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1.
A recent preliminary study using complete mitochondrial DNA sequences from 48 species of teleosts has suggested that higher teleostean phylogenies should be reinvestigated on the basis of more intensive taxonomic sampling. As a second step towards the resolution of higher teleostean phylogenies, which have been described as the "(unresolved) bush at the top of the tree," we reanalyzed their relationships using mitogenomic data from 100 purposefully chosen species that fully represented all of the higher teleostean orders, except for the Batrachoidiformes. Unweighted and weighted maximum parsimony analyses were conducted with the data set that comprised concatenated nucleotide sequences from 12 protein-coding genes (excluding 3rd codon positions) and 21 transfer RNA (tRNA) genes (stem regions only) from each species. The resultant trees were well resolved and largely congruent, with most internal branches being supported by high statistical values. All major, comprehensive groups above ordinal level as currently defined in higher teleosts (with the exception of the Neoteleostei and several monotypic groups), such as the Eurypterygii, Ctenosquamata, Acanthomorpha, Paracanthopterygii, Acanthopterygii, and Percomorpha, appeared to be nonmonophyletic in the present tree. Such incongruities largely resulted from differences in the placement and/or limits of the orders Ateleopodiformes, Lampridiformes, Polymixiiformes, Ophidiiformes, Lophiiformes, Beryciformes, Stephanoberyciformes, and Zeiformes, long-standing problematic taxa in systematic ichthyology. Of these, the resulting phylogenetic positions of the Ophidiiformes and Lophiiformes were totally unexpected, because, although they have consistently been considered relatively primitive groups within higher teleosts (Paracanthopterygii), they were confidently placed within a crown group of teleosts, herein called the Percomorpha. It should be noted that many unexpected, but highly supported relationships were found within the Percomorpha, being highly promising for the next investigative step towards resolution of this remarkably diversified group of teleosts.  相似文献   

2.
Percomorpha, comprising about 60% of modern teleost fishes, has been described as the “(unresolved) bush at the top” of the tree, with its intrarelationships still being ambiguous owing to huge diversity (> 15,000 species). Recent molecular phylogenetic studies based on extensive taxon and character sampling, however, have revealed a number of unexpected clades of Percomorpha, and one of which is composed of Syngnathoidei (seahorses, pipefishes, and their relatives) plus several groups distributed across three different orders. To circumscribe the clade more definitely, we sampled several candidate taxa with reference to the previous studies and newly determined whole mitochondrial genome (mitogenome) sequences for 16 percomorph species across syngnathoids, dactylopterids, and their putatively closely-related fishes (Mullidae, Callionymoidei, Malacanthidae). Unambiguously aligned sequences (13,872 bp) from those 16 species plus 78 percomorphs and two outgroups (total 96 species) were subjected to partitioned Bayesian and maximum likelihood analyses. The resulting trees revealed a highly supported clade comprising seven families in Syngnathoidei (Gasterosteiformes), Dactylopteridae (Scorpaeniformes), Mullidae in Percoidei and two families in Callionymoidei (Perciformes). We herein proposed to call this clade “Syngnathiformes” following the latest nuclear DNA studies with some revisions on the included families.  相似文献   

3.
The limits and relationships of the acanthomorph teleosts   总被引:3,自引:0,他引:3  
The phylogenetic status of the speciose euteleostean assemblage, the Acanthomorpha, is investigated. For the purposes of cladistic analysis attention is centred upon an examination of euteleostean buccal ligament systems, the occipital and ethmoid regions of the neurocranium, and the posttemporal/neurocranial association.
In this study four derived morphological features are identified which support the monophyly of the Acanthomorpha, and the previously 'problematical' genus Polymixia is determined to be the sistergroup of all the remaining acanthomorphs. The phylogenetic integrity of the sistergroup of the entire Acanthomorpha, the Myctophiformes (sensu Rosen, 1973), is attested by the presence of four derived features, and the monophyly of its major subdivisions (the Myctophidae and Neoscopelidae) is resolved.
Additional problems of euteleostean systematics and systematic methodology are discussed.  相似文献   

4.
Zhu M  Yu X  Choo B  Qu Q  Jia L  Zhao W  Qiao T  Lu J 《PloS one》2012,7(4):e35103

Background

The pectoral and pelvic girdles support paired fins and limbs, and have transformed significantly in the diversification of gnathostomes or jawed vertebrates (including osteichthyans, chondrichthyans, acanthodians and placoderms). For instance, changes in the pectoral and pelvic girdles accompanied the transition of fins to limbs as some osteichthyans (a clade that contains the vast majority of vertebrates – bony fishes and tetrapods) ventured from aquatic to terrestrial environments. The fossil record shows that the pectoral girdles of early osteichthyans (e.g., Lophosteus, Andreolepis, Psarolepis and Guiyu) retained part of the primitive gnathostome pectoral girdle condition with spines and/or other dermal components. However, very little is known about the condition of the pelvic girdle in the earliest osteichthyans. Living osteichthyans, like chondrichthyans (cartilaginous fishes), have exclusively endoskeletal pelvic girdles, while dermal pelvic girdle components (plates and/or spines) have so far been found only in some extinct placoderms and acanthodians. Consequently, whether the pectoral and pelvic girdles are primitively similar in osteichthyans cannot be adequately evaluated, and phylogeny-based inferences regarding the primitive pelvic girdle condition in osteichthyans cannot be tested against available fossil evidence.

Methodology/Principal Findings

Here we report the first discovery of spine-bearing dermal pelvic girdles in early osteichthyans, based on a new articulated specimen of Guiyu oneiros from the Late Ludlow (Silurian) Kuanti Formation, Yunnan, as well as a re-examination of the previously described holotype. We also describe disarticulated pelvic girdles of Psarolepis romeri from the Lochkovian (Early Devonian) Xitun Formation, Yunnan, which resemble the previously reported pectoral girdles in having integrated dermal and endoskeletal components with polybasal fin articulation.

Conclusions/Significance

The new findings reveal hitherto unknown similarity in pectoral and pelvic girdles among early osteichthyans, and provide critical information for studying the evolution of pelvic girdles in osteichthyans and other gnathostomes.  相似文献   

5.
We show that RNF213 is a nuclear gene suitable for investigating large scale acanthomorph teleosteans interrelationships. The gene recovers many clades already found by several independent studies of acanthomorph molecular phylogenetics and considered as reliable. Moreover, we performed phylogenetic analyses of three other independent nuclear markers, first separately and then of all possible combinations (Dettaï, A., Lecointre, G., 2004. In search of nothothenioid (Teleostei) relatives. Antarct. Sci. 16 (1), 71–85. URL http://dx.doi.org/10.1017/S0954102004) of the four genes. This was coupled with an assessment of the reliability of clades using the repetition index of Li and Lecointre (Li, B., Lecointre, G., 2008. Formalizing reliability in the taxonomic congruence approach. Article accepted by Zoologica Scripta. URL http://dx.doi.org/10.1111/j.1463-6409.2008.00361.x). This index was improved here to handle the incomplete taxonomic overlap among datasets. The results lead to the identification of new reliable clades within the ‘acanthomorph bush’. Within a clade containing the Atherinomorpha, the Mugiloidei, the Plesiopidae, the Blennioidei, the Gobiesocoidei, the Cichlidae and the Pomacentridae, the Plesiopidae is the sister-group of the Mugiloidei. The Apogonidae are closely related to the Gobioidei. A clade named ‘H’ grouping a number of families close to stromateids and scombrids (Stromateidae, Scombridae, Trichiuridae, Chiasmodontidae, Nomeidae, Bramidae, Centrolophidae) is related to another clade named ‘E’ (Aulostomidae, Macrorhamphosidae, Dactylopteridae). The Sciaenidae is closely related to the Haemulidae. Within clade ‘X’ (Dettaï, A., Lecointre, G., 2004. In search of nothothenioid (Teleostei) relatives. Antarct. Sci. 16 (1), 71–85. URL http://dx.doi.org/10.1017/S0954102004), the Cottoidei, the Zoarcoidei, the Gasterosteidae, the Triglidae, the Scorpaenidae, the Sebastidae, the Synanceiidae, and the Congiopodidae form a clade. Within clade ‘L’ (Chen, W.-J., Bonillo, C., Lecointre, G., 2003. Repeatability of clades as a criterion of reliability: a case study for molecular phylogeny of Acanthomorpha (Teleostei) with larger number of taxa. Mol. Phylogenet. Evol. 26, 262–288; Dettaï, A., Lecointre, G., 2004. In search of nothothenioid (Teleostei) relatives. Antarct. Sci. 16 (1), 71–85. URL http://dx.doi.org/10.1017/S0954102004) grouping carangoids with flatfishes and other families (Centropomidae, Menidae, Sphyraenidae, Polynemidae, Echeneidae, Toxotidae, Xiphiidae), carangids are the stem-group of echeneids and coryphaenids, and sphyraenids are the sister-group to the Carangoidei. The Howellidae, the Epigonidae and the Lateolabracidae are closely related. We propose names for most of the clades repeatedly found in acanthomorph phylogenetic studies of various teams of the past decade.  相似文献   

6.
7.
Series Atherinomorpha, with its plentiful number of species and highly diversified ecological and morphological characters, is the most successful fish group at the surface layer of the ocean and many freshwater habitats, comprising 1552 species classified into three orders, six suborders, 21 families, and 193 genera. The group includes one of the most important research model organisms, the medaka (Oryzias latipes), together with diverse fishes with morphological, physiological, and ecological specializations, such as highly developed pectoral fins to glide, self-fertilization, and live-bearing. In this study, we examined the whole mitochondrial genomes (mitogenomes) from 17 species representing all of the three orders and six suborders within Atherinomorpha, with data from 70 additional percomorph species as ingroups, and two non-percomorph outgroup species. We subjected the unambiguously aligned mitogenome sequences to partitioned maximum likelihood and Bayesian phylogenetic analyses. The resulting phylogenies recovered a monophyletic Atherinomorpha within the Percomorpha, and demonstrated its phylogenetic affinity to the percomorph fishes (including cichlids) spawning demersal eggs with filaments. This study, further, provided the first molecular evidence for the monophyly of the respective atherinomorph orders (Atheriniformes, Beloniformes, and Cyprinodontiformes) with high posterior probabilities and mostly high bootstrap values, providing an important basis for the future studies on the phylogeny and evolution of this diverse group.  相似文献   

8.
Analysis of the Dana collection of larval fishes yielded 36 exterilium larvae and 17 rubaniform larvae, referable to the Ophidiidae. Both larval types reach large sizes before transformation and are characterized by an exterilium gut, although it is less strongly expressed in rubaniform larvae. Both have early-forming, elongate, descending processes of the coracoid that serve to support the trailing intestines. Both have a greatly reduced pelvic girdle attached to a stalklike cartilaginous structure, resulting in a pelvic fin origin well posterior to the cleithral symphysis, a position that is without precedent in the family Ophidiidae. Both of these larval types also strongly display an anterior to posterior developmental sequence, lose the pelvic fin rays at transformation, and have extraordinarily elongate proximal radials supporting their dorsal and anal fins and modified proximal radials supporting the anterior dorsal fin rays. After examination of these larvae and reference to 5 previously described exterilium larvae and 1 previously described rubaniform larva, we conclude that they belong to Lamprogrammus (three species) and Brotulotaenia (four species), respectively. The most recent classification of the Ophidiidae places Brotulotaenia in the monotypic subfamily Brotulotaeniinae, and Lamprogrammus in the subfamily Neobythitinae along with 37 other genera. The latter subfamily is an unwieldy assemblage for which monophyly has never been established. Ontogenetic evidence suggests a closer relationship between Brotulotaenia and Lamprogrammus, and the most economical reorganization of the ophidiids would involve incorporating the latter genus into the Brotulotaeniinae.  相似文献   

9.
Mechanisms of natural selection can be identified using experimental approaches. However, such experiments often yield nonsignificant effects and imprecise estimates of selection due to low power and small sample sizes. Combining results from multiple experimental studies might produce an aggregate estimate of selection that is more revealing than individual studies. For example, bony pelvic armour varies conspicuously among stickleback populations, and predation by vertebrate and insect predators has been hypothesized to be the main driver of this variation. Yet experimental selection studies testing these hypotheses frequently fail to find a significant effect. We experimentally manipulated length of threespine stickleback (Gasterosteus aculeatus) pelvic spines in a mesocosm experiment to test whether prickly sculpin (Cottus asper), an intraguild predator of stickleback, favours longer spines. The probability of survival was greater for stickleback with unclipped pelvic spines, but this effect was noisy and not significant. We used meta‐analysis to combine the results of our mesocosm experiment with previously published experimental studies of selection on pelvic armour. We found evidence that fish predation indeed favours increased pelvic armour, with a moderate effect size. The same approach found little evidence that insect predation favours reduced pelvic armour. The causes of reduced pelvic armour in many stickleback populations remain uncertain.  相似文献   

10.
Evolution of the ischial spine and of the pelvic floor in the Hominoidea   总被引:1,自引:0,他引:1  
Study of the pelvis in 143 different mammals reveals that in quadrupeds the ischial spines are barely noticeable and are located posteriorly near the sacrum. In humans, the ischial spines are prominent and more anteriorly located. As a consequence of their position and size, the ischial spines in humans become an obstacle to parturition. Herein a theory is proposed to account for what appears to be an incongruous development and orientation of the ischial spines in humans. The pelvic diaphragm is a vertical pelvic "wall" in tailed mammals and is composed of muscles involved mostly with the motion of the tail. In humans, the muscles of the pelvic diaphragm have a very different anatomical orientation. They form a horizontal pelvic "floor," and their functions are first to support the abdominopelvic organs and resist intra-abdominal pressure that is exerted from above, and second, as levator ani, to control the anal sphincter. In humans the muscles and fascias of the pelvic diaphragm are inserted on the ischial spines either directly or indirectly through the sacrospinous ligament and the tendinous arch of the pelvic fascia. The result is a medial pull on the ischial spines to produce a more rigid and narrower pelvic floor. An inconstant ossification center for the ischial spines make them more prominent. The backward tilt of the sacrum placed the bispinal line in a diameter position. Pongids and even fossil hominids occupy an intermediate position between tailed mammals and Homo sapiens. The present form of the pelvis in Homo sapiens may be determined by a significant genetic component but may also be partly acquired during childhood and adolescence.  相似文献   

11.

Background

Pelvic incidence, sacral slope and slip percentage have been shown to be important predicting factors for assessing the risk of progression of low- and high-grade spondylolisthesis. Biomechanical factors, which affect the stress distribution and the mechanisms involved in the vertebral slippage, may also influence the risk of progression, but they are still not well known. The objective was to biomechanically evaluate how geometric sacral parameters influence shear and normal stress at the lumbosacral junction in spondylolisthesis.

Methods

A finite element model of a low-grade L5-S1 spondylolisthesis was constructed, including the morphology of the spine, pelvis and rib cage based on measurements from biplanar radiographs of a patient. Variations provided on this model aimed to study the effects on low grade spondylolisthesis as well as reproduce high grade spondylolisthesis. Normal and shear stresses at the lumbosacral junction were analyzed under various pelvic incidences, sacral slopes and slip percentages. Their influence on progression risk was statistically analyzed using a one-way analysis of variance.

Results

Stresses were mainly concentrated on the growth plate of S1, on the intervertebral disc of L5-S1, and ahead the sacral dome for low grade spondylolisthesis. For high grade spondylolisthesis, more important compression and shear stresses were seen in the anterior part of the growth plate and disc as compared to the lateral and posterior areas. Stress magnitudes over this area increased with slip percentage, sacral slope and pelvic incidence. Strong correlations were found between pelvic incidence and the resulting compression and shear stresses in the growth plate and intervertebral disc at the L5-S1 junction.

Conclusions

Progression of the slippage is mostly affected by a movement and an increase of stresses at the lumbosacral junction in accordance with spino-pelvic parameters. The statistical results provide evidence that pelvic incidence is a predictive parameter to determine progression in isthmic spondylolisthesis.  相似文献   

12.
INTRODUCTION: Constipation is a relatively common problem affecting 15 percent of adults in the Western world, and over half of these cases are related to pelvic floor disorders. This article reviews the clinical presentation and diagnostic approach to posterior pelvic floor disorders, including how to image and treat them. METHODS: A Pubmed search using keywords "rectal prolapse," "rectocele," "perineal hernia," and "anismus" was performed, and bibliographies of the revealed articles were cross-referenced to obtain a representative cross-section of the literature, both investigational studies and reviews, that are currently available on posterior pelvic floor disorders. DISCUSSION: Pelvic floor disorders can occur with or without concomitant physical anatomical defects, and there are a number of imaging modalities available to detect such abnormalities in order to decide on the appropriate course of treatment. Depending on the nature of the disorder, operative or non-operative therapy may be indicated. CONCLUSION: Correctly diagnosing pelvic floor disorders can be complex and challenging, and the various imaging modalities as well as clinical history and exam must be considered together in order to arrive at a diagnosis.  相似文献   

13.
It is generally thought that predation pressure drives the evolution of long spines and robust pelvic girdles in sticklebacks (Pisces: Gasterosteidae). However, the lack of these traits in some environments with intense predation pressure suggests that there may be a limit to which apparently defensive structures benefit sticklebacks. This paper focuses on a trade-off between defensive morphology and escape response performance in a genetically based polymorphic population of brook stickleback (Culaea inconstans), in which fish have fully developed pelvic girdles and pelvic spines (complete morph) or completely lack these defensive structures (absent morph). Startle response experiments revealed that the absent morph did better in all aspects of startle performance (displacement, maximum velocity, acceleration) than the complete morph. The absent morph also bent deeper than the complete morph during the initial phase of the startle response. The pelvic girdle polymorphism in this population may be maintained because individuals with a complete pelvic girdle and spines may be able to escape more easily from predators once they are captured, whereas individuals lacking these structures may better avoid capture when they are attacked.  相似文献   

14.

Background

Limb length Inequality (LLI) in children and adults may affect posture, gait, and several truncal parameters, and it can cause spinal scoliosis. In literature, however, there is a paucity of assessment of truncal and spinal changes due to mild LLI in children. This report presents children with LLI, and it aims to provide information in pelvic imbalance, spinal posture, and scoliotic curve, using surface topography analysis which is a novel methodological approach for this condition.

Study design

This is an ongoing prospective research study on patient series suffering LLI.

Material and method

Twenty children, attending the Scoliosis Clinic of the department, 7 boys, 13 girls, 9–15?years old, range 7.5–15, mean 15.5?years, having mild LLI, were assessed. The LLI was 0.5 to 2?cm, mean 1.2?cm. There was not any post-traumatic LLI. We evaluated the LLI in correlation to pelvic and spinal posture parameters. The 4D Formetric DIERS apparatus (4DF) was used for the surface topography assessment. The following were assessed: in the coronal plane, the coronal imbalance, the pelvic obliquity, the lateral deviation, and the 4DF scoliosis angle; in the sagittal plane, the sagittal imbalance, the 4DF kyphotic angle, the kyphotic apex, the 4DF lordotic angle, the lordotic apex, the pelvic tilt, and the trunk inclination; and in the transverse plane, the pelvis rotation, the pelvic torsion, the surface rotation, and the 4DF vertebral rotation. LLI was measured using a tape. The data were statistically analyzed, and reliability study for the LLI was also performed.

Results/discussion

The LLI was statistically significantly correlated to the 4DF reading of pelvis rotation, pelvic tilt (pelvic obliquity), and surface rotation. The scoliometer readings (angle trunk rotation ATR or trunk inclination ATI) in the lumbar region were statistically significantly correlated to the 4DF readings of pelvic tilt (pelvic obliquity). The normally symmetric truncal parameters were also statistically significantly changed (all these deviating from the line of gravity through the vertebral prominence). Interestingly, LLI was not correlated to the scoliosis angle and the scoliometer reading at the lumbar level.The following 4DF readings are presented: in the coronal plane, the coronal imbalance, pelvic obliquity, lateral deviation, and 4DF scoliosis angle; in the sagittal plane, the sagittal imbalance, kyphotic angle, kyphotic apex, lordotic angle, lordotic apex, pelvic tilt, and trunk inclination; and in the transverse plane, the pelvic rotation, pelvic torsion, surface rotation, and vertebral rotation.

Conclusions

Previous studies have reported the results after simulation of LLI in order to evaluate the effects on the pelvic balance and spinal posture parameters. This report is not a LLI simulation study but it presents the effects of mild LLI on truncal changes in the main cardinal planes in children suffering LLI. These changes undoubtedly affect not only the standing truncal posture but also the gait’s economy as well.As mild LLI affects the pelvic balance and spinal posture parameters, our therapeutic approach is that mild LLI (less than 2.0?cm) has to be corrected using shoe elevation, in order to equalize the pelvic obliquity and, consequently, the spinal posture parameters.
  相似文献   

15.

Background  

Fishes in the families Cichlidae and Labridae provide good probable examples of vertebrate adaptive radiations. Their spectacular trophic radiations have been widely assumed to be due to structural key innovation in pharyngeal jaw apparatus (PJA), but this idea has never been tested based on a reliable phylogeny. For the first step of evaluating the hypothesis, we investigated the phylogenetic positions of the components of the suborder Labroidei (including Pomacentridae and Embiotocidae in addition to Cichlidae and Labridae) within the Percomorpha, the most diversified (> 15,000 spp) crown clade of teleosts. We examined those based on 78 whole mitochondrial genome sequences (including 12 newly determined sequences) through partitioned Bayesian analyses with concatenated sequences (13,933 bp).  相似文献   

16.
17.

Objective

Combined spinal-epidural analgesia (CSEA) is sometimes used for difficult births, but whether it contributes to postpartum pelvic muscle disorder is unclear. This randomized controlled trial examined whether CSEA given during labor affects the electrophysiological index of postpartum pelvic floor muscle function.

Methods

A consecutive sample of primiparous women who delivered vaginally at term were randomly assigned to a CSEA group (n = 143) and control group (n = 142) between June 2013 and June 2014. All were assessed 6–8 weeks later for electrophysiological function of pelvic floor muscle.

Results

The two groups were similar in the degree of muscle strength, muscle fatigue, and pelvic dynamic pressure of pelvic floor muscle. The CSEA and control groups showed similar proportions of women with normal muscle strength (score ≥4) in type I pelvic fibers (23.1% vs. 14.1%, P = 0.051) and type II pelvic fibers (28.0% vs. 24.6%, P = 0.524). The groups also contained similar proportions of women who showed no fatigue in type I fibers (54.5% vs. 48.6%, P = 0.315) or type II fibers (88.8% vs. 87.3%, P = 0.699). Similarly low proportions of women in the CSEA group and control group showed normal pelvic dynamic pressure (11.2% vs. 7.7%, P = 0.321). However, women in the CSEA group spent significantly less time in labor than those in the control group (7.25 vs. 9.52 h, P <0.001).

Conclusions

CSEA did not affect the risk of postpartum pelvic muscle disorder in this cohort of primiparous women who gave birth vaginally. A significant shorter duration of labour was observed in the CSEA-group.

Trial Registration

ClinicalTrials.gov NCT02334150  相似文献   

18.

Objective

The decline in available oestrogen after menopause is a possible etiological factor in pelvic floor disorders like vaginal atrophy (VA), urinary incontinence (UI), overactive bladder (OAB) and pelvic organ prolapse (POP). This systematic review will examine the evidence for local oestrogen therapy in the treatment of these pelvic floor disorders.

Evidence Acquisition

We performed a systematic search in MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials and the non-MEDLINE subset of PubMed from inception to May 2014. We searched for local oestrogens and VA (I), UI/OAB (II) and POP (III). Part I was combined with broad methodological filters for randomized controlled trials (RCTs) and secondary evidence. For part I and II two reviewers independently selected RCTs evaluating the effect of topical oestrogens on symptoms and signs of VA and UI/OAB. In part III all studies of topical oestrogen therapy in the treatment of POP were selected. Data extraction and the assessment of risk of bias using the Cochrane Risk of Bias Tool was undertaken independently by two reviewers.

Evidence Synthesis

The included studies varied in ways of topical application, types of oestrogen, dosage and treatment durations. Objective and subjective outcomes were assessed by a variety of measures. Overall, subjective and urodynamic outcomes, vaginal maturation and vaginal pH changed in favor of vaginal oestrogens compared to placebo. No obvious differences between different application methods were revealed. Low doses already seemed to have a beneficial effect. Studies evaluating the effect of topical oestrogen in women with POP are scarce and mainly assessed symptoms and signs associated with VA instead of POP symptoms.

Conclusion

Topical oestrogen administration is effective for the treatment of VA and seems to decrease complaints of OAB and UI. The potential for local oestrogens in the prevention as well as treatment of POP needs further research.  相似文献   

19.
A test of the hypothesis that the members of the order Acipenseriformes (sturgeons and paddlefishes) possess a slowed rate of molecular evolution was carried out by conducting relative-rate comparisons with representatives of four groups of teleost fishes (Cypriniformes, Elopomorpha, Salmonidae, and Percomorpha) using 21 nuclear or mitochondrial protein loci and the nuclear and mitochondrial small subunit rRNA genes, obtained from the literature or our own research. In 70 out of 81 comparisons between individual taxa (86%), acipenseriform sequences showed slower rates of change than the homologous teleost loci examined. When teleost sequences are considered together, 21 of the 23 loci show slower rates of substitution in the acipenseriform lineage. Teleost proteins show 1.85 times as many unique amino acid differences as acipenseriform proteins, when both are compared with outlier sequences. These results support a hypothesis of slowed molecular evolutionary rate in the Acipenseriformes.  相似文献   

20.
Summary Histological and histochemical techniques have been employed to determine the structure and autonomic innervation of paraganglia located in the human pelvis. In foetal and early postnatal tissues, paraganglia formed rounded cellular masses which were frequently in company with the autonomic nerves and ganglia of the urinary bladder and other pelvic viscera. The constituent cells contained only small amounts of cholinesterase and were unrelated to enzyme positive autonomic nerves; acetylcholinesterase containing nerves were occasionally observed in the capsule and the fibrous septa of the pelvic paraganglia. In early postnatal specimens, pelvic paraganglia frequently contained single or multiple pacinian-like corpuscles, each possessing a central region which was rich in both acetyl and pseudocholinesterase. These structures were rarely observed within autonomic ganglia and were absent 4 1/2 years post partum. By means of a histochemical technique, pelvic paraganglia were found to contain catecholamine which was attributed to the presence of relatively large quantities of noradrenaline. These observations have been discussed with particular reference to the results of other studies on the autonomic innervation of paraganglia.  相似文献   

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