scholarly journals Comparative cranial biomechanics in two lizard species: impact of variation in cranial design

2021 ◽  
pp. jeb.234831
Author(s):  
Hugo Dutel ◽  
Flora Gröning ◽  
Alana C. Sharp ◽  
Peter J. Watson ◽  
Anthony Herrel ◽  
...  
Keyword(s):  
Cranial Bone ◽  
Cranial Morphology ◽  
Bone Strain ◽  
Lizard Species ◽  
Simulation Techniques ◽  
Lower Strain ◽  
Structural Resistance ◽  
Computer Based ◽  
Morphological Differences ◽  
Species Specific

Cranial morphology in lepidosaurs is highly disparate and characterized by the frequent loss or reduction of bony elements. In varanids and geckos, the loss of the postorbital bar is associated with changes in skull shape, but the mechanical principles underlying this variation remain poorly understood. Here, we seek to determine how the overall cranial architecture and the presence of the postorbital bar relate to the loading and deformation of the cranial bones during biting in lepidosaurs. Using computer-based simulation techniques, we compare cranial biomechanics in the varanid Varanus niloticus and the teiid Salvator merianae, two large, active foragers. The overall strain magnitudes and distribution across the cranium is similar in both species, despite lower strain gradients in Varanus niloticus. In Salvator merianae, the postorbital bar is important for the resistance of the cranium to feeding loads. The postorbital ligament, which partially replaces the postorbital bar in varanids, does not affect bone strain. Our results suggest that the reduction of the postorbital bar impaired neither biting performance nor the structural resistance of the cranium to feeding loads in Varanus niloticus. Differences in bone strain between the two species might reflect demands imposed by feeding and non-feeding functions on cranial shape. Beyond variation in cranial bone strain related to species-specific morphological differences, our results reveal that similar mechanical behaviour is shared by lizards with distinct cranial shapes. Contrary to mammals, the morphology of the circumorbital region, calvaria and palate appears to be important for withstanding high feeding loads in these lizards.

scholarly journals Sound signatures and production mechanisms of three species of pipefishes (Family: Syngnathidae)

PeerJ ◽  
2015 ◽  
Vol 3 ◽  
pp. e1471 ◽  
Author(s):  
Adam Chee Ooi Lim ◽  
Ving Ching Chong ◽  
Chiow San Wong ◽  
Sithi Vinayakam Muniandy
Keyword(s):  
Variable Structure ◽  
Acoustic Signals ◽  
Cranial Bone ◽  
Cranial Morphology ◽  
Acoustic Signatures ◽  
Fish Feeds ◽  
Double Staining Method ◽  
Species Specific ◽  
Cranial Kinesis ◽  
Production Mechanisms

Background.Syngnathid fishes produce three kinds of sounds, named click, growl and purr. These sounds are generated by different mechanisms to give a consistent signal pattern or signature which is believed to play a role in intraspecific and interspecific communication. Commonly known sounds are produced when the fish feeds (click, purr) or is under duress (growl). While there are more acoustic studies on seahorses, pipefishes have not received much attention. Here we document the differences in feeding click signals between three species of pipefishes and relate them to cranial morphology and kinesis, or the sound-producing mechanism.Methods.The feeding clicks of two species of freshwater pipefishes,Doryichthys martensiiandDoryichthys deokhathoidesand one species of estuarine pipefish,Syngnathoides biaculeatus, were recorded by a hydrophone in acoustic dampened tanks. The acoustic signals were analysed using time-scale distribution (or scalogram) based on wavelet transform. A detailed time-varying analysis of the spectral contents of the localized acoustic signal was obtained by jointly interpreting the oscillogram, scalogram and power spectrum. The heads of bothDoryichthysspecies were prepared for microtomographical scans which were analysed using a 3D imaging software. Additionally, the cranial bones of all three species were examined using a clearing and double-staining method for histological studies.Results.The sound characteristics of the feeding click of the pipefish is species-specific, appearing to be dependent on three bones: the supraoccipital, 1st postcranial plate and 2nd postcranial plate. The sounds are generated when the head of theDorichthyespipefishes flexes backward during the feeding strike, as the supraoccipital slides backwards, striking and pushing the 1st postcranial plate against (and striking) the 2nd postcranial plate. In theSyngnathoidespipefish, in the absence of the 1st postcranial plate, the supraoccipital rubs against the 2nd postcranial plate twice as it is pulled backward and released on the return. Cranial morphology and kinesis produce acoustic signals consistent with the bone strikes that produce sharp energy spikes (discrete or merged), or stridulations between bones that produce repeated or multimodal sinusoidal waveforms.Discussion.The variable structure of the sound-producing mechanism explains the unique acoustic signatures of the three species of pipefish. The differences in cranial bone morphology, cranial kinesis and acoustic signatures among pipefishes (and seahorses) could be attributed to independent evolution within the Syngnathidae, which warrants further investigation.

scholarly journals Comparative skull biomechanics in Varanus and Salvator ‘Tupinambis’

2017 ◽  
Author(s):  
Hugo Dutel ◽  
Alana C Sharp ◽  
Marc E H Jones ◽  
Susan E Evans ◽  
Micheal J Fagan ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Feeding Behaviour ◽  
Micro Computed Tomography ◽  
Lizard Species ◽  
Element Analysis ◽  
Joint Reaction Forces ◽  
Reaction Forces ◽  
Computer Based ◽  
Morphological Differences

The lizard species Salvator ‘Tupinambis’ merianae and Varanus ornatus evolved independently in South America and Africa but share similar ecology and feeding behaviour, despite having notable differences in their skull structure. Tupinambis has a compact, relatively short and wide snout, whereas that of Varanus is more slender and narrow. In addition, a postorbital bar (POB) is present in Tupinambis but absent in Varanus, and the former lacks the mid-frontal suture that is present in the latter. Here, we explore the biomechanical significance of these differences using 3D computer-based mechanical simulations based on micro-computed tomography, detailed muscle dissections, and in vivo data. First, we simulated muscle activity and joint-reaction forces during biting using Multibody Dynamics Analysis. Then, the forces calculated from these models were used as an input for Finite Element Analysis, to investigate and compare the strains of the skull in these two species. The effects of the presence/absence of structures, such as the POB, were investigated by constructing artificial models which geometry was altered. Our results indicate that strains in the skull bones are lower in Tupinambis than in Varanus, in particular at the back of the skull. The presence of a POB clearly reduces the strains in the bones during posterior biting in Tupinambis, but not in Varanus. Our results hence highlight how the morphological differences between these two taxa affect the mechanical behaviour of their respective skulls during feeding.

scholarly journals Comparative skull biomechanics in Varanus and Salvator ‘Tupinambis’

2017 ◽  
Author(s):  
Hugo Dutel ◽  
Alana C Sharp ◽  
Marc E H Jones ◽  
Susan E Evans ◽  
Micheal J Fagan ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Feeding Behaviour ◽  
Micro Computed Tomography ◽  
Lizard Species ◽  
Element Analysis ◽  
Joint Reaction Forces ◽  
Reaction Forces ◽  
Computer Based ◽  
Morphological Differences

The lizard species Salvator ‘Tupinambis’ merianae and Varanus ornatus evolved independently in South America and Africa but share similar ecology and feeding behaviour, despite having notable differences in their skull structure. Tupinambis has a compact, relatively short and wide snout, whereas that of Varanus is more slender and narrow. In addition, a postorbital bar (POB) is present in Tupinambis but absent in Varanus, and the former lacks the mid-frontal suture that is present in the latter. Here, we explore the biomechanical significance of these differences using 3D computer-based mechanical simulations based on micro-computed tomography, detailed muscle dissections, and in vivo data. First, we simulated muscle activity and joint-reaction forces during biting using Multibody Dynamics Analysis. Then, the forces calculated from these models were used as an input for Finite Element Analysis, to investigate and compare the strains of the skull in these two species. The effects of the presence/absence of structures, such as the POB, were investigated by constructing artificial models which geometry was altered. Our results indicate that strains in the skull bones are lower in Tupinambis than in Varanus, in particular at the back of the skull. The presence of a POB clearly reduces the strains in the bones during posterior biting in Tupinambis, but not in Varanus. Our results hence highlight how the morphological differences between these two taxa affect the mechanical behaviour of their respective skulls during feeding.

scholarly journals A Comprehensive Review of Cholinesterase Modeling and Simulation

Biomolecules ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 580
Author(s):  
Danna De Boer ◽  
Nguyet Nguyen ◽  
Jia Mao ◽  
Jessica Moore ◽  
Eric J. Sorin
Keyword(s):  
Modeling And Simulation ◽  
Binding Site ◽  
Catalytic Efficiency ◽  
Site Location ◽  
Simulation Techniques ◽  
Therapeutic Value ◽  
Docking Calculations ◽  
Computer Based ◽  
Dynamics Simulations ◽  
And Function

The present article reviews published efforts to study acetylcholinesterase and butyrylcholinesterase structure and function using computer-based modeling and simulation techniques. Structures and models of both enzymes from various organisms, including rays, mice, and humans, are discussed to highlight key structural similarities in the active site gorges of the two enzymes, such as flexibility, binding site location, and function, as well as differences, such as gorge volume and binding site residue composition. Catalytic studies are also described, with an emphasis on the mechanism of acetylcholine hydrolysis by each enzyme and novel mutants that increase catalytic efficiency. The inhibitory activities of myriad compounds have been computationally assessed, primarily through Monte Carlo-based docking calculations and molecular dynamics simulations. Pharmaceutical compounds examined herein include FDA-approved therapeutics and their derivatives, as well as several other prescription drug derivatives. Cholinesterase interactions with both narcotics and organophosphate compounds are discussed, with the latter focusing primarily on molecular recognition studies of potential therapeutic value and on improving our understanding of the reactivation of cholinesterases that are bound to toxins. This review also explores the inhibitory properties of several other organic and biological moieties, as well as advancements in virtual screening methodologies with respect to these enzymes.

scholarly journals Resurrection of the Butterfly-winged Comber, Serranus papilionaceus Valenciennes, 1832 (Teleostei, Serranidae) and its phylogenetic position within genus Serranus

ZooKeys ◽  
2021 ◽  
Vol 1017 ◽  
pp. 111-126
Author(s):  
Adriana Vella ◽  
Noel Vella ◽  
Carolina Acosta-Díaz
Keyword(s):  
Conservation Status ◽  
Valid Species ◽  
Phylogenetic Position ◽  
Mitochondrial Coi ◽  
Interspecific Divergence ◽  
Population Conservation ◽  
Status Assessment ◽  
Morphological Differences ◽  
Species Specific ◽  
High Level

The family Serranidae is represented by 92 genera and 579 valid species, with the genus Serranus Cuvier, 1816, containing 30 species. In this study, specimens of Butterfly-winged Comber, Serranus papilionaceus Valenciennes, 1832, were collected from the Canary Islands and compared morphologically and genetically to Painted Comber, Serranus scriba (Linnaeus, 1758), from the Mediterranean Sea. Morphological differences, especially in the colour banding pattern, were corroborated by genetic differences in mitochondrial (COI and ND2) and nuclear (Rhod and PTR) markers. The mitochondrial DNA markers revealed a high level of divergence and no shared haplotypes between the two species (interspecific divergence: COI 4.31%; ND2 8.68%), and a phylogenetic analysis showed that these two species are closely related sister species sharing common ancestry. This study is therefore offering to resurrect S. papilionaceus Valenciennes, 1832 as a valid species increasing the number of eastern Atlantic Serranus species to 11. This should direct new species-specific research, including its population conservation status assessment across its distribution.

scholarly journals The first Miocene fossils of Lacerta cf.trilineata(Squamata, Lacertidae) with a comparative study of the main cranial osteological differences in green lizards and their relatives

2019 ◽  
Author(s):  
Andrej Čerňanský ◽  
Elena V. Syromyatnikova
Keyword(s):  
Comparative Study ◽  
Late Miocene ◽  
Fossil Record ◽  
Calibration Point ◽  
Lizard Species ◽  
Podarcis Muralis ◽  
Modern Species ◽  
Zootoca Vivipara ◽  
Morphological Differences ◽  
Important Evidence

AbstractWe here describe the first fossil remains of a green lizardof theLacertagroup from the late Miocene (MN 13) of the Solnechnodolsk locality in southern European Russia. This region of Europe is crucial for our understanding of the paleobiogeography and evolution of these middle-sized lizards. Although this clade has a broad geographical distribution across the continent today, its presence in the fossil record has only rarely been reported. In contrast to that, the material described here is abundant, consists of a premaxilla, maxillae, frontals, parietals, jugals, quadrate, pterygoids, dentaries and vertebrae. The comparison of these elements to all extant green lizard species shows that these fossils are indistinguishable fromLacerta trilineata. Thus, they form the first potential evidence of the occurrence of this species in the Miocene. This may be also used as a potential calibration point for further studies. Together with other lizard fossils, Solnechnodolsk shows an interesting combination of survivors and the dawn of modern species. This locality provides important evidence for the transition of an archaic Miocene world to the modern diversity of lizards in Europe. In addition, this article represents a contribution to the knowledge of the comparative osteological anatomy of the selected cranial elements in lacertid. This study gives special emphasis to the green lizards, but new data are also presented for related taxa, e.g.,Timon lepidus, Podarcis muralisorZootoca vivipara. Although the green lizards include several cryptic species for which determination based on isolated osteological material would be expected to be difficult, our comparisons show several important morphological differences.

scholarly journals Unrestricted gene flow between two subspecies of translocated brushtail possums (Trichosurus vulpecula) in Aotearoa New Zealand

2021 ◽  
Author(s):  
Nimeshika Pattabiraman ◽  
Mary Morgan-Richards ◽  
Ralph Powlesland ◽  
Steven A. Trewick
Keyword(s):  
New Zealand ◽  
Trichosurus Vulpecula ◽  
Mitochondrial Dna Control Region ◽  
Aotearoa New Zealand ◽  
Nuclear Microsatellite ◽  
Morphological Differences ◽  
Mating Unit ◽  
Species Specific ◽  
Phenotypic Forms ◽  
Major Haplogroups

AbstractTwo lineages of brushtail possums (Trichosurus vulpecula) were historically introduced to Aotearoa New Zealand, and these two subspecies have different phenotypic forms. Despite over 100 years of potential interbreeding, they appear to retain morphological differences, which may indicate reproductive isolation. We examined this using population samples from a confined landscape and scored each specimen for phenotype using a number of fur colour traits. This resulted in a bimodal trait distribution expected for segregated grey and black lineages. We also sought evidence for genetic partitioning based on spatial and temporal effects. Genetic structure and rates of genetic mixing were determined using seven neutral, species-specific nuclear microsatellite markers and mitochondrial DNA control region sequence. Genotype analyses indicated high levels of variation and mtDNA sequences formed two major haplogroups. Pairwise tests for population differentiation of these markers found no evidence of subdivision, indicating that these brushtail possums behave as a single randomly mating unit. Despite maintenance of two main colour phenotypes with relatively few intermediates, previous inference of assortative mating and anecdotes of distinct races, our data indicate that New Zealand brushtail possums can freely interbreed, and that in some locations they have formed completely mixed populations where neutral genetic markers are unrelated to phenotype. This has implications for effective pest management towards eradication.

scholarly journals Lizard community structure across a grassland – creosote bush ecotone in the Chihuahuan Desert

2003 ◽  
Vol 81 (11) ◽  
pp. 1829-1838 ◽  
Author(s):  
Sean B Menke
Keyword(s):  
Chihuahuan Desert ◽  
Function Analysis ◽  
Larrea Tridentata ◽  
Desert Grassland ◽  
Creosote Bush ◽  
Lizard Species ◽  
Common Lizard ◽  
Risk Of Predation ◽  
Increased Risk ◽  
Species Specific

I investigated the distribution and abundance of lizard species (Aspidoscelis inornatus, Aspidoscelis tesselatus, Aspidoscelis tigris, Aspidoscelis uniparens, Cophosaurus texanus, Crotaphytus collaris, Eumeces obsoletus, Gambelia wislizenii, Holbrookia maculata, Phrynosoma cornutum, Sceloporus magister, and Uta stansburiana) across a desert grassland – creosote bush (Larrea tridentata) ecotone in Dona Ana County, New Mexico. The ecotonal area in the Jornada del Muerto basin has increased dramatically in the past 150 years because of the rapid spread of creosote bush. I asked four related questions: how large and where is the ecotone based on vegetative structure, and do lizard abundance and diversity change across the ecotone? Vegetation data were analyzed using discriminate function analysis to determine the extent of the ecotone. Changes in lizard abundance across the ecotone were analyzed by analysis of variance. During two summers, 677 individual lizards of 9 genera and 12 species were captured. Lizard abundance increased with increasing distance from the ecotone and was similar in grassland and creosote bush habitat. Grasslands had higher species richness than both the creosote bush and ecotone habitats. Grassland sites had greater habitat heterogeneity than did creosote bush sites. No ecotone specialist species were detected, and all common lizard species could be found in each habitat. Three potential explanations for decreased abundance in the ecotone are presented: (1) increased risk of predation, (2) decreased prey abundance, and (3) lack of species-specific microhabitat requisites.

scholarly journals Sintopy of two Tropidurus lizard species (Squamata: Tropiduridae) in a rocky Cerrado habitat in Central Brazil

2004 ◽  
Vol 64 (4) ◽  
pp. 775-786 ◽  
Author(s):  
R. G. Faria ◽  
A. F. B. Araujo
Keyword(s):  
Sympatric Species ◽  
Microhabitat Use ◽  
Lizard Species ◽  
Cerrado Vegetation ◽  
Central Brazil ◽  
Heterogeneous Landscapes ◽  
Interspecific Territoriality ◽  
Morphological Differences ◽  
Rocky Habitats ◽  
Ecological Differences

We studied the ecology of Tropidurus itambere and T. oreadicus that occur syntopically in rocky habitats of Cerrado vegetation in central Brazil during the dry season (April to September 2000). The two species are ecologically similar, but somewhat differentiated in vertical microhabitat use. The two species preferred rocky surface microhabitat. Both species demonstrated a unimodal activity pattern, with a peak between 10 and 15 h. Their diets were similar in composition and prey size. The most frequent item used by both species was ants, whereas the most important preys volumetrically were termites and ants. Small morphological differences observed between the two Tropidurus species could explain minor microhabitat divergence: T. itambere is slightly smaller, heavier, and more robust, and uses lower perches. T. oreadicus is larger, lankier, with longer extremities (tail, fore- and hindlegs), and uses a larger vertical microhabitat range. These ecological differences are slight, when compared with those observed between sympatric species of Tropidurus in spatially more heterogeneous landscapes. Considering the slight ecomorphological divergence between the two Tropidurus species and their high abundance in outcrops, we suggest that interspecific territoriality is the mechanism of coexistence.

Characterization of Waterhemp (Amaranthus tuberculatus) × Smooth Pigweed (A. hybridus) F1Hybrids

2006 ◽  
Vol 20 (1) ◽  
pp. 14-22 ◽  
Author(s):  
Federico Trucco ◽  
Tatiana Tatum ◽  
Kenneth R. Robertson ◽  
A. Lane Rayburn ◽  
Patrick J. Tranel
Keyword(s):  
Dna Content ◽  
Parental Species ◽  
Hybrid Sterility ◽  
Field Surveys ◽  
Amaranthus Tuberculatus ◽  
Cytogenetic Analyses ◽  
Morphological Differences ◽  
Species Specific ◽  
Natural Settings ◽  
Smooth Pigweed

In the state of Illinois, waterhemp and smooth pigweed are among the worst agricultural weeds. Previous research shows high potential for hybridization between these two species. However, the actual occurrence of hybrids in natural settings is still uncertain. Morphological similarity between hybrids and waterhemp makes field surveys of hybrids difficult to conduct. The main purpose of this study was to characterize the morphology of waterhemp × smooth pigweed F1hybrids, emphasizing evaluation of characters that may allow for hybrid discrimination in fieldAmaranthuscommunities. Concurrently, the study characterized hybrid reproductive fitness, chromosome number, and DNA content. To accomplish this, hybrids were obtained from field crosses. A species-specific polymorphism in theALSgene was used to verify hybrid identity. Significant differences (α = 0.05) between hybrids and individuals of the parental species were observed for five staminate and five carpellate characters. Of these, five characters differentiated hybrids from waterhemp. However, clustering analyses using these characters indicated that morphological differences were not reliable enough, by themselves, for unambiguous hybrid identification. Also, hybrid homoploidy (2n= 32) with respect to parental species excluded chromosome counts in hybridity determinations. However, DNA content analysis may be used for such purpose. Hybrids had an average of 1.21 pg of DNA per 2C nucleus, a value intermediate to that of parental species. Hybrids produced 3.3 or 0.7% the seed output of parental and sibling waterhemp individuals, respectively. Percent micropollen in hybrids was 95-times greater than in parental species. Hybrid sterility appears to be the most reliable feature for hybrid discrimination when conducting field surveys. However, molecular and cytogenetic analyses as employed in this study may be desired for ultimate identity corroboration.

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