Mandible Size Research Articles

Morphometric variations at an ecological scale: Seasonal and local variations in feral and commensal house mice

The time scales of evolutionary and ecological studies tend to converge, as shown by evidences that contemporary evolution can occur as fast as ecological processes. This opens new questions regarding variation of characters usually considered to change mostly along an evolutionary time scale, such as morphometric traits, including osteological and dental features such as mandibles and teeth of mammals. Using two-dimensional geometric morphometric approach, we questioned whether such features can change on a seasonal and local basis, in relation to the ecological dynamics of the populations. Our model comprised populations of house mice (Mus musculus domesticus) in two contrasted situations in mainland Western Europe: a feral population vs. two close commensal populations. Mitochondrial DNA (D-loop) provided insight into the diversity and dynamics of the populations.The feral population appeared as genetically highly diversified, suggesting a possible functioning as a sink in relation to the surrounding commensal populations. In contrast, commensal populations were highly homogeneous from a genetic point of view, suggesting each population to be isolated. This triggered morphological differentiation between neighboring farms. Seasonal differences in morphometric traits (mandible size and shape and molar size and shape) were significant in both settings, although seasonal variations were greater in the feral than in the commensal population. Seasonal variations in molar size and shape could be attributed to differential wear in young or overwintered populations. Differences in mandible shape could be related to aging in overwintered animals, but also possibly to differing growth conditions depending on the season. The impact of these ecological processes on morphometric traits is moderate compared to divergence over a large biogeographic scale, but their significance nevertheless underlines that even morphological characters may trace populations dynamics at small scale in time and space.

Sex estimation using computed tomography of the mandible.

Sex estimation of skeletal parts is of great value even in the DNA era. When computed tomography (CT) facilities were introduced to forensic institutes, new possibilities for sex estimation emerged. The aim of this study was to develop a CT-based method for sex estimation using the mandible. Twenty-five CT-based measurements of the mandible were developed and carried out on 3D reconstructions (volume rendering) and cross sections of the lower jaw of 438 adult individuals (214 males and 224 females). Intraobserver and interobserver variances of the measurements were examined using intraclass correlation coefficient (ICC) analysis. Five discriminant functions were developed using different states of completeness of the mandible. The success rates of these equations were cross validated twice. The measurements were found to be highly reliable (for intraobserver 0.838<ICC<0.995 and for interobserver 0.71<ICC<0.996). For a complete mandible, the correct classification rate was 90.8%. For incomplete mandibles, the correct classification rates varied from 72.9 to 85.6%. Cross-validation tests yielded similar success rates, for the complete mandible 89% and for the incomplete mandible 67.5 to 89%. We concluded that CT techniques are appropriate for estimating sex based on the mandible size and shape characteristics. Suggested discriminant functions for sex estimation are given with data on the correct classification rates.

Morph-Specific Weapon-Correlated Traits in a Male Dimorphic Stag Beetle Prosopocoilus inclinatus, (Coleoptera: Lucanidae)

Several male beetles that fight with rival males show dimorphic weapons. Major males have large weapons and fight aggressively with rival males. Minor males have small or no weapons and often adopt an alternative reproductive tactic without fighting. Suitable body shapes are likely to differ depending on the tactic. Thus, the set of body parts that are compatible with distinct weapons may be different in major and minor males according to their battle tactics. Many studies have reported correlations between weapons and some morphological traits, but few studies have shown the difference in the correlation patterns between major and minor males. Here, we show that in a male dimorphic stag beetle, Prosopocoilus inclinatus (Motschlsky), several morph-specific traits are correlated with weapon size. Mandible size correlates positively with eye size in major males only but correlates positively with the length of forelegs and negatively with abdomen weight in minor males only. These results suggest that the correlated trait sets are different between the morphs because each morph adopts different battle tactics and mating strategies.

Aftereffects of muskrat introduction in Western Siberia: Morphological and functional aspects

The muskrat (Ondatra zibethicus L.) allochronic samples at different stages of its introduction in Western Siberia are compared by geometric morphometrics; the comparison demonstrates directed changes in the size and shape of mandible as well as the changes in its morphological and functional characteristics as a feeding organ. As is shown, a rapid initial divergence of the northern (Yamal Peninsula) and southern (Kurgan oblast) muskrat populations, accompanied by emergence of morphological differences between them, is followed by biocenotic adaptation with gradual (over half a century) directed parallel changes in the mandible shape associated with its functional properties in the south and north of the region. The range of morphogenetic transformations of the allochronic samples of the northern group is larger as compared with the southern group, which is explainable by the more severe environmental conditions in the Yamal forest-tundra. Both populations display a statistically significant decrease in the morphological disparity of the mandible shape from the mid-20th century to its end. Leveling of the muskrat mandible size between the northern and southern populations by the end of the last century excludes any allometric effects in the observed geographic and chronographic differences in the mandible shape. Therefore, microevolutionary transformations of the morphogenesis of other invasive species can be implemented on a historical time scale, that is, relatively rapidly. This should be taken into account when forecasting potential local biocenotic crises. The model of the long-term morphogenetic aftereffects of the muskrat introduction in Western Siberia confirms the possibility of rapid adaptive morphogenetic, morphological, and functional changes in invasive mammalian species introduced into new communities.

Geographical variation in mandible morphologies specialised for collembolan predation depend on prey size in the ant Strumigenys lewisi

1. Ants in the genus Strumigenys are predator ants that feed on tiny soil arthropods. The mandibles are modified into high‐speed traps to capture swift collembolan prey. The peculiar mandible morphologies of these ants have evolved depending on characteristics of the prey. Specifically, the evolution of mandible size and shape may be directly driven by prey size.2. In the present study, the intraspecific variation of the morphological traits of Strumigenys lewisi populations were observed in central Japan. The relationships between the morphological variations and the prey body size were analysed.3. In workers and queens, three morphological traits, head width, mandible length, and mandible width were significantly different among the multiple sites. Specifically, the mandible length was shorter in southwestern Japan than in other sampling locations. The ancova model revealed that the allometry of the mandible length to the head width was different among the sites.4. As predicted, the mandible length was positively correlated with the average body size of collembolans in the Entomobryidae family. Furthermore, multiple regression analysis showed that the variation of the mandible length was affected by environmental factors represented as location information. However, the effect of collembolan body size was more effective at predicting mandible length. The study suggests that the geographical variation of mandible morphologies in S. lewisi has been selected by predator–prey interactions with collembolans.

The function of appendage patterning genes in mandible development of the sexually dimorphic stag beetle

One of the defining features of the evolutionary success of insects is the morphological diversification of their appendages, especially mouthparts. Although most insects share a common mouthpart ground plan, there is remarkable diversity in the relative size and shapes of these appendages among different insect lineages. One of the most prominent examples of mouthpart modification can be found in the enlargement of mandibles in stag beetles (Coleoptera, Insecta). In order to understand the proximate mechanisms of mouthpart modification, we investigated the function of appendage-patterning genes in mandibular enlargement during extreme growth of the sexually dimorphic mandibles of the stag beetle Cyclommatus metallifer. Based on knowledge from Drosophila and Tribolium studies, we focused on seven appendage patterning genes (Distal-less (Dll), aristaless (al), dachshund (dac), homothorax (hth), Epidermal growth factor receptor (Egfr), escargot (esg), and Keren (Krn). In order to characterize the developmental function of these genes, we performed functional analyses by using RNA interference (RNAi). Importantly, we found that RNAi knockdown of dac resulted in a significant mandible size reduction in males but not in female mandibles. In addition to reducing the size of mandibles, dac knockdown also resulted in a loss of the serrate teeth structures on the mandibles of males and females. We found that al and hth play a significant role during morphogenesis of the large male-specific inner mandibular tooth. On the other hand, knockdown of the distal selector gene Dll did not affect mandible development, supporting the hypothesis that mandibles likely do not contain the distal-most region of the ancestral appendage and therefore co-option of Dll expression is unlikely to be involved in mandible enlargement in stag beetles. In addition to mandible development, we explored possible roles of these genes in controlling the divergent antennal morphology of Coleoptera.

Histone deacetylases control module-specific phenotypic plasticity in beetle weapons

Nutritional conditions during early development influence the plastic expression of adult phenotypes. Among several body modules of animals, the development of sexually selected exaggerated traits exhibits striking nutrition sensitivity, resulting in positive allometry and hypervariability distinct from other traits. Using de novo RNA sequencing and comprehensive RNA interference (RNAi) for epigenetic modifying factors, we found that histone deacetylases (HDACs) and polycomb group (PcG) proteins preferentially influence the size of mandibles (exaggerated male weapon) and demonstrate nutrition-dependent hypervariability in the broad-horned flour beetle, Gnatocerus cornutus RNAi-mediated HDAC1 knockdown (KD) in G. cornutus larvae caused specific curtailment of mandibles in adults, whereas HDAC3 KD led to hypertrophy. Notably, these KDs conferred opposite effects on wing size, but little effect on the size of the core body and genital modules. PcG RNAi also reduced adult mandible size. These results suggest that the plastic development of exaggerated traits is controlled in a module-specific manner by HDACs.

Diet, bite force and skull morphology in the generalist rodent morphotype.

For many vertebrate species, bite force plays an important functional role. Ecological characteristics of a species' niche, such as diet, are often associated with bite force. Previous evidence suggests a biomechanical trade-off between rodents specialized for gnawing, which feed mainly on seeds, and those specialized for chewing, which feed mainly on green vegetation. We tested the hypothesis that gnawers are stronger biters than chewers. We estimated bite force and measured skull and mandible shape and size in 63 genera of a major rodent radiation (the myomorph sigmodontines). Analysis of the influence of diet on bite force and morphology was made in a comparative framework. We then used phylogenetic path analysis to uncover the most probable causal relationships linking diet and bite force. Both granivores (gnawers) and herbivores (chewers) have a similar high bite force, leading us to reject the initial hypothesis. Path analysis reveals that bite force is more likely influenced by diet than the reverse causality. The absence of a trade-off between herbivores and granivores may be associated with the generalist nature of the myomorph condition seen in sigmodontine rodents. Both gnawing and chewing sigmodontines exhibit similar, intermediate phenotypes, at least compared to extreme gnawers (squirrels) and chewers (chinchillas). Only insectivorous rodents appear to be moving towards a different direction in the shape space, through some notable changes in morphology. In terms of diet, natural selection alters bite force through changes in size and shape, indicating that organisms adjust their bite force in tandem with changes in food items.

Ecogeographical patterns of morphological variation in pygmy shrewsSorex minutus(Soricomorpha: Soricinae) within a phylogeographical and continental-and-island framework

Ecogeographical patterns of morphological variation were studied in the Eurasian pygmy shrew Sorex minutus to understand the species’ morphological diversity in a continental and island setting, and within the context of previous detailed phylogeographic studies. In total, 568 mandibles and 377 skulls of S. minutus from continental and island populations from Europe and Atlantic islands were examined using a geometric morphometrics approach, and the general relationships of mandible and skull size and shape with geographical and environmental variables was studied. Samples were then pooled into predefined geographical groups to evaluate the morphological differences among them using analyses of variance, to contrast the morphological and genetic relationships based on morphological and genetic distances and ancestral state reconstructions, and to assess the correlations of morphological, genetic and geographic distances with Mantel tests. We found significant relationships of mandible size with geographic and environmental variables, fitting the converse Bergmann’s rule; however, for skull size this was less evident. Continental groups of S. minutus could not readily be differentiated from each other by shape. Most island groups of S. minutus were easily discriminated from the continental groups by being larger, indicative of an island effect. Moreover, morphological and genetic distances differed substantially, and again island groups were distinctive morphologically. Morphological and geographical distances were significantly correlated, but not so the morphological and genetic distances indicating that morphological variation does not reflect genetic subdivision in S. minutus. Our analyses showed that environmental variables and insularity had important effects on the morphological differentiation of S. minutus.

Endocrine Control of Exaggerated Trait Growth in Rhinoceros Beetles.

Juvenile hormone (JH) is a key insect growth regulator frequently involved in modulating phenotypically plastic traits such as caste determination in eusocial species, wing polymorphisms in aphids, and mandible size in stag beetles. The jaw morphology of stag beetles is sexually-dimorphic and condition-dependent; males have larger jaws than females and those developing under optimum conditions are larger in overall body size and have disproportionately larger jaws than males raised under poor conditions. We have previously shown that large males have higher JH titers than small males during development, and ectopic application of fenoxycarb (JH analog) to small males can induce mandibular growth similar to that of larger males. What remains unknown is whether JH regulates condition-dependent trait growth in other insects with extreme sexually selected structures. In this study, we tested the hypothesis that JH mediates the condition-dependent expression of the elaborate horns of the Asian rhinoceros beetle, Trypoxylus dichotomus. The sexually dimorphic head horn of this beetle is sensitive to nutritional state during larval development. Like stag beetles, male rhinoceros beetles receiving copious food produce disproportionately large horns for their body size compared with males under restricted diets. We show that JH titers are correlated with body size during the late feeding and early prepupal periods, but this correlation disappears by the late prepupal period, the period of maximum horn growth. While ectopic application of fenoxycarb during the third larval instar significantly delayed pupation, it had no effect on adult horn size relative to body size. Fenoxycarb application to late prepupae also had at most a marginal effect on relative horn size. We discuss our results in context of other endocrine signals of condition-dependent trait exaggeration and suggest that different beetle lineages may have co-opted different physiological signaling mechanisms to achieve heightened nutrient-sensitive weapon growth.

Trophic niche partitioning between two Rock Nuthatches (Sitta tephronota&amp;Sitta neumayer) in a contact zone in Iran

AbstractTwo sympatric nuthatch species,Sitta tephronotaandS. neumayer, provided the exemplar case of character displacement when the term was coined. The two species are quite similar morphologically but have diverged from one another in sympatry, presumably because of competition‐driven selection favoring the partitioning of food resources. However, actual diet partitioning has never been shown. Here, we report the dietary composition of the two species by analyzing items recovered from the gastrointestinal tract. We found thatS. tephronatafed predominantly on Coleopterans, Hemipterans and Orthopterans with the most important seed plants taken beingAmygdalus lycioides, Ficus caricaand Fabaceae, whereas,S. neumayerfed mainly on Coleopterans, Hemipterans and Lepidopteran, withA. lycioides, Fabaceae andTritium aestivumas the most important plants taken. To determine whether the two species partition prey into different sizes, we examined two mostly abundant insect preys (Hemipterans and Coleopterans) and measured head length for Hemipterans and mandible size for Coleopterans as proxies for prey body size. We found a significant relationship between bird body size and prey size, asS. tephronata, which is larger, captured larger bugs and beetles. We also measured the ability of each species to crack seeds of different hardness, finding thatS. tephronatatakes larger and harder seeds thanS. neumayer. Analyses of trophic niche breadth and overlap showed (1) that trophic niche breadth forS. neumayerwas wider than that forS. tephronata;(2) overall trophic niche overlap was considerably high but (3) overlap in the size of the most frequently consumed insects was low, suggesting that the species may be partitioning resources by prey size. We conclude that the relative body size of consumed prey is an important axis of niche partitioning and may have driven character displacement in associated trophic traits, allowing the stable coexistence of the two species.

Harsh climate selects for small body size among Iceland's Arctic foxes

We studied the eff ect of the two environmental indices, the sub-polar gyre (SPG), and winter and summer North Atlantic Oscillation (NAO), together with mean annual winter and summer temperatures and geographic location on mandible size and body mass of Arctic foxes in Iceland (6345 and 2732 specimens, respectively) during the year of their death. We predicted that when favorable conditions prevailed, large specimens would be selected for, and vice versa. Body size and body mass were signifi cantly aff ected by the environmental parameters (i.e. SPG, NAO, ambient temperature and cloud cover) prevailing during the year of death. Th e eff ect of environmental conditions on body size was much stronger in the less productive region of eastern Iceland, apparently because in areas where food availability is meager, even a small diff erence in climate may tilt the balance from food suffi ciency to food shortage. Western Iceland comprises only a quarter of the total surface area of the country, but its productive seashores are twice as long as those of all the rest of the country combined. It is interesting to note that the eff ect of the SPG, a marine phenomenon in the oceans surrounding Iceland, is refl ected in the condition of the foxes more than the other climatic variables we used in this study, which are largely land-related. Because Arctic foxes in Iceland feed largely on marine birds and invertebrates, the SPG seems to encompass more accurate information regarding the direct ocean forces that aff ect food availability to the foxes.

Identification and functional analyses of sex determination genes in the sexually dimorphic stag beetle Cyclommatus metallifer.

BackgroundGenes in the sex determination pathway are important regulators of sexually dimorphic animal traits, including the elaborate and exaggerated male ornaments and weapons of sexual selection. In this study, we identified and functionally analyzed members of the sex determination gene family in the golden metallic stag beetle Cyclommatus metallifer, which exhibits extreme differences in mandible size between males and females.ResultsWe constructed a C. metallifer transcriptomic database from larval and prepupal developmental stages and tissues of both males and females. Using Roche 454 pyrosequencing, we generated a de novo assembled database from a total of 1,223,516 raw reads, which resulted in 14,565 isotigs (putative transcript isoforms) contained in 10,794 isogroups (putative identified genes). We queried this database for C. metallifer conserved sex determination genes and identified 14 candidate sex determination pathway genes. We then characterized the roles of several of these genes in development of extreme sexual dimorphic traits in this species. We performed molecular expression analyses with RT-PCR and functional analyses using RNAi on three C. metallifer candidate genes – Sex-lethal (CmSxl), transformer-2 (Cmtra2), and intersex (Cmix). No differences in expression pattern were found between the sexes for any of these three genes. In the RNAi gene-knockdown experiments, we found that only the Cmix had any effect on sexually dimorphic morphology, and these mimicked the effects of Cmdsx knockdown in females. Knockdown of CmSxl had no measurable effects on stag beetle phenotype, while knockdown of Cmtra2 resulted in complete lethality at the prepupal period. These results indicate that the roles of CmSxl and Cmtra2 in the sex determination cascade are likely to have diverged in stag beetles when compared to Drosophila. Our results also suggest that Cmix has a conserved role in this pathway. In addition to those three genes, we also performed a more complete functional analysis of the C. metallifer dsx gene (Cmdsx) to identify the isoforms that regulate dimorphism more fully using exon-specific RNAi. We identified a total of 16 alternative splice variants of the Cmdsx gene that code for up to 14 separate exons. Despite the variation in RNA splice products of the Cmdsx gene, only four protein isoforms are predicted. The results of our exon-specific RNAi indicated that the essential CmDsx isoform for postembryonic male differentiation is CmDsxB, whereas postembryonic female specific differentiation is mainly regulated by CmDsxD.ConclusionsTaken together, our results highlight the importance of studying the function of highly conserved sex determination pathways in numerous insect species, especially those with dramatic and exaggerated sexual dimorphism, because conservation in protein structure does not always translate into conservation in downstream function.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2522-8) contains supplementary material, which is available to authorized users.

Magnetic resonance imaging of intraoral hard and soft tissues using an intraoral coil and FLASH sequences.

ObjectivesTo ascertain the feasibility of MRI as a non-ionizing protocol for routine dentomaxillofacial diagnostic imaging. Wireless coils were used for MRI of intraoral hard and soft tissues.MethodsFLASH MRI was applied in vivo with a mandible voxel size of 250 × 250 × 500 μm3, FOV of 64 × 64 × 28 mm3 and acquisition time of 3:57 min and with a maxilla voxel size of 350 μm3 and FOV of 34 cm3 in 6:40 min. Ex vivo imaging was performed in 4:38 min, with a resolution of 200 μm3 and FOV of 36.5 cm3. Cone beam (CB) CT of the mandible and subjects were acquired. MRI was compared to CBCT and histological sections. Deviations were calculated with intraclass correlation coefficient (ICC) and coefficient of variation (cv).ResultsA high congruence between CBCT, MRI and specimens was demonstrated. Hard and soft tissues including dental pulp, periodontium, gingiva, cancellous bone and mandibular canal contents were adequately displayed with MRI.ConclusionsImaging of select intraoral tissues was achieved using custom MRI protocols with an easily applicable intraoral coil in a clinically acceptable acquisition time. Comparison with CBCT and histological sections helped demonstrate dimensional accuracy of the MR images. The course of the mandibular canal was accurately displayed with CBCT and MRI.Key points • MRI is a clinically available diagnostic tool in dentistry • Intraoral hard and soft tissues can be imaged with a high resolution with MRI • The dimensional accuracy of MRI is comparable to cone beam CT Electronic supplementary materialThe online version of this article (doi:10.1007/s00330-016-4254-1) contains supplementary material, which is available to authorized users.

Analysis of coupled geographic variation of three shrew species from Southern and Northern Ural taxocenes

Coupled and unidirectional geographical variability of the shape of the mandible in three shrew species of the genus Sorex (araneus, caecutiens, and minutus) has been revealed in a geometric morphometrics-based parallel comparison of cenopopulations forming the Ilmen’ (Southern Urals) and Kytlym (Northern Urals) taxocenes. Mandible centroid size (CS) was significantly larger and significantly more varied in all northern cenopopulations as compared to the southern ones. Discriminant analysis of Procrustes coordinates of the mandible shape in shrews of the southern and northern taxocenes without taking the animal species into account resulted in 94.8% correct assignment of the individuals to local taxocenes. Mandible allometry was detected in the northern cenopopulations of Laxmann’s (caecutiens) and pygmy (minutus) shrews, but not in the southern cenopopulations. Parallelism of geographical variation and high reliability of discrimination between individuals from the southern and northern taxocenes was preserved when the allometric effect was eliminated. The absence of association of this reaction to allometry provides direct proof for similar morphogenetic reactions of these species to climate change in the northern latitudes, and high potential for coevolutionary changes common to all sympatric species of the taxocene.

Functional mechanics of beetle mandibles: Honest signaling in a sexually selected system.

Male stag beetles possess colossal mandibles, which they wield in combat to obtain access to females. As with many other sexually selected weapons, males with longer mandibles win more fights. However, variation in the functional morphology of these structures, used in male-male combat, is less well understood. In this study, mandible bite force, gape, structural strength, and potential tradeoffs are examined across a wide size range for one species of stag beetle, Cyclommatus metallifer. We found that not only does male mandible size demonstrate steep positive allometry, but the shape, relative bite force, relative gape, and safety factor of the mandibles also change with male size. Allometry in these functionally important mandibular traits suggests that larger males with larger mandibles should be better fighters, and that the mandibles can be considered an honest signal of male fighting ability. However, negative allometry in mandible structural safety factor, wing size, and flight muscle mass suggest significant costs and a possible limit on the size of the mandibles. J. Exp. Zool. 325A:3-12, 2016. © 2015 Wiley Periodicals, Inc.

The mandibles of castrated male rhesus macaques (Macaca mulatta): The effects of orchidectomy on bone and teeth.

The objectives of this study were to evaluate the long-term effects of orchidectomy and low testosterone on the craniofaciodental development and maintenance of skeletal and oral health in rhesus macaques. Mandibles of four castrated and intact age-matched male rhesus monkeys (Macaca mulatta) from Cayo Santiago were compared for mandibular morphology and teeth, abnormalities, pathology, and cortical bone thickness and density using a digital sliding caliper and analysis of three-dimensional X-ray images. Although all four castrates were generally comparable to intact males in overall mandible and teeth size, there were some significant differences. In the castrates, (1) the distance between the two rami was narrower than in intact males leading to a relatively narrower and longer face; (2) both the mandibular body and ramus had thinner cortical bone leading to less total bone mass; and (3) the canines and molar teeth were slender with lower and less robust tooth cusps. In addition, the alveolar bone of two geriatric castrates was greatly receded with signs of periodontitis more severe than in intact aged males. Old castrates also had severe temporomandibular joint osteoarthritis. The findings suggest the importance of testosterone in craniofaciodental development, and maintenance of skeletal and oral health in male macaques. These results suggest that dental health professionals might want to include in their medical history questionnaires whether or not male patients have taken hormone (testosterone) replacement therapy.

Morphometrics, body condition, and growth of the ringed seal (Pusa hispida saimensis) in Lake Saimaa: Implications for conservation

AbstractMorphometrics and growth of the critically endangered Saimaa ringed seal (Pusa hispida saimensis), which inhabits a freshwater lake in Finland were studied using data from 344 carcasses. This study presents the first detailed information on ringed seal pup growth and body condition from birth to the age of one year. Newborn pups were on average 68 cm long and weighed 5 kg. Pups attained the majority of their first year growth during the nursing period. Body condition and growth declined after weaning, but pups recovered from postweaning nutritional deprivation at the age of 8 mo. The seals achieved their maximum body length, girth, and mandible size around the age of 4 yr, and asymptotic body mass two years later. Baculum growth indicated that males reached sexual maturity at age 5–6 yr. The Saimaa ringed seals' asymptotic body length and mass were 132 cm and 59 kg, respectively, which is similar to medium sized marine ringed seals. Saimaa ringed seals' survival to adulthood is extremely low due to high bycatch mortality; furthermore climate change may hamper pup growth and elevate mortality. Therefore we recommend continuation of fishing closures to improve pup survival.

New record of the genus Israelimeria Weiner &amp;amp; Kaprus’, 2005 (Collembola: Neanuridae: Pseudachorutinae) from Iran, with description of a new species

Israelimeria persica sp. nov. is described from Iran. The genus Israelimeria can be easily identified due to a reduction of the number of eyes and the complete absence of the postantennal organ and the furca. The new taxon, and also the second species of the genus, differs from I. poliakovae Weiner & Kaprus', 2005, known only from Judean Mts. in Israel, in size and shape of mandibles and many chaetotactic characters, especially number of setae in ocular area of the head, ventral tube, subcoxae "1" and microchaetae number in furcal area.

The treatment effects and mechanisms of pyrroloquinoline quinone on defective teeth and mandible in Bmi-1 knockout mice

To investigate the treatment effects and mechanisms of pyrroloquinoline quinine(PQQ) on defective teeth and mandible in Bmi-1 knockout mice. Male and female Bmi1(+/-) mice were paired with each other from the same nest. At the age of 7 weeks, the mice were divided into three groups, the wild type mice received normal diet(10 mice, WT group), Bmi1(-/-) mice received normal diet (10 mice, BKO group), and the Bmi1(-/-) mice received normal diet and PQQ diet(10 mice, BKO+PQQ group). X-ray and micro- CT were used to detect mandible and dental size and bone mineral density. HE staining, histochemical and immunohistochemical methods were respectively used to detect alveolar bone thickness of cortical bone, predentin thickness of mandibular first molar, mandibular osteoblast number and osteoclast number. Flow cytometry was used to detect reactive oxygen species(ROS) levels of various organs(femur, thymus and liver). The data were statistically analyzed with one-way ANOVA and t test. Compared with BKO mice, BKO+PQQ mice partially rescued total body phenotype, increased body weight and prolonged survival time. X- ray and micro- CT showed the size of the mandible and teeth and bone mineral density of PQQ+BKO mice increased compared with BKO mice. In PQQ+BKO mice, mandibular alveolar bone cortical thickness [(68.65 ± 0.25) µm] was significantly different from that in BKO mice [(42.45 ± 0.35) µm] (P<0.01). There was significant difference in predentin thickness of mandibular first molar between PQQ+BKO mice [(4.25 ± 0.15) µm] and BKO mice [(31.55 ± 0.35) µm] (P<0.001). The number of osteoblasts in the mandible of BKO+PQQ mice [(38.45 ± 0.25) cell/mm³] was significantly higher than that in the BKO mice [(18.15 ± 0.55) cell/mm³] (P<0.01). However, the number of osteoclasts in the BKO+PQQ mice [(9.45 ± 0.25) cell/mm³] was significantly lower than that in the BKO group [(14.25 ± 0.35) cell/mm³] (P<0.01). Compared with the BKO group, ROS levels of the femur, thymus and liver in the BKO+PQQ mice were significantly decreased (P<0.01). The results indicate that PQQ may have treatment effects on defective teeth and mandible through promoting osteoblast bone formation and reducing osteoclast bone resorption, scavenging ROS and reducing DNA damage.