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Fluctuating asymmetry is a result of the organism's inability to develop in a certain way and exhibits disruptions in its early-stage developmental stability. The analysis of fluctuating asymmetry levels in anuran populations allows for a parallel assessment of the quality of the living environment. Meristic traits of anurans, such as colour marks (stripes and spots) on the backside of the body and limbs, are suitable for measuring levels of fluctuating asymmetry. The current study applies the method of fluctuating asymmetry in meristic morphological traits in adult individuals of B. viridis as a biomarker for assessment of the environmental quality of two semi-natural habitats - Halm Bunardzhik Hill (site 1) and Mladezhki Halm Hill (site 2), located in a highly urbanised area of Plovdiv City, Bulgaria. This study recorded low levels of fluctuating asymmetry for individuals of B. viridis from both sites: 0.27 (site 1) and 0.25 (site 2) for both studied hills, respectively. The low asymmetry levels reported for individuals of B. viridis from both sites indicated that their early stages of development had occurred under good environmental conditions, with a minimum risk of disturbances in their developmental stability. These results suggested that the environmental conditions at both sites were good at the time of the study. [ABSTRACT FROM AUTHOR]

The Eurytemora affinis species complex (Copepoda: Calanoida) is widespread in coastal and estuarine waters in the northern hemisphere. The species Eurytemora carolleeae belongs to this complex. It was recently described and recognized as an invasive copepod for European waters. Since then, it was found in a few European estuaries. Based on molecular and morphological studies, we observed that E. carolleeae has expanded into new freshwater habitats in Central Europe. We carried out detailed morphological analysis for this species which indicates the potential higher stability of the populations in freshwater habitats compared to brackish waters. Fluctuating asymmetry did not significantly differ between freshwater and brackish water habitats, but the share of deformed specimens was considerably larger in brackish waters. We also found that season and habitat influenced the morphology of Eurytemora. In the molecular analyses, we focused on mitochondrial (COI) as well as nuclear gene markers (18S rDNA, ITS1-2) in E. carolleeae. In addition, for the first time, we analyzed the cytochrome b gene of the latter species. A wide distribution of E. carolleeae in the Oder River system in Central Europe indicates that it is a suitable habitat for the present populations and suggests further expansion of the species into continental waters. [ABSTRACT FROM AUTHOR]

Within-plant variation in seed size may merely reflect developmental instability, or it may be adaptive in facilitating diversifying bet-hedging, that is, production of phenotypically diverse offspring when future environments are unpredictable. To test the latter hypothesis, we analyzed patterns of variation in seed size in 11 populations of the perennial vine Dalechampia scandens grown in a common greenhouse environment. We tested whether population differences in the mean and variation of seed size covaried with environmental predictability at two different timescales. We also tested whether within-plant variation in seed size was correlated with independent measures of floral developmental instability and increased under stressful conditions. Populations differed genetically in the amount of seed-size variation occurring among plants, among infructescences within plants, and among seeds within infructescences. Within-individual variation was not detectably correlated with measures of developmental instability and did not increase under stress, but it increased weakly with short-term environmental unpredictability of precipitation at the source-population site. These results support the hypothesis that greater variation in seed size is adaptive when environmental predictability is low. [ABSTRACT FROM AUTHOR]

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Developmental noise is a variety that is not related to the usually distinguished sources of phenotypic diversity, i.e., differences in the genotype and in the environment. This variation arises in the process of the realization of genetic information and reflects the imperfection of ontogenetic processes. The most common measure of it is the value of fluctuating asymmetry as slight deviations from the symmetry. Developmental noise proves to be one of the main sources of intrapopulation phenotypic diversity. The magnitude of this variability is an ontogenetic response to environmental or genetic stress, and its assessment, in fact, provides a unique opportunity to estimate the developing system condition. The level of developmental noise, characterizing an organism’s condition, acts as another population parameter that allows to approach the evaluation of the community condition. Initial deviations in the system condition can be detected even against the background of optimal estimates of abundance, biodiversity, and ecosystem functioning.

Variation of the meristic characteristics of pholidosis in the sand lizard, Lacerta agilis, was studied both in laboratory experiments and in natural populations. The total phenotypic variability was assessed by the variation of the sum of the number of scales on the left and on the right sides of the body (l + r), while the measure of developmental stability, providing insight into the degree of fluctuating asymmetry, or developmental variability, was assessed by the variation of the difference in the character values on the left and on the right (l − r). Experimental incubation of eggs at different temperatures demonstrates that the minimal level of both kinds of variability corresponds to a certain temperature, which can be characterized as an optimal one, increasing both with an increase and with a decrease in the temperature from this regime. The data demonstrate the crucial role of the temperature impact for the phenotypic variation under study. An increase in the level of developmental variability to the north and to the south from the center part of the species range, in the absence of an obvious trend in geographic variation of the level of total phenotypic variability, assumes an increase in the role of developmental variability in the observed phenotypic diversity at the periphery of the species range. The results obtained indicate the importance of a population phenogenetic approach, based on the developmental stability study in natural populations, to provide certain information supposing the possible nature of phenotypic diversity in a species range.

In the area of zoology, it is of great interest to determine the degree of asymmetry existing in the different animal structures in order to establish it as a variable (biomarker). In this study, a new methodology is proposed for obtaining this variable ‘Asymmetry Index’. Forty-eight Iberian red deer antlers (Cervus elaphus hispanicus) from hunting reserves in the province of Jaen (Spain) have been used. The degree of asymmetry of their antlers between homologous points considered in the two right and left sides of each antler was obtained. The methodology is applied within a parametric Computer-Aided Design system from the photogrammetric restitution of the antler from two photographs. The procedure compares the degree of asymmetry in which the points of each of the right and left sides of the antler are found by means of lengths and angles with respect to an established reference plane based on the geometry of the specimen’s skull. As a result of the study, it has been observed that the Asymmetry Index obtained is lower in those specimens that have a high score in their hunting valuation, so it is considered that this factor can be taken into account as an objective and quantifiable indicator (biomarker).

Increased concentrations of chemicals in surface waters affect the development of fish and the state of water bodies in general. In turn, the human consumption of fish that have accumulated heavy metals can cause toxicological hazards and endanger health. The importance of this area and the lack of water quality assessment methods in Ukraine based on the fluctuating asymmetry level of fish and the chemical parameters of water informed the object and aim of the current research. The object of this study was the use of fish populations as a bioindicator of water quality. The study had three purposes: (1) the determination of the dominant fish species and a comparison of their fluctuating asymmetry in the studied rivers; (2) the evaluation of the sensitivity/tolerance of the selected fish populations for assessing water quality; and (3) the creation of a model for assessing the water quality of the studied rivers based on the determined fluctuating asymmetry of the typical fish populations. Each of the studied fish populations had different frequency of fluctuating asymmetry (FFA) levels: the common roach had the highest value, and the silver crucian carp had the lowest. The final stage of the study was building an artificial neural network (ANN) model for predicting water quality based on the FFA of meristic features. Optimal results were obtained for the ANN model with the ReLU activation function and SGD optimization algorithm (MAPE = 6.7%; R2 = 0.97187). Such values for the MAPE and R2 indicators demonstrated that the level of agreement between the target and forecast data was satisfactory. The novelty of this research lay in the development of a model for assessing water quality based on the comparison of the fluctuating asymmetry values of the typical fish populations in the studied rivers.

Background Developmental instability in archaeological samples can be detected through analysis of skeletal and dental remains. During life, disruptions to biological internal homeostasis that occur during growth and development redirect bodily resources to returning to homeostasis and away from normal processes such as symmetrical development. Because dental enamel does not remodel in life, any deviations from normal development are left behind. Even subtle disturbances to developmental trajectory may be detected in asymmetrical development of traits, specifically a random variation in sides termed fluctuating asymmetry. Human dental fluctuating asymmetry studies are common, but here we investigate the permanent dentition of a non-human primate Papio anubis, for potential fluctuating asymmetry relative to sex, weaning, and reproductive maturity. The sample stems from an outlier population that lives in the wettest and most humid habitat of any studied baboon group. Methods The skulls of adult baboons were collected after their natural death in Gashaka Gumti National Park, Nigeria. The permanent dentition of antimeric teeth (paired) were measured for maximum length and breadth using standard methods. The metrics were analyzed to assess the presence of fluctuating asymmetry in adult permanent mandibular and maxillary dentition. Measurement error and other forms of asymmetry (antisymmetry, directional asymmetry) were considered and dental measures expressing true fluctuating asymmetry were used to address three research questions. Results Males exhibit greater fluctuating asymmetry than females, suggesting that males experience greater overall instability during the developmental period. While weaning is not more stressful than other life history stages for males and females (using the first molar fluctuating asymmetry index as a proxy compared to other teeth), it is more stressful for females than males. The onset of reproduction is also not more stressful than other life history stages for males and females (using the third molar fluctuating asymmetry index as a proxy compared to other teeth), but it is more stressful for males than females. We explore possible explanations for these findings in the discussion.

Although symmetry, averageness, and sexual dimorphism are usually considered important to facial attractiveness, there are mixed findings regarding whether and how symmetry influences facial attractiveness. The present study introduced “facial normality” to explain the inconsistency of previous research. We hypothesized that symmetry only increased facial attractiveness when it improved facial normality. We manipulated symmetry and normality simultaneously on sixteen Chinese male faces and asked participants to rate the perceived symmetry, perceived normality, and facial attractiveness. The results demonstrated an interactive effect of symmetry and normality on facial attractiveness. The structural equation model results showed two paths from symmetry to facial attractiveness: (1) Symmetry reduced facial attractiveness by decreasing perceived normality; (2) Symmetry increased facial attractiveness by increasing the perceived symmetry and then improving perceived normality. In other words, perceived normality acted as a mediator between symmetry and facial attractiveness. The present study provides a solution to the different effects of symmetry on facial attractiveness in previous studies and suggests that future studies on symmetry and facial attractiveness should consider the mediating role of normality.

Objectives: Palate morphology is constantly changing throughout an individual's lifespan, yet its asymmetry during growth is still little understood. In this research, we focus on the study of palate morphology by using 3D geometric morphometric approaches to observe changes at different stages of life, and to quantify the impact of directional and fluctuating asymmetry on different areas at different growth stages. Materials and Methods: The sample consists of 183 individuals (1–72 years) from two identified human skeletal collections of 19th and early 20th Century Italian contexts. A 3D‐template of 41 (semi)landmarks was applied on digital palate models to observe morphological variation during growth. Results: Asymmetrical components of the morphological structure appears multidirectional on the entire palate surface in individuals <2 years old and become oriented (opposite bilateral direction) between 2 and 6 years of age. Specifically, directional asymmetry differentially impacts palate morphology at different stages of growth. Both the anterior and posterior palate are affected by mild alterations in the first year of life, while between 2 and 6 years asymmetry is segregated in the anterior area, and moderate asymmetry affects the entire palatal surface up to 12 years of age. Our results show that stability of the masticatory system seems to be reached around 13–35 years first by females and then males. From 36 years on both sexes show similar asymmetry on the anterior area. Regarding fluctuating asymmetry, inter‐individual variability is mostly visible up to 12 years of age, after which only directional trends can be clearly observed at a group level. Discussion: Morphological structure appears instable during the first year of life and acquires an opposite asymmetric bilateral direction between 2 and 6 years of age. This condition has been also documented in adults; when paired with vertical alteration, anterior/posterior asymmetry seems to characterize palate morphology, which is probably due to mechanical factors during the lifespan. Fluctuating asymmetry is predominant in the first period of life due to a plausible relationship with the strength of morphological instability of the masticatory system. Directional asymmetry, on the other hand, shows that the patterning of group‐level morphological change might be explained as a functional response to differential inputs (physiological forces, nutritive and non‐nutritive habits, para‐masticatory activity as well as the development of speech) in different growth stages. This research has implications with respect to medical and evolutionary fields. In medicine, palate morphology should be considered when planning orthodontic and surgical procedures as it could affect the outcome. As far as an evolutionary perspective is concerned the dominance of directional asymmetries in the masticatory system could provide information on dietary and cultural habits as well as pathological conditions in our ancestors. [ABSTRACT FROM AUTHOR]

We studied the variability of non-metric cranial traits, mainly foramina, of European wildcats (Felis silvestris silvestris) and domestic cats (Felis catus) from Germany based on 28 non-metric traits in 211 skulls. The domestic cats were grouped together as a statistical population. The wildcats were divided into two populations: Harz and Hesse, which were further subdivided, based on traffic infrastructure, natural landscape, and in the Harz, on time period. Epigenetic variability, epigenetic distance and the fluctuating asymmetry were calculated to assess genetic variability, possible depressions and population stability. The epigenetic variability Iev of the wildcat groups ranged from 0.27 (Hesse II) to 0.40 (Harz I). The difference in Iev between all specimens from Harz and Hesse respectively was less (Iev = 0.37 Harz and 0.31 Hesse). Compared to other studies these values are not assumed to indicate genetic depression. The epigenetic distance between the wildcat samples is 0.0774 overall, and in each case higher between sub-groups of the Harz and Hesse than between groups within these regions, respectively. The significant epigenetic distance between Harz and Hesse might indicate—at least past formerly—restricted connectivity between these regions. The fluctuating asymmetry for wildcats in total is 11.74% and in the sub-groups it ranges from 8.47 to 16.14%. These values are below 20% are at the lower range known from populations of other mammal species. The use of fluctuating asymmetry had also been discussed critically in its usefulness to assess viability of populations. [ABSTRACT FROM AUTHOR]

Objectives: Life history theory, a branch of evolutionary theory, predicts the existence of trade‐offs in energetic allocation between competing physiological functions. The core metabolic cost of self‐maintenance, measured by resting metabolic rate (RMR), represents a large component of human daily energy expenditure. Despite strong selective pressures for energetic frugality and high observed interindividual variation in RMR, the link between RMR and energetic allocation to life‐history traits remains understudied in humans. Materials: In a sample of 105 (m = 57, f = 48), we investigated the relationship between adult RMR and investment in growth quality, as measured by fluctuating asymmetry (FA). Results: Measurement of RMR and FA in university rowers revealed a significant positive correlation amongst males (n = 57, r = 0.344, p = 0.005, 1‐tailed; standardized 95% CI, 0.090 to 0.598). Convincing evidence for a correlation among females was not found (n = 48, r = 0.142, p = 0.169, 1‐tailed, standardized 95% CI, −0.152 to 0.435). Discussion: The data suggest that low‐quality asymmetrical growth is associated with later‐life metabolic inefficiencies in males. Energetic investment in processes (likely concerning the stress‐response) unrelated to growth during childhood may thereby trade‐off against adult metabolic efficiency. We suggest that the presence of a relationship between RMR and FA in males but not females may be explained by the additional metabolic strain associated with larger body size and increased male muscularity, which may amplify the inefficiencies arising from low‐quality growth. [ABSTRACT FROM AUTHOR]

Organisms face numerous environmental stressors, which can affect developmental precision, including symmetry of various physical characteristics. Fluctuating asymmetry (FA) has therefore been suggested as a simple and efficient tool for assessing sub-lethal stress levels. We analyzed FA in two sympatric lizard species (Iberolacerta horvathi and Podarcis muralis) to determine potential effects of interspecific competition and urbanization, as proxies of stress, taking into account sexual dimorphism and environmental conditions. We sampled 16 syntopic and allotopic populations and used geometric morphometrics of head morphology. We detected significant but mixed effects on the head asymmetry from the environment and the syntopic occurrence that differed between species. P. muralis lizards had more asymmetric heads at higher altitudes, while I. horvathi lizards did at mid altitudes, which may be explained by P. muralis experiencing environmental stress of colder conditions at higher altitudes. The mid-altitude effect on asymmetries in I. horvathi might be explained by a lower availability of stony walls and higher abundance of P. muralis , thus higher competition. The asymmetry of supraciliary granules was affected by the presence of other species. However, lizards from allotopic populations attained larger asymmetries compared to lizards from syntopic populations, which was the opposite from what was expected. There was no effect of urbanization in P. muralis , which could be due to relatively low pollution and habitat degradation in study locations. Overall, we highlighted the possibility of using lizards and FA for bioindication of environmental stressors and especially improved the knowledge gap in the research of biotic stressors. [ABSTRACT FROM AUTHOR]

Rapid climate change is currently altering species distribution ranges. Evaluating the long-term stress level in wild species undergoing range expansion may help better understanding how species cope with the changing environment. Here, we focused on the white-footed mouse (Peromyscus leucopus), a widespread small mammal species in North-America whose distribution range is rapidly shifting northward. We evaluated long-term stress level in several populations of P. leucopus in Quebec (Canada), from the northern edge of the species distribution to more core populations in Southern Quebec. We first tested the hypothesis that populations at the range margin are under higher stress than more established populations in the southern region of our study area. We then compared four measures of long-term stress level to evaluate the congruence between these commonly used methods. We did not detect any significant geographical trend in stress level across our study populations of P. leucopus. Most notably, we found no clear congruence between the four measures of stress level we used, and conclude that these four commonly used methods are not equivalent, thereby not comparable across studies. [ABSTRACT FROM AUTHOR]

Background: Developmental instability in archaeological samples can be detected through analysis of skeletal and dental remains. During life, disruptions to biological internal homeostasis that occur during growth and development redirect bodily resources to returning to homeostasis and away from normal processes such as symmetrical development. Because dental enamel does not remodel in life, any deviations from normal development are left behind. Even subtle disturbances to developmental trajectory may be detected in asymmetrical development of traits, specifically a random variation in sides termed fluctuating asymmetry. Human dental fluctuating asymmetry studies are common, but here we investigate the permanent dentition of a non-human primate Papio anubis, for potential fluctuating asymmetry relative to sex, weaning, and reproductive maturity. The sample stems from an outlier population that lives in the wettest and most humid habitat of any studied baboon group. Methods: The skulls of adult baboons were collected after their natural death in Gashaka Gumti National Park, Nigeria. The permanent dentition of antimeric teeth (paired) were measured for maximum length and breadth using standard methods. The metrics were analyzed to assess the presence of fluctuating asymmetry in adult permanent mandibular and maxillary dentition. Measurement error and other forms of asymmetry (antisymmetry, directional asymmetry) were considered and dental measures expressing true fluctuating asymmetry were used to address three research questions. Results: Males exhibit greater fluctuating asymmetry than females, suggesting that males experience greater overall instability during the developmental period. While weaning is not more stressful than other life history stages for males and females (using the first molar fluctuating asymmetry index as a proxy compared to other teeth), it is more stressful for females than males. The onset of reproduction is also not more stressful than other life history stages for males and females (using the third molar fluctuating asymmetry index as a proxy compared to other teeth), but it is more stressful for males than females. We explore possible explanations for these findings in the discussion. [ABSTRACT FROM AUTHOR]

Developmental instability is a component of non-genetic variation that results from random variation in developmental processes. It is considered a sensitive indicator of the physiological state of individuals. It is reflected in various ways, but in this study we focussed on its reflection in fluctuating asymmetry (FA) and morphological integration. To assess how, if at all, variations of facial morphology mirror developmental instability across childhood with respect to sex, growth rate and socioeconomic/environmental factors. A set of 210 three-dimensional facial models (of children aged between 6.3 and 14.3 years) originating from the FIDENTIS 3D Face Database was subjected to landmark-based methods of geometric morphometrics to quantify the degree of facial asymmetry and facial morphological integration. In addition, the association with age, sex, and socioeconomic factors was assessed. Our results showed a nonlinear increase of FA with age up to the age of 14 years. The pattern of sex-related variants in facial FA differed in relation to age, as girls exhibited higher values of FA than boys up to the age of 9 years. We found that a signal of modularity based on functional demands and organisation of the face is of particular importance. Here, girls exhibited higher morphological covariation among modules. During more rapid adolescence-related growth, however, covariation among modules at the asymmetrical level decreased in both sexes. We can conclude that facial morphology was shown to be strongly integrated, particularly until adolescence. This covariation can facilitate an increase of FA. In addition, the results of this study indicate there is a weak association between socioeconomic stress and facial asymmetries. In contrast, sex and growth rate are reflected in developmental instability. [ABSTRACT FROM AUTHOR]

Saccular otolith shape and size were analysed for the first time in 120 adult individuals of D. vulgaris collected from two localities, the Bizerte and Ghar El Melh lagoons (north-east Tunisia). The objectives were (1) to examine the specific inter- and intra-individual variation in the otolith shape using elliptical Fourier analysis combined with measures of length (LO), width (WO) and area (AO); (2) to use the otolith shape and size analysis as a phenotypic-based approach to discriminate the stock structure of this species in the two localities to investigate whether they represent two separate stocks to inform on appropriate management procedures; and (3) to test for biases resulting from potential fluctuating asymmetry (FA) in the otolith size on the discrimination of stock structure. Discriminant function analysis performed with the normalized elliptical Fourier descriptors coefficients showed statistically significant differences (P < 0.0001) in the otolith contour shape, i.e. asymmetry, either between the left and right sides or between the same sides (left-left and right-right) within and among individuals of the two localities. Besides, a significant asymmetry (P < 0.05) was found in WO and AO among individuals within the Bizerte locality and in WO only within the Ghar El Melh locality. Moreover, significant FA was observed in the otolith size parameters among individuals of the two localities. This significant asymmetry detected in the otolith shape, as well as in the size due to FA, within and among individuals of D. vulgaris collected from the Bizerte and Ghar El Melh localities confirms that the two stocks could be discriminated from each other and should be managed separately. This asymmetry is discussed in light of the instability of development caused either by environmental stress associated with the variation in water temperature, salinity, depth, feeding conditions and pollutants that have led to abnormalities in the development of individuals or by the presence of poor living conditions for the larvae resulting from unfavourable environments. [ABSTRACT FROM AUTHOR]

Since the 20th century, as research on the fluctuating asymmetry (FA) of otoliths in sedentary fish has deepened in a gradual way, many scholars have focused on exploring the ability of their otolith FA to indicate different environmental pressures. In this study, a typical benthic fish – Cynoglossus joyneri from three artificial habitats (artificial reef area (ARA), oyster reef area (ORA) and kelp cultivation area (NCA)) and a natural habitat (natural area (NA)) of Haizhou Bay (Lianyungang, Jiangsu Province, China) was selected as the research object, of which four otolith characters (length, width, perimeter, and area) were used to detect FA based on the squared coefficient of asymmetry variation (CV2 a). The results showed that the CV2 a of otolith in C. joyneri tended to decrease as their body length increased. In terms of indicating environmental pressure, the CV2 a of otolith length in NA was significantly higher than those in the other area (P < 0.05); the CV2 a of otolith width in NA was significantly higher than those in ARA and ORA (P < 0.05), and those in NCA were significantly higher than those in ORA (P < 0.05); and the CV2 a of otolith area in NA was significantly higher than those in ARA (P < 0.05), and those in NCA were significantly higher than those in ORA (P < 0.05). Generally, the otolith FA of C. joyneri in artificial habitats has lower CV2 a than that in natural habitats, indicating that the environmental pressure in artificial habitats is lower than that in natural habitats. We believe that C. joyneri can serve as an indicator species for environmental pressure between different habitats, which could be considered as a groundbreaking milestone in the study of otolith FA in fish. The findings not only advance the ability to assess environmental pressure in sedentary fish, which provide new insights into evaluating environmental pressure in artificial and natural habitats. • to explore the environmental pressure using otolith fluctuating asymmetry. • to indicate artificial and natural habitats using otolith fluctuating asymmetry. • to expand the database of fluctuating asymmetry of coastal water. [ABSTRACT FROM AUTHOR]

The assessment of the state of atmospheric air quality is presented with the use of indicators of fluctuating asymmetry of Betula pendula, Padus avium and Crataegus sanduinea sheet plastics. The study was carried out at the junction of the Western spurs of the Eastern Sayan and Minusinsk basin between the rivers Sissim, Syda and their tributaries. Leaf samples were taken from four sites. Leaf collection was carried out at the end of the growing season in 2017, during the stop of leaf growth by the method of V. M. Zakharov (2000). The sample of leaves from one site is 30 pieces, a total of 120 leaves are processed. The results were processed according to the method of S. I. Marchenko (2008). The indicator "width of the left and right halves of the leaf" is variable according to the results of the study. The size of the left and right halves of the leaves varies in Crataegus sanguinea within 0.65 mm, for Betula pendula the width of the leaf blades varies in the range of 0.45 mm, for Padus avium the width of the leaf blades varies by 0.15 mm. the Sample from the forest is characterized by low integral indices of asymmetry. The nature of environmental quality is characterized as an initial deviation from the norm. Pesticides and carbon dioxide emissions from vehicles are likely to be stress factors for the environment in the study area. The ecological condition of the natural area is characterized on average as satisfactory.

The properties of five bilaterally symmetrical features of the leaf blades of the small-leaved linden (Tilia cordata Mill.) in four populations of the Moscow Region in 2014–2017 were studied. The angle trait was excluded, because it possessed the property of directional asymmetry. Instead, a new linear trait was used: the distance between the base of the second vein of the first order and the base of the first vein of the second order on the first vein of the first order. The population difference in fluctuating asymmetry (FA) was found only in the first two traits (leaf width and distance between the bases of the first vein of the first order and the second vein of the second order). The largest value of FA was in the urban environment, the smallest was in the rural areas. A weak negative correlation was obtained between the magnitude of linear characteristics and the value of FA, as well as a weak positive correlation relationship between the values of FA in five traits. The first trait had the highest fluctuation variability, and the second one had the highest plastic variability. The regression dependence of the fluctuation variability on the plastic variability (b1 = 0.25, p

Asymmetry of bilateral anatomical structures is widely found in nature. Fluctuating asymmetry, i.e. mostly tiny random deviations from perfect symmetry in bilateral structures, is mainly interpreted within the framework of developmental instability. This interpretation is mainly due to the fact, that higher fluctuating asymmetry is often found in association with various pathological conditions but also from increased stress during somatic development. Directional asymmetry, in contrast, describes a distinct pattern of bilateral variation in a group of individuals, characterized by the tendency to find the larger side mainly at the same side for all individuals. This kind of asymmetry is mostly caused by behavioral lateralization. Somatic stress during development affect not only asymmetry patterns, it is has also an adverse effect on somatic growth. Therefore, the present study tested the hypothesis, that increased asymmetry is associated with decreased body height as well as postcranial length and robustness dimensions. The association patterns between fluctuating as well as directional asymmetry and parameters of somatic growth and robustness are analyzed among 236 !Kung San and 248 Kavango people of Namibia between the ages of 18 and 65 years. Fluctuating asymmetry was determined by ear length and ear breadth. Directional asymmetry was determined by hand length and hand breadth dimensions. Fluctuating as well as directional asymmetry correlated significantly negatively with body height and length dimensions, the correlations however, were weak. The results are interpreted as a corroboration of the theory that developmental stress may increase fluctuating asymmetry but on the other hand may decrease body size.

The use of fluctuating asymmetry (FA) as a measure of developmental instability and its relationship to stress and fitness is highly controversial. We examined whether the selection of different FA indices and traits influences the results of FA analysis. We chose four meristic traits and three FA indices (two single-trait and two multiple-trait indices) to assess FA levels in the common wall lizard (Podarcis muralis) from three different habitat types (urban, suburban and natural). Urbanization has already been linked to developmental instability in P. muralis. We therefore expected to detect different FA levels among the habitats. However, we also wanted to see whether we obtained the same patterns using different indices and traits. Our results showed that different traits can yield different FA patterns between habitats. The only statistically significant difference between habitats was detected for the FA2 index in femoral pores. The highest level of FA was detected in the urban population, while the lowest level was in the natural population. It is clear that caution must be exerted when deciding on which traits and indices are to be used for FA analysis. [Projects of the Serbian Ministry of Education, Science and Technological Development, Grant no. OI173043, Grant no. III43001]

Fluctuating asymmetry (FA) may serve as a reliable indicator of the functional importance of structures within an organism. Primary locomotor structures often display lower levels of FA than other paired structures, highlighting that selection can maintain symmetry in fitness-enhancing traits. Polyphenic species represent an attractive model for studying the fine-scale relationship between trait form and function, because multiple morphs exhibit unique life history adaptations that rely on different traits to maximize fitness. Here, we investigated whether individuals of the wing polyphenic sand field cricket (Gryllus firmus) maintain higher levels of symmetry in the bilateral structures most vital for maximizing fitness based on their specific life history strategy. We quantified FA and directional asymmetry (DA) across a suite of key morphological structures indicative of investment in somatic growth, reproduction, and flight capability for males and females across the flight-capable longwing (LW) and flight-incapable shortwing (SW) morphs. Although we did not find significant differences in FA across traits, hindwings lacked DA that was found in all other structures. We predicted that functionally important traits should maintain a higher level of symmetry; however, locomotor compensation strategies may reduce the selective pressures on symmetry or developmental constraints may limit the optimization between trait form and function.

The symmetry of a human organism’s structure is an expression of the general law of development regarding organic life. Assessing the symmetry of the face and its individual components is one of the most important factors when it comes to the overall assessment of a patient’s stomatognathic system and is essential in the planning of orthodontic and prosthetic treatment. The aim of this study is to assess the symmetry of the occurrence and the measurement parameters of the pre-angular notch of the mandible. The study included computed tomography scans of 187 patients who all exhibited a visible pre-angular notch in the mandible. There was a noticeable and measurable asymmetry in the length of the angle of the notches as well as in the area of the notch angles. The differentiation of the right- and left-side measurements points to the existence of a fluctuating asymmetry. Other measurements which describe the pre-angular notch of the lower jaw do not show asymmetry.

The development of an organism is a controlled process, which can be disrupted by genetic or environmental stress. Although fluctuating asymmetry is widely used as an indicator of developmental instability, its effectiveness has been questioned due to the contradictory results produced by this technique which, at least in part, probably reflects methodological inappropriateness. Here, we investigated if wing asymmetry of drosophilids increases when they develop during the dry season in the Brazilian savanna, considered a stressful season for these insects. Using protocols designed to avoid methodological problems, we analysed the wings of Zaprionus indianus and three species of the genus Drosophila (D. mercatorum, D. simulans, and D. sturtevanti). There was no significative difference in wing asymmetry in any of the four species between the dry and rainy seasons. The similar wing asymmetry levels between seasons may mean that during the dry season drosophilids are submitted to strong natural selection and the asymmetric individuals have less chance of surviving. Alternatively, environmental drought may not affect the wing symmetry. Although our study added more data to the relationship between asymmetry and stress, this discussion seems to be far from being solved.

Fluctuating asymmetry (random fluctuations between the left and right sides of the body) has been interpreted as an index to quantify both the developmental instabilities and homeostatic capabilities of organisms, linking the phenotypic and genotypic aspects of morphogenesis. However, studying the ontogenesis of fluctuating asymmetry has been limited to mostly model organisms in postnatal stages, missing prenatal trajectories of asymmetry that could better elucidate decoupled developmental pathways controlling symmetric bone elongation and thickening. In this study, we quantified the presence and magnitude of asymmetry during the prenatal development of bats, focusing on the humerus, a highly specialized bone adapted in bats to perform under multiple functional demands. We deconstructed levels of asymmetry by measuring the longitudinal and cross-sectional asymmetry of the humerus using a combination of linear measurements and geometric morphometrics. We tested the presence of different types of asymmetry and calculated the magnitude of size-controlled fluctuating asymmetry to assess developmental instability. Statistical support for the presence of fluctuating asymmetry was found for both longitudinal and cross-sectional asymmetry, explaining on average 16% of asymmetric variation. Significant directional asymmetry accounted for less than 6.6% of asymmetric variation. Both measures of fluctuating asymmetry remained relatively stable throughout ontogeny, but cross-sectional asymmetry was significantly different across developmental stages. Finally, we did not find a correspondence between developmental patterns of longitudinal and cross-sectional asymmetry, indicating that processes promoting symmetrical bone elongation and thickening work independently. We suggest various functional pressures linked to newborn bats’ ecology associated with longitudinal (altricial flight capabilities) and cross-sectional (precocial clinging ability) developmental asymmetry differentially. We hypothesize that stable magnitudes of fluctuating asymmetry across development could indicate the presence of developmental mechanisms buffering developmental instability.

Urbanization causes the loss of large amounts of habitat and produces significant changes in environmental conditions with consequences in the individual’s behavior, morphology, and physiology in natural populations. The urbanization can impact in the individual’s development instability (DI) that may be measured with the fluctuating asymmetry (FA) level making it an environmental quality bioindicator. In addition, the FA of each trait should be interpreted considering the trait functional importance, morphogenesis and history of selection pressures. In this paper, we evaluated the impact of two decades of increasing urbanization levels over a population of the pampean scorpion Bothriurus bonariensis. We analyze the FA level in somatic and genital traits in adult individuals of both sexes, collected every ~ 10 years (1997, 2008, 2018). Interestingly, in this study the somatic traits (pedipalp chelae) would be under directional selection and are shaped throughout the individual’s growth. In contrast, the genital traits (male’s hemispermatophore) are involved in the sperm transfer process and could be under stabilizing selection. Also, hemispermatophores are affected for less time by environmental stressors since they are formed once the individual has reached sexual maturity. Our results showed a significant increase in the FA levels in somatic traits of males and females, according to the increase of urbanization along years. In contrast, genital traits showed no changes in the level of FA in females, and only a few male genital traits presented an increase in the FA level. This work shows evidence that the measured scorpion traits (under different selective pressures and morphogenesis) might present differences in their susceptibility to environmental stress. We discuss these results in a context of DI of individuals caused by urbanization. We support the idea that the level of FA can be useful as an index to evaluate the effects of environmental stress on invertebrate populations. Furthermore, our paper presents the scorpions as a good model that could be used as an indicator group for studying the impact of the anthropogenic disturbance factors on natural ecosystems.

In the face, symmetry is established when bilateral streams of neural crest cells leave the neural tube at the same time, follow identical migration routes and then give rise to the facial prominences. However, developmental instability exists, particularly surrounding the steps of lip fusion. The causes of instability are unknown but inability to cope with developmental fluctuations are a likely cause of congenital malformations, such as non-syndromic orofacial clefts. Here, we tracked cell movements over time in the frontonasal mass, which forms the facial midline and participates in lip fusion, using live-cell imaging of chick embryos. Our mathematical examination of cell velocity vectors uncovered temporal fluctuations in several parameters, including order/disorder, symmetry/asymmetry and divergence/convergence. We found that treatment with a Rho GTPase inhibitor completely disrupted the temporal fluctuations in all measures and blocked morphogenesis. Thus, we discovered that genetic control of symmetry extends to mesenchymal cell movements and that these movements are of the type that could be perturbed in asymmetrical malformations, such as non-syndromic cleft lip. [ABSTRACT FROM AUTHOR]

Fluctuating asymmetry (FA) is a useful ecological indicator of trace metal exposure in plants and animals. This study was conducted to observe the effects of different levels and duration of cadmium exposure on developmental instability of freshwater fish, Channa striata, indicated by assessing the FA of its pectoral and pelvic fins. In this study, four treatment groups of C. striata were exposed to different concentrations of cadmium at 0.000 mg/L (control), 0.005 mg/L, 0.010 mg/L and 0.015 mg/L, respectively for 16 weeks. The FA of paired fin lengths were measured after the first four weeks and subsequent biweekly measurement for 12 weeks. There was an increasing trend observed in average FA associated with the increased of cadmium level and duration of exposure in C. striata, although they were not statistically significant. While FA has been shown to be a useful tool to indicate developmental instability in fish, this study found that it is not a significantly effective model to be applied to C. striata in order to study cadmium pollution. The results suggested that higher level and duration of cadmium exposure may influence higher FA of paired fin lengths of C. striata. [ABSTRACT FROM AUTHOR]

Humans are rapidly changing the marine environment through a multitude of effects, including increased greenhouse gas emissions resulting in warmer and acidified oceans. Elevated CO2 conditions can cause sensory deficits and altered behaviours in marine organisms, either directly by affecting end organ sensitivity or due to likely alterations in brain chemistry. Previous studies show that auditory-associated behaviours of larval and juvenile fishes can be affected by elevated CO2 (1000 µatm). Here, using auditory evoked potentials (AEP) and micro-computer tomography (microCT) we show that raising juvenile snapper, Chrysophyrs auratus, under predicted future CO2 conditions resulted in significant changes to their hearing ability. Specifically, snapper raised under elevated CO2 conditions had a significant decrease in low frequency (less than 200 Hz) hearing sensitivity. MicroCT demonstrated that these elevated CO2 snapper had sacculus otolith's that were significantly larger and had fluctuating asymmetry, which likely explains the difference in hearing sensitivity. We suggest that elevated CO2 conditions have a dual effect on hearing, directly effecting the sensitivity of the hearing end organs and altering previously described hearing induced behaviours. This is the first time that predicted future CO2 conditions have been empirically linked through modification of auditory anatomy to changes in fish hearing ability. Given the widespread and well-documented impact of elevated CO2 on fish auditory anatomy, predictions of how fish life-history functions dependent on hearing may respond to climate change may need to be reassessed. [ABSTRACT FROM AUTHOR]

Asymmetry, the abnormality of an organism or a part of it from its perfect symmetry, is represented by three different categories: fluctuating asymmetry, directional asymmetry, and antisymmetry. Fluctuating asymmetry attributes to random developmental variation of a morphological character, whereas directional asymmetry attributes one of the body sides to be more prominent than the other. Antisymmetry appears whenever one body side of a biological body shows greater morphological appearance than the other. Since more environmental stress often produces greater effect of fluctuating asymmetry, it can be a good indicator of physiological stress in the morphological characteristic of a biological being. Applying, so far, the first geometric morphometric methods on any Byzantine fauna, this study aimed to determine the kind and direction of skull asymmetry occurred in Byzantine dog skulls. Aiming this, asymmetries in 16 adult Byzantine dog skulls unearthed form Yenikapı-Marmaray excavation (ancient Theodosius Harbor) in İstanbul, were compared with 39 adult skulls of modern pet dog breeds. Seventeen landmarks (3 midline and 14 bilateral) were selected on the digital pictures of the ventral aspect of each skull, and used for detailed analysis. The results showed a greater percentage of fluctuating asymmetry in the Byzantine dog skulls, suggesting them not to be the remains of pets or housed dogs but perhaps the labor or stray dogs in the Byzantine capital Constantinople. [ABSTRACT FROM AUTHOR]

Developmental instability (DI) reflects an organism's inability to develop an ideal phenotype when challenged by genetic and environmental insults. DI can be estimated via the proxy measure of fluctuating asymmetry (FA), i.e., the small random deviations from perfect bilateral symmetry observed in the morphology of paired traits. The mechanisms involved in the genesis of FA in human populations are relatively unknown, though animal research indicates that hormonal processes may be involved. As maternal stress during pregnancy is detrimental to various developmental processes, elevated prenatal cortisol may represent a causal factor in the subsequent emergence of an asymmetrical phenotype. The main purpose of this pre-registered meta-analysis based on three empirical studies was to investigate whether mid-trimester amniotic cortisol levels predict subsequent FA in finger lengths of infants from Germany, Portugal, and the UK. No statistically significant relationships were observed, and meta-analytic combination of the effect size estimates yielded a null result. We did, however, detect significant positive correlations between the cortisol present in the amniotic fluid and maternal plasma in the Portuguese cohort, and observed that FA in the German cohort was significantly lower at 70-months than at either 9- or 20-months. Taken together, the current findings run contrary to animal research showing that elevated prenatal corticosterone exposure leads to increased FA. However, this may be because a single cortisol assay obtained via amniocentesis is an inadequate proxy for average gestational exposure, and/or that prenatal cortisol levels at an earlier (i.e., first rather than second trimester) stage of pregnancy is what explains variance in subsequent FA. [ABSTRACT FROM AUTHOR]

In bovines, fore and hind lateral claws are larger than the medial claws and the heel are deeper and the sole thicker. On this anatomical basis, we hypothesized that it must imply a form (size+shape) asymmetry of the digits. To test this hypothesis, we studied the acropodiums (digital series) of 15 young bovines belonging to Brown Pyrenean breed, irrespective of the gender. Dorso-plantar radiographies were obtained for each hindlimb and the form was studied in a sample of 30 hindlimbs (15 right and 15 left). Images were studied by geometric morphometric methods. A set of 7 paired landmarks on medial and lateral digital series and one axial landmark was used for the study. Lateral and medial digits were uneven both in size and shape, expressing both fluctuating and directional asymmetries. Directional asymmetries would suggest a different function in weight bearing. We hypothesize lateral digits serve to stabilize the centre of gravity to a greater extent than medial digits. These findings prompt careful reassessment of the function of each of the digital series during standing and during locomotion in future researches.

Static, developmental, and evolutionary variation are different sources of morphological variation which can be quantified using morphometrics tools. In the present study we have carried out a comparative multiple level study of integration (i.e., static, developmental, and evolutionary) to acquire insight about the relationships that exist between different integration levels, as well as to better understand their involvement in the evolutionary processes related to the diversification of Drosophila’s wing shape. This approach was applied to analyse wing evolution in 59 species across the whole genus in a large dataset (~10,000 wings were studied). Static integration was analysed using principal component analysis, thus providing an integration measurement for overall wing shape. Developmental integration was studied between wing parts by using a partial least squares method between the anterior and posterior compartments of the wing. Evolutionary integration was analysed using independent contrasts. The present results show that all Drosophila species exhibit strong morphological integration at different levels. The strong integration and overall similarities observed at multiple integration levels suggest a shared mechanism underlying this variation, which could result as consequence of genetic drift acting on the wing shape of Drosophila.

Fluctuating asymmetry (FA) is a morphometric tool used to measure developmental instability in organisms which have been exposed to stress or other adverse conditions. Phenotypic variability in response to stressors are the result of interactions between genomes and the environment, acting in a noisy developmental system. Most of the organisms have bilateral symmetry with a repetition of structures in different positions or orientations; asymmetrical variation has been a morphological response associated with insecticide application inducing disturbances in endocrinal system product of the chemicals. Triatoma infestans (is the main vector of Chagas disease in South America. The availability of food sources varies for populations of T. infestans living in different habitats; insects that inhabit the intradomicile feed preferentially on human blood, whereas insects that develop in the peridomicile feed on the blood of the other mammals and birds. The following research evaluate the FA to the different ecotopes in two geographical areas of Chuquisaca Bolivia; Yamparáez/Sotomayor of the high inter-Andean valleys and Huacaya/Imbochi of the boreal Chaco and a CIPEIN laboratory strain population. A combination of advanced morphometrics tools and multivariate analysis were used to quantify the levels of asymmetry produced by pyretroid near to the peridomiciles in Bolivia. Populations from Yamparáez/Sotomayor were found to have higher levels of FA which the combination of environmental conditions such as low temperatures avoid greater permanence in the habitat and more exposition to insecticide. A better understanding of the combination of these tools will allow researchers to implement better public policies to regulate insecticide applications and to understand how certain organisms adapt to multiple stressors.

Fluctuating asymmetry (FA) is hypothesized to be a useful predictor of population canalization, especially for organisms at risk from environmental change.Identification of traits that meet statistical criteria as FA measures remains a challenge.Here, a laboratory experiment subjected immature butterflies (Vanessa cardui) to diet and temperature conditions of varying stress levels. Variation in dietary macronutrient ratio (protein: carbohydrate) and rearing temperature (optimal: 25°C; elevated: 32°C) was introduced as stressors. Temperature and nutrition are key variables influencing ectotherm growth and fitness and so are likely to be important stressors that influence FA.Individuals subjected to stressful conditions were predicted to show elevated FA of three wing size traits, as well as increased mortality and decreased adult body size.Trait FA did not vary across treatments. Instead, treatment levels impacted viability: The combined incidence of pupal death and expression of significant wing malformations increased in treatment levels designated as stressful. Variation in adult dry mass also reflected predicted stress levels. Results suggest that individuals predicted to display increased FA either died or displayed gross developmental aberrations.This experiment illustrates important constraints on the investigation of FA, including selection of appropriate traits and identification of appropriate levels of stressors to avoid elevated mortality. The latter concern brings into question the utility of FA as an indicator of stress in vulnerable, natural populations, where stress levels cannot be controlled, and mortality and fitness effects are often not quantifiable. [ABSTRACT FROM AUTHOR]

The European pond turtle (Emys orbicularis) is a widely distributed freshwater species inhabiting much of Europe, but it is often in population decrease or is locally extinct. In this study, we sampled five central European populations, of which four were autochthonous and one was introduced outside the native range. Moreover, two of the native populations were relatively isolated and at the periphery of the species, range. Using the frequency of shell anomalies, a geometric morphometric framework and an analysis of fluctuating asymmetry, we aimed to determine the degree of morphological differentiation among different populations. Significantly, a smaller number of individuals with a malformed shell or scutes occurred in the native core range population, which potentially has a high level of gene flow (Hungary). Although neither canonical variate analysis nor the morphological disparity analysis showed distinct differences between populations, we found significantly higher shell asymmetry in the two marginal populations (Austria and Slovakia) compared with the core range populations. Our results might thus support the central–marginal hypothesis and indicate potential genetically based conservation problems owing to demographic bottlenecks and/or isolation in marginal populations. [ABSTRACT FROM AUTHOR]

By adopting a longitudinal study design and through geometric morphometrics methods, we investigated size and shape regulation in the head capsule during the larval development of the cabbage butterfly Pieris brassicae under laboratory conditions. We found evidence of size regulation by compensatory growth, although not equally effective in all larval stages. Size compensation is not attained through the regulation of developmental timing, but rather through the modulation of per‐time growth rate. As for the shape, neither the variance of the symmetric component of shape, nor the level of fluctuating asymmetry show any evidence of increase across stages, either at the population or individual level, which is interpreted as a mark of ontogenetic shape regulation. In addition, also the geometry of individual asymmetry is basically conserved across stages. While providing specific documentation on the ontogeny of size and shape variation in this insect, this study may contribute to a more general understanding of developmental regulation and its influence on phenotypic evolution. Research Highlights: We investigated the ontogenetic progression of size and shape variation (including fluctuating asymmetry) in the butterfly Pieris brassicae with a longitudinal study‐design. Larval development of this insect shows the mark of several forms of developmental regulation, both in size and shape, which exhibit a certain degree of independence from each other. [ABSTRACT FROM AUTHOR]

The research is dedicated to the phytoindicative evaluation of explored areas according to the integrated evaluation of an individual and sustainable development breach of the tree plant Quercus longipes Stev. which developed in the natural and urboecosystem on the Samur-Divichi lowland of Azerbaijan. The obtained results were compared with the same species of plants cultivated in the Absheron region, which is environmentally tougher. The absolute prices of the level change of fluctuating bilateral asymmetry’s indicators of a morphometric sign have been statistically processed in special software on the leaves of Q. longipes. The pollution hypothesis of the environment has been checked by the ANOVA test and the availability to give an initial forecast about the environmental quality has been determined within the confidential interval limits. Fluctuating asymmetry refers to the non-directional, small, random deviations from symmetry caused by developmental instability. The results of the research showed that an early warning model allowed to predict how much the contamination risk of investigated areas might be. [ABSTRACT FROM AUTHOR]

Sheep (Ovis aries) play an important role in the economy of Turkey and the Balkan Peninsula due to their use in farming. As a domesticated species, sheep's morphometric and morphological diversity is likely determined by selective breeding practices rather than geographic distribution. This study aimed to analyse four different sheep breed skulls and reveal skull asymmetry using geometric morphometric methods. For this purpose, 2D images of 52 sheep skulls from different breeds were analysed from the dorsal view of the skull, using 28 landmarks. In the comparison of sheep skulls from the dorsal view, the first principal components for directional asymmetry (DA) and fluctuating asymmetry (FA) were 32.98% and 39.62% of the total variation, respectively. Sharri and Ivesi (Awassi) sheep breeds had the broadest distribution of skull shapes among the breeds, while Lara e Polisit was the most conservative breed. DA was used as a measure of biomechanical constraints, and FA was used as an indicator of environmental stress. Consistent with DA, both differences in centroid size and shape between breeds were statistically significant. No differences between males and females related to asymmetry were revealed. Ivesi sheep revealed the highest fluctuating asymmetry. Geometric morphometric methods proved to be a useful tool for distinguishing differences in the shape of the skull of different sheep breeds and also can be useful for taxonomic purposes., (© 2024 Wiley‐VCH GmbH. Published by John Wiley & Sons Ltd.)

Dogs are animals with strong bite force. This strong bite mechanism has led to significant changes in the skeletal system such as fossa masseterica. It can be thought that one side is used more than the other side in chewing and is related to the preference of using the same side's hand, eye and foot. In the study, directional asymmetry and fluctuating asymmetry, which occurs as a result of chewing asymmetry, were examined on the first molar teeth and the fossa masseterica in 85 dog mandibles including a wide diversity of morphotypes. The association of high PC1 values for directional asymmetry with a pronounced cranial index, as evident in breeds like Pekingese, Pomeranian and Bulldog, indicates a potential evolutionary or selective breeding trend favouring brachycephaly. On the contrary, guardian breeds like the German shepherd and Bernese mountain dog, which typically require strong jaws for their roles, showcased reduced PC1 values, which might be related to their functional morphology. Similarly, the PCA results for the first molar teeth shape variations also highlighted the influence of cranial shape, with boxer dogs displaying notably higher PC1 values. The fluctuating asymmetrical distributions provided valuable insights into individualistic variations. Interestingly, no specific breed distribution trend was observed for these asymmetries, indicating a more individual-based variation rather than breed-based. It is essential to note that while these results provide valuable insights, further studies are required to understand the underlying causes better. Factors like genetic variations, developmental processes, dietary habits and external environmental factors could play pivotal roles in these observed morphological differences., (© 2024 Wiley‐VCH GmbH. Published by John Wiley & Sons Ltd.)

The semicircular canals of the inner ear are involved in balance and velocity control. Being crucial to ensure efficient mobility, their morphology exhibits an evolutionary conservatism attributed to stabilizing selection. Release of selection in slow-moving animals has been argued to lead to morphological divergence and increased inter-individual variation. In its natural habitat, the house mouse Mus musculus moves in a tridimensional space where efficient balance is required. In contrast, laboratory mice in standard cages are severely restricted in their ability to move, which possibly reduces selection on the inner ear morphology. This effect was tested by comparing four groups of mice: several populations of wild mice trapped in commensal habitats in France; their second-generation laboratory offspring, to assess plastic effects related to breeding conditions; a standard laboratory strain (Swiss) that evolved for many generations in a regime of mobility reduction; and hybrids between wild offspring and Swiss mice. The morphology of the semicircular canals was quantified using a set of 3D landmarks and semi-landmarks analyzed using geometric morphometric protocols. Levels of inter-population, inter-individual (disparity) and intra-individual (asymmetry) variation were compared. All wild mice shared a similar inner ear morphology, in contrast to the important divergence of the Swiss strain. The release of selection in the laboratory strain obviously allowed for an important and rapid drift in the otherwise conserved structure. Shared traits between the inner ear of the lab strain and domestic pigs suggested a common response to mobility reduction in captivity. The lab-bred offspring of wild mice also differed from their wild relatives, suggesting plastic response related to maternal locomotory behavior, since inner ear morphology matures before birth in mammals. The signature observed in lab-bred wild mice and the lab strain was however not congruent, suggesting that plasticity did not participate to the divergence of the laboratory strain. However, contrary to the expectation, wild mice displayed slightly higher levels of inter-individual variation than laboratory mice, possibly due to the higher levels of genetic variance within and among wild populations compared to the lab strain. Differences in fluctuating asymmetry levels were detected, with the laboratory strain occasionally displaying higher asymmetry scores than its wild relatives. This suggests that there may indeed be a release of selection and/or a decrease in developmental stability in the laboratory strain., (© 2024 Anatomical Society.)

Structural asymmetries of brain regions associated with lateralised functions have been extensively studied. However, there are fewer morphometric analyses of asymmetries of the gyri and sulci of the entire cortex. The current study assessed cortical asymmetries in a sample of healthy adults (N = 175) from an admixed population from South America. Grey matter volume and surface area of 66 gyri and sulci were quantified on T1 magnetic resonance images. The departure from zero of the differences between left and right hemispheres (L-R), a measure of directional asymmetry (DA), the variance of L-R, and an index of fluctuating asymmetry (FA) were evaluated for each region. Significant departures from perfect symmetry were found for most cortical gyri and sulci. Regions showed leftward asymmetry at the population level in the frontal lobe and superior lateral parts of the parietal lobe. Rightward asymmetry was found in the inferior parietal, occipital, frontopolar, and orbital regions, and the cingulate (anterior, middle, and posterior-ventral). Despite this general pattern, several sulci showed the opposite DA compared to the neighbouring gyri, which remarks the need to consider the neurobiological differences in gyral and sulcal development in the study of structural asymmetries. The results also confirm the absence of DA in most parts of the inferior frontal gyrus and the precentral region. This study contributes with data on populations underrepresented in the databases used in neurosciences. Among its findings, there is agreement with previous results obtained in populations of different ancestry and some discrepancies in the middle frontal and medial parietal regions. A significant DA not reported previously was found for the volume of long and short insular gyri and the central sulcus of the insula, frontomarginal, transverse frontopolar, paracentral, and middle and posterior parts of the cingulate gyrus and sulcus, gyrus rectus, occipital pole, and olfactory sulcus, as well as for the volume and area of the transverse collateral sulcus and suborbital sulcus. Also, several parcels displayed significant variability in the left-right differences, which can be partially attributable to developmental instability, a source of FA. Moreover, a few gyri and sulci displayed ideal FA with non-significant departures from perfect symmetry, such as subcentral and posterior cingulate gyri and sulci, inferior frontal and fusiform gyri, and the calcarine, transverse collateral, precentral, and orbital sulci. Overall, these results show that asymmetries are ubiquitous in the cerebral cortex., (© 2024 Anatomical Society.)

Background: This article is an attempt to apply fluctuating asymmetry as amorphometric method of studying changes in specific structures of the right and the left side of the body to determine variables which may affect morphogenesis and, consequently, human morphology in adulthood. The main aim of this study was to use the fluctuating asymmetry level as an indicator of adverse living conditions in childhood by determining the impact of environmental components (socio-economic factors and air pollution) on the level of body asymmetry in young women and men., Materials and Methods: Data were collected from 877 students from various Polish universities, including 483 women and 394 men. Anthropometric data and questionnaire responses were recorded. As part of the surveys, respondents provided information about their place of residence, socio-economic status and lateralisation. The composite body FA (cFA) was assessed based on six bilateral features: the length of fingers II and IV of both hands, the length and width of the ear, and the length and width of the foot., Results and Conclusions: The present study supports the hypothesis that asymmetry increases as socioeconomic status decreases and air pollution levels increase. Differences in asymmetry, depending on environmental factors, socioeconomic status (SES) and air quality, were in most cases greater in men than in women. The results confirm that variable asymmetry is a sensitive indicator of an individual's exposure to unfavorable environmental factors during ontogenesis. Moreover, the results of the conducted research suggest that environmental factors may influence the structure of the human body, and irreversible morphological alterations are the result of unfavorable conditions occurring in the early stages of biological development.

We measured gill slit fluctuating asymmetry (FA), a measure of developmental noise, in adults of three invertebrate deuterostomes with different feeding modes: the cephalochordate Branchiostoma floridae (an obligate filter feeder), the enteropneusts Protoglossus graveolens (a facultative filter feeder/deposit feeder) and Saccoglossus bromophenolosus (a deposit feeder). FA was substantially and significantly low in B. floridae and P. graveolens and high in S. bromophenolosus. Our results suggest that the gills of species that have experienced a relaxation of the filter feeding trait exhibit elevated FA. We found that the timing of development of the secondary collagenous gill bars, compared to the primary gill bars, was highly variable in P. graveolens but not the other two species, demonstrating an independence of gill FA from gill bar heterochrony. We also discovered the occasional ectopic expression of a second set of paired gills posterior to the first set of gills in the enteropneusts and that these were more common in S. bromophenolosus. Moreover, our finding that gill slits in enteropneusts exhibit bilateral symmetry suggests that the left‐sidedness of larval cephalochordate gills, and the directional asymmetry of Cambrian stylophoran echinoderm fossil gills, evolved independently from a bilaterally symmetrical ancestor. [ABSTRACT FROM AUTHOR]

This study provides an updated vision of the study of Geometric Morphometrics and its most recent application in ecology and evolutionary biology, covering a wide variation in methodology occurring in the last 5 years since the first version published in the International Journal of Morphology. Geometric Morphometrics is a tool that allows evaluating morphological variations with underlying factors, with a higher sensitivity than traditional morphology, so that minimum changes of morphological variation can be detected. Therefore, it has turned into an outstanding tool to answer questions of comparative biology focused on anatomic characters. At the beginning, it was a tool mainly used to answer taxonomic questions and for differentiation at individual, population or species level. However, in the last years, the number of questions and problematic on which it is applied, has diversified considerably, turning it into a very accurate tool to answer questions of morphological variation in ecologic and evolutionary contexts. Almost half a decade has elapsed since the last revision of the method, so this work is intended to analyze the methodological changes and the new approaches used in Geometric Morphometrics, including a brief introductory guideline to these new methods, their uses and applications. [ABSTRACT FROM AUTHOR]

Abstract The ability of an individual to withstand random perturbations during its development is considered a good indicator of environmental and genetic stress. A common means of assessing developmental stability is through analysis of fluctuating asymmetry (FA) in bilateral traits. Tortoises, with their large, solid plastron, allow for measurement of body geometry. Their bilateral shell scutes are ideal candidates for asymmetries researches. With this issue in mind we assessed, as a preliminary study, levels of plastron scute asymmetry in a sample of 46 red-footed tortoise Chelonoidis carbonaria from Arauca, N Colombia. We found significative fluctuating asymmetry (FA) but no directional asymmetry, the former not increasing with carapace size and thus indicating that tortoise shells do not become increasingly asymmetrical with age, or in other words, signaling that FA is not being influenced by pholidosis (variability of scale cover mosaic according to the development of the scutes). Asymmetry in plastron shape, although not necessarily apparent at first glance, varied, with gender with males exhibiting higher levels of FA than females. Although we can not identify the potential sources of variation responsible for the observed patterns of developmental instability, we consider this detected form of asymmetry due to unfavorable environmental conditions.

Symmetric growth and the origins of fluctuating asymmetry are unresolved phenomena of biology. Small, and sometimes noticeable, deviations from perfect bilateral symmetry reflect the vulnerability of development to perturbations. The degree of asymmetry is related to the magnitude of the perturbations and the ability of an individual to cope with them. As the left and right sides of an individual were presumed to be genetically identical, deviations of symmetry were traditionally attributed to non-genetic effects such as environmental and developmental noise. In this review, we draw attention to other possible sources of variability, especially to somatic mutations and transposons. Mutations are a major source of phenotypic variability and recent genomic data have highlighted somatic mutations as ubiquitous, even in phenotypically normal individuals. We discuss the importance of factors that are responsible for buffering and stabilizing the genome and for maintaining size robustness and quality through elimination of less-fit or damaged cells. However, the important question that arises from these studies is whether this self-correcting capacity and intrinsic organ size controls are sufficient to explain how symmetric structures can reach an identical size and shape. Indeed, recent discoveries in the fruit fly have uncovered a conserved hormone of the insulin/IGF/relaxin family, Dilp8, that is responsible for stabilizing body size and symmetry in the face of growth perturbations. Dilp8 alarm signals periphery growth status to the brain, where it acts on its receptor Lgr3. Loss of Dilp8-Lgr3 signaling renders flies incapable of detecting growth perturbations and thus maintaining a stable size and symmetry. These findings help to understand how size and symmetry of somatic tissues remain undeterred in noisy environments, after injury or illnesses, and in the presence of accumulated somatic mutations.