Dynamic body acceleration increases by 20% during flight ontogeny of greylag geese Anser anser

Despite our knowledge of the biophysical and behavioural changes during flight ontogeny in juvenile birds, little is known about the changes in the mechanical aspects of energy expenditure during early flight development, particularly in migratory species. Here, we investigate in a unique experimental setup how energy expended during flights changes over time beginning with early ontogeny. We calculate overall dynamic body acceleration (ODBA) as a proxy for energy expenditure in a group of hand raised greylag geese Anser anser trained to fly behind a microlight aircraft. We propose two potential hypotheses; energy expenditure either increases with increasing physiological suitability (the ‘physical development hypothesis’), or decreases as a result of behavioural improvements mitigating flight costs (the ‘behavioural development hypothesis’). There was a significant temporal increase of flight duration and ODBA over time, supporting the ‘physical development hypothesis’. This suggests that early on in flight ontogeny behavioural development leading to flight efficiency plays a weaker role in shaping ODBA changes than the increased physical ability to expend energy in flight. We discuss these findings and the implications of flight development on the life history of migratory species.     

AGE-DEPENDENT VARIATIONS OF THE HUMAN N-ACETYL-β-D-HEXOSAMINIDASES

The total N-acetyl-β-d -hexosaminidase (hexosaminidase A plus B) activity of the human brain increases during life until the age of 70 years to about twice the activity found in the foetal brain. This activity roughly parallels the increasing level of brain ganglio-sides. Simultaneously, the ratio between the hexosaminidases A and B changes from approx. 3.4 to 1.1 as established by the microscale isoelectric focussing of the enzymes from crude extracts. Age-dependent variations can be also demonstrated for other glycosidase activities: The β-d -glucosidase is shown to increase, the α-d -mannosidase and α-l -fucosidase to decrease during life. The enzyme values are related to the protein content, the age-dependent shift of which we have determined in the human brain. In different organs and body liquids distinct differences are found for the levels of the total hexosaminidase activity as well as for the hexosaminidase pattern. The relation of the hexosaminidase activity to the ganglioside degradation during the human development is discussed.     

Brain size predicts behavioural plasticity in guppies (Poecilia reticulata): An experiment

Understanding how animal personality (consistent between‐individual behavioural differences) arises has become a central topic in behavioural sciences. This endeavour is complicated by the fact that not only the mean behaviour of individuals (behavioural type) but also the strength of their reaction to environmental change (behavioural plasticity) varies consistently. Personality and cognitive abilities are linked, and we suggest that behavioural plasticity could also be explained by differences in brain size (a proxy for cognitive abilities), since accurate decisions are likely essential to make behavioural plasticity beneficial. We test this idea in guppies (Poecilia reticulata), artificially selected for large and small brain size, which show clear cognitive differences between selection lines. To test whether those lines differed in behavioural plasticity, we reared them in groups in structurally enriched environments and then placed adults individually into empty tanks, where we presented them daily with visual predator cues and monitored their behaviour for 20 days with video‐aided motion tracking. We found that individuals differed consistently in activity and risk‐taking, as well as in behavioural plasticity. In activity, only the large‐brained lines demonstrated habituation (increased activity) to the new environment, whereas in risk‐taking, we found sensitization (decreased risk‐taking) in both brain size lines. We conclude that brain size, potentially via increasing cognitive abilities, may increase behavioural plasticity, which in turn can improve habituation to novel environments. However, the effects seem to be behaviour‐specific. Our results suggest that brain size likely explains some of the variation in behavioural plasticity found at the intraspecific level.     

TOMATO TRICHOMES AND MUTATIONS AFFECTING THEIR DEVELOPMENT

A new trichome type for the genus Lycopersicon is described in L. esculentum Mill. It is a short (0.03–0.08 mm), pendant, glandular hair with a club-shaped head consisting of 8–12 cells. Two previously described “hairless” mutations were examined microscopically. One, hl, does not affect the frequency of hairs nor the number of cells per hair, but causes abnormal enlargement of the stalk cells of all hair types, and thus produces shortened, extremely bent and twisted hairs. Observations on the time of action of this gene indicate that in trichome development two to four cell divisions occur prior to any appreciable cell enlargement. The second mutation, h, affects only the large type of trichome. This mutation effects a developmental shift from trichome to stomatal apparatus at the apex of the multicellular base normally supporting the large trichomes.     

Transcriptional profiling identifies critical steps of cell cycle reprogramming necessary for Plasmodiophora brassicae‐driven gall formation in Arabidopsis

Plasmodiophora brassicae is a soil‐borne biotroph whose life cycle involves reprogramming host developmental processes leading to the formation of galls on its underground parts. Formation of such structures involves modification of the host cell cycle leading initially to hyperplasia, increasing the number of cells to be invaded, followed by overgrowth of cells colonised by the pathogen. Here we show that P. brassicae infection stimulates formation of the E2Fa/RBR1 complex and upregulation of MYB3R1, MYB3R4 and A‐ and B‐type cyclin expression. These factors were previously described as important regulators of the G2?M cell cycle checkpoint. As a consequence of this manipulation, a large population of host hypocotyl cells are delayed in cell cycle exit and maintained in the proliferative state. We also report that, during further maturation of galls, enlargement of host cells invaded by the pathogen involves endoreduplication leading to increased ploidy levels. This study characterises two aspects of the cell cycle reprogramming efforts of P. brassicae: systemic, related to the disturbance of host hypocotyl developmental programs by preventing cell cycle exit; and local, related to the stimulation of cell enlargement via increased endocycle activity.     

THE EFFECT OF INTERTIDAL STRESS ON PADINA SANCTAE-CRUCIS (PHAEOPHYTA)1

The hypothesis is that plants growing in the intertidal region display developmental and morphological differences from subtidal plants of the same species. Intertidal and subtidal populations of Padina sanctae-crucis Börg. Were compared, emphasizing morphological and developmental features. Plant size in relation to number of reproductive bands, vegetative cell sizes and the rate of spore development were analyzed to evaluate the hypothesis. The results indicate that environmental stress tends to dwarf intertidal plants through reduction in cell size. Spores from both intertidal and subtidal populations were cultured in the laboratory under standard conditions. No significant differences were found between the growth rates. The results may be interpreted to mean that cell enlargement is inhibited by intertidal stress.     

Grandma plays favourites: X-chromosome relatedness and sex-specific childhood mortality

Biologists use genetic relatedness between family members to explain the evolution of many behavioural and developmental traits in humans, including altruism, kin investment and longevity. Women''s post-menopausal longevity in particular is linked to genetic relatedness between family members. According to the ‘grandmother hypothesis’, post-menopausal women can increase their genetic contribution to future generations by increasing the survivorship of their grandchildren. While some demographic studies have found evidence for this, others have found little support for it. Here, we re-model the predictions of the grandmother hypothesis by examining the genetic relatedness between grandmothers and grandchildren. We use this new model to re-evaluate the grandmother effect in seven previously studied human populations. Boys and girls differ in the per cent of genes they share with maternal versus paternal grandmothers because of differences in X-chromosome inheritance. Here, we demonstrate a relationship between X-chromosome inheritance and grandchild mortality in the presence of a grandmother. With this sex-specific and X-chromosome approach to interpreting mortality rates, we provide a new perspective on the prevailing theory for the evolution of human female longevity. This approach yields more consistent support for the grandmother hypothesis, and has implications for the study of human evolution.     

Effects of inbreeding on behavioural plasticity of parent–offspring interactions in a burying beetle

Inbreeding depression is defined as a fitness decline in progeny resulting from mating between related individuals, the severity of which may vary across environmental conditions. Such inbreeding‐by‐environment interactions might reflect that inbred individuals have a lower capacity for adjusting their phenotype to match different environmental conditions better, as shown in prior studies on developmental plasticity. Behavioural plasticity is more flexible than developmental plasticity because it is reversible and relatively quick, but little is known about its sensitivity to inbreeding. Here, we investigate effects of inbreeding on behavioural plasticity in the context of parent–offspring interactions in the burying beetle Nicrophorus vespilloides. Larvae increase begging with the level of hunger, and parents increase their level of care when brood sizes increase. Here, we find that inbreeding increased behavioural plasticity in larvae: inbred larvae reduced their time spent associating with a parent in response to the length of food deprivation more than outbred larvae. However, inbreeding had no effect on the behavioural plasticity of offspring begging or any parental behaviour. Overall, our results show that inbreeding can increase behavioural plasticity. We suggest that inbreeding‐by‐environment interactions might arise when inbreeding is associated with too little or too much plasticity in response to changing environmental conditions.     

Behavioural Responses of European Roe Deer to Temporal Variation in Predation Risk

In natural environments, predation risk varies over time. The risk allocation hypothesis predicts that prey is expected to adjust key anti‐predator behaviours such as vigilance to temporal variation in risk. We tested the predictions of the risk allocation hypothesis in a natural environment where both a species‐rich natural predator community and human hunters are abundant and where the differences in seasonal and circadian activity between natural and anthropogenic predators provided a unique opportunity to quantify the contributions of different predator classes to anti‐predator behaviour. Whereas natural predators were expected to show similar levels of activity throughout the seasons, hunter activity was high during the daytime during a clearly defined hunting season. According to the risk allocation hypothesis, vigilance should then be higher during the hunting season and during daytime hours than during the non‐hunting season and night‐time hours. Roe deer (Capreolus capreolus) on the edge of Bia?owie?a Primeval Forest in Eastern Poland displayed vigilance behaviour consistent with these predictions. The behavioural response of roe deer to temporarily varying predation risks emphasises the behavioural plasticity of this species and suggests that future studies of anti‐predator behaviour need to incorporate circadian variation in predation pressure as well as risk gradients of both natural and anthropogenic predators.     

Some factors affecting the chloroplast replication in the mossPlagiomnium trichomanes

Summary Some factors affecting the chloroplast replication were studied using the leaf cells of the mossPlagiomnium trichomanes. There was a significant positive correlation between chloroplast number per cell and cell volume in leaves of any developmental stage. However, when the detached leaves were cultured on nutrient agar, it was observed that the chloroplast replication occurred without cell enlargement regardless of the developmental stage of leaves. This implies that cell enlargement is not an essential factor for the chloroplast replication, but one of the environmental factors affecting it. Light is essential for the chloroplast replication which response to the light intensity. In the dark, there was little increase in chloroplast number per cell. With a light intensity of 50 lux, the increase rate of chloroplast number per cell was about half of that with 3,000 lux. Day length also affected significantly the chloroplast replication.     

Male or female soldiers? An evaluation of several factors which may influence soldier sex ratio in lower termites

In termites, the soldiers’ sex ratio is often biased toward one sex. Unlike in the Hymenoptera, this bias cannot easily be explained by relatedness asymmetries because termites are diploid. Matsuura proposed that when large body size is adaptive for colony defence (e.g. in case of phragmotic defence) then the larger sex (given sexual size dimorphism exists) should be more likely to reach a threshold size and develop into soldiers. This would explain biased sex ratios. Matsuura validated his hypothesis for four Reticulitermes species. Here, we tested his hypothesis for two species of Cryptotermes with phragmotic defence. These drywood termites have a life type that is thought to be ancestral in termite’s evolution, thus giving us potential insights into the evolution of the soldier caste. In one of these species, the sex ratio of soldiers was highly female biased, but we could not support Matsuura’s hypothesis. Both species lacked sexual size dimorphism in all castes. Additionally, in both species, the sex ratio of helpers and sexuals did not deviate from a 1:1 ratio, and hence can also not account for the bias observed in soldiers. However, this study showed that there were behavioural differences between the sexes in both species, which could shed some light on biased sex ratio in soldiers. Our findings also indicate that the developmental pathway taken by individuals reflects a ‘decision’ at the colony level. The discovery of behavioural differences between sexes in termites should open the way to similar studies in other taxa with helpers/ workers of both sexes, as it might reveal more task partitioning in colonies than previously thought and it raises questions concerning the selective pressures that acted on caste evolution in termites. Received 30 October 2007; revised 17 January and 27 February; accepted 4 March 2008.     

Thermoregulation behaviour in codling moth larvae

Abstract. The thermoregulation behaviour of the codling moth, Cydia pomonella, is investigated in temperature gradient experiments with larvae feeding within apples, and with mature larvae searching for cocooning sites. Feeding larvae appear to prefer the apple hemisphere with a higher temperature (i.e. they build larger cavities in the radiated, warmer part of the fruit). The proportion of larval cavities in the warmer hemisphere is positively related to increasing apple temperature on that side, as well as to the temperature difference between the warm and the cool fruit hemisphere. The mechanism in feeding larvae can be termed as cryptic basking because, during microhabitat selection, the caterpillars exploit temperature differences that are caused explicitly by incident solar radiation. Fifth-instar larvae in search of cocooning sites show no temperature preference within the large gradient offered (9–29 °C), with no difference between males and females. During larval development, the insect changes its thermoregulation behaviour in response to a possible shift in benefits of an elevated body temperature with respect to environmental conditions. Both the thermoregulation behaviour and such a shift of behavioural response should be respected when simulating body temperatures of the species.     

Early nutritional stress impairs development of a song-control brain region in both male and female juvenile song sparrows (Melospiza melodia) at the onset of song learning

Birdsong is a sexually selected trait and is often viewed as an indicator of male quality. The developmental stress hypothesis proposes a model by which song could be an indicator; the time during early development, when birds learn complex songs and/or local variants of song, is of rapid development and nutritional stress. Birds that cope best with this stress may better learn to produce the most effective songs. The developmental stress hypothesis predicts that early food restriction should impair development of song-control brain regions at the onset of song learning. We examined the effect of food restriction on song-control brain regions in fledgling (both sexes, 23-26 days old) song sparrows (Melospiza melodia). Food restriction selectively reduced HVC volume in both sexes. In addition, sex differences were evident in all three song-control regions. This study lends further support to a growing body of literature documenting a variety of behavioural, physiological and neural detriments in several songbird species resulting from early developmental stress.     

Opening the Black Box of Developmental Experiments: Behavioural Mechanisms Underlying Long‐Term Effects of Early Social Experience

Typically, animals spend a considerable portion of their time with social interactions involving mates, offspring, competitors and group members. The social performance during these interactions can strongly depend on the social environment individuals have experienced early in life. Despite a considerable number of experiments investigating long‐term effects of the early social environment, our understanding of the behavioural mechanisms mediating these effects is still limited, mainly for two reasons. (1) Only in few experimental studies have researchers actually observed and quantified the behaviour of their study animals during the social treatment. (2) Even if differences in social interactions between social rearing treatments are reported, these differences might not be causally linked to any observed long‐term effects later in life. The aim of this review was to investigate whether behavioural records of animals during the experimental manipulation of their social environment can help (1) identifying behavioural mechanisms involved in a long‐term effect and (2) obtaining a better understanding of the long‐term consequences of early manipulations. First, I review studies that manipulated the social environment at an early stage of the ontogeny, observed the social interactions and behaviour during the social experience phase and subsequently tested the performance in social and non‐social behavioural tasks at a later life stage. In all reviewed studies, treatment differences were reported both in social interactions during the social experience phase and in social and/or non‐social behaviours later in life. Second, I discuss four classes of behavioural mechanisms that can cause the reported long‐term effects of social experience, namely learning by experience, social learning, sensory stimulation and social cueing. I conclude that social interactions during the social experience phase should always be recorded for at least two reasons. Knowledge about how the social interactions differ between rearing treatments (1) permits researchers to formulate hypotheses about candidate mechanisms causing long‐term effects on behaviour and (2) can help to interpret unexpected outcomes of developmental experiments. Finally, I propose that as a crucial ultimate step towards understanding effects of the early social environment, we should develop targeted experiments testing for the causality of identified candidate mechanism.     

Ontogenetic habitat shifts in fusiliers (Lutjanidae): evidence from Caesio cuning at Lizard Island,Great Barrier Reef

Planktivorous reef-associated fishes provide a significant nutrient input to the reef, linking pelagic and reef environments. Highly mobile and relatively large body-sized fusiliers (Lutjanidae) often dominate reef fish biomass, but their role in ecosystem processes is poorly understood. We therefore combined fish counts and behavioural observations at Lizard Island, Great Barrier Reef, to investigate: (1) the spatial distribution and biology of fusiliers on a lagoonal coral reef system, and (2) how does fusilier behaviour and size distribution change from exposed to sheltered locations. We found higher abundances of large-sized fusiliers (≥ 20 cm total length) on exposed reef sites. Sheltered sites had almost exclusively small individuals (< 20 cm total length). We interpret this pattern as indicative of an ontogenetic habitat shift. This shift was estimated to occur at about 11.15 cm total length; the size at which the likelihood of an individual being in exposed or sheltered locations was equal. The age corresponding to this length was 1.01 years, based on a von Bertalanffy growth model using size-at-age data from otolith rings of Caesio cuning, the most abundant fusilier species in this location. This suggested that the shift in distribution occurred prior to the onset of sexual maturity. This apparent ontogenetic shift to more exposed habitats with increasing size, especially in C. cuning, was also associated with a distinct behavioural profile: larger fish at the exposed sites travelled further off reef, occupied deeper habitats, and formed larger schools compared to smaller individuals. This study provides the first evidence of seascape-scale ontogenetic habitat shifts in a planktivorous reef fish, providing a foundation for future detailed analyses of the ecological roles of fusiliers.

     

Gill remodelling during terrestrial acclimation in the amphibious fish Polypterus senegalus

Fishes are effectively weightless in water due to the buoyant support of the environment, but amphibious fishes must cope with increased effective weight when on land. Delicate structures such as gills are especially vulnerable to collapse and loss of surface area out of water. We tested the ‘structural support’ hypothesis that amphibious Polypterus senegalus solve this problem using phenotypically plastic changes that provide mechanical support and increase stiffness at the level of the gill lamellae, the filaments, and the whole arches. After 7 d in terrestrial conditions, enlargement of an inter-lamellar cell mass filled the water channels between gill lamellae, possibly to provide structural support and/or reduce evaporative water loss. Similar gill remodelling has been described in several other actinopterygian fishes, suggesting this may be an ancestral trait. There was no change in the mechanical properties or collagen composition of filaments or arches after 7 days out of water, but 8 months of terrestrial acclimation caused a reduction in gill arch length and mineralized bone volume. Thus, rather than increasing the size and stiffness of the gill skeleton, P. senegalus may instead reduce investment in supportive gill tissue while on land. These results are strikingly similar to the evolutionary trend of gill loss that occurred during the tetrapod invasion of land, raising the possibility that genetic assimilation of gill plasticity was an underlying mechanism.     

Comparison of personality between juveniles and adults in clonal gecko species

The developmental perspectives of animal personality enhance our understanding of how personality structure changes in relation to life stage. Clonal animals are ideal models for developmental studies because personality differences can be solely attributed to environmental factors. Here, I investigated the presence of personality within a species of clonal gecko, Lepidodactylus lugubris, at different developmental stages. For juveniles and adult geckos, I measured exploration (reaction to a novel situation) and boldness (risk-prone tendency) and evaluated repeatability and correlation of these behavioural traits. Each gecko exhibited different exploration and boldness with significant repeatability through time but no correlation between these behavioural traits. Small juveniles were composed of only bold and low explorative individuals but large juveniles and adults were composed of various personality type individuals. These results demonstrate that subject geckos have a similar personality structure across life stages and that exploration and boldness are independent personality without forming behavioural syndrome structure. Biased composition of personality type between life stages suggests that appearance of different personality type individuals during an early ontogenetic stage generates personality variation within the clonal population. This study provides developmental insight about personality structure and its composition in clonal animals living in the wild.     

Life History Dependent Behavioural Variation in Water Striders,Aquarius remigis

We investigated behavioural consequences of life history states in Aquarius (Gerris) remigis, a hemipteran surface predator and scavenger of small North American streams. A repeated-measures field study comparing reproductive and non-reproductive first summer generation females and males during the same time in summer showed that non-reproductive males and females, which were foraging to survive the winter, behaved essentially alike, often being territorial. In contrast, reproductives of both sexes were more mobile than non-reproductives, reproductive males being much more mobile than reproductive females, always in search of and attacking potential mates. This resulted in reproductive males showing litde territoriality and having lower foraging success than all other categories, while reproductive females had higher foraging success than non-reproductive females or males, thus likely increasing their fecundity. Many behavioural variables did not change with time. Exceptions were a decrease in the mating activity of reproductives of both sexes, the number of mating attempts, mobility, and the stride rate of reproductive males, and an increase in overall foraging activity of all individuals. This indicates that the behaviour of reproductive males converged towards that of non-reproductive males as the season progressed. Individuals were assigned to either state post-hoc according to whether they had been seen mating at least once during the study period (July and August). Females were further tested to ascertain if they laid eggs. These results support the hypothesis that diapause and reproductive state to some degree predetermine behaviour, thus constraining behavioural flexibility. Attributing behavioural variation to various proximate causes can be central to the interpretation of alternative strategies and tactics.     

A strong genetic correlation underlying a behavioural syndrome disappears during development because of genotype–age interactions

In animal populations, as in humans, behavioural differences between individuals that are consistent over time and across contexts are considered to reflect personality, and suites of correlated behaviours expressed by individuals are known as behavioural syndromes. Lifelong stability of behavioural syndromes is often assumed, either implicitly or explicitly. Here, we use a quantitative genetic approach to study the developmental stability of a behavioural syndrome in a wild population of blue tits. We find that a behavioural syndrome formed by a strong genetic correlation of two personality traits in nestlings disappears in adults, and we demonstrate that genotype–age interaction is the likely mechanism underlying this change during development. A behavioural syndrome may hence change during organismal development, even when personality traits seem to be strongly physiologically or functionally linked in one age group. We outline how such developmental plasticity has important ramifications for understanding the mechanistic basis as well as the evolutionary consequences of behavioural syndromes.