Innervation of the receptors present at the various joints of the pereiopods and third maxilliped of Homarus gammarus (L.) and other macruran decapods (crustacea)

Summary This paper gives a full account of the number and structure of the chordotonal organs present at all joints between the coxopodite and dactylopodite of the pereiopods and 3rd maxilliped of the macruran Homarus gammarus L. (H. vulgaris M. Ed.). Some comparative data is supplied for other macruran decapods. As the form of the receptors depends to some degree upon the structure of the joint we have included details of musculature, planes of movement and degrees of freedom at each of the joints.The third maxilliped has a smaller number of chordotonal organs than the pereiopod, in particular at the mero-carpopodite and carpopodite-propodite joints where only one organ is present. In some species the propodite-dactylopodite organ is absent from this limb.The electrical activity recordable from the receptors in the 3rd maxilliped shows considerable differences from the corresponding receptors in the pereiopod.The structure of the carpopodite-propodite joint of both limbs is discussed in detail as this joint differs greatly from that of the Brachyura. In the 3rd maxilliped and 2nd pereiopod three muscles are present. In the latter the joint is capable of rotation about the longitudinal axis but the third muscle does not appear to produce this rotation. A small number of units in the CP₂ receptor respond to rotation.A receptor is described in the basipodite of the pereiopod and 3rd maxilliped situated just proximal to the plane through which the limb breaks at autotomy or autospasy. This receptor does not monitor joint movement and may detect cuticular strain, thus preventing accidental autotomy of limbs. A similar receptor has been observed in Carcinus.Cuticular receptor structures (CAP organs) are described as present at the M-C and C-P joints in both limbs, and at the I-M joint of the pereiopod.     

泥河湾盆地虎头梁发现披毛犀化石

泥河湾盆地是中国北方第四纪地层发育最为齐全的地区之一,多处哺乳动物化石产地及旧石器遗址中均有披毛犀化石产出（卫奇,１９９７）,但报道产出的化石多数只是骨体碎片或零星的牙齿。１９６５年夏天,中国科学院古脊椎动物与古人类研究所前太原工作站王择义、王向前和武文杰在泥河湾盆地河北省阳原县东城乡虎头梁一带进行旧石器调查时,从褐黄色含细砾砂质粘土层中采集到一些披毛犀化石,产出地点位于虎头梁旧石器遗址ＮＥ５５°方向３５０ｍ处,地层层位位于旧石器产出层位之下的泥河湾组上部,时代为早更新世末期。这些技毛犀化石是该…     

锦鲤咽齿替换及齿胚的解剖学观察,前插1

从鱼类解剖学和口腔医学的角度,观察和讨论了锦鲤咽齿、齿胚的形态结构和咽齿的替换,并对咽齿和咬合板做了扫描电镜观察.发现锦鲤咽齿替换与齿胚有密切关系;咽齿替换分为两侧不同名齿同时替换、同侧两枚不同名齿同时替换和单侧一枚齿自主替换3种类型;咽齿替换是终生发生的,遵循着"被替换咽齿的骨性支持从基骨骨孔开始吸收-同名齿胚的移行与就位-旧齿脱落与新齿支持组织改建为骨性"的过程.认为齿胚的发育是启动咽齿替换的起始因素;锦鲤与野生鲤有近缘关系.     

The evolution of centipede venom claws – Open questions and possible answers

The maxilliped venom claw is an intriguing structure in centipedes. We address open questions concerning this structure. The maxillipeds of fossil centipedes from the Carboniferous (about 300 million years old) have been described, but not been depicted previously. Re-investigation demonstrates that they resemble their modern counterparts. A Jurassic geophilomorph centipede (about 150 million years old) was originally described as possessing a rather leg-like maxilliped. Our re-investigation shows that the maxilliped is, in fact, highly specialized as in modern Geophilomorpha. A scenario for the evolution of the centipede maxilliped is presented. It supports one of the two supposed hypotheses of centipede phylogeny, the Pleurostigmophora hypothesis. Although this hypothesis appears now well established, many aspects of character evolution resulting from this phylogeny remain to be told in detail. One such aspect is the special joint of the maxilliped in some species of Cryptops. Cryptops is an in-group of Scolopendromorpha, but its maxilliped joint can resemble that of Lithobiomorpha or even possess a mixture of characters between the both. Detailed investigation of fossils, larger sample sizes of extant species, and developmental data will be necessary to allow further improvements of the reconstruction of the evolutionary history of centipedes.     

Dissimilarity of corpora lutea within the same ovaries or those from right and left ovaries of pigs during the oestrous cycle

A total of 48 corpora lutea from the right and left ovaries of 2 gilts on Day 9 and 2 gilts on Day 13 of the oestrous cycle were analysed for gonadotrophin binding, progesterone concentration and 3 enzyme activities. The weights of corpora lutea from the right and left ovaries on Days 9 and 13 did not differ, but the values on Day 13 were lower than those on Day 9. The specific binding of 125I-labelled hCG, progesterone concentration, and activities of cytochrome c oxidase (a mitochondrial enzyme), beta-N-acetyl-D-glucosaminidase (a lysosomal enzyme) and glucose 6-phosphate dehydrogenase (a cytosol enzyme) differed, with some exceptions, among the corpora lutea within the same ovaries and those from the right and left ovaries on Days 9 and 13 of the cycle. The gonadotrophin binding differences amongst the corpora lutea appeared to be due to the differences in the total number of available receptors rather than in the receptor affinities. There was no strict correspondence between the magnitude of gonadotrophin binding and luteal progesterone concentration. These data show that porcine corpora lutea within the same ovaries, and those from the right and the left ovary, are quite dissimilar.     

Influence of sex on children's body measurements and indices of biological age (findings from a study of twins of different sexes)

By antropometry and roentgenography methods in 52 twin pairs of different sex, body dimensions, the third metacarpal bone and the phalange of the third right hand finger, as well as the terms of permanent teeth eruption were studied. The investigation revealed no timely coincident periods in growth activity between girls and boys. During the first period (6,5--10 years), predominance of some dimentions is observed in boys, during the second (8,5--14 years)--in girls, and during the third (11--17 years)--in boys again. Somewhat different terms for permanent teeth eruption make it possible to distinguish two periods: 7 years when the boys surpass the girls in the number of permanent teeth (two teeth in average) and 8--14 years when the boys lag behind the girls in the number of permanent teeth.     

Lumbar lateral motor columns and hindlimbs of two Xenopus laevis chromosome mosaics

Two chromosome mosaic Xenopus laevis, one tadpole and one metamorphic animal, both with different sizes of neurons on the left and right sides of their brains and spinal cords, have left and right lumbar lateral motor columns (L-LMCs) of equal lengths but composed of strikingly different numbers of motoneurons (40% fewer motoneurons on the side composed of larger cells). One portion of the lumbar cord in the metamorphic animal is bilaterally symmetrical; the cells on both sides are small and the numbers of motoneurons per section are the same. The mosaics demonstrate that column length and motoneuron density (number per section) are, or can be, regulated bilaterally and that changing cell size affects factors controlling cell density but not column length. Except for the peripheral nerves, there is no evidence of any side-to-side differences in the hindlimb tissues. Whether the side-to-side difference in L-LMC motoneuron number in the stage 66 mosaic corresponds to any feature of the hindlimbs is unknown, but similar side-to-side differences in an early and a late stage mosaic animal support the idea that whatever creates the initial number may also determine the final number of motoneurons.     

Repeatability of strain magnitude and strain rate measurements in the periodontal ligament using fibre Bragg gratings: An ex vivo study in a swine model

Measurement of periodontal ligament (PDL) strain in an ex vivo or in vivo setting of a complete tooth-PDL-bone complex (TPBC) has yet to be achieved in the literature. The objective of this study was to investigate inter- and intra-TPBC PDL strain measurement using fibre Bragg grating (FBG) strain sensors. Second and third premolars from the left and the right side of four swine mandibles were removed to yield sixteen TPBC samples. Samples were secured in a miniature load-frame equipped with a digital actuator used to apply apical-directed displacement to the tooth. The same tooth on left and right sides of the mouth were exposed to the same loading condition over ten trials allowing for comparisons in a split-mouth study. Displacements of 0.2 and 0.3 mm were considered along with displacement rates of 0.025, 0.05, and 0.1 mm/s, yielding six loading combinations. Hypothesis testing between left and right teeth revealed FBGs did not always measure the same strain between left and right TPBCs. For all strain measures, the average coefficient of variation (CV) (all data collected) was 2.16 (range: 0.274–10.71). For repeated measures in single TPBCs, the minimum CV ranged from 0.037 to 0.449, and generally coincided with the time of maximum strain measured over the test duration. Based on the findings of this study, it is suggested that FBGs can provide repeatable ex vivo strain measures in the PDL of complete TPBCs.     

A new species of the ghost shrimp genus Neocallichirus Sakai, 1988 (Decapoda: Axiidea: Callianassidae) from the southwestern Atlantic

ABSTRACT

A new species of ghost shrimp, Neocallichirus pinheiroi, is described based on specimens collected in subtidal habitats of Saquaira beach, northeastern coast of Brazil. This new species resembles N. lemaitrei Manning, 1993, but differs from it primarily in having a third maxilliped propodus expanded ventrally, and in the case of males, a large subtriangular tooth on the cutting edge of the major cheliped dactylus. Diagnostic features of the new species include: (i) frontal margin of carapace with rounded lateral projections not exceeding rostrum distal margin, (ii) third maxilliped carpus with row of sclerotized setae on median internal surface, (iii) minor cheliped with cutting edge of dactylus microscopically pectinate, (iv) endopod of male second pleopod with appendices interna and masculina. This is the seventh described species of the genus Neocallichirus from the western Atlantic and the fourth report of this genus in Brazil. A key for identification of western Atlantic species belonging to the genus is provided.     

The effect of tooth loss on the TM-joint articular eminence inclination

The inclination between the posterior wall of the articular eminence and the referential plane (Frankfurt line) was measured on 137 dry skull specimens (78 with complete dental arches and 59 edentulous). Both left and right joints were measured using direct craniometric method. The results were compared with respect to the loss of teeth, side and sex. A large range of measured values of the eminence inclination shows great individual differences, so that the mean values can have only orientational significance. The mean value of eminence inclination for all measured specimens was 61.9 angular degree. The difference between the two groups established upon dental status is very small and without any statistical significance (P > 0.05). The right joint shows a slightly steeper eminence inclination compared to the left one, but without any statistical significance (P > 0.05). Asymmetry between the right and left joint appears almost as a rule, while maximum measured differences reach up to 33 degrees, with mean absolute difference of 6.9 degrees. The group of edentulous specimens shows a greater symmetry and less differences between the left and right joint, which indicates that different bimechanical conditions in the joint, due to tooth loss might lead to remodellation of the articular eminence. The eminence inclination was significantly steeper in male specimens in all subgroups (P < 0.001), which confirms sexual dimorphism.     

Jaw muscles in older overdenture patients

Objective: To determine, using computer tomography (CT), whether the retention of a small number of teeth in the older adult used to support overdentures could affect the cross‐sectional area (CSA) and X‐ray density of two jaw closing muscles. Design: Cross‐sectional study of a group of older patients subdivided into dentate, edentulous and those wearing overdentures supported by two to five teeth. Subjects: The sample consisted of 24 subjects aged 55–68 years. Outcome measures: CSA and X‐ray density of two jaw closing muscles, masseter and medial pterygoid were measured and evaluated using CT. Results: There were no significant differences between left and right jaw muscles, but the CSA of the masseter muscles were significantly larger than the medial pterygoid muscles. The CSA of the masseter and medial pterygoid muscles was significantly smaller in edentulous subjects compared with dentate subjects but no significant difference was observed between subjects wearing overdentures and those with a natural dentition. No significant differences were observed with the X‐ray density between different muscles or dental states. Conclusion: The retention of a small number of teeth in the older adult used to support overdentures appears to sustain the CSA of two jaw closing muscles and therefore could enhance these patients’ masticatory ability compared with those who were edentulous.     

Empathy Moderates the Effect of Repetitive Transcranial Magnetic Stimulation of the Right Dorsolateral Prefrontal Cortex on Costly Punishment

Humans incur considerable costs to punish unfairness directed towards themselves or others. Recent studies using repetitive transcranial magnetic stimulation (rTMS) suggest that the right dorsolateral prefrontal cortex (DLPFC) is causally involved in such strategic decisions. Presently, two partly divergent hypotheses are discussed, suggesting either that the right DLPFC is necessary to control selfish motives by implementing culturally transmitted social norms, or is involved in suppressing emotion-driven prepotent responses to perceived unfairness. Accordingly, we studied the role of the DLPFC in costly (i.e. third party) punishment by applying rTMS to the left and right DLPFC before playing a Dictator Game with the option to punish observed unfair behavior (DG-P). In addition, sham stimulation took place. Individual differences in empathy were assessed with the German version of the Interpersonal Reactivity Index. Costly punishment increased (non-significantly) upon disruption of the right – but not the left – DLPFC as compared to sham stimulation. However, empathy emerged as a highly significant moderator variable of the effect of rTMS over the right, but not left, DLPFC, suggesting that the right DLPFC is involved in controlling prepotent emotional responses to observed unfairness, depending on individual differences in empathy.     

陕西彬县晚中新世猪类化石

本文记述了陕西彬县发现的晚中新世哺乳动物群中的猪类化石,共两属两种.双齿尖河猪 (Dicoryphochoerus binxianensis),为—新种其性质较印度 Chinji 组的 D. chisholmi 进步,而比我国蓝田组的 D. medius 又略显得原始;弓颌猪 (Chleuastochoerus stehlini) 是我国特有的一个属种,是北方三趾马动物群中的成员.     

Conduction left-to-right and right-to-left across the crista terminalis

A line of block between the vena cava and the crista terminalis (CT) region is important for atrial flutter (AFL), but whether it is fixed or functional is controversial. To test the hypothesis that conduction across the CT normally occurs, but when block occurs in this region it is functional, we analyzed atrial activation during right and left atrial pacing (cycle lengths of 500--130 ms), AFL, and atrial fibrillation in 15 dogs with sterile pericarditis and 7 normal dogs. Electrograms from 396 right, left, and septal atrial sites were simultaneously recorded. Activation across the CT occurred during atrial pacing, AFL, and atrial fibrillation. Activation wave fronts from the right to the left atrium and vice versa traveled over several routes, including Bachmann's bundle and inferior to the inferior vena cava, as well as across the CT. In these models, there is no fixed conduction block across the CT, and when block in the CT region occurs, as during AFL, it is functional.     

Sex and age differences of relationships among stepping parameters for evaluating dynamic balance in the elderly

This study aimed to examine the relationships among various stepping parameters, sex, and age in the elderly. Healthy elderly Japanese individuals 60-85 years old (50 males and 61 females) performed 4 types of stepping motions for 20 s. Stepping motions included bilateral stepping (back/forth and right/left) and unilateral stepping (back/forth and right/left). The number of steps, the average connecting time of a foot during one step, and the average time of both feet touching the floor at the same time (bilateral connecting time) were measured with a foot switch sheet. The trial-to-trial reliability was very high (above 0.86) except for the bilateral connecting time in the bilateral stepping back/forth test for 70-85 year olds (males: 0.67, females: 0.68). With age, the number of steps was significantly smaller, and the average connecting time and the bilateral connecting time were shorter in all stepping tests. There were significant sex differences in bilateral connecting time for bilateral stepping right and left and the number of steps for the bilateral stepping back and forth and the unilateral stepping right and left tests. The number of steps and average connecting time showed high correlations between bilateral stepping right/left and back/forth (r=0.71-0.94) and between unilateral stepping back/forth and right/left (r=0.87-0.99). There were significant correlations of the average connecting time between bilateral and unilateral stepping motions (r=0.51-0.83), but both stepping motions are considered to have different motion properties from the viewpoint of center of gravity sway. The correlations between the bilateral connecting time and the number of steps in bilateral stepping were relatively low (males: /r/<0.70, females: /r/<0.57). The bilateral connecting time was near 0 s in many males; thus, it may depend greatly on individual or sex differences in stepping strategy. These results suggest that the stepping motions used in this study can evaluate dynamic balance ability, and that the unilateral test may be useful for the elderly who cannot walk independently with ease.     

Incremental lines in root cementum of human teeth —A reliable age marker?

In root cementum of teeth, alternating dark and light lines become visible in cross-sections under the light microscope. These lines bear an apparent resemblance to the annual rings of trees. Numerous studies have been done to correlate the number of cementum lines with the dental age by examining a great number of teeth of known age. Our study used a different approach. If lines in root cementum develop in an annual rhythm and are thus comparable to annual rings of trees, the same or at least a very similar number of these structures should be found in all areas of the root cementum of the same tooth. We counted cementum lines in the buccal, lingual, distal and mesial region of different sections, all from the middle third of the same root. This was repeated in eight teeth. To our surprise, we had immense difficulty in counting reproducible line numbers in the same cementum area at repeated counts. Nevertheless, the same tooth was found to differ markedly in the number of lines in different sections as well as in different regions of the same sections. These differences cannot be ascribed to variations caused by difficulties with reproducible line counting. Therefore, we are more than skeptical about the reliability of counting lines in root cementum as a method for determining the age of human teeth.     

Fluctuating asymmetry in fetuses of diabetic rhesus macaques

This study examines dental fluctuating asymmetry (FA) in two samples of fetal rhesus monkeys, one composed of 19 fetuses from diabetic mothers (FDM) and the other of 20 fetuses from nondiabetic mothers. Seventeen measurements were taken on the deciduous dentition of right and left mandibles. The degree of FA was assessed by comparing FDM to fetuses of normal mothers by correlation between right and left sides, and analysis of variation differences between right and left sides. Significant FA was found for three traits based on the correlation between right and left sides and for seven traits by the between-treatment ratio of variance between sides. Distal teeth, both within and outside of a morphologic field, exhibit significantly greater FA than mesial teeth. Our results support the hypothesis that developmental instability is detectable by dental FA.     

Molar surface morphology in Streptocephalus coomansi (Crustacea: Branchiopoda: Anostraca)

Except for the posterio-dorsal margin, the circumference of the molar surface exhibits flagellated processes which become simple at the posterioventral margin. Four topographic regions are distinguished: (A) a posterodorsal region, (B) a peripheral region, (C) a transitional zone, and (D) a central region. The postero-dorsal region of the left mandible has one row of widely spaced, stout, conical teeth, while in the right mandible two rows of slender teeth, which become multi-branched anteriorly, are present. The peripheral molar region stretches between the bordering flagellated processes and the central region and consists of several parallel, dorso-ventral rows of armed teeth. The maximum number of teeth in one dorso-ventral row is higher at the ventral than at the dorsal side and in the left than in the right mandible. In the transitional zone, the number of cusps on each tooth is progressively reduced. The central region, a perforated thickened cuticular plate, extends over the majority of the molar surface. This region is unique among the anostracans studied in this respect and may reflect a different feeding ecology. The strongly diversified molar surface probably allows the species to exploit a wide trophic spectrum. It remains to be tested if these observations may be extrapolated to the entire genus. © 1994 Wiley-Liss, Inc.     

Evolutionary diversification of the auditory organ sensilla in Neoconocephalus katydids (Orthoptera: Tettigoniidae) correlates with acoustic signal diversification over phylogenetic relatedness and life history

Neoconocephalus Tettigoniidae are a model for the evolution of acoustic signals as male calls have diversified in temporal structure during the radiation of the genus. The call divergence and phylogeny in Neoconocephalus are established, but in tettigoniids in general, accompanying evolutionary changes in hearing organs are not studied. We investigated anatomical changes of the tympanal hearing organs during the evolutionary radiation and divergence of intraspecific acoustic signals. We compared the neuroanatomy of auditory sensilla (crista acustica) from nine Neoconocephalus species for the number of auditory sensilla and the crista acustica length. These parameters were correlated with differences in temporal call features, body size, life histories and different phylogenetic positions. By this, adaptive responses to shifting frequencies of male calls and changes in their temporal patterns can be evaluated against phylogenetic constraints and allometry. All species showed well‐developed auditory sensilla, on average 32–35 between species. Crista acustica length and sensillum numbers correlated with body size, but not with phylogenetic position or life history. Statistically significant correlations existed also with specific call patterns: a higher number of auditory sensilla occurred in species with continuous calls or slow pulse rates, and a longer crista acustica occurred in species with double pulses or slow pulse rates. The auditory sensilla show significant differences between species despite their recent radiation, and morphological and ecological similarities. This indicates the responses to natural and sexual selection, including divergence of temporal and spectral signal properties. Phylogenetic constraints are unlikely to limit these changes of the auditory systems.