Biased ligand bonds to make right calls—laboratory of signal transduction reveals molecular mechanism for functional selectivity of GPCR

<正>In a recent study,Professor Rui-Ping Xiao and her research group at Institute of Molecular Medicine of Peking University has provided an essential experimental evidence to support the new paradigm of functional selectivity for G protein-coupled receptor(GPCR)signal transduction.The study was published online on May 15 in The Journal of Biological Chemistry[1].The GPCR superfamily,a class of membrane proteins     

BEHAVIORAL SIGNIFICANCE OF UNDERWATER VOCALIZATIONS OF CAPTIVE LEOPARD SEALS, HYDURGA LEPTONYX

Two groups of underwater vocalizations were identified in a three-year study of two captive leopard seals, Hydurga leptonyx (one female and one male at Taronga Zoo, Sydney). This was supplemented by recordings over three months from a male at Marineland, New Zealand. The sexual state of the seals at Taronga was deduced from serum hormonal concentrations: the female was considered to be in estrus at specific times during the breeding season. The seal at Marineland, New Zealand was assumed to be sexually mature on the basis of size and age. Of 12 different underwater sound types recorded, six were produced by the seals at Taronga Zoo during agonistic interactions (local calls) and were heard through most of the year. The other six sound types were produced by lone seals. These broadcast calls were produced by the female only when sexually receptive, and by the mature male during December and January, months believed to be the breeding season of wild leopard seals. We propose that underwater acoustic behavior is important in the mating system of this species, and that broadcast calls are used by mature females to advertise their sexual receptivity, and possibly by mature males in search of mates.     

Vocal communication in captive golden monkeys (Rhinopithecus roxellanae)

The Sichuan golden snub-nosed monkey,Rhinopithecus roxellanae, is an endangered Colobine endemic to China. The behavior and biology of this species are little known, and it has rarely been kept in captivity outside China. Results from 42 hr of observations of a male-female golden monkey pair provide preliminary information on the vocal behavior of this species in captivity. Vocalizations by the animals often occurred within antiphonal sequences, which were primarily initiated by the female. Sequences were brief (2–3 calls), showed little or no temporal overlap, and were emitted primarily when the animals were distal from one another, suggesting that sequences may function as contact calls in nature. Some vocalizations appeared to be cryptic, i.e. unaccompanied by mouth or body movement, and these were observed more often than noncryptic calls in both animals. Vocal communication appears to be complex in this species, and remains poorly understood.     

Call types of Bigg’s killer whales (Orcinus orca) in western Alaska: using vocal dialects to assess population structure

Bigg’s killer whales (Orcinus orca; i.e. ‘transient’ ecotype), as apex predators, are important to the dynamics of marine ecosystems, but little is known about their population structure in western Alaska. Currently, all Bigg’s killer whales in western Alaska are ascribed to a single broad stock for management under the US Marine Mammal Protection Act. However, recent nuclear microsatellite and mitochondrial DNA analyses indicate that this stock is likely comprised of genetically distinct sub-populations. In accordance with what is known about killer whale vocal dialects in other locations, we used the spatial distribution of group-specific call types to investigate the population structure of Bigg’s killer whales in this part of Alaska. Digital audio recordings were collected from 33 Bigg’s killer whale encounters throughout the Aleutian and Pribilof Islands in the summers of 2001–2007 and 2009–2010. Recorded calls were qualitatively classified into discrete types and then quantitatively described using 12 structural and time-frequency measures. Resulting call categories were validated using a random forest approach. A total of 36 call types and subtypes were identified across the entire study area, and regional patterns of call type use revealed three distinct dialects which correspond to proposed genetic delineations. Our results suggest that there are at least three acoustically and genetically distinct sub-populations in western Alaska, and we present an initial catalogue for this area describing the regional vocal repertoires of Bigg’s killer whale call types.     

Representational signalling in birds

Some animals give specific calls when they discover food or detect a particular type of predator. Companions respond with food-searching behaviour or by adopting appropriate escape responses. These signals thus seem to denote objects in the environment, but this specific mechanism has only been demonstrated for monkey alarm calls. We manipulated whether fowl (Gallus gallus) had recently found a small quantity of preferred food and then tested for a specific interaction between this event and their subsequent response to playback of food calls. In one treatment, food calls thus potentially provided information about the immediate environment, while in the other the putative message was redundant with individual experience. Food calls evoked substrate searching, but only if the hens had not recently discovered food. An identical manipulation had no effect on responses to an acoustically matched control call. These results show that chicken food calls are representational signals: they stimulate retrieval of information about a class of external events. This is the first such demonstration for any non-primate species. Representational signalling is hence more taxonomically widespread than has previously been thought, suggesting that it may be the product of common social factors, rather than an attribute of a particular phylogenetic lineage.     

Labile sex differences in long calling in cotton-top tamarins

Sex differences in behavior are quite common among nonhuman primates. In sexually monomorphic species, sex differences might be expected to be less evident than in polygynous and highly dimorphic species. Callitrichid primates (marmosets and tamarins) are cooperative breeders that exhibit little sexual size dimorphism. However, several sex differences in the structure and usage of vocalizations have been reported. In one such study, McConnell and Snowdon [Behaviour 97:273-296, 1986] reported that female cotton-top tamarins (Saguinus oedipus) emitted significantly more normal long calls than males during simulated intergroup encounters. In the course of collecting a library of normal long calls, we replicated a portion of that study 20 years later with the same colony and similar methods. To our surprise we found a reversal of sex differences. In the same experimental situation, males gave significantly more normal long calls than females. In a further replication 2 years later, males still called more but the effect was less pronounced. The dramatic change in sex differences within the same species and colony over a 22-year period suggests that behavioral sex differences in callitrichids may be quite labile, and that repeated sampling over several years may be necessary to establish true sex differences.     

Why do shrews twitter? Communication or simple echo-based orientation

Shrews are very vocal animals. We tested behaviourally whether the high-pitched laryngeal ‘twittering’ calls of as-yet unclear function serve for communication or echo-based orientation. We used a representative species from each of the two largest phylogenetic groups of shrews. In both species, experimental manipulation of substrate density, but not of the likelihood of conspecific presence, affected the shrews'' call rate when exploring an unknown environment. This adaptation of call rate to the degree of habitat clutter parallels bat echolocation and suggests that shrews may use the echoes and reverberations of their calls for identifying routes through their habitat or for probing habitat type. To assess the acoustic feasibility of shrew echo orientation, we ensonified shrew habitats in the field with an ‘artificial shrew’ (small speaker mounted close to a sensitive microphone). The data showed that shrew-like calls can indeed yield echo scenes useful for habitat assessment at close range, but beyond the range of the shrews'' vibrissae.