Differences In Overall Shape Research Articles

Detecting Phylogenetic Signal and Adaptation in Papionin Cranial Shape by Decomposing Variation at Different Spatial Scales.

Phylogenetic reconstruction based on morphometric data is hampered by homoplasies. For example, many similarities in cranial form between primate taxa more strongly reflect ecological similarities rather than phylogenetic relatedness. However, the way in which the different cranial bones constitute cranial form is, if at all, of less functional relevance and thus largely hidden from selection. We propose that these “constructional details” are better indicators of phylogenetic history than any large-scale shape feature or raw form variable. Within a geometric morphometric context, we show how to analyze the relative extent of bones independently of differences in overall shape. We also show how to decompose total shape variation into small-scale and large-scale shape variation. We apply both methods to the midsagittal cranial morphology of papionin monkeys, which are well known for the discrepancy between morphological similarities and phylogenetic relationships. We study phylogenetic signal and functional adaptation using a molecular phylogeny and contextual data on feeding ecology and locomotor behavior. As expected, total cranial shape, bone outline shape, and large-scale shape features were only weakly associated with phylogenetic distance. But the relative bone contributions and small-scale shape features were both highly correlated with phylogenetic distances. By contrast, the association with ecological and behavioral variables was strongest for the outline shape and large-scale shape features. Studies of morphological adaptation and phylogenetic history thus profit from a decomposition of shape variation into different spatial scales. [Adaptation; canalization; cranial shape; geometric morphometrics; papionini; partial warps; phylogeny.]

A Trilobite Cluster from the Silurian Rochester Shale of New York: Predation Patterns and Possible Defensive Behavior

Evidence of predator-prey interactions in the fossil record offers important insights into extinct ecosystems. As direct predator-prey relationships are rarely preserved, records of failed predation upon prey species are often considered. The biomineralized exoskeleton of trilobites is exemplary for recording injuries that have resulted from predation. Despite the extensive documentation of trilobite injuries, abnormal specimens are often documented in isolation, with examples of injuries among clustered individuals being poorly known. Here we document a well-preserved body cluster of 18 individuals of the large lichid trilobite Arctinurus boltoni from the mid-Silurian (Wenlock) Rochester Shale of New York, with eight specimens showing injuries. Landmark geometric morphometrics of the specimens is used to explore possible patterns between injured and noninjured specimens. Results of the morphometric analysis indicate that injured and noninjured specimens do not show any systematic difference in overall shape of the exoskeleton, but many of the larger specimens have injuries. The majority of injuries are posteriorly located and right-side dominant, highlighting the possibility of predator or prey lateralization. Biostratinomic evidence suggests that the cluster represents a biological aggregation that was rapidly buried in situ. Potential reasons for this gregarious behavior are discussed, including the possibility that individuals of A. boltoni grouped together to provide “safety in numbers” against predatory attack.

Maternal environment and craniofacial growth: geometric morphometric analysis of mandibular shape changes with in utero thyroxine overexposure in mice.

An estimated 3% of US pregnancies are affected by maternal thyroid dysfunction, with between one and three of every 1000 pregnancies being complicated by overactive maternal thyroid levels. Excess thyroid hormones are linked to neurological impairment and excessive craniofacial variation, affecting both endochondral and intramembranous bone. Using a geometric morphometric approach, this study evaluates the role of in utero thyroxine overexposure on the growth of offspring mandibles in a sample of 241 mice. Canonical variate analysis utilized 16 unilateral mandibular landmarks obtained from 3D micro-computed tomography to assess shape changes between unexposed controls (n = 63) and exposed mice (n = 178). By evaluating shape changes in the mandible among three age groups (15, 20 and 25 days postnatal) and different dosage levels (low, medium and high), this study found that excess maternal thyroxine alters offspring mandibular shape in both age- and dosage-dependent manners. Group differences in overall shape were significant (P < 0.001), and showed major changes in regions of the mandible associated with muscle attachment (coronoid process, gonial angle) and regions of growth largely governed by articulation with the cranial base (condyle) and occlusion (alveolus). These results compliment recent studies demonstrating that maternal thyroxine levels can alter thecranial base and cranial vault of offspring, contributing to a better understanding of both normal and abnormal mandibular development, as well as the medical implications of craniofacial growth and development.

Identification of five Pampus species from the coast of China based on sagittal otolith morphology analysis

Sagittal otoliths morphology were compared to identify five Pampus species of the Chinese coast (Chinese pomfret Pampus chinensis, grey pomfret P. cinereus, southern lesser pomfret P. minor, plumage pomfret P. punctatissmus, and Pampus sp.). Otoliths demonstrated species-specific characteristics with noticeable differences in overall shape, margin and anterior region among species. With species divergence, otoliths get thinner following further developed rostrum and anti-rostrum. Interspecies variation in otolith could associate with experienced different temperature and water column. The discriminant analysis presented a high classification accuracy of 96.6%, which confirms the inter-specific distinction of otolith shape and enable the species identification.

Cranial Morphology of the Brachystelechid 'Microsaur' Quasicaecilia texana Carroll Provides New Insights into the Diversity and Evolution of Braincase Morphology in Recumbirostran 'Microsaurs'.

Recumbirostran ‘microsaurs,’ a group of early tetrapods from the Late Carboniferous and Early Permian, are the earliest known example of adaptation to head-first burrowing in the tetrapod fossil record. However, understanding of the diversity of fossorial adaptation within the Recumbirostra has been hindered by poor anatomical knowledge of the more divergent forms within the group. Here we report the results of μCT study of Quasicaecilia texana, a poorly-known recumbirostran with a unique, broad, shovel-like snout. The organization of the skull roof and braincase of Quasicaecilia is found to be more in line with that of other recumbirostrans than previously described, despite differences in overall shape. The braincase is found to be broadly comparable to Carrolla craddocki, with a large presphenoid that encompasses much of the interorbital septum and the columella ethmoidalis, and a single compound ossification encompassing the sphenoid, otic, and occipital regions. The recumbirostran braincase conserves general structure and topology of braincase regions and cranial nerve foramina, but it is highly variable in the number of ossifications and their extent, likely associated with the reliance on braincase ossifications to resist compression during sediment compaction and mechanical manipulation by epaxial and hypaxial musculature. Expansion of the deep ventral neck musculature in Quasicaecilia, autapomorphic among recumbirostrans, may reflect unique biomechanical function, and underscores the importance of future attention to the role of the cervical musculature in contextualizing the origin and evolution of fossoriality in recumbirostrans.

Forewing Shape Variability Between Sexes and Across Populations of the Rice Bug, Leptocorisa varicornis Fabricius (1803) Using Geometric Morphometrics

Leptocorisa varicornis (F.) (1803) rice bug is a serious pest of rice. Misidentification of this pest had led to non-effective management strategies resulting to possible emergence of insecticide resistance. Proper identification of this species is necessary in developing effective management strategies against this pest, and correct identification needs accurate examination of the insect’s morphology. Geometric morphometrics (GM) statistically analyzes shape variability allowing better understanding of the nature and variability of the insect in relation to the evolvability of characters and its possible implications to adaptability of the organism. This study made use of GM to determine forewing shape variability between sexes and across populations of L. varicornis (F.) from selected localities in Northern Mindanao, Philippines. Exploratory results initially showed that variations between sexes were generally characterized by differences in overall shape of forewing, apex and wing base. Variations across populations were associated largely with differences in overall forewing shape, contour of inner margin, and shape of wing base. Series of confirmatory tests obtained highly significant results, which all confirmed presence of intersexual and interpopulation variations in L. varicornis. Environmental stressors like seasonal cropping, flood and application of pesticides might influence differences in forewings of rice bugs since rice bugs have to fly to long distance after cropping or change location when existing habitat conditions are no longer suitable for their survival. Thorough understanding of the biological basis of the observed variations is essential for the effective control against this species.  Keywords: environmental stressors, insect, insect’s morphology, intersexual variations, pest. Â

Descriptions of five new species in the genus Metriaclima (Teleostei: Cichlidae) from Lake Malaŵi, Africa

Five new species of rock-dwelling cichlids from Lake Malaŵi are described. All five species phenotypically resemble Metriaclima aurora based on the absence of a black band in the dorsal fin and occupying the rock-sand interface of the lake. Differences in overall shape, meristics, and coloration distinguish these new species from each other and from previously described species within this group. The new species Metriaclima glaucos, M. mossambicus, M. nkhunguensis, and M. xanthos originate from the Mozambique coast of the lake, while M. sciasma is restricted to Tanzanian waters.

Comparative Morphometrics and Associated Growth Trends of Two Benthophagous Cichlid Species from Lake Malawi (Pisces, Perciformes)

Body shape differences between two benthophagous, sympatric cichlid species, Ctenopharynx pictus and Otopharynx sp. “heterodon nankhumba” were examined for 14 morphometric characters using measurements obtained from 11 morphological landmarks and additional 6 characters from the head region using principal component and regression analyses. The two species, though not closely related, superficially resemble each other and, being benthic feeders, directly compete for food resources unless morphological differences lead to trophic specialization. Hence, the present study explores the presence of such morphological variations. Principal component analysis (PCA), revealed that only four characters loaded highly on PC II and, therefore, account for most of the variations in the external morphology between the two species. C. pictus has longer lower jaws reflecting longer gape, and a shorter abdominal cavity than O. sp. “heterodon nakhumba”. The regression analyses showed significant differences in the allometric coefficients of the lower jaw and abdominal cavity, which might have contributed to differences in overall shape detected between the two species. The difference in gape size between the two species may be related to different feeding habits employed by each species, and such specializations are suggested to reduce interspecific competition for food resources. We suggest that the ensuing ecological separation promotes sympatry of these two species.

Structural requirements for the modulatory effect of 6-substituted pterins on interleukin 2 receptor binding

(6 R)-5,6,7,8-Tetrahydrobiopterin is produced by stimulated human T lymphocytes, and is known to affect various aspects of interleukin-2-directed T cell proliferation. Using an increased apparent affinity of interleukin 2 receptor to interleukin 2 as a measure of activity, this study explores whether other 6-substituted pterins might have the same effect, and what structural features are necessary for activity. Of the compounds tested, only the T-lymphocyte-derived (6 R)-5,6,7,8-tetrahydrobiopterin was active. The diastereomeric (6S)-5,6,7,8-tetrahydrobiopterin was inactive, as were 7,8-dihydrobiopterin, sepiapterin, 5,6,7,8-tetrahydroneopterin, 6,7-dimethyl-5,6,7,8-tetrahydropterin and 6-hydroxymethylpterin. 7,8-Dihydroneopterin and neopterin were also found to be inactive. It follows that neither of these compounds participates in the feedback modulation of IL-2 receptor affinity, although both of them can be detected upon IFN-γ stimulation of human monocytes/macrophages. A computer-based molecular modelling study of (6 R)-5,6,7,8-tetrahydrobiopterin and (6 R)-5,6,7,8-tetrahydroneopterin revealed substantial differences in overall shape between the two molecules, with certain features figuring prominently in the low-energy conformers of (6 R)-5,6,7,8-tetrahydrobiopterin.

Reference-Rotated Eigenshape Analysis of Sands and Sandstones: ABSTRACT

Sedimentary particles with minor differences in overall shape are selectively sorted according to shape during transport. Krumbein in 1942 demonstrated a difference in fall velocity for disks and rollers, and Nagle in 1967 showed that right and left pelecypod valves transported by the same longshore current ended up at different locations along a beach. Selective shape sorting of sand-size particles occurs at various rates and in distinct patterns during different modes of transport, but the subtle shape differences are hard to recognize by conventional techniques. Visual comparison methods for and have such low accuracy and reproducibility as to be virtually meaningless. Also, two particles can have equal sphericity and roundness and yet be o different overall shape. The Corey shape factor (widely used by civil engineers) with its various modifications is inadequate for subtle shape variations. In two-dimensional projection, simple symmetrical shapes (i.e., ellipse) are fully defined by two measurements: length of major and minor axes. Less symmetrical shapes (i.e., oval or kidney bean) need more than two measurements. Griffiths in 1967 stated that n measurements are needed for an irregular shape (where n is not known in advance). Eigenshape analysis is a method of reducing a large number of measurements (i.e., 36 radial lengths at equal angular increments) to the minimum number of linear combinations needed to portray a significant proportion (80 to 90%) of observed shape variation. Reference-rotation is needed for sand grains in order to compare the wide variety of shapes that occur; when comparing only similar objects, reference-rotation may not be necessary. Unlike Fourier shape analysis, which as currently used involves only small-scale irregularities, Eigenshape analysis is a new approach to quantifying larger scale shape characteristics. Laboratory experiments designed to simulate shape-sorting effects of sediment transport (slow versus fast fall velocity in a sedimentation tube; inner versus outer ring in a gold prospecting pan) separated quartz sand samples composed of grains of the same sieve size into two subsamples. These showed recognizably different assemblages of shape types by Reference-Rotated Eigenshape Analysis. Similar Eigenshape distinctions were observed when the same size fraction of two sands with different Eigenshape signatures were mixed in 2:1 ratio and then separated by selective shape sorting as above. Eigenshape analysis achieved similar results with thin-section input data. Artificial rocks were made with the above sands by lithifying with epoxy resin. Thin sections were made perpendicular and parallel to bedding and at other orientations. Eigenshape analysis was performed on the grains as seen in section (not maximum projection). Results from bedding-parallel sections most closely resemble results from loose-grain mounts. Inferences about provenance, transport mode, transport distance, mixing from different sources and/or different transport histories, and depositional environments are made from Eigenshape analysis results. The intrinsic R-mode factor analysis approach helps untangle these intermixed effects. End_of_Article - Last_Page 529------------

Morphometrics of Romanomermis culicivorax Ross and Smith, 1976 (Nematoda: Mermithidae)

Intraspecific variability and the influence of environmental factors on the morphometrics of Romanomermis culicivorax Ross and Smith, 1976 were determined by rearing the progeny of a single mating pair under different parasite intensities, host species, and temperatures. Individual measurements were frequently affected by environment and discriminant analysis revealed differences in overall shape between sibling populations. These effects were not constant within or between sexes. The growth relationships between measurements were examined and because of allometry a number of ratios commonly used in mermithid taxonomy at the species level were rejected. This led to an evaluation of morphometrics in species diagnosis.

Scanning electron microscopy of Haller's organ in immature stages of (Say) and olenev (acari: ixodida)

Abstract Haller's organ, a chemoreceptor and hygrosensor located dorsally on tarsi l of the Ixodida was viewed in immature stages of Dermacentor variabilis (say) and Ornithodoros tartakovskyi Olenev by scanning electron microscopy (SEM). Larval and nymphal specimens of D. variabilis (Figs. 1, 2) exhibited characteristics differences in overall shape of organ, shape of posterior capsule aperture, shape of anterior trough, number and arrangement of trough sensillae, and shape of the distal transverse wall of the anterior trough. Differences between larvae and late instar nymphs of O. tartakovskyi (Figs. 3, 4) were primarily in trough shape and numbers of sensillae present. Subsurface articulations within the posterior capsule of both Dermacentor ticks were obscured due to the emarginate apertures (Fig. 2). The open apertures found in both stages of Ornithodoros allowed the viewing of numerous digitate processes within the capsule (Fig. 4). A nodiform sensillum (Figs. 3, 4), medially located within the proximal cluster of trough sensillae in O. tartakovskyi , had no similar counterpart in D. variabilis .