Ontogenetic Factors Research Articles

Vocalisations of wild common marmosets are influenced by diurnal and ontogenetic factors

The vocalisations of wild common marmosets, Callithrix jacchus, were recorded to investigate whether call rate by individuals is affected by time of day, age, sex or dominance rank within a group. We also investigated how vocalisation pitch was affected by age, focussing on a single common call, the trill call. Adults vocalised more than juveniles or infants during the majority of daylight hours. Only the call rate of juveniles varied significantly over the day. No differences were found between either sex or dominance rank with respect to rate of vocalisations. The trill calls emitted by young wild common marmosets were of a higher pitch than those emitted by adults. We conclude that the auditory communication of wild common marmosets is related to the age of the animals, both in terms of call rate and the physical characteristics of their vocalisations.

The ontogeny of the shell in side‐necked turtles, with emphasis on the homologies of costal and neural bones

Although we are starting to understand the molecular basis of shell development based on the study of cryptodires, basic comparative ontogenetic data for the other major clade of living turtle, the pleurodires, are largely missing. Herein, the developmental and phylogenetic relation between the bony shell and endoskeleton of Pleurodira are examined by studying histological serial sections of nine specimens of three different species, including an ontogenetic series of Emydura subglobosa. Emphasis is given to the portion of the carapace in which ribs and vertebral spinous processes become part of the carapace. Central questions are how neurals and costals are formed in pleurodiran turtles, whether costals and neurals are of endoskeletal or exoskeletal origin, and what ontogenetic factors relate to neural reduction of some Pleurodira. The neurals and costals do not develop as independent ossification centers, but they are initial outgrowths of the periosteal collar of endoskeletal ribs and neural arches. Slightly later in development, the ossification of both shell elements continues without a distinct periosteum but by metaplastically ossifying precondensed soft-tissue integumentary structures. Through ontogeny, ribs of the turtles studied are closely associated with the hypaxial intercostalis musculature while epaxial interspinalis musculature connects the neural arches. We here propose an alternative structural hypothesis for the neural reduction and, ultimately, the complete loss of the neural series. The complete reduction of neurals in Emydura spp. may be linked to heterochrony, accompanied by a restricted influence of epaxial musculature and epidermal-dermal interaction in shell bone formation.

Sensorimotor experience enhances automatic imitation of robotic action

Recent research in cognitive neuroscience has found that observation of human actions activates the 'mirror system' and provokes automatic imitation to a greater extent than observation of non-biological movements. The present study investigated whether this human bias depends primarily on phylogenetic or ontogenetic factors by examining the effects of sensorimotor experience on automatic imitation of non-biological robotic, stimuli. Automatic imitation of human and robotic action stimuli was assessed before and after training. During these test sessions, participants were required to execute a pre-specified response (e.g. to open their hand) while observing a human or robotic hand making a compatible (opening) or incompatible (closing) movement. During training, participants executed opening and closing hand actions while observing compatible (group CT) or incompatible movements (group IT) of a robotic hand. Compatible, but not incompatible, training increased automatic imitation of robotic stimuli (speed of responding on compatible trials, compared with incompatible trials) and abolished the human bias observed at pre-test. These findings suggest that the development of the mirror system depends on sensorimotor experience, and that, in our species, it is biased in favour of human action stimuli because these are more abundant than non-biological action stimuli in typical developmental environments.

Effect of harvest period on foliage production and dry matter distribution in five cassava cultivars during the second plant cycle

The objective of this work was to study the leaf production pattern and dry matter distribution in cassava during the second plant cycle. The completely randomized experimental design with four replications was used, with five cultivars in the main plots and ten harvest times in the sub-plots. Foliage production was affected by plant age, being higher in hot periods. Leaf blades and petioles dry matter content presented a linear increase due to a progressive decrease in the amount of young leaves and ontogenetic factors. The stems provided, temporarily, carbohydrates to the plant re-growth, delaying the availability and use of storage roots dry matter. The dry matter content in the storage roots was lower during the vegetative and higher during rest period. The storage roots diameter increased considerably when the amount of leaves was higher, indicating the importance of leaf area in the cassava plant production.

Phylogenetic, ecological, and ontogenetic factors influencing the biochemical structure of the blubber of odontocetes

To explore ecological, phylogenetic, and developmental factors affecting the structure of blubber in Odontocetes (toothed whales), lipid composition of this specialized adipose tissue was determined in 260 specimens (30 species representing all families except the river dolphins), most of which were collected between 1995 and 2005, from all over the world. In most odontocetes, blubber contained primarily triacylglycerols; the blubber of beaked and sperm whales was dominated by wax esters (WE), exhibiting ontogenetic patterns of deposition. WEs may represent an adaptation to deep diving for marine mammals that do not rely on blubber for stored energy. Fatty acid (FA) composition was stratified through blubber depth, with higher concentrations of dietary FA in the inner and endogenous FA in the outer layers of the blubber. Stratification can be considered a characteristic feature of odontocetes, and is likely the result of differential metabolism through the blubber. Small body size appears to constrain blubber lipid content to be high. Thermal habitat also represents an important selective pressure for blubber composition. Species inhabiting colder waters exhibited both higher lipid content and increased FA stratification in blubber, compared to species from warm/tropical habitats. The isolation of mobilization to inner blubber may permit metabolic enzymes to function without limitation by lower temperatures. The variation in composition and distribution of blubber lipids in odontocetes suggests that different species may have evolved slightly diverse arrays of secondary functions for this specialized tissue as adaptations for specific ecological niches.

Trace metal variations in the shells of Ensis siliqua record pollution and environmental conditions in the sea to the west of mainland Britain

Shells of the pod razor shell ( Ensis siliqua) from 13 locations around the west coast of mainland Britain have been analysed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for a range of trace metals including Zn, Cd, Pb, U, Ba, Sr and Mg. The trace metal record in these shells is a proxy record for changes in seawater chemistry during the 1990s. Regional variations exist in the median concentrations of the analysed metals. Barium concentrations are related to increased productivity from sewage sludge dumping at sea. Strontium shows a local relationship to salinity, but there is no clear relationship over the study area, instead high Sr is often associated with high Ba, and may reflect ontogenetic factors such as growth rate. Magnesium shows a seasonal variation within individual shells and can be used to calculate sea surface temperatures from groups of shells. Contaminant metals show a clear regional relationship with known sources, thus high Pb and Zn are typically associated with former metal mining areas (e.g. Cardigan Bay, Anglesey), and high Pb, Zn, Cd and U are associated with industrial activity in Liverpool Bay. Anomalies such as the high U in shells from northern Scotland cannot at present be explained. A seasonal variation of Pb is also seen in Cardigan Bay and Liverpool Bay, relating to increased winter fluxes of these metals to the marine environment. The regional distribution of these metals is consistent with known sources of contamination and patterns of seawater migration around the coast of Britain.

Influences of Root Diameter, Tree Age, Soil Depth and Season on Fine Root Survivorship in Prunus avium

The rapid turnover of the fine root system is a major pathway of carbon and nutrient flow from plant to soil in forest ecosystems. In order to quantify these fluxes there is a need to understand how fine root demography is influenced by edaphic, environmental and plant ontogenetic factors. We studied the influence of four major factors (season, depth, root diameter and tree age) on the survivorship and longevity of fine roots of Prunus avium L. (wild cherry) over two years in North East Scotland. Survival analysis of data derived from minirhizotron observations showed that, for the range of root diameters studied, an increase in root diameter of 0.1 mm was associated with a 16% decrease in the risk of death. Depth was also an important factor; roots present at a depth of 10 cm had significantly lower survivorship than did roots at all lower depths studied. The effects of tree age and season on root production were more complex. Roots of old trees were more likely to die in the spring and roots of young trees were more likely to die in the autumn. Our data illustrate the complex factors that must be taken into account when scaling up information from individual observations of root longevity to model the contribution of fine roots to C and nutrient fluxes in forest ecosystems.

Developmental mechanics of the primate cerebral cortex

The idea that the brain is shaped through the interplay of predetermined ontogenetic factors and mechanisms of self-organization has a long tradition in biology, going back to the late-nineteenth century. Here we illustrate the substantial impact of mechanical forces on the development, morphology, and functioning of the primate cerebral cortex. Based on the analysis of quantitative structural data for prefrontal cortices of the adult rhesus monkey, we demonstrate that (1) the characteristic shape of cortical convolutions can be explained by the global minimization of axonal tension in corticocortical projections; (2) mechanical forces resulting from cortical folding have a significant impact on the relative and absolute thickness of cortical layers in gyri and sulci; (3) folding forces may affect the cellular migration during cortical development, resulting in a significantly larger number of neurons in gyral compared to non-gyral regions; and (4) mechanically induced variations of morphology at the cellular level may result in different modes of neuronal functioning in gyri and sulci. These results underscore the significant contribution of mechanical forces during the self-organization of the primate cerebral cortex. Taking such factors into account within a framework of developmental mechanics can lead to a better understanding of how genetic specification, the layout of connections, brain shape as well as brain function are linked in normal and pathologically transformed brains.

26 Fine particle exposure and adverse health effects

Mammalian bone has shown a variety of responses to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure in experimental and wildlife studies. Although many responses have been well characterized in the postcranial skeleton, dioxin-induced effects on the cranium are largely unknown. In this study, we investigated the effects of chronic adult exposure to TCDD on cranial size and shape in dioxin-resistant Han/Wistar (H/W) and dioxin-sensitive Long–Evans (L–E) rat strains. Three-dimensional landmark configurations for the face, vault, and base of the cranium were recorded and analyzed using geometric morphometrics (GM) and dose–response modeling. The strongest effects were shown by L–E and H/W rats with daily exposures of 100 and 1000 ng TCDD/kg bw/day, respectively, resulting in significant reductions in centroid size (CS) in all three cranial modules for both strains except for the vault in H/W rats. Consistent with previous evidence of intraspecific variation in TCDD resistance, the benchmark doses (CEDs) for cranial size reduction in L–E rats were roughly 10-fold lower than those for H/W rats. For both strains, the face showed the greatest size reduction from the highest doses of TCDD (i.e., 3.6 and 6.3% decreases in H/W and L–E rats, respectively), most likely related to dose-dependent reductions in limb bone size and body weight gain. However, intrinsic morphological differences between strains were also observed: although the control groups of H/W and L–E rats had vaults and bases of comparable size, the face was 6.4% larger in L–E rats. Thus, although H/W rats possess an altered aryl hydrocarbon receptor (AhR) that appears to mediate and provides some resistance to TCDD exposure, their smaller reductions in facial size may also relate to strain-specific patterns of cranial development and growth. Future research will be aimed at understanding how ontogenetic factors may modulate toxic effects of prenatal and lactational exposure on the mammalian skeleton.

Ontogenetic constraints on the evolution of right-handedness

Ontogenetic factors constrain the evolution of species-typical traits. Because human infants are born “prematurely” relative to other pri- mates, the development of handedness during infancy can reveal impor- tant ontogenetic influences on handedness that may have contributed to the evolution of the human species-typical trait of a population-level right- hand dominance.

Osteological differentiation among Iberian <i>Pelodytes</i> (Anura, Pelodytidae)

The morphological differentiation among Pelodytes species is analysed based on a sample of disarticulated bones from the main osteological regions of the male adult skeleton. A set of 35 interspecifically diagnostic characters, analysed under different outgroup hypotheses, clearly shows that P. ibericus and P. punctatus are a sister-group with respect to P. caucasicus. The Caucasian species retains a very primitive morphology, with only 17-23 % derived character-states, while both living Iberian species reach percentages of derivation over 68 %. There is little difference between P. ibericus and P. punctatus in their relative degree of evolutionary transformation, and when using P. caucasicus as the outgroup the percentage of derived character-states is 45 and 60 % respectively. Differentiation rates are calculated in darwin units for several characters, and we show that the skull components have higher rates than the traits directly related with locomotion. Several adult growth trajectories, different between species, are described and identified as diverse allometric heterochronies. Three factors have been detected that might have grouped several characters as coevolutionary units. These factors are: a) an ontogenetic factor, operating through heterochronic processes, expressed as a tendency to reduce ossification; b) a functional morphological integration, detected in the elements involved in skull size and proportions; and c) an ecomorphological factor, presumably an adaptive response, can be assumed for characters related to limb shape.

Hind-Limb Regeneration in the Dwarf African Clawed Frog, Hymenochirus boettgeri (Anura: Pipidae)

The ability to regenerate lost or amputated limbs varies greatly among amphibians. To gain a better understanding of phylogenetic and ontogenetic factors influencing regenerative ability, regeneration in tadpoles of Hymenochirus boettgeri is described for the first time, then compared to data from closely related Xenopus laevis. Hind limbs of tadpoles of H. boettgeri were amputated at two different levels along the proximo-distal axis of the limb (at the knee and ankle joints), at stages ranging from 52 to 59. Tadpoles were allowed to recover for 15 or 20 days, at which times the amount of regeneration was examined. Observations were made through external morphology and whole-mount histological staining. Hymenochirus, like X. laevis and indeed like most anurans, gradually loses the ability to regenerate hind-limb structures as it progresses through metamorphosis, and this loss occurs in a proximo-distal direction; the ability to regenerate is retained longer, distally. Hymenochirus and Xenopus show similar patterns of limb and digit regeneration. In both pipid species, loss of regenerative ability appears to be correlated with the onset of ossification in the hind limb, although timing of this event differs between the two species.

Hind-Limb Regeneration in the Dwarf African Clawed Frog, Hymenochirus boettgeri (Anura: Pipidae)

The ability to regenerate lost or amputated limbs varies greatly among amphibians. To gain a better understanding of phylogenetic and ontogenetic factors influencing regenerative ability, regeneration in tadpoles of Hymenochirus boettgeri is described for the first time, then compared to data from closely related Xenopus laevis. Hind limbs of tadpoles of H. boettgeri were amputated at two different levels along the proximo-distal axis of the limb (at the knee and ankle joints), at stages ranging from 52 to 59. Tadpoles were allowed to recover for 15 or 20 days, at which times the amount of regeneration was examined. Ob- servations were made through external morphology and whole-mount histological staining. Hymenochirus, like X. laevis and indeed like most anurans, gradually loses the ability to regenerate hind-limb structures as it progresses through metamorphosis, and this loss occurs in a proximo-distal direction; the ability to regenerate is retained longer, distally. Hymenochirus and Xenopus show similar patterns of limb and digit regeneration. In both pipid species, loss of regenerative ability appears to be correlated with the onset of ossification in the hind limb, although timing of this event differs between the two species.

Anatomical and ontogenetic factors producing variation in HVc neuron number in zebra finches

The volume of nucleus HVc of the avian song system varies greatly both among and within songbird species, and is positively correlated to song complexity in many species. Moreover, the number of neurons in HVc predicts the ability of individual zebra finches to imitate song accurately. To better understand this brain/behavior relationship, we used the retrograde tracer Fast Blue to assess how specific HVc neuronal subpopulations contribute to variation in overall HVc neuron number in adult male zebra finches. We also investigated whether sibling order predicts the number of HVc neurons and/or yolk levels of testosterone, a hormone that might regulate the development of HVc. We report that total HVc neuron number is consistently and independently predicted by the size of each of its two projection populations, suggesting that the proportional makeup of HVc is tightly regulated at least in male zebra finches. Also, while we failed to detect a significant effect of sibling order on either the number of neurons in HVc or yolk testosterone concentration, we found that clutch of origin made a large contribution to variation in both early hormone levels and HVc neuron number.

The binding problem.

Both Ghose and Maunsell and Shadlen and Movshon point out what is perhaps the fundamental problem with the binding hypothesis: even supposing that temporal coding is the vehicle for signaling which neural populations should be bound together, the theory does not adequately address how those combinations are computed. In a sense, the binding problem is pushed back one level, for it must be solved at least partially for the necessary temporal correlations to be established. Are neurons with appropriate receptive field properties and anatomical connectivity a sufficient basis for the generation of correlated signals? What is the role of top-down connections in establishing proper synchrony? These questions are difficult to answer and difficult to model with biological realism. A similar problem rests with the output side of the temporal binding hypothesis—if correlations are the signal for binding, how are those signals read out? The readout problem is one of the most puzzling and fundamental problems for systems neuroscience in general: how is the firing of populations of neurons interpreted and transformed by other neurons to result in decision, action, perception, etc? This problem plagues most, if not all, models of brain function, for in modeling it is the modeler that attributes semantics to nodes in a network. One way to potentially avoid that problem would be to close the loop between the model and the world, so that the world impinges upon the network, which then acts upon and affects the world, thus generating semantics through action.This brings me to mention (by virtue of my editorial license) what is perhaps the most mystifying binding problem of all: the problem of consciousness. How does something as simple and mechanistic as neural firing add up to subjectivity, raw feelings, a self? Are the mechanisms that allow us to attribute the correct color and shape to an object the same ones that lead to the unity of phenomenal experience? Will the solution of the binding problem be the solution to the mystery of consciousness? I will not belabor the point, since answers will be long in coming, but although none of the scientists who authored the reviews that follow discuss binding with respect to consciousness, I will wager that the a good part of the interest, excitement, and contentiousness that surrounds the binding debate is attributable to the magnitude of the issues with which it is connected. The following pieces provide a comprehensive review of the status of the binding problem at the dawn of the new millenium. It will be extremely interesting to repeat this exercise in a decade or two, to chart the progress that we as scientists make on one of the most puzzling and fascinating issues that the brain and cognitive sciences have ever faced.*E-mail: aroskies@cell.com.

Exogenous Glutamate Enhances Glutamate Receptor Subunit Expression during Selective Neuronal Injury in the Ventral Arcuate Nucleus of Postnatal Mice

Administration of high doses of glutamate (Glu) leads to selective neurodegeneration in discrete brain regions near circumventriclular organs of the early postnatal mouse. The arcuate nucleus-median eminence complex (ARC-ME) appears to be the most Glu-sensitive of these brain regions, perhaps because of the intimate relationships between its neurons and specialized astroglial tanycytes. To investigate the mechanism of Glu-induced neuronal loss, we administered graded doses of the sodium salt of glutamate (MSG) to postnatal mice, measured their plasma Glu concentrations, and performed microscopic analyses of the ARC-ME region 5 h after treatment. Nursing, 7-day-old mouse pups (CD1, Charles River, Hollister, Calif.) were injected subcutaneously with single doses of 0.1–0.5 or 1.0–4.0 mg of MSG per g BW, or with water vehicle alone. Mice were decapitated 5 h later and the brains immediately fixed by immersion in buffered aldehydes. Frontal vibratome tissue sections at comparable levels of the ARC-ME were examined by light microscopy. A dose of 4.0 mg MSG/g BW caused neurodegeneration throughout the ARC region, while 1.0 mg/g MSG resulted in less extensive damage. Injection of 0.2 mg MSG/g BW, which raised plasma Glu concentrations 17-fold after 15 min, was the minimum dose tested at which nuclear and cytoplasmic changes were observed in a small group of subependymal neurons near the lateral recesses of the third ventricle. Higher doses of 0.3–0.5 mg MSG caused injury to additional neurons situated farther laterally, but damage remained confined to the ventral region of the ARC nucleus. Ultrastructural examination showed some subependymal neurons with pyknotic nuclei, reduced cytoplasmic volume, and swollen subcellular organelles, while others had fragmented and condensed nuclear material. Immunostaining for tyrosine hydroxylase indicated that dopamine neurons were spared at the threshold dose, but suffered damage after higher doses of MSG. Immunostaining for Glu receptor subtypes revealed that 0.2 mg MSG/g BW enhanced neuronal expression of NMDAR1 and of GluR2/4, and that higher doses of MSG preferentially increased NMDAR1 expression in injured neurons. These results extend previous reports of Glu sensitivity in the ARC-ME region of 7-day postnatal mice. A dose of 0.2 mg MSG/g BW s.c. causes clear but discrete injury to specific subependymal neurons of undetermined phenotype near the base of the third ventricle. Slightly higher doses of MSG evoke damage of additional neurons confined to the ventral region of the ARC traversed by tanycytes. These same greater amounts of MSG promote dose-related increase in the expression of NMDAR1 more than of GluR2/4 in injured ARC neurons, suggesting that elevated Glu receptor levels may contribute to or be related to neuronal cell death. Taken together with previous findings, the data suggest that Glu responsitivity in the ARC-ME of the postnatal mouse may result from transient developmental conditions involving the numerical ratios and juxtaposition between tanycytes and neurons, expression of Glu receptors, and perhaps other ontogenetic factors which may not persist in the mature adult.

War: some psychological causes and consequences

Acts of individual aggression can not be ascribed simply to aggressive motivation: to understand their aetiology it is necessary to come to terms with ontogenetic factors acting early in life, predisposing factors, and eliciting factors, and the relations between them. Intergroup aggression involves also further principles of group dynamics. The term 'war' includes a broad spectrum from large scale intergroup conflict to international war. It is best seen as an institution, with a large number of constituent roles: the incumbents of each role are motivated primarily by the duties and rights associated with it. Thus war is not caused by individual aggressiveness, but may cause individuals to be aggressive. Group dynamics are important at several levels of complexity. In spite of its horrors, war is still sometimes seen as an acceptable means for resolving disputes. Factors that contribute to this include everyday issues (e.g. war literature, war toys), pervasive cultural factors (e.g. some uses of religion, nationalism), and the military–industrial–scientific complex. The consequences of war can not be fully indicated by figures for killed and wounded, for the psychological consequences may be severe and longlasting.

Threat Sensitivity in Bicolor Damselfish: Effects of Sociality and Body Size

AbstractThreat sensitivity involves graded antipredator responses that reflect the degree of predatory threat encountered. Models of predatory Atlantic trumpetfish (Aulostomus maculatus) were presented to differently sized juvenile bicolor damselfish (Pomacentrus partitus) that occurred singly or in small groups to test for threat sensitivity. Bicolor damselfish displayed threat sensitivity by responding more strongly: 1. To large models than to small models; and 2. As models were brought closer. Solitary damselfish showed stronger responses than did fish in small groups. However, no habituation to threat occurred, no correlation was found between response strength and fish size, and many individuals gave strong, ungraded responses to predator models. Comparisons between juvenile bicolor damselfish and threespot damselfish suggest that bicolor are weakly threat sensitive in that they respond strongly regardless of threat (hypersensitivity). Solitary fish are more hypersensitive than grouped fish. Threespot damselfish show a stronger influence of damselfish body size: small threespot exhibit graded responses in proportion to degree of threat (pure threat sensitivity), whereas large threespot show relatively weak responses (nonchalance). These interspecific comparisons indicate the potential range that characterizes threat sensitivity and the possible influence of social and ontogenetic factors on that range.

Expression of Drosophila mushroom body mutations in alternative genetic backgrounds: a case study of the mushroom body miniature gene (mbm).

Mutations in 12 genes regulating Drosophila melanogaster mushroom body (MB) development were each studied in two genetic backgrounds. In all cases, brain structure was qualitatively or quantitatively different after replacement of the "original" genetic background with that of the Canton Special wild-type strain. The mushroom body miniature gene (mbm) was investigated in detail. mbm supports the maintenance of MB Kenyon cell fibers in third instar larvae and their regrowth during metamorphosis. Adult mbm1 mutant females are lacking many or most Kenyon cell fibers and are impaired in MB-mediated associative odor learning. We show here that structural defects in mbm1 are apparent only in combination with an X-linked, dosage-dependent modifier (or modifiers). In the Canton Special genetic background, the mbm1 anatomical phenotype is suppressed, and MBs develop to a normal size. However, the olfactory learning phenotype is not fully restored, suggesting that submicroscopic defects persist in the MBs. Mutant mbm1 flies with full-sized MBs have normal retention but show a specific acquisition deficit that cannot be attributed to reductions in odor avoidance, shock reactivity, or locomotor behavior. We propose that polymorphic gene interactions (in addition to ontogenetic factors) determine MB size and, concomitantly, the ability to recognize and learn odors.

Ontogenetic and Social Factors Affect the Endocrinology and Timing of Reproduction in the Female Leopard Gecko (Eublepharis macularius)

Ontogenetic and Social Factors Affect the Endocrinology and Timing of Reproduction in the Female Leopard Gecko (Eublepharis macularius)