Geometric Morphometric Study Research Articles

MORPHOLOGICAL VARIATIONS IN MUD CLAM Polymesoda erosa (Lightfoot) USING FLUCTUATING ASYMMETRY ANALYSIS IN LA UNION, CABADBARAN CITY, AGUSAN DEL NORTE, PHILIPPINES

A geometric morphometric study was conducted on the population of Polymesoda erosa in La Union, Cabadbaran City, to investigate the morphological variations using fluctuating asymmetry (FA) analysis. FA acts as a reliable indicator of ecological stress and developmental instability since it detects genetic or environmental changes that an organism experiences. A total of ninety (90) individual mud clams were randomly collected and analyze. Water and soil samples were also collected to gather data on the degree of body variations and the impact of external factors on P. erosa. The result of the analysis using the SAGE software revealed a highly significant fluctuating asymmetry (P 0.0001). Significant variations in individuals, sides, and the interaction between individuals and sides symmetry were mostly responsible for the substantial variances seen in mud clam species. Particularly, landmarks 10 (dorsal margin maxima) and 13 (anterior margin maxima) exhibited notable variations. For the water quality results, the mud clam's internal valve was likely to be relatively unaffected or minimally impacted, but the level of nickel was high. In conclusion, the fluctuating asymmetry of P. erosa can be attributed to a stressed environment. Unfavorable environmental factors cause an organism's morphology to change, affecting its symmetry.

Geometric Morphometric Study on Distinguishing Metopic Craniosynostosis from Metopic Ridging.

Craniosynostosis, a common congenital anomaly, results from premature fusion of the cranial sutures. One of the forms of craniosynostosis is premature fusion of the metopic suture, referred to as trigonocephaly, but the diagnosis of metopic suture synostosis remains controversial. The purpose of this study was to clarify, using geometric morphometric analysis, if a metopic ridge alone observed in cases of mild trigonocephaly represents a pathological phenomenon. Three different cranial morphologies were compared among patients up to 2 years old who were categorized into the true group, the mild group, and the normal group, based on the presence or absence of specific symptoms, history of cranioplasty for trigonocephaly, or lack of any abnormality on computed tomography. Using the obtained computed tomography images, 235 anatomical landmarks and semi-landmarks were plotted on the entire cranial surface for analysis of neurocranial morphology, and the cranial shapes represented by landmarks were analyzed using geometric morphometrics. Principal components of shape variations among specimens were then computed, based on the variance-covariance matrix of the Procrustes residuals of all specimens, and statistically analyzed. The principal component analyses of the variations in endocranial shape, frontal bone shape, and occipital bone shape did not show any significant differences in cranial morphology between mild trigonocephaly and normal skulls; however, true trigonocephaly was found to differ significantly from mild trigonocephaly and normal skulls. These findings suggest that in assessments of cranial morphology, the presence of a ridge alone cannot be diagnosed as fundamentally pathological, and may represent normal morphology.

Variation in the shape and size of the scale of the Tigris bream (Acanthobrama marmid, Heckel, 1843) from the Tigris River, Türkiye attributed to Seasonality, Age and Sex: A geometric morphometric study

In this study, the Tigris bream Acanthobrama marmid individuals (44 females and 31 males) were captured from the Tigris River. The scale size (as centroid size) and shape were analyzed separately using 2–dimensional geometric morphometric methods. Procrustes ANOVA revealed significant differences in scales size between sexes, while no difference in shape was observed. Groups based on season and age showed significant differences in both size and shape. Female individuals had larger scale sizes than males, with the scales of the Autumn group being larger than those of the Spring and Summer groups. Scale size also increased with age groups. PCA analysis showed variation in the first five components when examined by age, season, and gender. CVA and DFA results indicated significant differences in shape between different age groups and seasonal groups, but no significant differences between sexes were observed.

Geometric Morphometric Study of Wing Shape in Leva indica (Acrididae: Gomphocerinae) from Different Environmental Sites of Coimbatore, India

A landmark based geometric morphometric study was carried out to describe the variation in wing of male and female Leva indica from different environmental sites of Coimbatore, Tamil Nadu, India. A total of 60 male and 60 female forewings were used in this study. To demonstrate the variation in wing shape, landmark data of each individual was examined through the morphometric softwares namely tps-Util, tps-Dig, tps-Relw, tps-Small and integrated software PAST. In total, 19 landmarks were identified in both male and female wings of L. indica. Based on the landmark coordinates, the first two relative warp analysis showed significant variation within and between the male and female wing shape from different sites. Procrustes vs. tangent space distance showed that the distances were similar within males and females but significant differences appeared between the male and female wings of L. indica. Principal Component Analysis (PCA) between the male and female wings scatter plots also showed clear distinction from the result. The obtained results indicate that each sex of L. indica from different regions displays morphological differences in wing shape. These morphological changes could have occurred as a result of phenotypic plasticity.

Variation in mandible shape and size due to osteoporosis: Geometric morphometrics study

Variation in mandible shape and size due to osteoporosis: Geometric morphometrics study

Morphological changes of the frontal sinus with age: A two-dimensional geometric morphometric study

BackgroundAge estimation of unidentified human remains is an essential for establishing the biological profile of unidentified human remains. Previous studies have investigated the value linear measurements of the frontal sinus for age estimation while the value of two-dimensional (2D) geometric morphometric measurements have not been explored for this purpose. ObjectiveThis study aims to evaluate the morphological variation of frontal sinus among adults Malaysian for age estimation using 2D geometric morphometric methods. MethodsLateral skull radiographs of 453 adult Malaysians, comprising 151 young adults (20–39 years old), 150 middle-aged adults (40–59 years old) and 152 old adults (60–79 years old), were retrieved retrospectively. Eight 2D landmarks were applied to digitalized radiographs using TPSDig2 software. 2D geometric morphometric analysis was performed by MorphoJ software. ResultsProcrustes ANOVA revealed no significant differences in shape and size (p-value > 0.05) of frontal sinus between the three age groups. However, Canonical Variate Analysis showed significant differences for Mahalanobis and Procrustes distances (p-value < 0.05) between young and old adult groups. Discriminant Function Analysis after cross-validation demonstrated an age classification accuracy of 53.5 %. ConclusionThe study suggests that 2D geometric morphometric analysis of the frontal sinus cannot be reliably used to estimate the age of an unknown Malaysian individual.

Is shape in the eye of the beholder? Assessing landmarking error in geometric morphometric analyses on live fish.

Geometric morphometrics is widely used to quantify morphological variation between biological specimens, but the fundamental influence of operator bias on data reproducibility is rarely considered, particularly in studies using photographs of live animals taken under field conditions. We examined this using four independent operators that applied an identical landmarking scheme to replicate photographs of 291 live Atlantic salmon (Salmo salar L.) from two rivers. Using repeated measures tests, we found significant inter-operator differences in mean body shape, suggesting that the operators introduced a systematic error despite following the same landmarking scheme. No significant differences were detected when the landmarking process was repeated by the same operator on a random subset of photographs. Importantly, in spite of significant operator bias, small but statistically significant morphological differences between fish from the two rivers were found consistently by all operators. Pairwise tests of angles of vectors of shape change showed that these between-river differences in body shape were analogous across operator datasets, suggesting a general reproducibility of findings obtained by geometric morphometric studies. In contrast, merging landmark data when fish from each river are digitised by different operators had a significant impact on downstream analyses, highlighting an intrinsic risk of bias. Overall, we show that, even when significant inter-operator error is introduced during digitisation, following an identical landmarking scheme can identify morphological differences between populations. This study indicates that operators digitising at least a sub-set of all data groups of interest may be an effective way of mitigating inter-operator error and potentially enabling data sharing.

Cranial variation between coastal and offshore bottlenose dolphins, Tursiops truncatus (Cetacea: Delphinidae) in Ecuador and the Mediterranean: a three-dimensional geometric morphometric study

Abstract Skull shape analysis provides useful information on wildlife ecology and potential local adaptations. Common bottlenose dolphins (Tursiops truncatus) often differentiate between coastal and offshore populations worldwide, and skull shape analyses can be particularly useful in this context. Here we quantify skull shape variation between coastal populations from the Gulf of Guayaquil (Ecuador) and the Mediterranean Sea, compared to offshore specimens from multiple oceans. We analysed skull shape differences using 3D models from museum specimens through geometric morphometrics (3DGM). Two complementary landmark approaches included single-point semi-landmarks in homologous features, as well as pseudo-landmarks placed automatically. Results show skull shape distinction between both coastal populations and offshore specimens. Offshore specimens showed little differentiation between distinct locations. Skull shape patterns mostly diverged in the shape and length of rostrum, as well as the shape of the ascending processes of the maxilla, pterygoids, and occipital bones. However, both coastal populations differed in the patterns and direction of change of those features and were also morphologically distinct. Our results are consistent with local data on site fidelity and social structure in the coastal populations. Skull shape changes suggest divergent feeding and sound production patterns are potential drivers, probably specific to the local environment of each community.

Covariance patterns between ramus morphology and the rest of the face: A geometric morphometric study

The growth and development of the mandible strongly depend on modeling changes occurring at its ramus. Here, we investigated covariance patterns between the morphology of the ramus and the rest of the face. Lateral cephalograms of 159 adults (55 males and 104 females) with no history of orthodontic treatment were collected. Geometric morphometrics with sliding semi-landmarks was used. The covariance between the ramus and face was investigated using a two-block partial least squares analysis (PLS). Sexual dimorphism and allometry were also assessed. Differences in the divergence of the face and anteroposterior relationship of the jaws accounted for 24.1% and 21.6% of shape variation in the sample, respectively. Shape variation was greater in the sagittal plane for males than for females (30.7% vs. 17.4%), whereas variation in the vertical plane was similar for both sexes (23.7% for males and 25.4% for females). Size-related allometric differences between the sexes accounted for the shape variation to a maximum of 6% regarding the face. Regarding the covariation between the shapes of the ramus and the rest of the face, wider and shorter rami were associated with a decreased lower anterior facial height as well as a prognathic mandible and maxilla (PLS 1, 45.5% of the covariance). Additionally, a more posteriorly inclined ramus in the lower region was correlated with a Class II pattern and flat mandibular plane. The width, height, and inclination of the ramus were correlated with facial shape changes in the vertical and sagittal planes.

Three-dimensional geometric morphometric study of the Xuchang 2 cranium

Results of traditional metric and nonmetric assessments suggest that the Xuchang hominin shares features with Neanderthals. To comprehensively compare the nuchal morphology of XC 2 to those of the genus Homo, we conduct a three-dimensional geometric morphometric study with 35 cranial landmarks and surface semilandmarks of XC 2, Homo erectus, Middle Pleistocene humans, Neanderthals, and early and recent modern humans. Results reveal that the centroid size of XC 2 is larger than that of early and recent modern humans and can only be compared to that of Middle Pleistocene humans and H. erectus. Early and recent modern humans share a nuchal morphology distinct from archaic hominins (Ngandong H. erectus, Middle Pleistocene humans, and Neanderthals), except for SM 3, Sangiran 17, and Asian and African H. erectus. Although Ngandong specimens differ from the other H. erectus, it is unclear whether this represents a temporal or spatial trend in the process of evolution of this species. The nuchal morphological resemblance between Middle Pleistocene humans and Neanderthals may be attributed to similar cranial architecture and cerebellar shape. The great nuchal morphological variation shared by recent modern humans may indicate a particular developmental pattern. In conclusion, the nuchal morphology of different human groups is highly variable and may be caused by different factors including brain globularization and developmental plasticity. XC 2 shares similar nuchal morphology with Middle Pleistocene humans and Neanderthals, but these results are insufficient to fully resolve the taxonomic status of XC 2.

Palatal shape covariation in extraction versus nonextraction borderline patients: A geometric morphometric study

This study aimed to evaluate changes in palatal shape after orthodontic treatment from a borderline sample of extraction and nonextraction patients with a Class I relationship. A borderline sample regarding premolar extractions was obtained through discriminant analysis and comprised 30 nonextraction and 23 extraction patients. The digital dental casts of these patients were digitized with 3 curves and 239 landmarks placed on the hard palate. Procrustes superimposition and principal component analysis were implemented to assess group shape variability patterns. The success of the discriminant analysis in identifying a borderline sample regarding the extraction modality was validated using geometric morphometrics. Concerning palatal shape, no sexual dimorphism was found (P= 0.78). The first 6 principal components that were statistically significant accounted for 79.2% of the total shape variance. Palatal changes were 61% more pronounced in the extraction group, which exhibited a decrease in palatal length (P= 0.02; 10,000 permutations). In contrast, the nonextraction group showed an increase in the palatal width (P<0.001; 10,000 permutations). Intergroup comparisons indicated that the nonextraction group exhibited longer palates, whereas the extraction group exhibited higher palates (P= 0.02; 10,000 permutations). Considerable changes in palatal shape were seen for the nonextraction and extraction treatment group, with the latter exhibiting more pronounced changes, mainly in terms of palatal length. Further investigations are needed to clarify the clinical significance of the palatal shape changes in borderline patients after extraction and nonextraction treatment.

Identifying intentional flake production at the dawn of technology: A technological and 3D geometric morphometric study

The production of sharp-edged stone flakes is often viewed as a unique adaptation specific to the hominin lineage. The discovery of large stone cores and flakes dated to 3.3 Ma has shown that the earliest evidence of hominin stone flake production differs from the later Oldowan (dated to 2.6 Ma) record. Recent discoveries have shown that capuchin monkeys (Sapajus libidinosus) can unintentionally produce sharp-edged flake assemblages as a by-product of percussive behaviour. Capuchin monkeys are the only wild primate to intentionally strike two stones together (stone-on-stone percussion) to produce quartz powder. In doing so, they unintentionally produce high frequencies of sharp-edged flakes. It has been suggested that these possess the same technological attributes commonly used to describe intentional hominin stone flakes. Here we directly compare the basic morphometric descriptions, technological and 3D morphometric properties of unintentional capuchin flakes with experimentally produced flakes derived from two intentional flaking techniques employed during the Plio-Pleistocene, freehand and passive hammer knapping and a sample of Oldowan freehand flakes from Olduvai Gorge (Tanzania). Our results show that unintentional stone-on-stone flakes overlap in terms of their shape, size and technological attributes with those produced through intentional knapping techniques. We, however, identify attributes that may be critical for differentiating between intentional knapping techniques documented in the early archaeological record and unintentional flakes. Using these data we show that Oldowan flakes more closely resemble intentional freehand techniques.

Geometric Morphometric Investigation of Incus in Horse (Equus ferus caballus) and Donkey (Equus Asinus)

In this study, it was aimed to determine the shape of the incus in horse and donkey by geometric morphometric method and to evaluate the shape differences between horse’s and donkey’s incus. The left incus bone of 5 adult horses and 5 donkeys were used in the study. Incus were photographed at same lateral direction. Thirteen homologous landmarks were marked from the photographs using TpsUtil (Version 1.79) and TpsDig2 (Version 2.31) software. As a result of the study, the first principal component explained 38,642% of the total shape variation. In the PC1 plot, samples were clearly clustered by group. Acording to canonical varians analysis, in the wire frame warp graphic, the corpus incudis edges (right, left, and bottom) were flatter in donkeys. Angle at the LM13 level was more pronounced on the crus breve. The apex of the crus longum (Landmark 4, 5, and 6) was wider in donkey. In the study, the morphological features of horse’s and donkey’s incus were determined by geometric morphometric method. This study is important in that it is the first geometric morphometric study on the incus that is one of the ossicula auditus in horse and donkey. We think that the study will contribute to the anatomy of the ossicula auditus in the equide family.

“Tip of the Tongue”: Experimental Reconstruction of Handaxes at the Baise Basin (South China) and Implications for Lithic Standardization

ABSTRACT Geometric morphometric studies in the Baise Basin in South China have documented unique tongue-like tip morphologies in handaxes sampled from the fourth terrace of the Youjiang River Valley. With this study, we report on a new handaxe assemblage found at the Natang site and present data that further document the prevalence of these rounded tip morphologies in the region. We use experimental replications to recreate the unique morphology of the handaxes, and demonstrate that a specific tip rounding strategy was employed by hominins as an economic and effective way to produce wider, more rounded and thinner distal tips. We suggest that these tongue-like tips indicate a predetermined design, and consequently, reflect a level of shape standardization that is heightened in functional tool portions. Moreover, this study provides further documentation of the regionally unique tool-making preferences that Pleistocene hominins employed when flexibly adapting to local environmental conditions and resource availabilities.

A Geometric Morphometric Study on Sexual Dimorphism in Viscerocranium.

Simple SummarySex estimation is a crucial step in the identification of unknown bone remains. The accuracy of sex estimation methods depends on the level of sexual dimorphism manifested by the human bones. Therefore, the evaluation of sex differences of particular bones of the skeleton is an important preceding stage. We have used geometric morphometric techniques to investigate the sexual dimorphism in the size and shape of the facial part of the skull and its subregions. Our results show that the facial skeleton in males and females differs more in size than in shape, so its overall size is a more useful sex indicator than its shape. The same result is observed for all facial subregions studied here. However, the best discrimination between the male and female skulls is achieved when both size and shape are considered together.The level of sexual dimorphism manifested by human bones is an important factor for development of effective sex estimation methods. The aim of the study was to investigate the sexual dimorphism in the size and shape of the viscerocranium using geometric morphometric techniques. It also aimed to explore the sex differences in distinct viscerocranial regions and to establish the most dimorphic region with regard to size and shape. Computed tomography images of 156 males and 184 females were used in the study. Three-dimensional coordinates of 31 landmarks were acquired. Five landmark configurations were constructed from the viscerocranium and its orbital, nasal, maxillary, and zygomatic region. Generalized Procrustes superimposition, principal component analysis, and discriminant analysis were applied to each configuration. The significance of the sex differences in size and shape was assessed and significant differences were found in all configurations. The highest accuracy was obtained from both shape and size of the whole viscerocranium. Based on size only, the highest accuracy was achieved by the nasal region. The accuracy based on shape was generally low for all configurations, but the highest result was attained by the orbital region. Hence, size is a better sex discriminator than shape.

Geometric morphometric study of anterior branches of external carotid artery and carotid bifurcation by 3D-CT angiography.

The aim of our study was to determine the variations of the anterior branches of the external carotid artery (ECA) and investigate the morphometric and geometric features of the anterior branches of the ECA and carotid bifurcation (CB). A total of 563 ECAs were included from 288 patients in the study. Classification and exit angles of anterior branches of ECA and determination of vertebral levels of CB and anterior branches were performed. The anterior branch variants of the ECA were observed in 8 different subgroups. The most common variations were type Ia 42.3% (n = 120) on the right and type Ib 40.9% (n = 114) on the left. When looking at the vertebral levels, CB was detected at C4 level in 32.9% of total ECAs (n = 185), STA was at C4 level in 33.4% of total ECAs (n = 188), LA was at C3 level in 50.1% of total ECAs (n = 282), and FA was at C2 level in 37.3% of total ECAs. The mean CB angle in all cases was 59.93° ± 16.04. In the anterior branches of the ECA in cases belonging to the Type I group, the widest angle belonged to FA (R = 116.88 ± 27.04°, L = 110.32° ± 25.94). In conclusion, a new classification of the variations of the anterior branches of the ECA was made on the basis of the CTA images to gain more practicality in surgical procedures. This study revealed for the first time the angular and level relationship between CB and ECA anterior branches.

Effect of Diet Consistency on Rat Mandibular Growth: A Geometric Morphometric and Linear Cephalometric Study.

Simple SummaryCraniofacial growth is affected by different environmental factors. One of these factors that seems to affect mandibulofacial growth is mastication. Diet consistency leads to different masticatory forces during mastication. Various researchers looked over the effect of diet consistency on craniofacial growth and more specifically on the mandible. The question of how diet consistency affects mandibular growth is still controversial since various studies had different results on that aspect. The results of this study support that there is a major effect of diet consistency on mandibular morphology. Thus, it contributes to a better understanding of evolution of mandibular growth.Background: Our study intended to investigate the null hypothesis that there is no effect of diet consistency on rat mandibular growth. Methods: A total sample of 24 female wistar rats, 30 days old, was used in this study. In the first group, the rats were fed soft diet and in the second group, they were fed hard diet for 60 days. On the 60th day, the rats were sedated and lateral cephalometric X-rays were taken. Lateral cephalometric X-rays were digitized with 7 craniofacial landmarks for the linear measurements, as well as with 12 curves and 90 landmarks, of which 74 were semilandmarks and 16 were fixed landmarks for morphometric analysis. These landmarks were exposed to Procrustes superimposition and Principal Component Analysis (PCA) to describe the shape variability of the mandible. Results: Means measurements of the soft diet group compared to those of the hard diet group were significantly different in linear and morphometric analysis measurements. The soft diet group of wistar rats revealed significant changes on the condyle (smaller), the angle of the mandible, and on the body of the mandible. Conclusions: Diet consistency affects the craniofacial growth of rats. Soft diet could be responsible for less mandibular growth.

Cranial morphology in metopism: A comparative geometric morphometric study

BackgroundCranial sutures are active bone growth sites and any alteration in their normal formation, patency and closure influences the overall cranial morphology. This comparative study aims to establish whether the cranial shape and size are significantly modified when metopic suture persists into adulthood using geometric morphometric analyses. MethodsThe sample consisted of 63 metopic and 184 non-metopic dry adult male crania. Three-dimensional polygonal models of the crania were generated using a hand-held laser scanner Creaform VIUscan. A total of 50 landmarks were digitized on the three-dimensional models and eight landmark configurations delineating the cranium and its compartments were constructed and analyzed. Geometric morphometric analyses were applied to investigate separately the size and shape differences between the metopic and non-metopic series in each of the landmark configurations. ResultsSignificant size differences were established solely in the neurocranium, but not in its total size, rather in its parts. The size modification was expressed by an enlargement of the anterior part of the neurocranium at the expense of the middle and posterior ones. All investigated landmark sets differed significantly between the series regarding the shape. In metopic series, the shape alteration was mainly in a mediolateral widening and an anteroposterior shortening contributing to a more rounded overall shape of the cranium. ConclusionsThe slight modification of the cranial morphology in metopism suggests that the metopic suture persistence is not an isolated variation limited to the frontal bone. It is rather a complex condition associated with a combination of specific phenotypic characteristics.

Immature instars of three species of Rhodnius St\xe5l, 1859 (Hemiptera, Reduviidae, Triatominae): morphology, morphometry, and taxonomic implications

BackgroundAmong the 18 genera of the Triatominae subfamily, three stand out for their diversity and epidemiological importance: Triatoma, Panstrongylus, and Rhodnius. Rhodnius includes 21 species that can transmit Trypanosoma cruzi (the etiological agent of Chagas disease, also known as American trypanosomiasis) and Trypanosoma rangeli. The Rhodnius prolixus complex comprises seven species, including Rhodnius marabaensis, Rhodnius prolixus, and Rhodnius robustus, which occur in the northern region of Brazil. Since both adults and immatures can carry T. cruzi, in this study the five nymphal instars of the three species mentioned were dorsally characterized.MethodsUsing microscopy, morphometrics, and geometric morphometrics, the present work measures and describes the morphological characters of the five nymphal instars of R. marabaensis, R. prolixus, and R. robustus.ResultsThe study enabled the characterization of all five nymphal instars, as well as the distinction between the three species in each of their instars.ConclusionsThe morphological, morphometrics of the head, thorax, and abdomen and geometric morphometrics studies of the head enabled the specific distinction of these three species in all five instars.Graphical

Size and shape variations in wing morphology of Anopheles maculipennis s.s. Meigen, 1818 (Diptera: Culicidae) from northeastern Turkey

Anopheles maculipennis Meigen, 1818 (Diptera: Culicidae) complex was discovered as the first sibling species complex among mosquito species and identified as a highly important malaria vector in the Middle East and Europe. Anopheles maculipennis s.s. is the nominotypical member species of the complex, and widely spread across the whole of Europe. Body size and shape are the most important characters of organisms and is related to numerous variables. Biological size and shape may be affected by altitude and altitudinal differences. In this study, the variation in wing size and shape of An. maculipennis s.s. populations collected from four sampling stations in Iğdır Province (Mürşitali, Sürmeli, Yukarıçıyrıklı and Zülfikarköy) and two sampling stations in Kars Province (Kötek and Kozlu) at different altitudes and in different habitats from northeastern Turkey in 2019 were investigated. It was assumed that altitude and the environmental differences related with altitude may affect the wing (body) size or shape of An. maculipennis s.s. This is the first comparative geometric morphometric study of An. maculipennis s.s. populations in Turkey and the results indicate size and shape differences among some populations. While centroid size did not show a linear association with altitude, samples from the highest altitude population had larger wings than the other populations.