Iridescent scales signal male fighting ability to access females in the jewelled splitfin Xenotoca variata.

Jewelled splitfin males (Xenotoca variata) possess multi-colour iridescent scales (speckles) on the flanks. This study tested the hypothesis that the number of speckles could be a good proxy for predicting fighting ability in contests for access to females. The experiments consisted in observing and recording males' agonistic behaviour, courtship displays and mating attempts in mixed-sex groups. The data were analysed and presented based on a Bayesian approach, which revealed that the density (cm-2 ) of speckles was positively correlated with the increase observed in the proportional frequency of attacks. Similarly, the density of speckles was positively associated with the increase observed in the frequency of courtship behaviour and with the frequency of mating attempts. Male-male aggressions drastically diminished (by eightfold) when females were removed from the observation tanks. These results indicate that the number of speckles is a consistent predictor of successful access to females and therefore, speckled males are likely to be able to gain more mating opportunities. This finding highlights the ubiquitous role iridescent colours play in visual signalling.

Pharmacological characterization and differential expression of NMDA receptor subunits in the chicken vestibular system during development.

Previous studies demonstrated that in vitro preparations of the isolated vestibular system of diverse animal species still exhibit stable resting electrical activity and mechanically evoked synaptic transmission between hair cells and primary afferent endings. However, there are no reports related to their neurodevelopment. Therefore, this research aimed to examine whether NMDA receptors mediate these electrical signals in an isolated preparation of the chicken vestibular system at three developmental stages, E15, E18, and E21. We found that the spontaneous and mechanically evoked discharges from primary afferents of the posterior semicircular canal were modulated by agonists NMDA and glycine, but not by the agonist d-serine applied near the synapses. Moreover, the individually applied by bath perfusion of three NMDA receptor antagonists (MK-801, ifenprodil, and 2-naphthoic acid) or high Mg2+ decreased the resting discharge rate, the NMDA response, and the discharge rate of mechanically evoked activity from these primary afferents. Furthermore, we found that the vestibular ganglion shows a stage-dependent increase in the expression of NMDA receptor subunits GluN1, GluN2 (A-C), and GluN3 (A-B), being greater at E21, except for GluN2D, which was inversely related to the developmental stage. However, in the crista ampullaris, the expression pattern remained constant throughout development. This could suggest the possible existence of presynaptic NMDA receptors. Our results highlight that although the NMDA receptors are functionally active at the early embryonic stages of the vestibular system, NMDA and glycine reach their mature functionality to increase NMDA responses close to hatching (E21).

A Laboratory Method to Measure Contagious Yawning in Rats.

Communication is an essential aspect of animal social life. Animals may influence one another and come together in schools, flocks, and herds. Communication is also the way sexes interact during courtship and how rivals settle disputes without fighting. However, there are some behavioral patterns for which it is difficult to test the existence of a communicatory function, because several types of sensory modalities are likely involved. For example, contagious yawning is a communicatory act in mammals that potentially occurs through sight, hearing, smell, or a combination of these senses depending on whether the animals are familiar to one another. Therefore, to test hypotheses about the possible communicatory role of such behaviors, a suitable method is necessary to identify the participating sensory modalities. The method proposed here aims to obtain yawn contagion curves for familiar and unfamiliar rats and evaluate the relative participation of visual and olfactory sensory modalities. The method uses inexpensive materials, and with some minor changes, it can also be used with other rodent species such as mice. Overall, the method involves the substitution of clear dividers (with or without holes) with opaque dividers (with or without holes) that either allow or prevent communication between rats placed in adjacent cages with holes in adjoining sides. Accordingly, four conditions can be tested: olfactory communication, visual communication, both visual and olfactory communication, and neither visual nor olfactory communication. As social interaction occurs between the rats, these test conditions simulate what may occur in a natural environment. In this respect, the method proposed here is more effective than traditional methods that rely on video presentations whose biological validity can raise concerns. Nonetheless, it does not discriminate between the potential role of hearing and roles of smell and vision in yawn contagion.

Visual Detection of Speckles in the Fish Xenotoca variata by the Predatory Snake Thamnophis melanogaster in Water of Different Turbidity.

Semi-aquatic snakes integrate visual and chemical stimuli, and prey detection and capture success are therefore linked to the display of visual predatory behavior. The snake Thamnophis melanogaster responds preferentially to individuals of the fish Xenotoca variata with a greater number of bright, colorful spots (lateral speckles) compared with those with a smaller number; however, water turbidity can reduce underwater visibility and effect the vulnerability of fish. In this study, we tested whether the presence of iridescent speckles on the flanks of male X. variata interacted with water turbidity to modify the predatory behavior displayed by the snake T. melanogaster. We predicted that in an experimental laboratory test, the snakes would increase the frequency of their predatory behavior to the extent that the water turbidity decreases. The snakes were tested at six different levels of water turbidity, in combination with three categories of male fish (with few, a median number of, or many speckles). The results showed that in a pool with high or zero turbidity, the number of speckles is not a determining factor in the deployment of the predatory behavior of the snake T. melanogaster toward X. variata. Our findings suggest that snakes can view the fish at intermediate percentages of turbidity, but the number of speckles in male X. variata is irrelevant as an interspecific visual signal in environments with insufficient luminosity. The successful capture of aquatic prey is influenced by integration between chemical and visual signals, according to environmental factors that may influence the recognition of individual traits.

Smell facilitates auditory contagious yawning in stranger rats.

Most vertebrates yawn in situations ranging from relaxation to tension, but only humans and other primate species that show mental state attribution skills have been convincingly shown to display yawn contagion. Whether complex forms of empathy are necessary for yawn contagion to occur is still unclear. As empathy is a phylogenetically continuous trait, simple forms of empathy, such as emotional contagion, might be sufficient for non-primate species to show contagious yawning. In this study, we exposed pairs of male rats, which were selected for high yawning, with each other through a perforated wall and found that olfactory cues stimulated yawning, whereas visual cues inhibited it. Unexpectedly, cage-mate rats failed to show yawn contagion, although they did show correlated emotional reactivity. In contrast, stranger rats showed auditory contagious yawning and greater rates of smell-facilitated auditory contagious yawning, although they did not show correlated emotional reactivity. Strikingly, they did not show contagious yawning to rats from a low-yawning strain. These findings indicate that contagious yawning may be a widespread trait amongst vertebrates and that mechanisms other than empathy may be involved. We suggest that a communicatory function of yawning may be the mechanism responsible for yawn contagion in rats, as contagiousness was strain-specific and increased with olfactory cues, which are involved in mutual recognition.

Single delivery of an adeno-associated viral construct to transfer the CASQ2 gene to knock-in mice affected by catecholaminergic polymorphic ventricular tachycardia is able to cure the disease from birth to advanced age.

BACKGROUND: Catecholaminergic polymorphic ventricular tachycardia is an inherited arrhythmogenic disorder characterized by sudden cardiac death in children. Drug therapy is still insufficient to provide full protection against cardiac arrest, and the use of implantable defibrillators in the pediatric population is limited by side effects. There is therefore a need to explore the curative potential of gene therapy for this disease. We investigated the efficacy and durability of viral gene transfer of the calsequestrin 2 (CASQ2) wild-type gene in a catecholaminergic polymorphic ventricular tachycardia knock-in mouse model carrying the CASQ2(R33Q/R33Q) (R33Q) mutation. METHODS AND RESULTS: We engineered an adeno-associated viral vector serotype 9 (AAV9) containing cDNA of CASQ2 wild-type (AAV9-CASQ2) plus the green fluorescent protein (GFP) gene to infect newborn R33Q mice studied by in vivo and in vitro protocols at 6, 9, and 12 months to investigate the ability of the infection to prevent the disease and adult R33Q mice studied after 2 months to assess whether the AAV9-CASQ2 delivery could revert the catecholaminergic polymorphic ventricular tachycardia phenotype. In both protocols, we observed the restoration of physiological expression and interaction of CASQ2, junctin, and triadin; the rescue of electrophysiological and ultrastructural abnormalities in calcium release units present in R33Q mice; and the lack of life-threatening arrhythmias. CONCLUSIONS: Our data demonstrate that viral gene transfer of wild-type CASQ2 into the heart of R33Q mice prevents and reverts severe manifestations of catecholaminergic polymorphic ventricular tachycardia and that this curative effect lasts for 1 year after a single injection of the vector, thus posing the rationale for the design of a clinical trial.

Female vibration discourages male courtship behaviour in the Amarillo fish (Girardinichthys multiradiatus).

Amarillo fish females (Girardinichthys multiradiatus) vibrate when conspecific males approach them; the reason behind this behaviour is unclear. Hypotheses are that females vibrate either to avoid aggression from males or to court them. We prevented females from vibrating by temporarily blocking their lateral line organs and eyes, on the assumption that they rely on these senses to detect approaching males. Females with the lateral line organs obstructed vibrated less frequently than females with the lateral line intact, indicating that the mechanosensory lateral line system is necessary for perceiving approaching males. Males displayed more courtship behaviour to sighted females with the lateral line organs obstructed than to sighted females with the lateral line intact. A general tendency indicated that the less the females vibrated the more the males courted them. These findings indicate that female vibration discourages male courtship behaviour.

Punishment-induced fear modifies the daily course of yawning in rats.

A challenge in the study of yawning behavior is understanding the way external factors may modify it. This study investigated whether response-dependent punishment or random punishment decreased yawning by the application of buzzer noise paired with electric shocks in a high-yawning strain of Sprague-Dawley male rats. Yawn rate increased daily in response to the experimental cage, and also to the buzzer noise. Two alternate periods of no punishment and punishment were followed by a final period of buzzer noise occurring alone. Punishment did not diminish yawning significantly in either condition although the yawn rate increased in the following period of no punishment and in the buzzer-noise period, relative to the period of yawn-dependent punishment. Yawn rate increased in the buzzer-noise period relative to the first period of no punishment and first period of random punishment. These findings indicate that there are constraints that impede the suppression of yawning using punishment, and that yawning is a delayed response to fear produced by response-dependent punishment.

Genetic and littermate influences on yawning in two selectively bred strains of rats.

This study was made to separate genetic from postnatal maternal influences on yawning in two strains of Sprague-Dawley rats selected for high- (HY) and low-yawning frequency (LY). Foster mothers of the two strains reared litters of pups in the four possible combinations and yawning was recorded in a novel environment when the adult offspring were 75-day-old. Yawning frequency of males and females was affected by pup strain but not by the strain of the foster mothers, when litter size was made constant; HY adult offspring yawned more than LY adult offspring. Yawning frequency was higher in HY male offspring than in HY female offspring. An interaction term between pup sex and the strain of the foster mothers revealed that while males reared by LY mothers yawned more than males reared by HY mothers, females reared by HY mothers yawned more than females reared by LY mothers. Mean frequency of yawning increased with the sex ratio of HY litters. These findings indicate that genetic and genotype-correlated littermate effects influence yawning frequency of adult offspring in response to a novel environment.

Genotype-dependent effect of ACTH1-24 on grooming and yawning in two inbred strains of rats.

It has long been known that the intracerebroventricular administration of ACTH1-24 increases the duration of grooming episodes and the frequency of yawning in rats. The objective of this study was to investigate in what way these episodes are prolonged and whether and to what extent genotype influences such effects. We compared the effect of increasing doses of intracerebroventricular injections of ACTH1-24 on grooming and yawning in males of two inbred strains of Sprague-Dawley rats with distinct yawning frequency, high-yawning (HY) and low-yawning (LY). In LY rats the duration of grooming episodes increased, while in HY rats grooming episodes augmented both in number and duration. In LY rats the duration of grooming components increased likewise, in HY rats however, neither the number nor the duration of the components changed. The grooming rate in both strains of rats was slowed, though more so in LY than in HY rats. Yawning increased in LY rats but not in HY rats. We conclude therefore that ACTH1-24 increases the duration of grooming episodes by slowing the grooming rate according to genotype, and may or may not alter the frequency of yawning.

Behavioral differences between selectively bred rats: D1 versus D2 receptors in yawning and grooming.

We used SKF 38393 and quinpirole for determining whether activation of D(1) and D(2) receptors, respectively, is involved in behaviors of rats selectively bred for high or low rates of yawning. After injection of SKF 38393, yawning diminished more markedly in high-yawning (HY) than in low-yawning (LY) rats, whereas this drug increased the number and duration of grooming episodes similarly in both strains. After injection of quinpirole, yawning increased more markedly in HY than in LY rats, whereas this drug decreased the number and duration of grooming episodes similarly in both rat strains. After coadministration of SKF 38393 and quinpirole, yawning increased similarly in both rat strains, whereas the combination of drugs failed to reliably affect grooming behavior. We interpret our findings as indicating that D(2) receptors are more important than D(1) receptors for differences in yawning behavior between HY and LY rats.

Grooming and yawning trace adjustment to unfamiliar environments in laboratory Sprague-Dawley rats (Rattus norvegicus).

The authors studied grooming and yawning caused by mild stress in laboratory Sprague-Dawley rats (Rattus norvegicus). Two groups received 3 and 6 sequences of 5 foot shocks at random intervals (RI) and fixed intervals (FI), respectively. A 3rd group was not shocked (NS). The groups were exposed for 60 min twice. Grooming did not differ among groups, but yawning diminished with RI. Yawning increased and grooming decreased with the 2nd exposure, except in RI in which grooming increased. In NS and FI, grooming prevailed during the first 20 and 30 min, respectively, whereas yawning dominated the remainder of the time. In RI, grooming occurred more than yawning. An upward shift on this scale causes grooming to substitute yawning, whereas a downward shift causes the reverse effect.

Bombesin decreases yawning in a high-yawning subline of Sprague-Dawley rats.

This study analysed the effect of the intracerebroventricular administration of bombesin (BN) at doses of 0.001, 0.005, 0.1 and 1.0 microg/2 microl on yawning, grooming and other behavioral correlates in two inbred strains of male rats. These were selected for high-yawning (HY) and low-yawning (LY) frequency, a difference that correlates with novelty-induced grooming. Grooming increased with BN in a strain-specific manner, and yawning decreased in HY rats. Principal component analysis (PCA) showed that rats' behaviors changed from yawning to grooming with BN. Such change differed between the strains. While the first principal component was dominated by grooming in both strains, the second principal component was dominated by stretching and penile erections in HY rats, and by scratching in LY rats. While LY rats spent more time in scratching both within and outside grooming bouts, HY rats tended to favour the latter category. An increment in mean duration of grooming bouts characterized the effect of the highest dose. These findings show that BN inhibits yawning and increases grooming, suggesting that this peptide enhances the initial response to novel environments. The study shows the importance of combining studies on inbred strains with appropriate multivariate methods to separate drug-induced behavioral patterns.