Lower Levels of Vestibular Developmental Stability in Slow-Moving than Fast-Moving Primates

The vestibular system of the mammalian inner ear senses angular and linear velocity of the head and enables animals to maintain their balance. Vestibular anatomy has been studied extensively in order to link its structure to particular kinds of locomotion. Available evidence indicates that, in primates, slow-moving species show higher levels of vestibular variation than fast-moving taxa. We analysed intraspecific morphological variation and fluctuating asymmetry (FA) levels in the semicircular canal systems of six species of lorisiform primates: three slow-moving lorisids and three fast-moving galagids. Our results showed clear differences in levels of intraspecific variation between slow-moving and fast-moving taxa. Higher levels of variation were responsible for deviations from coplanarity for synergistic pairs of canals in slower taxa. Lorisids also presented higher levels of FA than galagids. FA is a better indicator of agility than intraspecific variation. These results suggest that in order to function efficiently in fast taxa, semicircular canal systems must develop as symmetrically as possible, and should minimise the deviation from coplanarity for synergistic pairs. Higher levels of variation and asymmetry in slow-moving taxa may be related to lower levels of stabilising selection on the vestibular system, linked to a lower demand for rapid postural changes.

Associations among leaf developmental stability, canalization and phenotypic plasticity in response to population density in Abutilon theophrasti under contrasting soil conditions at different growth stages

Most studies on animals have conducted comparative studies to deduce the possible relationships among developmental stability, canalization and phenotypic plasticity, there is a lack of direct evidence in plants, which should be better study materials. To investigate the correlations among developmental stability, canalization and plasticity in plants, we conducted a field experiment with Abutilon theophrasti, by subjected plants to three densities under infertile vs. fertile soil conditions, and measured leaf size, leaf fluctuating asymmetry (FA), and calculated coefficient of variation among leaves within individuals (CVleaf) and among individuals (CVin) and relative plasticity (PIrel) and its degree in leaf size at three growth stages, to analyze the responses of their correlations to density and how they may vary with soil conditions or growth stages. Results showed a decrease of FA, CVleaf and PIrel and an increase of CVin in leaf size, with increased density. In most cases, there were no correlations among these variables, but negative correlations between CVin and PIrel, positive correlations between FA and PIrel at high density and/or in fertile soil, in infertile soil. It suggested that higher FA may indicate the state of faster growth rather than an indicator of environmental stresses; there are correlations among developmental stability, canalization and plasticity, which may be complex, affected by other factors. The loss of developmental stability may be beneficial for plant response to environmental stresses, while decreased canalization can be either disadvantageous or advantageous, depending on that the size variation results from an increase or decrease of smaller individuals, and whether its correlations with other variables reflect beneficial or adverse environmental effects.

Canalization and developmental stability of the yellow-necked mouse (Apodemus flavicollis) mandible and cranium related to age and nematode parasitism

Background Mammalian mandible and cranium are well-established model systems for studying canalization and developmental stability (DS) as two elements of developmental homeostasis. Nematode infections are usually acquired in early life and increase in intensity with age, while canalization and DS of rodent skulls could vary through late postnatal ontogeny. We aimed to estimate magnitudes and describe patterns of mandibular and cranial canalization and DS related to age and parasite intensity (diversity) in adult yellow-necked mice (Apodemus flavicollis). Results We found the absence of age-related changes in the levels of canalization for mandibular and cranial size and DS for mandibular size. However, individual measures of mandibular and cranial shape variance increased, while individual measures of mandibular shape fluctuating asymmetry (FA) decreased with age. We detected mandibular and cranial shape changes during postnatal ontogeny, but revealed no age-related dynamics of their covariance structure among and within individuals. Categories regarding parasitism differed in the level of canalization for cranial size and the level of DS for cranial shape. We observed differences in age-related dynamics of the level of canalization between non-parasitized and parasitized animals, as well as between yellow-necked mice parasitized by different number of nematode species. Likewise, individual measures of mandibular and cranial shape FA decreased with age for the mandible in the less parasitized category and increased for the cranium in the most parasitized category. Conclusions Our age-related results partly agree with previous findings. However, no rodent study so far has explored age-related changes in the magnitude of FA for mandibular size or mandibular and cranial FA covariance structure. This is the first study dealing with the nematode parasitism-related canalization and DS in rodents. We showed that nematode parasitism does not affect mandibular and cranial shape variation and covariance structure among and within individuals. However, parasite intensity (diversity) is related to ontogenetic dynamics of the levels of canalization and DS. Overall, additional studies on animals from natural populations are required before drawing some general conclusions.

Phenotypic plasticity, canalisation and developmental stability of Triatoma infestans wings: effects of a sublethal application of a pyrethroid insecticide

Background Triatomine control campaigns have traditionally consisted of spraying the inside of houses with pyrethroid insecticides. However, exposure to sublethal insecticide doses after the initial application is a common occurrence and may have phenotypic consequences for survivors. Here, using Triatoma infestans (the main vector of Chagas disease in the Southern Cone of South America) as a model species, we quantified the effects of exposure to a sublethal dose of pyrethroid insecticide on wing morphology. We tested if the treatment (i) induced a plastic effect (change in the character mean); (ii) altered environmental canalisation (higher individual variation within genotypes); (iii) altered genetic canalisation (higher variation among genotypes); and (iv) altered developmental stability (higher fluctuating asymmetry [FA]). Methods Each of 25 full-sib families known to be susceptible to pyrethroid insecticides were split in two groups: one to be treated with a sublethal dose of deltamethrin (insecticide-treated group) and the other to be treated with pure acetone (control group). Wings of the emerging adults were used in a landmark-based geometric morphometry analysis to extract size and shape measurements. Average differences among treatments were measured. Levels of variation among families, among individuals within families and among sides within individuals were computed and compared among treatments. Results Wing size and shape were affected by a sublethal dose of deltamethrin. The treated insects had larger wings and a more variable wing size and shape than control insects. For both wing size and shape, genetic variation was higher in treated individuals. Individual variations and variations in FA were also greater in deltamethrin-treated insects than in control ones for all full-sib families; however, the patterns of shape variation associated with genetic variation, individual variation and FA were different. Conclusions Insects exposed to a sublethal dose of deltamethrin presented larger, less symmetrical and less canalised wings. The insecticide treatment jointly impaired developmental stability and genetic and environmental canalisation. The divergent patterns of shape variation suggest that the related developmental buffering processes differed at least partially. The morphological modifications induced by a single sublethal exposure to pyrethroids early in life may impinge on subsequent flight performance and consequently affect the dynamics of house invasion and reinfestation, and the effectiveness of triatomine control operations. Graphical Abstract

Tracking Technical Skill Development in Young Basketball Players: The INEX Study

This study investigated developmental stability, or tracking, in the development of technical skills in youth male basketball players and retrospectively profiled stable and unstable tracking patterns over time. A total of 97 basketball players were tracked bi-annually over 3 consecutive years. Players were divided into two age-categories according to their age at baseline: under-12; and under-14. Technical skills were assessed using the American Alliance for Health, Physical Education, Recreation and Dance test battery. Anthropometric, body composition, biological maturation and physical performance data were collected. Cohen’s kappa (κ) was used to estimate tracking. With the exception of defensive movement in the under-12 age-category, tracking was low in all skill tests for both under-12 (0.22 ≤ κ ≤ 0.33) and -14 (0.20 ≤ κ ≤ 0.26) groupings. The overall technical skill showed moderate tracking for under-12 players (κ = 0.47) and low tracking for under-14 players (κ = 0.26). At baseline, players who were consistently more skilled or became more skillful (in the under-12 age-category) over time had a better growth-motor performance profile and most of them were selected to be members of regional teams. In conclusion, tracking of individual skill trajectories was low-to-moderate. Moreover, a better growth-motor performance profile seems crucial to maintain high levels of skill performance over time. It is recommended that basketball coaches track the developmental trajectories of their players to better understand the erratic nature of skill development and help design more effective practice regimes.

Developmental stability, canalization and phenotypic plasticity in annual herbaceous species under different biotic and abiotic conditions

The relationships among developmental stability, canalization and phenotypic plasticity have not been well understood. Inconsistent conclusions from different studies suggested the complexity of their associations, probably depending on specific traits, environmental contexts and plant growth stages. To address this issue, we conducted three experiments (EXP I ~ III) with several annual herbaceous species, to investigate the relationships among leaf (or cotyledon) developmental stability, canalization and plasticity and their variations with different biotic and abiotic environmental conditions and plant growth stages, with comparisons among different species at their early growth stage. We analyzed variations in mean trait value, lamina fluctuating asymmetry (FA), coefficient of variation (CV) and plasticity (RDPIs) and their correlations for lamina size (LS) of individual plants, for LS, petiole length (PL) and petiole angle (PA) of different plant layers in Abutilon theophrasti at three densities in infertile and fertile (or only fertile) soil conditions at three (or two) stages, and for cotyledon size (CS) of five species in contrasting light conditions and seeding depths. High vs. low density decreased LS (with negative RDPIs), FA indexes and CVs, either for individual plants or different layers, especially in fertile soil. Shading was more likely to increase CS (except for A. therophrasti) and FA and decrease CV; deep seeding increased CS of some species in full light, but decreased CS and FA of other species in shading (except for A. therophrasti). FA indexes more likely had positive correlations with mean value, CV and RDPIs of traits; correlations between CV and RDPIs can be positive, negative or insignificant. Correlations among the three variables were more likely positive or insignificant for traits of LS, CS and PL, but more likely negative or insignificant for PA. High density and infertile soil may favor more positive over negative correlations among variables. Results suggested higher levels of lamina FA more likely indicate higher growth rates of plants or modules. Developmental stability was more likely to have positive correlations with canalization, and negative correlations with plasticity, indicating certain common mechanisms associated with them. Environmental stresses can lead to greater phenotypic variations at different levels, facilitating cooperation between the three processes in dealing with environmental challenges.

Determination of Plant Developmental Stability in Plant Lighting with Hyperspectral Imaging

The authors showed that a convenient, accurate and fast way of assessing the degree of influence of environmental factors on plants was needed to optimize photoculture. They emphasized the importance of non-destructive monitoring of crops physiological state of, for which they used phenomics technologies, for example, remote sensing using hyperspectral cameras.(Research purpose) To reveal the possibility of using hyperspectral imaging to determine the plant developmental stability.(Materials and methods) As a measure of the favorable impact of environmental factors on the growth and development of plants, their developmental stability was taken, numerically characterized by the fluctuating asymmetry value. The authors proposed to use vegetation indices determined from the leaf reflection spectra as a bilateral feature. The object of experimental research was juvenile cucumber plants. The studies were carried out in laboratory conditions. The spectral characteristics of cucumber leaves grown under different light quality of radiation were determined using a Specim IQ hyperspectral camera. Information on the spectral reflectances was extracted from the resulting data hypercube. As an example calculations were performed for Normalized Difference Vegetation Index.(Results and discussion) The authors revealed differences in the productivity indicators of plants grown under different light quality. They revealed a significant frequency of occurrence of Normalized Difference Vegetation Index asymmetry in two halves of the cucumber leaf surface. The fluctuating nature of this asymmetry was confirmed. They found that with a light quality providing a higher productivity of plants, lower values of fluctuating asymmetry were observed, which indicate greater stability of plant development.(Conclusions) The authors proposed a method for determining the plant developmental stability using a hyperspectral camera. The method was based on the assessment of the fluctuating asymmetry of vegetation indices calculated for points on the leaf surface, characterized by the same location conditions relative to the border of its left and right halves. A preliminary assessment of the possibility of determining the developmental stability by the results of phenotyping using the example of cucumber plants showed the feasibility of the method and its practical applicability.