Recognition of position-specific properties of tectal cell membranes by retinal axons in vitro

In order to test the preference of growing axons for membrane-associated positional specificity a new in vitro assay was developed. In this assay, membrane fragments of two different sources are arranged as a carpet of very narrow alternating strips. Axons growing on such striped carpets are simultaneously confronted with the two substrates at the stripe borders. If there is a preference of axons for one or the other substrate they become oriented by the stripes and grow within the lanes of the preferred substrate. Such preferential growth could, in principle, be due to affinity to attractive factors on the preferred stripes or avoidance of repulsive factors on the alternate stripes. This assay system was used to investigate growth of chick retinal axons on tectal membranes. Tissue strips cut from various areas of the retina were explanted and the extending axons were confronted with stripes of cell membranes from various areas within the optic tectum. Tectal cell membranes prove to be an excellent substrate for the growth of retinal axons. Nasal and temporal axons can grow well on membranes of both posterior and anterior tectal cells. If, however, temporal axons are given a choice and encounter the border between anterior and posterior membranes they show a marked preference for growth on membranes of the anterior tectum, their natural target area. Nasal axons do not show a preference in this assay system. The transition from nasal to temporal properties within the retina is abrupt. In contrast, the transition from anterior to posterior properties of the tectal cell membranes occurs as a smooth gradient. Significantly, the positional differences of tectal membrane properties are only seen during the period of development of the retinotectal projection and are independent of tectal innervation by retinal axons. These anterior-posterior differences disappear by embryonic day 14.     

Goldfish retinal axons respond to position-specific properties of tectal cell membranes in vitro

Using a special in vitro assay, we tested whether retinal ganglion cell axons in an adult vertebrate, the goldfish (which can regenerate a retinotopic projection after optic nerve section), recognize position-specific differences in cell surface membranes of their target, the tectum opticum. On a surface consisting of alternating stripes of membranes from rostral and caudal tectum, temporal axons accumulate on membranes derived from their retinotopically related rostral tectal half. Nasal axons grow randomly over both types of membranes. Nasal and temporal axons can elongate on both rostral and caudal membranes. A quantitative growth test, however, revealed that caudal membranes are less permissive substrates for the outgrowth of temporal axons than rostral membranes, and than rostral or caudal membranes for nasal axons.     

Kin-informative recognition cues in ants

Although social groups are characterized by cooperation, they are also often the scene of conflict. In non-clonal systems, the reproductive interests of group members will differ and individuals may benefit by exploiting the cooperative efforts of other group members. However, such selfish behaviour is thought to be rare in one of the classic examples of cooperation--social insect colonies--because the colony-level costs of individual selfishness select against cues that would allow workers to recognize their closest relatives. In accord with this, previous studies of wasps and ants have found little or no kin information in recognition cues. Here, we test the hypothesis that social insects do not have kin-informative recognition cues by investigating the recognition cues and relatedness of workers from four colonies of the ant Acromyrmex octospinosus. Contrary to the theoretical prediction, we show that the cuticular hydrocarbons of ant workers in all four colonies are informative enough to allow full-sisters to be distinguished from half-sisters with a high accuracy. These results contradict the hypothesis of non-heritable recognition cues and suggest that there is more potential for within-colony conflicts in genetically diverse societies than previously thought.     

Discharges of tectal neurons evoked by electrical stimulation of single retinal ganglion cells in frogs

"EEG quanta" — extracellular monosynaptic PSPs evoked by action potentials of a single axon — were recorded in the frog thalamus at a depth of 200–700 µ during electrical stimulation of the retina by single, double, or triple pulses of current of threshold strength. With an interval of 5–25 msec between consecutive stimuli, a negative spike, increasing as the microelectrode was inserted deeper, was observed at the peak of the testing EEG quanta, which were enlarged 1.5–2.5 times. It is postulated that this spike is the synchronous discharge of neuron bodies (population spike), evoked by an action potential of a single retinotectal axon. This axon branches in layers F or G. Discharges appear in neurons of layers 6–8. The possibility that the volley discharge of one class 3–5 detector excites tectal ganglion cells, whose axons mainly form the tecto-bulbospinal tract, is discussed.Research Institute of Cardiology and Laboratories of Electroencephalography and Neurocybernetics, Medical Institute, Kaunas, Lithuania. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 829–835, November–December, 1984.     

Species recognition by male swordtails via chemical cues

Species recognition can often play a key role in female matingpreferences. Far less is known about conspecific mate recognitionfrom the male perspective. In many closely related taxa, femalesexhibit few obvious visual differences and males might haveto attend to chemical cues in mate recognition, a possibilitythat has rarely been explored in vertebrates. Here, we examinemale species recognition via odor cues in the swordtail fish,Xiphophorus birchmanni. In dichotomous choice experiments wefirst tested whether males respond to female odor cues. We foundthat males were attracted to conspecific female odor and thoseof a related allopatric congener, Xiphophorus malinche, overa water control. Males did not, however, respond to the femaleodor of the more distantly related sympatric platyfish, Xiphophorusvariatus. We then gave male X. birchmanni the choice betweenconspecific and heterospecific female stimuli. Males, in thisscenario, significantly preferred the conspecific odor whenthe alternative was platyfish. However, when offered odor cuesof X. malinche, male X. birchmanni actually preferred the heterospecificfemale cue. The complex array of preferences reported here,previously documented only in females, underscores the needto consider the behavior of both sexes in dictating actual matingoutcomes.     

Weak electric fields serve as guidance cues that direct retinal ganglion cell axons in vitro

Growing axons are directed by an extracellular electric field in a process known as galvanotropism. The electric field is a predominant guidance cue directing retinal ganglion cell (RGC) axons to the future optic disc during embryonic development. Specifically, the axons of newborn RGCs grow along the extracellular voltage gradient that exists endogenously in the embryonic retina (Yamashita, 2013 [8]). To investigate the molecular mechanisms underlying galvanotropic behaviour, the quantification of the electric effect on axon orientation must be examined. In the present study, a culture system was built to apply a constant, uniform direct current (DC) electric field by supplying an electrical current to the culture medium, and this system also continuously recorded the voltage difference between the two points in the medium. A negative feedback circuit was designed to regulate the supplied current to maintain the voltage difference at the desired value. A chick embryo retinal strip was placed between the two points and cultured for 24 h in an electric field in the opposite direction to the endogenous field, and growing axons were fluorescently labelled for live cell imaging (calcein-AM). The strength of the exogenous field varied from 0.0005 mV/mm to 10.0 mV/mm. The results showed that RGC axons grew in the reverse direction towards the cathode at voltage gradients of ≥0.0005 mV/mm, and straightforward extensions were found in fields of ≥0.2–0.5 mV/mm, which were far weaker than the endogenous voltage gradient (15 mV/mm). These findings suggest that the endogenous electric field is sufficient to guide RGC axons in vivo.     

Species-specific recognition of beetle cues by the nematode Pristionchus maupasi

SUMMARY The environment has a strong effect on development as is best seen in the various examples of phenotypic plasticity. Besides abiotic factors, the interactions between organisms are part of the adaptive forces shaping the evolution of species. To study how ecology influences development, model organisms have to be investigated in their environmental context. We have recently shown that the nematode Pristionchus pacificus and its relatives are closely associated with scarab beetles with a high degree of species specificity. For example, P. pacificus is associated with the oriental beetle Exomala orientalis in Japan and the northeastern United States, whereas Pristionchus maupasi is primarily isolated from cockchafers of the genus Melolontha in Europe. Here, we investigate how Pristionchus nematodes identify their specific insect hosts by using chemotaxis studies originally established in Caenorhabditis elegans . We observed that P. maupasi is exclusively attracted to phenol, one of the sex attractants of Melolontha beetles, and that attraction was also observed when washes of adult beetles were used instead of pure compounds. Furthermore, P. maupasi chemoattraction to phenol synergizes with plant volatiles such as the green leaf alcohol and linalool, demonstrating that nematodes can integrate distinct chemical senses from multiple trophic levels. In contrast, another cockchafer-associated nematode, Diplogasteriodes magnus , was not strongly attracted to phenol. We conclude that interception of the insect communication system might be a recurring strategy of Pristionchus nematodes but that different nematodes use distinct chemical cues for finding their beetle hosts.     

Rotation of the tectal primordium reveals plasticity of target recognition in retinotectal projection

Retinotectal projection is precisely organized in a retinotopic manner. In normal projection, temporal retinal axons project to the rostral part of the tectum, and nasal axons to the caudal part of the tectum. The two-dimensional relationship between the retina and the tectum offers a useful experimental system for analysis of neuronal target recognition. We carried out rotation of the tectal primordium in birds at an early stage of development, around the 10-somite stage, to achieve a better understanding of the characteristics of target recognition, especially the rostrocaudal specificity of the tectum. Our results showed that temporal retinal axons projected to the rostral part of the rotated tectum, which was originally caudal, and that nasal axons projected to the caudal part of the rotated tectum, which was originally rostral. Therefore, the tectum that had been rotated at the 10-somite stage received normal topographic projection from the retinal ganglion cells. Rostrocaudal specificity of the tectum for target recognition is not determined by the 10-somite stage and is acquired through interactions between the tectal primordium and its surrounding structures.     

The use of volatile cues in recognition of kin eggs by predatory mites

1. Several animal species are known to distinguish between their own eggs and eggs of unrelated conspecifics. However, the cues involved in this discrimination are often unknown. These cues were studied using the predatory mite Gynaeseius liturivorus Ehara.
2. Adult females of these predatory mites oviposit in clusters and avoid oviposition close to eggs laid by other females, resulting in reduced cannibalism between offspring. Because predatory mites are blind, it was tested whether volatiles of eggs were used as a cue for egg recognition.
3. Adult female predatory mites were offered volatile cues of their own eggs and of unrelated conspecific eggs, and females were prevented from contacting the eggs. Predatory mites oviposited closer to their own eggs than to unrelated eggs. This preference was observed even when one own and one unrelated egg were offered as a volatile source.
4. These results suggest that adult female predatory mites can determine kinship using volatiles released from the eggs.

     

Retinal encoding of ultrabrief shape recognition cues

Shape encoding mechanisms can be probed by the sequential brief display of dots that mark the boundary of the shape, and delays of less that a millisecond between successive dots can impair recognition. It is not entirely clear whether this is accomplished by preserving stimulus timing in the signal being sent to the brain, or calls for a retinal binding mechanism. Two experiments manipulated the degree of simultaneity among and within dot pairs, requiring also that the pair members be in the same half of the visual field or on opposite halves, i.e., across the midline from one another. Recognition performance was impaired the same for these two conditions. The results make it likely that simultaneity of cues is being registered within the retina. A potential mechanism is suggested, calling for linkage of stimulated sites through activation of PA1 cells. A third experiment confirmed a prior finding that the overall level of recognition deficit is partly a function of display-set size, and affirmed submillisecond resolution in binding dot pairs into effective shape-recognition cues.     

Cross-species axial signaling, with realignment of retinal axes, in embryonic Xenopus eyes

The locus specificities which enable retinal ganglion cells to assemble a topographic retinotectal map are patterned about a pair of (anteroposterior and dorsoventral) retinal axes set down in the early eye bud. We have transplanted a Xenopus laevis eye bud, at stage $\text{23}\text{24}$ when the retinal field is still responsive to the axial signals from the surrounding tissues, into the enucleated eye socket of a comparable stage Ambystoma maculatum embryo. Three days later, when the Xenopus eye had reached early larval stages and was no longer responsive to extraocular signals, the eye was retransplanted into the socket of the Xenopus final carrier embryo. The pattern of retinotectal connections between the eye and the carrier's optic tectum was examined by electrophysiological analysis of the visuotectal projections. The results indicated that many of the retinae had patterned locus specificities about axes derived from the salamander intermediate host. We infer that axial signaling involves fundamental cellular processes which have been highly conserved during evolution.     

The use of olfactory and other cues for social recognition by juvenile pigs

Social recognition is essential for the maintenance of a stable group structure. Failure to recognise familiar conspecifics in social groups of juvenile pigs may initiate agonistic encounters that can compromise welfare and productivity. Current housing systems may allow build up of atmospheric ammonia that might, in turn, interfere with the olfactory system and compromise olfactory perception. In the present study, 16 juvenile pigs were housed in fresh air while another 16 pigs were kept in an ammoniated atmosphere (approximately 36ppm) for 1 week prior to test and another week during testing. We then assessed the role of olfaction in social recognition and determined whether chronic exposure to ammonia compromised discrimination based on olfactory perception by comparing the pigs' responses to selected cues from a familiar and an unfamiliar pig presented simultaneously in separate chambers of a modified Y-maze in each of two test situations (near, remote). Visual, auditory, olfactory, and tactile cues were all provided in the "near" test situation; here, the stimulus pigs were presented in two separate chambers behind clear perspex walls containing an aperture that allowed nose-to-nose contact between the test and stimulus pigs. On the other hand, the "remote" test provided only olfactory cues via air passed from the chambers containing the stimulus pigs into the test chamber. Each test lasted 5min and the pigs' behaviour was recorded via overhead video cameras; we then measured the accumulated times spent near and the numbers of visits made to the familiar and the unfamiliar stimulus pigs as well as the transitions between them. Overall, pigs made more visits to and spent significantly longer near both the stimulus pigs in the near test than in the remote one (ANOVA, P<0.001). They also made more transitions between the stimuli in the former test than the latter (P<0.001). Pigs from both the ammonia and the fresh-air treatment groups showed social discrimination. However, pigs that had received chronic exposure to ammonia visited the familiar pig more often and spent longer near it than the unfamiliar one regardless of the test situation (P<0.05) whereas those reared in fresh air spent longer near the unfamiliar animal (P<0.05). The present results suggest that pigs from both treatment groups employed olfactory cues in social recognition, but that chronic exposure to ammonia did not interfere with this ability. However, ammonia treatment seemingly affected social preferences, thus indicating an unknown and more fundamental effect of living in ammoniated atmospheres.     

Nestmate recognition in Parischnogaster striatula (Hymenoptera Stenogastrinae), visual and olfactory recognition cues

The recognition of nestmates from alien individuals is a well known phenomenon in social insects. In the stenogastrine wasp Parischnogaster striatula, we investigated the ability of females to recognize nestmates and the cues on which such recognition is based. Recognition of nestmates was observed in naturally occurring interactions between wasps approaching a nest and the resident females on that nest. This recognition was confirmed in experiments in which nestmates or alien conspecifics were presented to resident females. In naturally occurring interactions, nestmates generally approach their nest with a direct flight, while aliens usually hover in front of the nest before landing. In experiments in which the presented wasps were placed close to the nest in a direct manner, antennation of the presented wasp generally occurred, indicating that chemical cues are involved. Experiments in which dead alien individuals, previously washed in hexane, and then reapplied with extracts were recognized by colonies giving further evidence that chemical cues mediate nestmate recognition. Epicuticular lipids, known to be nestmate recognition cues in social insects, were chemically analysed by GC-MS for 44 P. striatula females from two different populations (13 different colonies). Discriminant analysis was performed on the data for the lipid mixture composition. The discriminant model showed that, in the samples from these two populations, 68.2% and 81.9% of the specimens could be correctly assigned to their colony.     

Adsorption of proteins by artificial mineral fibers: in vitro experiments

Since previous studies reported that in vitro some proteins and phospholipids were absorbed by asbestos fibres, namely chrysotile, in this study, man made filamentous glass fibers are been tested in vitro at the presence of proteins. The objective was to obtain evidence to evaluate whether continuous glass fibers have a behaviour similar to asbestos fibres. A sample of chrysotile fibres was used as control. Uptake of bovine serum albumin and horse spleen ferritin on these continuous glass fibres has been observed. However on glass fibres adsorbed less proteins per weight unit (22 mg/g and 12 mg/g respectively for albumin and ferritin) than asbestos chrysotile fibres (42 mg/g and 49 mg/g respectively for albumin and ferritin).     

Biomimics of fungal cell-cell recognition by use of lectin-coated nylon fibers.

When the mycoparasitic, biocontrol fungus Trichoderma harzianum was allowed to grow on nylon fibers treated with concanavalin A or Sclerotium rolfsii lectin, it coiled around the nylon fibers and produced hooks in a pattern similar to that observed with the real host hyphae. The incidence of interaction between T. harzianum and S. rolfsii lectin-treated fibers was significantly higher than that of the controls (untreated or blocked activated fibers). These findings provide direct evidence for the role of lectins in mycoparasitism.