Ultrasonic vocalizations and social learning of food preferences by female Norway rats

We examined whether ultrasonic vocalizations facilitate social learning of food preferences in female Norway rats, Rattus norvegicus. Females produced ultrasonic vocalizations at higher rates when they were reunited with a familiar conspecific if one member of the reunited pair had eaten an unfamiliar food while the pair members were separated. However, the influence of demonstrator rats on food choices of their observers was as great in pairs of rats that had been devocalized surgically as it was in sham-operated controls. The latter result is not consistent with the hypothesis that ultrasonic vocalizations facilitate social learning of food preferences in Norway rats.     

Aggregate formation in a freshwater bacterial strain induced by growth state and conspecific chemical cues

We investigated the induction of aggregate formation in the freshwater bacterium Sphingobium sp. strain Z007 by growth state and protistan grazing. Dialysis bag batch culture experiments were conducted in which these bacteria were grown spatially separated from bacteria or from co‐cultures of bacteria and predators. In pure cultures of Sphingobium sp. strain Z007, the concentrations of single cells and aggregates inside and outside the dialysis membranes developed in a similar manner over 3 days of incubation, and the proportions of aggregates were highest during the exponential growth phase. Cell production of Sphingobium sp. strain Z007 was enhanced in the presence of another isolate, Limnohabitans planktonicus, from an abundant freshwater lineage (R‐BT065) outside the bags, and even more so if that strain was additionally grazed upon by the bacterivorous flagellate Poterioochromonas sp. However, the ratios of single cells to aggregates of Sphingobium sp. strain Z007 were not affected in either case. By contrast, the feeding of flagellates on Sphingobium sp. strain Z007 outside the dialysis bags led to significantly higher proportions of aggregates inside the bags. This was not paralleled by an increase in growth rates, and all cultures were in a comparable growth state at the end of the experiment. We conclude that two mechanisms, growth state and the possible release of infochemicals by the predator, may induce aggregate formation of Sphingobium sp. strain Z007. Moreover, these infochemicals only appeared to be generated by predation on cells from the same species.     

Chemical cues produced by conspecific larvae deter oviposition by the coccidophagous ladybird beetle, Cryptolaemus montrouzieri

Experimental evidence shows that oviposition in Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) is deterred by the presence of conspecific larvae. A similar deterrent effect is also recorded when females are tested in an experimental set up that previously housed conspecific larvae. It is shown that an oviposition-deterring pheromone is associated with the abundant wax filaments produced by the larvae of C. montrouzieri.     

Effects of ovariectomy on the presence of a maturation-delaying pheromone in the urine of female mice

A sequence of three experiments investigated whether ovariectomy affects the production and/or excretion of a pheromone from grouped female mice which delays puberty in young females. The first two experiments demonstrated that ovariectomy does not influence the presence of the puberty-delaying pheromone in either excreted or bladder urine of group-caged females. The third experiment showed that the blocking effect associated with the urethras of singly caged female mice which inhibits the activity of the maturation-delaying pheromone is not affected by ovariectomy.     

Effects of adrenalectomy on the presence of a maturation-delaying pheromone in the urine of female mice

A sequence of three experiments investigated whether adrenalectomy affects a pheromone from grouped female mice which delays puberty in young females. The first two experiments demonstrated that the presence of the adrenal glands is a necessary condition for production and/or excretion of the puberty-delaying pheromone in excreted and bladder urine. The third experiment showed that a blocking effect associated with the urethras of singly caged female mice which inhibits the activity of the maturation-delaying pheromone is not affected by adrenalectomy.     

Chromosome pairing and germ cell loss in male and female mice carrying a reciprocal translocation

Female carriers of the T(5;12)31H reciprocal translocation had an average reduction of 73% in oocyte numbers compared with normal litter mates, which was of a magnitude similar to the reduction in sperm counts of male carriers. Analysis of synaptonemal complexes showed that the translocated chromosomes appeared as quadrivalents, or trivalents and univalents, or bivalents in both sexes. Quadrivalents were of three types: fully synapsed, with asynapsis confined to breakpoints, and with unsynapsed ends. There was more pairing in spermatocytes than in oocytes: 37% of spermatocytes, but only 14% of oocytes, contained a fully synapsed quadrivalent, and trivalents were also more frequently fully synapsed in spermatocytes. When these results are compared with those previously obtained for other chromosome anomalies, it becomes evident that there are considerable differences in chromosome pairing between males and females, and that different chromosome rearrangements differ in the relative amount of pairing failure occurring in male and female carriers.     

Effect of short-term food deprivation on reproduction in female mice

CF-1 female mice were subjected to 24 or 48 h of food deprivation beginning when they were in estrus or diestrus, or when they were 2 or 12 days pregnant, or on Days 2 or 12 of lactation. Ovulation was delayed by a week or more when 48 h of food deprivation was initiated when the female was in diestrus; lesser delays occurred when food deprivation began in estrus. There was little effect of acute food deprivation on pregnancy. Most females deprived of food beginning on Day 2 of lactation ate their young, but females deprived on Day 12 of lactation rarely did so. These results are discussed in terms of the complexity of interacting factors that determine the degree to which each stage of the female's reproductive cycle is susceptible to disruption by acute food deprivation.     

Female preference for conspecific males based on olfactory cues in a Lake Malawi cichlid fish

Research on reproductive isolation in African cichlid fishes has largely focused on the role of nuptial colours, but other sensory modes may play an important role in mate choice. Here, we compare the relative importance of visual and olfactory cues in mate recognition by females of a Lake Malawi cichlid species. Female Pseudotropheus emmiltos were given a choice of spawning next to a conspecific male or a male of the closely-related sympatric Pseudotropheus fainzilberi. Significant preference for conspecific males only occurred when olfactory cues were present. This suggests that divergence of olfactory signals may have been an important influence on the explosive radiation of the East African species flock.     

Differential sensitivity to conspecific and allospecific cues in chimpanzees and humans: a comparative eye-tracking study

Previous studies have shown that a variety of animals including humans are sensitive to social cues from others and shift their attention to the same objects attended to by others. However, little is known about how animals process conspecifics'' and another species'' actions, although primates recognize conspecific faces better than those of another species. In this study, using unrestrained eye-tracking techniques, we first demonstrated that conspecific social cues modulated looking behaviours of chimpanzees more than human cues, whereas human observers were equally sensitive to both species. Additionally, first pass gaze duration at the face indicates that chimpanzees looked at the chimpanzees'' face longer than the human face, suggesting that chimpanzees might extract more referential information from a conspecific face. These results also imply that a unique ability for extracting referential information from a variety of social objects has emerged during human evolution.     

Workers of a polistes paper wasp detect the presence of their queen by chemical cues

Differences in long-chain hydrocarbon mixtures among reproductive and nonreproductive individuals have been often revealed in social insects. However, very few papers demonstrated that these signatures actually act as contact pheromones used by nonreproductive to recognize the presence of a related queen in the colony. Cuticular and glandular hydrocarbons of Polistes paper wasps have been extensively studied, but, until now, the perception and recognition of such cues was not demonstrated. In this paper, we show, for the first time in Vespidae, that Polistes gallicus workers distinguish nestmates from alien individuals and queens from workers by the hydrocarbon mixtures of the Van der Vecht organ secretion (VVS). We also demonstrated that stroking behavior (a peculiar behavior of Polistes by which queens probably lay VVS on the nest) acts as an inhibitor of ovarian development in workers.     

Stimulatory effects on the reproductive axis in female songbirds by conspecific and heterospecific male song

Courtship vocalizations of male songbirds can profoundly enhance the reproductive physiology and behavior of conspecific females. However, no study has fully investigated the selectivity of conspecific song effects on reproductive development in birds. We studied the effects of conspecific and heterospecific song on reproductive development in domesticated (canaries) and wild songbirds (song sparrows). As expected, conspecific song enhanced follicular development. Unexpectedly, however, birds exposed to heterospecific song also underwent enhanced follicular development (compared to birds exposed to no song); conspecific and heterospecific songs were equally effective in enhancing ovarian development. In canaries exposed to 18L:6D, conspecific song induced oviposition earlier and at a greater frequency than in heterospecific and no song groups, with the fewest eggs being laid in the no song group. These results indicate that conspecific and heterospecific male song can enhance reproductive activity in female songbirds. Whether or not activation of the reproductive axis in female songbirds by heterospecific song occurs in the wild remains unclear. It is also unclear as to whether the ability of the reproductive axis to respond to heterospecific song performs a specific function, or whether it is simply a consequence of greater selection pressure acting upon behavioral responses to song.     

Antipredator behaviour mediated by chemical cues: the role of conspecific alarm signalling and predator labelling in the avoidance response of a marine gastropod

Gastropods represent a challenge in the understanding of alarm signalling. We studied predator avoidance (climbing behaviour) of the marine snail Tegula funebralis in laboratory experiments. Snails were exposed to crude extract of conspecifics, and to water conditioned by actively feeding or non-feeding predatory crabs. Crabs had previously been maintained on different diets, and were accordingly labelled by chemical cues of various origins. Tegula -extract alone released climbing behaviour in May, but not in June. However, during both these months, snails responded to chemical cues from crabs that were actively feeding on Tegula . Crabs labelled by Tegula -diet, and actively feeding on Tegula , also caused more climbing responses compared to crabs labelled by other diets. Chemical cues derived from crabs actively feeding on another snail species, or from non-feeding crabs, did not induce snail climbing no matter the previous feeding history of the predators. When snails received Tegula -extract combined with water conditioned with a non-feeding, Tegula -labelled crab, no climbing occurred. However, when the non-feeding, Tegula -labelled crab was present in the solution of Tegula -extract, moderate climbing responses were obtained. The results imply that climbing responses of T. funebralis are in general caused by the action of a two-component system. This system seems to be a mixture of chemical cues leaking from the tissue of conspecifics when being eaten, and latent conspecific chemicals that are modified in crabs and presumably released with the urine of chemically labelled predators. The modified chemical labels appear to be fully released by crabs when feeding, and moderately released when detecting food. The responses obtained in May with crude extract alone may result from a seasonal change in alarm signalling properties, or a change in behavioural responsiveness of snails exposed to a variable predator regime.     

Habitat structure,conspecific presence and spatial variation in the recruitment of a temperate reef fish

Pronounced spatial variation in recruitment occurs in many marine invertebrate and fish populations and is thought to be critical to the demography of these species. In this study I examined the importance of habitat structure and the presence of conspecific residents to spatial variation in larval settlement and recruitment in a temperate fish Tautogolabrus adspersus. I define settlement as the movement of individuals from the water column to the benthic habitat, while I refer to recruitment as numbers of individuals surviving some arbitrary period of time after settlement. Experiments in which standard habitats were stocked with conspecifics showed that resident conspecifics were not an important factor contributing to small-scale variability in recruitment. Further correlative analyses demonstrated that large-scale variation in recruitment could not be explained by variability in older age classes. By contrast, manipulations of macroalgal structure within a kelp bed demonstrated that recruitment was significantly higher in habitats with a dense understory of foliose and filamentous algae than in habitats with only crustose algae. Understory algae varied in their pattern of disperison among sites, and the dispersion of fish matched that of the plants. In order to determine the effects of differences in patterns of algal dispersion on the demography of associated T. adspersus populations, I used experimental habitat units to manipulate patterns of dispersion. Settlement was significantly greater to randomly placed versus clumped habitats; however, no differences in recruitment between random and clumped habitats were detected. Because recruitment is a function of the numbers of settlers minus the subsequent loss of settlers, rates of mortality or migration must have been higher in the randomly placed habitats. These results are counter to the current paradigm for reef fishes which suggests that larval settlement is the crucial demographic process producing variability in population abundance. In this experiment patterns of settlement were modified by varying the patch structure of the habitat.Contribution number 278 from the Center for Marine Biology, University of New Hampshire     

Influence of conspecific and heterospecific aggregation cues and alarm odors on shelter choice by syntopic spiny lobsters

In spiny lobsters, conspecific scents ("aggregation cues") may mediate gregarious diurnal sheltering, but scents from injured conspecifics ("alarm odors") may elicit avoidance behavior. In laboratory experiments, individuals of two coexisting species, Panulirus guttatus (a reef-obligate) and P. argus (a temporary reef-dweller), significantly chose shelters emanating conspecific aggregation cues and responded randomly to shelters emanating heterospecific aggregation cues. However, despite evidence that the two species perceived each other's alarm odors to a similar extent, P. guttatus responded randomly to shelters emanating either conspecific or heterospecific alarm odors, whereas P. argus significantly avoided both. This differential influence of alarm odors likely reflects interspecific differences in life history, sociality, and behavior. The less social, reef-obligate P. guttatus lobsters forage close to their reef dens, into which they retract deeply upon perception of risk. This cryptic behavior may offset the need to avoid conspecific (and heterospecific) alarm odors. In contrast, avoidance of conspecific alarm odors by P. argus is consistent with its ontogenetic habitat shifts and greater sociality. Furthermore, because reef-dwelling P. argus lobsters forage across open areas away from the reef, an ability to avoid alarm odors from P. guttatus upon returning to their reef dens may increase their fitness.     

Perception of female reproductive state from vocal cues in a mammal species

While acoustic signalling by males is known to affect male-male competition, mate attraction and the timing of ovulation, the extent to which sexual selection has shaped the evolution of female acoustic signals is poorly understood. Among mammals, experimental evidence indicates that females attract mating partners by using olfactory and visual signals to advertise their reproductive state. Whether or not males ascertain female reproductive state from vocal signals has, however, never been systematically tested. In this study, we use playbacks of recorded vocalizations to demonstrate that male Barbary macaques, Macaca sylvanus, can discriminate between female copulation calls given at different stages of the oestrous cycle, responding more strongly to those given around the time when conception is most likely to occur. Acoustic analysis suggests that the mean dominant frequency of call units and a number of temporal parameters could provide males with the information necessary to discern the proximity of ovulation in this way Our results provide the first experimental evidence that the calls of female mammals may contain information on reproductive state, which males can perceive and use in such a way as to increase their reproductive success.     

Ultrasonic vocalization in response to unavoidable aversive stimuli in rats: effects of benzodiazepines

The effects of two benzodiazepine derivatives (diazepam, 0.5-1 mg/kg; alprazolam, 1.25-2.5 mg/kg) on ultrasonic calling elicited in adult rats by unavoidable aversive stimuli (footshocks) were investigated. The results show that either diazepam or alprazolam affected the duration of ultrasonic calls. In particular, a significant decrease in the length of ultrasounds was found in the group of animals treated with these benzodiazepines. The effects of diazepam were counteracted by the benzodiazepine-antagonist Ro 15-1788. On the other hand, neither a neuroleptic agent, such as haloperidol (0.5-1 mg/kg), nor an antidepressant, such as desipramine (5-10 mg/kg) influenced the parameters of ultrasonic emission in this experimental situation. The present results suggest that ultrasonic vocalization in response to unavoidable aversive stimuli could be considered as a potential new tool for studying drugs with antianxiety properties.