Why birds eat colourful grit: colour preferences revealed by the colour of gizzard stones

Colour preferences from sexual or social contexts are assumed to have arisen owing to preferences for specific kinds of food, representing a sensory bias, but once colour preferences have evolved in a sexual context, they may also be expressed during foraging. We tested whether preferences for specific body colours (i.e. plumage and soft parts) were related to colour preferences for grit ingested by birds. Birds eat grit to facilitate break down of food by the gizzard, and this function is independent of the colour of grit, but depends on the physical properties of stones. Bird species were significantly consistent in colour of grit, and grit of different colours varied in prevalence among species, even when analyses were restricted to a sample from a single locality. There were positive correlations between presence of lilac and red grit in the gizzard and presence of sexually dichromatic lilac and red colour on the body. There was a positive correlation between red grit colour and red sexually monochromatic body colour. Bird species with many different sexual colours, but not sexually monochromatic colours on their body had many different colours of grit. Males had more lilac and red grit than females, with this effect differing among species, whereas that was not the case for grit of other colours. These findings are consistent with the sensory bias hypothesis that birds express preferences for grit of specific colours and a high diversity of colours related to sexual colouration of the body, even when the colour of such grit is only visible to the individual at the moment of ingestion.     

重庆盾腹吸虫一新种(吸虫纲:盾腹目:盾腹科)

记述了盾腹吸虫1新种,即重庆盾腹吸虫Aspidogaster chongqingensis sp.nov.并与其它相似种进行比较。新种体呈椭圆形,盾盘较大,几占虫体腹面大部,由48－50个小槽组成,分为4排;口直径0．144－0．169mm,咽椭圆形,较大。     

Visual sex discrimination in goldfish: seasonal, sexual, and androgenic influences

The olfactory signals used by goldfish for sexual and aggressive communication have been studied extensively, but little work has addressed the role of other sensory modalities in social communication in this species. We therefore investigated the role that visual stimuli play in sex discrimination and the ability of androgens, which masculinize courtship behavior, to affect behavioral responses toward female visual stimuli. We found that males selectively orient toward female visual stimuli during the breeding season but not outside it, whereas prostaglandin F2-alpha (PGF2alpha)-injected females do not differentially approach male and female visual stimuli, even during the breeding season. Implanting adult females with testosterone (T) and 11-ketotestosterone (KT), however, induced orientation responses toward female visual stimuli similar to those observed in males. These results indicate that visual sexual stimuli are likely important for reproductive signaling in goldfish, potentially helping males identify ovulating females from a distance in a shoal of fish, and that androgens can influence mechanisms associated with orientation responses toward such stimuli.     

日本棘隙吸虫体被超微结构的研究

本文报道扫描电镜观察下日本棘隙吸虫皮式、体棘和3种感觉乳突的形态和分布。     

Mammalian species richness on islands on the Sunda Shelf,Southeast Asia

Summary A rich mammalian fauna is found on islands that lie on the Sunda Shelf, a continental shelf extending from Vietnam to Borneo and Java that was periodically exposed as dry land during the Pleistocene. The correlation between log of island area and number of species is high (r ²=0.94); the slope of the curve is moderate (z=0.235). Distance from small islands to source areas (=Borneo, Sumatra, and the Malay Peninsula) does not appear to affect species richness, nor does depth of water to source area (a measure of isolation time). A species-area curve for forest reserves of varying sizes on the Malay Peninsula has a low slope (z=0.104); comparison of the mainlaind and island curves indicates that decreasing island area is strongly correlated with increased extinction. Extinction has left reduced but ecologically balanced sets of species on all islands, except that carnivores are under-represented on all but the largest islands. Initial body size and rarity appear to play a significant role in determining the probability of extinction of individual species.     

Terrestrial activity,movements and spatial ecology of an Australian freshwater turtle,Chelodina longicollis,in a temporally dynamic wetland system

Animal movements, use of space, activity patterns and habitat use are in part determined by proximal factors such as the landscapes they occupy, seasonal or environmental cues and individual attributes such as sex and body size. Using radio‐telemetry and a drift fence, we examined the contribution of these factors to variation in movements, use of space and terrestrial activity in a freshwater turtle, Chelodina longicollis (Testudines: Chelidae), in south‐east Australia. Movements and use of space depended strongly on landscape attributes, while sex and body size were less important. Movements and use of space also varied seasonally and were partly correlated with rainfall. The high overall vagility of turtles, irrespective of sex and adult body size (13.8 ± 2.8 ha (±SE) home range, 2608 ± 305 m total distance moved, 757 ± 76 m range length), probably reflects a common need to be mobile in a landscape characterized by fluctuating resources in temporary wetlands. Use of temporary wetlands also drives C. longicollis into terrestrial habitats for movements between wetlands and extended refuge. Timing of inter‐wetland movements was associated with rainfall, but most notably for immature individuals and for those moving towards temporary wetlands. Movements of adults, evacuation of the drying wetland and periods of extended refuge (i.e. aestivation) were less dependent upon rainfall if at all. We conclude that movements about and use of the landscape by C. longicollis are under the strong influence of several interacting factors such as patch configuration, seasonal and environmental cues, and in part, body size. We argue that such behaviours are also ultimately under selection from the costs and benefits of these behaviours in the context of fluctuating resources.     

Copulatory courtship by bushcricket genital titillators revealed by functional morphology, μCT scanning for 3D reconstruction and female sense structures

Genitalia are rapidly evolving morphological structures most likely under sexual selection. Due to their internal nature they are often hidden inside the body, thus morpho-functional studies of animal genitalia are broadly lacking. Males of some bushcricket taxa bear paired genital appendices called titillators, the exact function of which is unknown since they are obscured inside the female body during pairing. To investigate titillator morphology and possible function during copulation, we studied the bushcricket Metrioptera roeselii (Hagenbach, 1822) using a novel combination of independent, yet complementary, techniques. Copulating pairs were snap-frozen and scanned by X-ray micro-computed tomography (μCT) to visualize the coupling of male and female genitalia in situ. Video recordings of copulating pairs also showed rhythmical insertion of male titillators into the female's genital chamber, where they percuss a softened structure on the female's subgenital plate. Movements did not induce damage to the female's structure, which lacks any sclerotized genital counterparts. Instead, scanning electron microscopy and histological sections show the female subgenital plate to be covered with two different types of sensory receptors at the contact zone between the male's titillator and the female genital chamber. We interpret the non-harmful function of the titillator processes, the lack of a genital counter-structure and the presence of sensory cells on the female's subgenital plate as indicators of a copulatory courtship function of titillators, subject to sexual selection by female choice.     

Atrial natriuretic factor-like immunoreactivity in spinal cord and in primary sensory neurons of spinal and trigeminal ganglia of guinea-pig: correlation with tachykinin immunoreactivity*

Summary Atrial natriuretic factor (ANF) is a cardiac hormone with various functions in body homeostasis. It is also processed in the brain and in the peripheral nervous system where it appears to play a role as a neuromodulator. Little is known about the presence of ANF throughout the spinal cord of the guinea-pig. We therefore examined the distribution of ANF and its possible interrelation with primary sensory afferents in this species. Using enzyme- and fluorescence-immunohistochemistry on deparaffinized sections, ANF-like immunoreactivity was found to be present in nerve fibers in laminae I/II of the spinal cord and in neurons of spinal and trigeminal ganglia. Tachykinins and ANF coexisted in very few fibers of the spinal cord but did not coexist in primary sensory spinal or trigeminal neurons. Our results indicate that spinal ANF-immunoreactive fibers are of dual origin, primary sensory and non-primary sensory. The possibly heterogeneous source of the non-primary sensory ANF, its possible coexistence with other co-transmitters and functional implications are discussed.Preliminary aspects of this study have been reported at the 2nd World Congress of Neuroscience in Budapest (Weihe et al. 1987) and at the Versammlung der Anatomischen Gesellschaft in Zürich (Nohr et al. 1989)     

Temperature and the tropical tortoise Kinixys spekii: constraints on activity level and body temperature

Movements of five Kinixys spekii were measured continuously during six weeks of their activity season, by thread-trailing. The mean daily movement distance was negatively correlated with maximum shade air temperature, but not significantly related to minimum temperature, rainfall, or humidity. There was a midday period of inactivity of increasing length as maximum air temperature exceeded 29° C. Temperatures of models suggest that lower activity on hot days was due to the risk of overheating in this small (mean mass 617 g) tortoise. Kinixys spekii had a mean field body temperature (T^b) of 27° C, which is low compared to other tortoises (including sympatric Geochelone pardulis, mean T^b= 32.5° C), but salivated at a similar T^b (38.4° C). This pattern also occurs in other small species; mean and maximum field T^bs of tortoises are positively correlated with body mass, but salivation and critical maximum T_bs do not vary with body mass. Low field T_b provides a wide safety margin before evaporation of water becomes necessary. Kinixys sprkii had a short annual activity period, with about 95% of sightings in four months (December to March). Monthly sightings of K. spekii were correlated with rainfall, but not significantly related to temperature or humidity. Seasonal activity is therefore related to rainfall, but within the rainy season the level and pattern of daily activity is related to temperature.     

Species and sex-specific songs and courtship behaviour in the genus Zaprionus (Diptera-Drosophilidae)

Courtship behaviour and songs of six Zaprionus species show differences not only between species but also between sexes. Courtship behaviour differs from that in the related genus Drosophila. In most species, males produce two song types which may alternate or be repeated. Singing occurs during courtship displays, mounting, after copulation and briefly during male-to-male interactions. Females produce a loud whine and body rocking movements in refusal but have a species-specific pulsed song produced during normal courtship which differs from the conspecific male song. One species produces an irregular male song but a regular female song. Sex-specific songs may have selective advantages but pose problems for the sensory template hypothesis.     

The Ontogeny of Encephalization: Tradeoffs Between Brain Growth,Somatic Growth,and Life History in Hominoids and Platyrrhines

This study examines variation in brain growth relative somatic growth in four hominoids and three platyrrhines to determine whether there is a trade-off during ontogeny. I predicted that somatic growth would be reduced during periods of extensive brain growth, and species with larger degrees of encephalization would reach a smaller body size at brain growth completion because more energy is directed towards the brain. I measured cranial capacity and skeletal size in over 500 skeletal specimens from wild populations. I calculated nonlinear growth curves and velocity curves to determine brain/body growth allometry during ontogeny. In addition, I calculated linear regressions to describe the brain/body allometry during the postnatal period prior to brain size reaching an asymptote. The results showed that somatic growth is not substantially reduced in species with extensive brain growth, and body size at brain growth completion was larger in species with greater degrees of encephalization. Furthermore, large body size at brain growth completion was not correlated with interbirth interval, but was significantly correlated with prolonged juvenile periods and late age at maturity when data were corrected for phylogeny. These results indicate that neither reduction in body growth nor reproductive rate are compensatory mechanisms for the energetic costs of brain growth. Other avenues for meeting energetic costs must be in effect. In addition, the results show that somatic growth in encephalized species is particularly slow during the juvenile period after brain growth at or near completion, suggesting that these growth patterns are explained by reasons other than energetic costs.     

Temporal variation in diets and trophic partitioning by coexisting lizards (Ctenotus: Scincidae) in central Australia

Summary The diets of five syntopic species of Ctenotus were examined over a two-year period on a 60 ha spinifex grassland site in central Australia. The aims of the study were to test predictions that termites were an important part of the food web for syntopic Ctenotus in spinifex grasslands, and to examine seasonal changes in prey use and dietary overlap between the species. Environmental conditions during the first season of the study were dry resulting in generally low invertebrate abundance. In contrast the second season was relatively moist and overall invertebrate abundance was higher than in the first season. Diets of five species of Ctenotus contained a range of terrestrial prey although one species (C. pantherinus) was relatively termite-specialized at all times. Dietary overlap at the ordinal level between the species was generally higher during dry periods when prey abundance was low, and higher for species-pairs that were similar in body size. During the driest period of the study most species of Ctenotus ate a high proportion of termite prey which accounted for the high dietary overlap. However, each species of Ctenotus consumed different genera or foraging guilds of termites. The results suggest that most of these lizards were opportunistic in their selection of prey but that during dry periods when prey are scarce, termites may play a significant role in supporting a high -diversity of Ctenotus.     

Formation of the head-trunk boundary in the animal body plan: an evolutionary perspective

Gene expression analyses and anatomical studies suggest that the body plans of protostomes and deuterostomes are phylogenetically related. In the central nervous system (CNS), arthropods and vertebrates (as well as their closest related phyla the urochordates and cephalochordates) share a nerve cord with rostral specification: the cerebral neuromeres in Drosophila, cerebral sensory vesicle of ascidians and lancelets and the large brain of craniates. Homologous genes, in particular of the otd/Otx and Hox families, are at play in these species to specify the anterior and posterior CNS territories, respectively. In contrast, homologies in the establishment of boundary regions like those separating head and trunk structures in arthropods or mid- and hindbrain domains in chordates are still unclear. We compare in these species the formation, properties and molecular characteristics of these boundaries during embryonic development. We also discuss recent findings suggesting that insects and vertebrates might have co-opted factors of related families to control the formation of these boundary regions, the evolution of which would then appear dramatically different from that of the anterior and posterior CNS domains.     

A second cricket cereal sensory system: bristle hairs and the interneurons they activate

Summary A new sensory system, in the abdomen of the cricketAcheta domesticus, is described. It consists of hair-like receptors, which we have called bristles, distributed on the cercus and abdomen. The sensory neurons, innervating bristles of a wide variety of shapes and sizes, project to a common area of the terminal abdominal ganglion. This region is distinct from the area called the cereal glomerulus which receives input from other receptor types.Three interneurons, whose dendrites are located exclusively in the projection area of bristle sensory neurons, are then described. These interneurons respond to tactile stimuli of the cercus and abdomen, but not to infrasound or to body orientation as do previously described interneurons. Based on the anatomical segregation of the afferents and interneurons, as well as the functional distinction from previously described cereal sensory systems, it is becoming clear that the cereal system is a multimodal sensory system.     

A strand receptor with a central cell body synapses upon spiking local interneurones in the locust

Summary Movements of the femoro-tibial joint of a locust hind leg are monitored by three classes of proprioceptors; a chordotonal organ (Usherwood et al. 1968), multipolar joint receptors (Coillot and Boistel 1968) and a strand receptor innervated by a single afferent with a central cell body (Bräunig 1985). All three classes are excited by imposed or voluntary extension of the tibia. The strand receptor (fe-tiSR) spikes tonically and at a frequency dependent upon the position of the joint whilst the multipolar joint receptors give overlapping information but for a more restricted range. The afferent from the strand receptor makes an excitatory connection with a spiking local interneurone in the midline group of the metathoracic ganglion. The central latency and consistency with which the EPSP follows each sensory spike suggests that the connection is direct. This interneurone also receives convergent inputs from neurones in the chordotonal organ, but not from multipolar joint receptors. Neither the strand receptor nor the multipolar joint receptors apparently synapse upon leg motor neurones that we have tested, in contrast to receptors in the chordotonal organ.     

Multisensory Integration and Behavioral Plasticity in Sharks from Different Ecological Niches

The underwater sensory world and the sensory systems of aquatic animals have become better understood in recent decades, but typically have been studied one sense at a time. A comprehensive analysis of multisensory interactions during complex behavioral tasks has remained a subject of discussion without experimental evidence. We set out to generate a general model of multisensory information extraction by aquatic animals. For our model we chose to analyze the hierarchical, integrative, and sometimes alternate use of various sensory systems during the feeding sequence in three species of sharks that differ in sensory anatomy and behavioral ecology. By blocking senses in different combinations, we show that when some of their normal sensory cues were unavailable, sharks were often still capable of successfully detecting, tracking and capturing prey by switching to alternate sensory modalities. While there were significant species differences, odor was generally the first signal detected, leading to upstream swimming and wake tracking. Closer to the prey, as more sensory cues became available, the preferred sensory modalities varied among species, with vision, hydrodynamic imaging, electroreception, and touch being important for orienting to, striking at, and capturing the prey. Experimental deprivation of senses showed how sharks exploit the many signals that comprise their sensory world, each sense coming into play as they provide more accurate information during the behavioral sequence of hunting. The results may be applicable to aquatic hunting in general and, with appropriate modification, to other types of animal behavior.     

Playing it cool: Characterizing social play,bout termination,and candidate play signals of juvenile and infant Tibetan macaques(Macaca thibetana)

Play behaviors and signals during playful interactions with juvenile conspecifics are important for both the social and cognitive development of young animals.The social organization of a species can also influence juvenile social play. We examined the relationships among play behaviors, candidate play signals, and play bout termination in Tibetan macaques(Macaca thibetana) during juvenile and infant social play to characterize the species play style. As Tibetan macaques are despotic and live in groups with strict linear dominance hierarchies and infrequent reconciliation, we predicted that play would be at risk of misinterpretation by both the individuals engaged in the play bout and by those watching, possibly leading to injury of the players. Animals living in such societies might need to frequently and clearly signal playful intent to play partners and other group members to avoid aggressive outcomes. We gathered video data on 21 individually-identified juvenile and infant macaques(one month to five years of age)from the Valley of the Wild Monkeys, Mt. Huangshan,China. We used all-occurrence sampling to record play behaviors and candidate play signals based on an ethogram. We predicted that play groups would use multiple candidate play signals in a variety of contexts and in association with the number of audience members in proximity to the players and play bout length. In the 283 playful interactions we scored,juvenile and infant macaques used multiple body and facial candidate play signals. Our data showed that juvenile and infant Tibetan macaques use a versatile repertoire of play behaviors and signals to sustain play.