Variation In External Morphology Research Articles

Morphological and Genetic Variations of the Freshwater Leech, Hirudinaria spp., in Peninsular Malaysia

In this study the genetic diversity of local freshwater leeches (Hirudinaria spp.) was inferred using mtDNA COI gene analysis and compared with the gross external variations of 26 freshwater leech specimens obtained from the wild and leech farms. Based on a neighbor-joining tree generated from 516 COI base sequences, four distinct clades of Hirudinaria were seen with interspecific genetic divergence in the range of 7.6-14.5%. The external morphological variations based on the presence of stripes, location of gonopores, and anus separated the samples into four morphologically distinct groups matching the four clades obtained from the molecular data. Two black stripes at the ventral region were observed only in specimens found clustered with clades that contained the GenBank-reported H. manillensis, whereas the brown or dark green coloration without stripes on the ventral region was seen in samples that clustered with H. javanica and H. bpling clades.

The Radix Entomolaris : Non-surgical Approach in Endodontics

Mandibular molars often have an additional root located lingually (the radix entomolaris) or buccally (the radix paramolaris). If present, an awareness and understanding of this unusual root and its root canal morphology can contribute to the successful outcome of root canal treatment. This report discusses endodontic treatment of a mandibular molar with a radix entomolaris, which is a rare macrostructure. The prevalence, the external morphological variations and internal anatomy of the radix entomolaris are described. Avoiding procedural errors during endodontic therapy demand an adapted clinical approach to diagnosis and successful non-surgical endodontic treatment. DOI: http://dx.doi.org/10.3329/updcj.v3i1.17986 Update Dent. Coll. j: 2013; 3 (1): 49-53

Micro-finite element (μFE) modeling of the siamang (Symphalangus syndactylus) third proximal phalanx: The functional role of curvature and the flexor sheath ridge

Phalangeal curvature is a commonly used morphological feature for the interpretation of extant and fossil primate locomotor behaviour. Here, we build on a recent biomechanical study (Richmond, 2007) in two ways: first, we use a 3D micro-FE model, which models the real internal microstructure (i.e., cortical thickness and trabecular bone structure) and, second, we model four siamang third proximal phalanges. We test identical 2D homogenized FE models and two 3D micro-FE phalanx models that are mathematically straightened to isolate the biomechanical significance of curvature. We further investigate how varying the loading configuration (e.g., boundary constraints) and modeling (e.g., 2D versus 3D) affects the biomechanical behaviour of the phalanx. Finally, we examine how intraspecific variation in external and internal bony morphology affects the biomechanical behaviour of the phalanx.Simulation results demonstrate that the general pattern of strain and displacement is similar between the 3D micro-FE and 2D homogenized FE models but the absolute values differ substantially. The biomechanical behaviour of the 3D FE models more closely match the relative strain patterns from the validation experiment than the 2D homogenized FE models, indicating the 3D microstructure model is preferable. Varying the loading configuration can have dramatic effects on the biomechanical behaviour of the phalanx depending on individual morphology, but overall a cantilevered beam model is an equally valid, if not better, configuration for modeling the phalanx as other previously-proposed models. Variation in flexor ridge morphology has a substantial effect on phalanx strain; the taller the ridge, the less strain incurred by other regions of the palmar shaft. Finally, phalangeal curvature reduces overall strain experienced by the phalanx, but does not necessarily reduce bending or increase the compression-to-tension ratio. These results confirm the adaptive role of phalangeal curvature during flexed-finger grasping postures and demonstrate that modeling variation in cortical thickness and flexor ridge morphology improves the behaviour of the FE model, which has important implications for the functional interpretation of phalanx form.

The radix entomolaris: a rare entity in endodontics

Mandibular molars can have an additional root located lingually (the radix entomolaris) or buccally (the radix paramolaris). If present, an awareness and understanding of this unusual root and its root canal morphology can contribute to the successful outcome of root canal treatment. This report discusses endodontic treatment of one Mandibular molar with a radix entomolaris or paramolaris, both of which are rare macrostructures in the Caucasian population. The prevalence, the external morphological variations and internal anatomy of the radix entomolaris and paramolaris are described. Avoiding procedural errors during endodontic therapy demand an adapted clinical approach to diagnosis and root canal treatment.

한국산 황기의 분류학적 위치 및 유전적 분화

To clarify the taxonomic position for Astragalus nakaianus and provide correct scientific name for A. mongholicus cultivar in South Korea, we examined external morphological characters and sequence variations from ITS and five cp non-coding DNA regions. Genetic structure was also analyzed for 61 individuals from three populations using nine microsatellite loci. We found no significant difference between the South Korean cultivar and A. mongholicus var. dahuricus when morphology and ITS sequences were considered. Morphologically, A. nakaianus specimens varied somewhat from A. mongholicus var. mongholicus and var. dahuricus in habit, plant height, and lengths of leaf axis and leaflet. Although sequence data from ITS and cp noncoding DNA regions could not distinguished A. nakaianus from A. mongholicus, microsatellite analysis revealed strong structuring between the cultivar and A. nakaianus. Therefore, we conclude that the South Korean A. mongholicus cultivar should be treated as A. mongholicus var. dahuricus and that A. nakaianus should be merged into A. mongholicus as a variety, i.e., A. mongholicus var. nakaianus.

A cadaveric study involving variations in external morphology of gall bladder

Background : Variations in the pattern of the extra hepatic biliary tract are usual and are commonly encountered during some radiological investigations or in operation theaters. Such Variations of the morphology of Gall bladder have been well documented in the literature for many years but a detail morphological study of variations of the gall bladder and its incidence is very rare. In this era of quick results, increasing use of diagnostic and interventional procedures makes it important to study variations of gall bladder morphology. Most of the interventional procedures in this modern era are done laparoscopically and there is tremendous increase in the number of laparoscopic cholecystectomies. So, sound knowledge of possible variations in morphology of gall bladder is important. Materials and Methods : This study was undertaken on 90 cadaveric liver and gall bladder specimens in terms of length, maximum transverse diameter, shape, external variations of gall bladder, Interior and length of gall bladder below the inferior border of the liver. Results: GB had length ranging between 7 and 10 cm, transverse diameter between 2 and 5 cm. The commonest shape observed in this study was pear shaped in 82.22% of cases. The length of gall bladder below the inferior border of liver varied between 0.4 and 2.5 cm. Conclusion: The growing importance of such variations, lie not only from the point of biliary disease but also with respect to the various invasive techniques in the diagnosis and treatment of gall bladder and extrahepatic bile duct disease.

The reliability of morphometric discriminant functions in determining the sex of Chilean flamingos Phoenicopterus chilensis

Abstract Monomorphic birds cannot be sexed visually and discriminant functions on the basis of external morphological variations are frequently used. Our objective was to evaluate the reliability of sex classification functions created from structural measurements of Chilean flamingos Phoenicopterus chilensis museum skins for the gender assignment of live birds. Five measurements were used to develop four discriminant functions: culmen, bill height and width, tarsus length and middle toe claw. The functions were tested on a sample of live flamingos from a zoo. The best classification for museum flamingos was given by a function using tarsus length, bill width and middle toe claw (97%). However, this function did not give the best classification for the zoo-based flamingos (81%) which had the best sex assignment by a function including measurements of tarsus, culmen and bill height and width (85%). This shows that a function giving good results in the sample from which it originated may not be as good when applied to another group of animals. Our study emphasizes the need for assessing the accuracy of a function by testing it with other methods to ensure its suitability when being applied.

Mitochondrial DNA variation in Tibetan macaque (Macaca thibetana)

Tibetan macaques (Macaca thibetana) are a threatened primate species endemic to China. The current taxonomy of the species is based on external morphological and anatomical variations. To further understand the intraspecific variation and relationships among populations, we analyzed 44 mitochondrial DNA control region sequences (475 bp fragment) from individuals across the species range. Results revealed 11 major haplotypes with a high nucleotide diversity (0.792), but nucleotide diversity within haplotype lineages was only 0.042. Neighbor-joining phylogenetic analyses indicated support for four distinct haplotype clades corresponding to regional groups consistent with the recognized subspecies M .t. thibetana, M. t. guizhonensis, M. t. huangshanensis and M. t. pullus. As a result of regional geographic variation and genetic differences, we recommend the four subspecies should be considered different management units for conservation efforts.

The Radix Entomolaris – An Endodontic Challenge : Case Reports

Mandibular molars can have an additional root located lingually (the radix entomolaris) or buccally (the radix paramolaris). If present, an awareness and understanding of this unusual root and its root canal morphology can contribute to the successful outcome of root canal treatment. This report discusses endodontic treatment of three mandibular molars with a radix entomolaris. The prevalence, the external morphological variations and internal anatomy of the radix entomolaris and paramolaris are described.

Endodontic Management Of Radix Entomolaris - Two Case Reports

A mandibular first molar with two distal roots is an interesting example of anatomic variation. This paper describes 2 case reports of mandibular first molar with three roots (one mesial and two distal) and four canals (two in mesial and one in each distobuccal and distolingual root). The canals were shaped with protaper rotary files and irrigated with 2.5% sodium hyochlorite and 0.2%w/v of chlorhexidine gluconate and normal saline as the final irrigant. The prevalence, the external morphological variations and internal anatomy of the radix entomolaris and paramolaris are described.

Clinicalmanagement Of Radix Entomolaris And Radix Paramolaris In Endodontics- Case Reports

Treatment of mandibular molars have always kept the endodontist sharp and alert as it is one of the teeth that show variations in its external and internal morphology to the extreme. This reaches its epitome in the presence of an additional root located lingually (the radix entomolaris) or buccally (the radix paramolaris). When present an awareness and understanding of this unusual root and its root canal morphology contributes to the successful outcome of root canal treatment. This report discusses endodontic treatment of two mandibular molars with a radix entomolaris or paramolaris. The prevalence, the external morphological variations and internal anatomy of the radix entomolaris and paramolaris are described.

Phylogeography of the Australian sugar glider (Petaurus breviceps): evidence for a new divergent lineage in eastern Australia

The sugar glider (Petaurus breviceps) shows considerable variation in external morphology and mitochondrial DNA (mtDNA) diversity across its distribution in New Guinea and Australia. Here we investigate the phylogeography of P. breviceps in Australia using data from two mitochondrial genes (ND2 and ND4) and a nuclear gene (ω-globin). Phylogenetic analyses revealed the existence of two divergent mtDNA clades that are distributed over distinct geographical regions, one from coastal New South Wales and south-eastern Queensland and a second over the remaining distributional range of the species in Australia. The two groups generally had distinct ω-globin haplotypes that differed by one or two mutational steps. Analyses of Molecular Variation further supported the presence of at least two populations, accounting for 84.8% of the total mtDNA variation and 44% of the ω-globin variation. The general concordance of phylogeographic and population analyses suggests that population subdivision, possibly resulting from the combined influences of aridification after the Pliocene and uplift of the Great Dividing Range has impacted the evolution of P. breviceps. Our results also show that the geographical distribution of the two evolutionary lineages does not correspond with the distribution of the current morphological subspecies and we further propose that they be considered as separate Evolutionarily Significant Units for the purposes of conservation management.

A revision of the Oligodon taeniatus (Günther, 1861) group (Squamata: Colubridae) , with the description of three new species from the Indochinese Region

The group of Asian colubrid species morphologically similar to Oligodon taeniatus (Günther, 1861), previously containing only O. taeniatus, Oligodon mouhoti (Günther, 1864) and Oligodon barroni (Smith, 1916), is revised on the basis of variation in external morphology and dentition of 175 specimens. The confused nomenclatural history of O. taeniatus and its name bearing type is discussed. A neotype is described for Simotes quadrilineatus Jan & Sordelli, 1865, a synonym of O. taeniatus. The holotype of Simotes taeniatus var. mouhoti Boulenger, 1914 is identified. Three new species within this group are described. Oligodon pseudotaeniatus spec. nov. is described on the basis of specimens from central Thailand. This species is morphologically similar to Oligodon taeniatus, but differs by the combination of 17 dorsal scale rows at midbody, 8 supralabials, the absence of dark dorsal and tail blotches and the presence of a vertebral stripe edged with black but no dorsolateral stripes. Oligodon deuvei spec. nov. is described on the basis of specimens from southern Vietnam and Laos; it differs from other known species of the group by the combination of 12–15 maxillary teeth, 17 dorsal scale rows at midbody, usually seven supralabials, the absence of dark dorsal and tail blotches and the presence of a broad vertebral stripe, often conspicuously orange or rusty red. This species is most similar to Oligodon barroni but differs from the latter by a higher number of maxillary teeth and the absence of dark dorsal and tail blotches. Lastly, Oligodon moricei spec. nov. is described on the basis of a single specimen from southern Vietnam. It differs from other species by the combination of a broad rusty brown vertebral stripe edged with two broad black stripes, 12 maxillary teeth, 17 dorsal scale rows, a high number of ventral scales, seven supralabials and a dark cloudy or smoky venter. These new species are compared with other species known from the Indo-Chinese Region. The diagnoses of O. taeniatus, O. mouhoti and O. barroni are revised. A key to members of the group is given.

Morphological and genetic structuring in the Utah Lake sucker complex

Population decline in the federally endangered June sucker (Chasmistes liorus), a lakesucker unique to Utah Lake, Utah, has been attributed in part to hybridization with the more widespread Utah sucker (Catostomus ardens). As a group, suckers in Utah Lake exhibit considerable external morphological variation. Meristic and morphological ambiguities, presumably the result of hybridization, create a continuum of intermediate forms between Chasmistes and Catostomus extremes and prevent definitive identification to species. Here we describe and evaluate the morphological and genetic variation in suckers in Utah Lake by comparing a morphological analysis with amplified fragment length polymorphism and microsatellite analyses. Suckers were morphologically differentiated using mouth characters associated with different feeding strategies: planktivory (June sucker) and benthivory (Utah sucker). Although we found no genetic evidence for a deep divergence between June and Utah morphs, significant, but slight population structuring accompanied the substantial morphological variation. Bayesian model-based genetic clustering analyses detected two sucker populations in Utah Lake; however, these clusters were not strongly concordant with morphological groupings or between marker systems. The suckers in Utah Lake present an interesting dilemma regarding conservation: should one conserve (breed and stock) a subset of the morphotypic variation in the Utah Lake sucker complex, focusing on the endangered June sucker morphotype, or should one conserve both June sucker and Utah sucker morphotypes in this complex, possibly maximizing evolutionary potential? We explore this question in the context of current genetic and morphological variation in the Utah Lake sucker complex as well as historical information on this complex and other lakesuckers.

Genetic diversity of Nymphon (Arthropoda: Pycnogonida: Nymphonidae) along the Antarctic Peninsula with a focus on Nymphon australe Hodgson 1902

Sea spiders are conspicuous, and often abundant, members of the Antarctic benthic community. Nymphonidae (Pycnogonida) in Southern Ocean waters comprise over 240 species which are often difficult to assign due to their intraspecific ‘highly variable’ morphology. In particular, Nymphon australe, the numerically dominant species in Antarctic waters is known to have a high level of phenotypic variation in external morphology and is also reported to have a circumpolar distribution. Circumpolarity seems contradictory to the pycnogonid’s brooding lifestyle and presumably limited dispersal. Here we examine the genetic diversity of several Nymphon species collected in the Antarctic Peninsular region. Concomitantly, we assess the genetic structure of N. australe to gain insight into Nymphon dispersal capacity. Cytochrome c oxidase subunit I (COI) and 16S ribosomal gene data suggest a recent common history and/or recent gene-flow of N. australe populations across nearly 800 km of the Antarctic Peninsula. Furthermore, these data support that the Antarctic Peninsula region may hold two previously unrecognized species of Nymphon.

Morphometric variation associated with teat-number differences in Antechinus agilis and A. swainsonii ? Observations from the Otway Ranges, Victoria

That there is intraspecific variation in teat-number in Antechinus agilis (agile antechinus) and A. swainsonii (dusky antechinus) has been known for a long time. Our aim was to determine whether other key morphometric traits differed among individuals with different numbers of teats. External body dimensions and pelage characteristics were measured on live individuals and compared. Within-species variation in some external body dimensions (tail, pes, and snout-vent length) coincided with teat-number differentiation in both antechinus species in the Otway Ranges, Victoria. Disparities in pelage colour and markings were apparent between A. agilis 6- and 10-teat phenotypes, but were not obvious among A. swainsonii teat phenotypes. Although small sample sizes obviated statistical analysis, we tentatively concluded that female A. agilis with 7, 8, or 9 teats in the Otway Ranges probably displayed morphometric and pelage characteristics intermediate between those of 6- and 10-teat individuals. A comparison of morphometric traits among 6-teat A. agilis from different geographic areas (Otways, Portland and Wilsons Promontory) also revealed some variation. This result was consistent with an expectation of clinal variation in external morphology among antechinus. Overall, this study indicates that localized disparities that are associated with teat-number, as well as clinal differences occurring over large geographic distances, contribute to intraspecific variation in external morphology in antechinus.

Nuclear DNA from old collections of avian study skins reveals the evolutionary history of the Old World suboscines (Aves, Passeriformes)

Museum study skins represent an invaluable source of DNA for phylogenetics, phylogeography and population genetics. This becomes evident by comparing the number of study skins of birds housed in museums worldwide (c. 10 million) with the corresponding number of tissue samples (probably fewer than 500 000). While the laboratory techniques used hitherto have primarily allowed PCR‐based studies of mitochondrial genes from museum skins, we present here the first avian phylogeny based on a large number of nuclear sequences. The targeted fragment sizes and the properties of the primers used are important contributory factors to obtain good amplification results. In this study we routinely amplified fragments of c. 350 bp nuclear DNA. This advance in methodology opens up a new avenue for the use of avian museum skins, as nuclear DNA is especially useful when studying ancient patterns of diversification. The phylogenetic hypothesis of the Old World suboscines (Eurylaimides) presented herein strongly supports a monophyletic origin of the pittas (Pittidae). The phylogeny further suggests that pittas could be divided into three major groups, in agreement with the external morphological variation found in this group. The broadbills (Eurylaimidae) as currently defined are, on the other hand, found to be a paraphyletic family, as both Sapayoa aenigma and the asities (Philepittidae) are nested among them. Based on the phylogenetic results we suggest a revised classification of the Old World suboscines (Eurylaimides).

The Radix Entomolaris and Paramolaris: Clinical Approach in Endodontics

Mandibular molars can have an additional root located lingually (the radix entomolaris) or buccally (the radix paramolaris). If present, an awareness and understanding of this unusual root and its root canal morphology can contribute to the successful outcome of root canal treatment. This report discusses endodontic treatment of three mandibular molars with a radix entomolaris or paramolaris, both of which are rare macrostructures in the Caucasian population. The prevalence, the external morphological variations and internal anatomy of the radix entomolaris and paramolaris are described. Avoiding procedural errors during endodontic therapy demand an adapted clinical approach to diagnosis and root canal treatment.

The effect of endurance exercise on the morphology of muscle attachment sites

The morphology of muscle attachment sites, or entheses, has long been assumed to directly reflect in vivo muscle activity. The purpose of this study is to examine whether variations in muscle activity that are within normal physiological limits are reflected in variations in external attachment site morphology. This study tests the hypothesis that increased muscle activity (magnitude, number and frequency of loading cycles) results in the hypertrophy of muscle attachment sites. The attachment sites of six limb muscles and one muscle of mastication (control) in mature female sheep were measured and compared in exercised (weighted treadmill running for 1 h per day for 90 days) and sedentary control animals. Attachment site surface morphology was assessed by quantifying the size (3D surface area) and complexity (fractal dimension parallel and perpendicular to soft tissue attachment) of the surfaces. The results of this study demonstrate no effect of the exercise treatment used in this experiment on any measure of enthesis morphology. Potential explanations for the lack of exercise response include the mature age of the animals, inappropriate stimulus type for inducing morphological change, or failure to surpass a hypothetical threshold of load for inducing morphological change. However, further tests also demonstrate no relationship between muscle size and either attachment site size or complexity in sedentary control animals. The results of this study indicate that the attachment site morphological parameters measured in this study do not reflect muscle size or activity. In spite of decades of assumption otherwise, there appears to be no direct causal relationship between muscle size or activity and attachment site morphology, and reconstructions of behavior based on these features should be viewed with caution.

Ecotypic differentiation of native rainbow trout (Oncorhynchus mykiss) populations from British Columbia

We sampled 34 native rainbow trout (Oncorhynchus mykiss) populations over a wide geographic area of British Columbia to determine whether variation in morphology is related to differences in habitat or fish community characteristics experienced by a population. After correcting for differences in body size, the most dramatic differences occurred in external characteristics between stream- and lake-dwelling populations. Rainbow trout from streams had more robust bodies with larger caudal peduncles and heads and longer paired fins than rainbow trout from lakes. Unlike other lake populations, piscivorous rainbow trout populations had relatively large heads and mouths that were more similar in size to those of stream-dwelling populations. We found fewer differences in the size of internal organs across ecotypes, producing little predictive ability of these characteristics to differentiate populations of rainbow trout. We also sampled 27 additional rainbow trout populations with unknown fish communities to determine how well large-scale patterns predict morphological differentiation over a smaller spatial scale. Of the five ecotypes that we detected at a smaller scale, the largest differences again occurred between stream and lake populations. Our data suggest that external morphological variation among populations of rainbow trout covaries with ecological conditions at a variety of spatial scales, particularly between lakes and rivers.