viewing a mirror reflection of their hand holding a pencil. The 20-Hz activity in the left or the right M1 was examined after the right or the left median nerve stimulation, respectively, and the suppression of the stimulus-induced 20-Hz in the M1 by viewing directly one hand holding a pencil or by viewing the mirror image of the hand holding a pencil was assumed to indicate the activation of the M1. The results indicated that the M1 innervating the dominant hand was suppressed either by viewing directly the dominant hand holding a pencil or by viewing the mirror image of the non-dominant hand holding a pencil. On the other hand, the M1 innervating the non-dominant hand was activated by viewing the mirror image of the dominant hand holding a pencil, but was not activated by viewing directly the non-dominant hand holding a pencil. The M1 innervating either the dominant or the non-dominant hand, however, was not activated by viewing the hand on the side ipsilateral to the M1 examined or the mirror image of the hand on the side contralateral to the M1 exaimined. Such activation of the M1 might induce some therapeutic effects of mirror therapy.     

A morphological study and hybridization analysis of Caloglossa leprieurii (Ceramiales, Rhodophyta) from Japan, Singapore and Australia

Morphological and hybridization experiments were performed on Caloglossa leprieurii (Montagne) J. Agardh collected from Japan, Singapore and Australia in order to evaluate taxonomic characters of this species. Within C. leprieurii at least four mating groups were recognized from the Indo-Pacific region. These mating groups could be characterized by the blade width at the inter-node and the cell-row numbers on the opposite side derived from the first axial cell at the main axis, though these properties showed a certain variability even in the same plant under both field and culture conditions. The phylogenetic relationship and geographic distribution of the four mating groups are discussed.     

Mirror-imaged doublets of Tetmemena pustulata: implications for the development of left-right asymmetry

Ciliated protozoa possess cellular axes reflected in the arrangement of their ciliature. Upon transverse fission, daughter cells develop an identical ciliary pattern, ensuring perpetuation of the cellular phenotype. Experimentally manipulated cells can be induced to form atypical phenotypes, capable of intraclonal propagation and regeneration after encystment. One such phenotype in the ciliate Tetmemena pustulata (formerly Stylonychia pustulata) is the mirror-imaged doublet. These cells possess two distinct sets of ciliature, juxtaposed on the surfaces in mirror image symmetry, with a common anterior-posterior axis. We have examined whether individual ciliary components of Tetmemena mirror-image doublets are mirror imaged. Ultrastructural analysis indicates that despite global mirror imaging of the ciliature, detailed organization of the membranelles is reversed in the mirror-image oral apparatus (OA), such that the ciliary effective stroke propels food away from the OA. Assembly of compound ciliary structures of both OAs starts out identically, but as the structures associated with the mirror-image OA continue to form, the new set of membranelles undergoes a 180° planar rotation on the ventral surface relative to the same structures in the typical OA. The overall symmetry of the OA thus appears to be separable from the more localized assembly of individual basal bodies. True mirror imagery of the membranelles would require new enantiomorphic forms of the individual ciliary components, particularly the basal bodies, which is never observed. These observations suggest a mechanistic hypothesis with implications for the development of left-right asymmetry not only in ciliates, but perhaps also in development of left-right asymmetry in general.     

Structure of horse carbonmonoxyhaemoglobin

The structure is based on a difference Fourier synthesis at 2.8 Å resolution, using observed structure amplitudes and calculated phases, derived from a refinement of horse methaemoglobin at 2.0 Å resolution. Carbonmonoxyhaemoglobin has the same quaternary structure as methaemoglobin, but differs from it by slight changes in tertiary structure in the immediate vicinity of the haems. On transition from met- to carbonmonoxyhaemoglobin the distal histidines move away from the haem ligands towards the molecular surface, and both the haems and F-helices rotate slightly and shift towards the distal side. In methaemoglobin the sulphydryl group of cysteine F9(93)β is in equilibrium between two alternative positions: one external and the other half-buried in the “tyrosine pocket” between helices F and H. In carbonmonoxyhaemoglobin all the electron density for the sulphydryl group is in the half-buried position, so that the side chain of tyrosine HC2(145)β is completely displaced from its pocket. The difference map shows that the CO oxygen lies off the haem axis in both subunits, but the carbon cannot be seen as it coincides with the water molecule in methaemoglobin. A preliminary refinement of carbonmonoxyhaemoglobin suggests that the carbon may be displaced from the haem axis in the same direction as the oxygen. The haem pocket is so constructed that it fits an oxygen molecule in the bent conformation, but not a CO molecule which has its axis normal to the haem plane, because of steric hindrance by N_? of the distal histidine and by C_γ2 of the distal valine. These two side chains apparently push the CO oxygen off the haem axis. The difference map indicates that in methaemoglobin the α-haem is ruffled and that on transition from met- to carbonmonoxyhaemoglobin it becomes flattened; in the β-haem the iron appears to move towards the porphyrin plane. The resolution is not sufficient to determine the exact position of the iron atoms and the proximal histidines relative to the porphyrins.     

Evaluation of the Shape Symmetry of Bilateral Normal Corneas in a Chinese Population

Purpose

To investigate the bilateral symmetry of the global corneal topography in normal corneas with a wide range of curvature, astigmatism and thickness values

Design

Cross-Sectional Study

Methods

Topography images were recorded for the anterior and posterior surfaces of 342 participants using a Pentacam. Elevation data were fitted to a general quadratic model that considered both translational and rotational displacements. Comparisons between fellow corneas of estimates of corneal shape parameters (elevation, radius in two main directions, R_x and R_y, and corresponding shape factors, Q_x and Q_y) and corneal position parameters (translational displacements: x₀, y₀ and z₀, and rotational displacements: α, β and γ) were statistically analyzed.

Results

The general quadratic model provided average RMS of fit errors with the topography data of 1.7±0.6 µm and 5.7±1.3 µm in anterior and posterior corneal surfaces. The comparisons showed highly significant bilateral correlations with the differences between fellow corneas in R_x, R_y, Q_x and Q_y of anterior and posterior surfaces remaining insignificantly different from zero. Bilateral differences in elevation measurements at randomly-selected points in both corneal central and peripheral areas indicated strong mirror symmetry between fellow corneas. The mean geometric center (x₀, y₀, z₀) of both right and left corneas was located on the temporal side and inferior-temporal side of the apex in anterior and posterior topography map, respectively. Rotational displacement angle α along X axis had similar distributions in bilateral corneas, while rotation angle β along Y axis showed both eyes tilting towards the nasal side. Further, rotation angle γ along Z axis, which is related to corneal astigmatism, showed clear mirror symmetry.

Conclusions

Analysis of corneal topography demonstrated strong and statistically-significant mirror symmetry between bilateral corneas. This characteristic could help in detection of pathological abnormalities, disease diagnosis, measurement validation and surgery planning.     

THE “PARADOX” DIATOM BACILLARIA PAXILLIFER (BACILLARIOPHYTA) REVISITED1

Defined by its unique colonial locomotion, Bacillaria paxillifer (O. F. Müll.) Hendey was recognized as a single, pandemic species by many phycologists. However, reinvestigation of colonies from different habitats revealed three distinct groups: (A) brackish/freshwater, (B) marine littoral, and (C) marine planktonic taxa. Groups differed in colony and cell form, raphe flanges (RFs), shape and position of transapical ribs (Tr's), and morphogenesis. Linear‐shaped species were restricted to group A: Tr's thickened principally to the interior. Lanceolate forms were confined to groups B and C: valve formation proceeded from an internal base layer to the exterior. The planktonic species differed in the shape of its raphe slit, and the transformation of girdle bands (GBs) into “winglets.” Taxa also differed in chloroplast shape and number. All species formed motile colonies. Siblings adhered via elastic fibrils secreted through their raphe. Raphe ribs were held in position by siliceous clamps (fibulae), anchored in an extra pair of axial ribs (fibular ribs) parallel to the raphe ribs. This raphe system resembled that of Cylindrotheca rather than the “canal raphe” of Nitzschia. Many valves were asymmetric along the apical axis due to protruding RFs shuttling in a 1:1 ratio within a colony, but raphe slits were mirror images, as were the growth direction of fibulae and position of plastids, with pyrenoids tilted in the same direction. Species possessed four open GBs per epitheca; the third band invariably bore an internal, organic ridge to aid in adhesion of the plasmalemma during cleavage. The results suggested that these taxa are a natural phylogenetic group, requiring precise determination of their taxonomic position.     

Gap junction structures. IV. Asymmetric features revealed by low- irradiation microscopy

Micrographs of mouse liver gap junctions, isolated with detergents, and negatively stained with uranyl acetate, have been recorded by low-irradiation methods. Our Fourier-averaged micrographs of the hexagonal junction lattice show skewed, hexameric connexons with less stain at the threefold axis than at the six indentations between the lobes of the connexon image. These substructural features, not clearly observed previously, are acutely sensitive to irradiation. After an electron dose less than that normally used in microscopy, the image is converted to the familiar doughnut shape, with a darkly stained center and a smooth hexagonal outline, oriented with mirror symmetry in the lattice. Differences in appearance among 25 reconstructed images from our low-irradiation micrographs illustrate variation in staining of the connexon channel and the space between connexons. Consistently observed stain concentration at six symmetrically related sites approximately 34 A from the connexon center, 8 degrees to the right or left of the (1, 1) lattice vector may reveal an intrinsic asymmetric feature of the junction structure. The unexpected skewing of the six-lobed connexon image suggests that the pair of hexagonal membrane arrays that form the junction may not be structurally identical. Because the projected image of the connexon pair itself appears mirror symmetric, each pair may consist of two identical connexon hexamers related by local (noncrystallographic) twofold axes in the junctional plane at the middle of the gap. All connexons may be chemically identical, but their packing in the hexagonal arrays on the two sides of the junction appears to be nonequivalent.     

Improvement of the microcinematography technic for the study of cell cycles

An improvement of time-lapse microcinematography technique is described. It consists in directly printing the time on the microscopical frame, at the moment of the shooting. The time (digital watch), as well as other relevant parameters (temperature etc.) are displayed on a "parameter board", the image of which is encrusted into the microscopical frame by means of an auxiliary two-component lens system. These lenses (current type of microscopical and photographical objectives) are centered on an axis perpendicular to the microscope-camera axis and provide a reduced image of the "parameter board", which is projected on the film edge after deflection by a 45 degree mirror. The latter (aluminized perspex sheet) is located above the photographical eyepiece; it is pierced at the place of the eyepoint in order to give way to the light rays coming out of the cellular culture.     

Cochlodinium fulvescens sp. nov. (Gymnodiniales, Dinophyceae), a new chain-forming unarmored dinoflagellate from Asian coasts

Cellular morphology and the phylogenetic position of a new unarmored photosynthetic dinoflagellate Cochlodinium fulvescens Iwataki, Kawami et Matsuoka sp. nov. were examined by light microscopy and molecular phylogenetic analyses based on partial large subunit ribosomal DNA (LSU rDNA) and small subunit ribosomal DNA (SSU rDNA) sequences. The cells of C. fulvescens closely resemble C. polykrikoides, one of the most harmful red tide forming dinoflagellates, due to it possessing a cingulum encircling the cell approximately twice, a spherical nucleus positioned in the anterior part of the cell and an eyespot‐like orange pigmented body located in the dorsal side of the epicone, as well as formation of cell‐chains. However, this species is clearly distinguished from C. polykrikoides based on several morphological characteristics, namely, cell size, shape of chloroplasts and the position of narrow sulcus situated in the cell surface. The sulcus of C. fulvescens is located at the intermediate position of the cingulum in the dorsal side, whereas that of C. polykrikoides is situated immediately beneath the cingulum. LSU rDNA phylogenies indicated that C. fulvescens is clearly distinct from, but closely related to C. polykrikoides among dinoflagellates.