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PubMed2006

Rapid evolution of sessility in an endemic species flock of the freshwater bivalve Corbicula from ancient lakes on Sulawesi, Indonesia.

The fauna of ancient lakes frequently contains taxa with highly derived morphologies that resulted from in situ radiation of lacustrine lineages with high antiquity. We employed a molecular mtDNA phylogeny to investigate this claim for corbiculid freshwater bivalves in two ancient lake systems on the Indonesian island Sulawesi. Among the otherwise mobile corbiculid species flock, only one taxon, Posostrea anomioides, in the ancient Lake Poso exhibits a unique habit, i.e. cementing one valve to the substrate. Our data show that Corbicula on Sulawesi is polyphyletic, with the endemic riverine taxa in terminal position, and the lacustrine species flock being paraphyletic. Surprisingly, Posostrea is not confirmed as a genus distinct from Corbicula and genetic distances suggest a rather recent origin from the only other corbiculid species endemic to Lake Poso, the non-cementing Corbicula possoensis. While the cementing anomioides, despite its unique behavioural and morphological characteristics, clusters together with non-sessile Corbicula species, the latter exhibit strong genetic distances in the absence of morphological disparity and fall into several genetically rather distinct clades. These findings suggest that developmental plasticity of animals in ancient lakes rather than the antiquity of lineages might account for the unique morphology of some species.

Animals↗
PubMed1992

[Phylogeny of Trichostrongyloidea nematodes as seen through some of their vertebrate hosts].

Reconstruction of the phylogenetic history of a parasitic group is clearly difficult due to a lack of fossil forms. Among the nematodes parasites of vertebrates, the superfamily Trichostrongyloidea is one of the richest groups in terms of number of species (more than 1000 described) and genera (175) and they therefore offer excellent opportunities to reconstruct their phylogeny. Trichostrongyles occur in the gut and less commonly in the stomach and the lungs of all classes of terrestrial vertebrates except the Perissodactyls and the Proboscidian. They have a world wide distribution and direct life cycle. The criteria used in the classification of the Trichostrongyloidea are essentially morphological. Morphological characters are numerous and an attempt has been made to distinguish their relative value. Information concerning the synlophe, which is the apparatus of locomotion and attachment of the worms in the gut of the hosts, has been found essential in order to construct a classification of the superfamily and understand its evolution. This analysis was greatly facilitated by information from two sources: 1) the morphology of free-living rhaditids, which are the ancestors of the trichostrongyles; 2) the ontogeny of the synlophe. The classification established above takes into account the different morphological characters, but only concerns extant animals. Data provided by the hosts permit us to date the appearance of different lineages and to follow their evolution in time and space. These data come from extant hosts and from paleobiogeography. 1) The evidence from extant host species includes the host distribution of the trichostrongyles in relation to the geographic distribution of the hosts. 2) The evidence from extinct forms includes the date of appearance of the host in the geological record as well as mammalian migration in geologic time periods: a) The date of the appearance of the hosts in the geological records permits us to date the origin of the different families of parasites. b) The manner in which host migration interacts with the parasite is very complex and a few examples will be considered, mainly from the caviomorphs, the sciuromorphs and the myomorphs. The combination of evidence from the morphology of the worms and evidence from the paleobiogeography of the hosts allows us not only to explain the present day host and geographic distributions of the parasites but also to reconstruct their evolutionary history. The phylogenetic tree of the Trichostrongyloidea proposed with Chabaud consists of three main branches which are morphologically clearly defined.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1999

Molecular control of vertebrate limb development, evolution and congenital malformations.

The vertebrate limb is a powerful model system for studying the cellular and molecular interactions that determine morphological pattern during embryonic development. Recent advances in our understanding of these interactions have shed new light on the molecular mechanisms of vertebrate limb development, evolution and congenital malformations. The transfer of information has, until recently, been largely one way, with developmental studies informing our understanding of the fossil record and clinical limb anomalies; however, evolutionary and clinical studies are now beginning to shed light onto one another and onto basic developmental processes. In this review, we discuss recent advances in these fields and how they are interacting to improve our understanding of vertebrate limb biology.

Animals↗
PubMed2006

Particle-wire-tube mechanism for carbon nanotube evolution.

The synthesis of carbon nanotubes (CNTs) has been proved to be greatly promoted by vapor metal catalysts, but the fast reaction feature and the required high-temperature environment involved in CNT evolution usually make it difficult for an insight into the evolution mechanism. Here, we successfully freeze the synthetic reaction at intermediary stages and observe the detailed morphologies and structures of the obtained intermediates and various objects related to carbon nanotubes. It is unveiled that there is a kindred evolution linkage among carbon nanoparticles, nanowires, and nanotubes in the vapor catalyst-involved synthetic processes: tiny carbon nanoparticles first form from a condensation of gaseous carbon species and then self-assemble into nanowires driven by an anisotropic interaction, and the nanowires finally develop into nanotubes, as a consequence of particle coalescence and structural crystallization. The function of metals is to promote the anisotropic interactions between the nanoparticles and the structural crystallization. An annealing transformation of carbon nanoparticles into nanotubes is also achieved, which gives further evidence for the evolution mechanism.

Journal Article↗
PubMed2006

Early evolution of animal cell signaling and adhesion genes.

In stark contrast to the rapid morphological radiation of eumetazoans during the Cambrian explosion, the simple body plan of sponges (Phylum Porifera) emerged from the Cambrian relatively unchanged. Although the genetic and developmental underpinnings of these disparate evolutionary outcomes are unknown, comparisons between modern sponges and eumetazoans promise to reveal the extent to which critical genetic factors were present in their common ancestors. Two particularly interesting classes of genes in this respect are those involved in cell signaling and adhesion. These genes help guide development and morphogenesis in modern eumetazoans, but the timing and sequence of their origins is unknown. Here, we demonstrate that the sponge Oscarella carmela, one of the earliest branching animals, expresses core components of the Wnt, transforming growth factor beta, receptor tyrosine kinase, Notch, Hedgehog, and Jak/Stat signaling pathways. Furthermore, we identify sponge homologs of nearly every major eumetazoan cell-adhesion gene family, including those that encode cell-surface receptors, cytoplasmic linkers, and extracellular-matrix proteins. From these data, we infer that key signaling and adhesion genes were in place early in animal evolution, before the divergence of sponge and eumetazoan lineages.

Animals↗
PubMed1987

The evolution of membranous glomerulonephritis reconsidered: new insights from a study on relapsing disease.

Membranous glomerulonephritis (MGN) has a highly variable clinical course. The morphological basis for this variability has not been fully elucidated. We studied 10 patients with relapsing MGN and compared the findings with those in other clinical courses. The mean duration of follow-up was 10.4 years. Clinical remission occurred, on average, 1.5 years and relapse, on average, 5.6 years after onset. Thirty-one renal biopsies obtained at various clinical phases were studied, 22 of them electron microscopically. The ultrastructural and clinical alterations paralleled each other closely. Subepithelial electron-dense deposits were present during the primary nephrotic phase, were replaced by intramembranous lucent deposits during remission, and reappeared again during relapse. Light microscopic changes (projections, thickening) of the glomerular capillary basement membrane (GBM) were variable. Both ultrastructural and light microscopic changes were unreliable indicators of the duration of illness. A comparative analysis of the present and previous findings suggests that the length of time during which new deposit material is formed determines the evolution of the membranous lesion and the corresponding clinical course. Thus, a short duration results in a single generation of deposits, a morphologically and clinically healing course, and no thickening of the GBM. A repeated formation of deposit material results in a new generation of subepithelial deposits, and a relapsing course. A prolonged formation results in a continuous presence of subepithelial deposits, a thickening of the GBM, and a protracted or progressive course. The morphologic staging currently in use pertains to one particular evolution and course of MGN and therefore should not be used.

Adult↗
PubMed2000

28S rDNA evolution in the Eumalacostraca and the phylogenetic position of krill.

The Malacostraca are an ancient and morphologically diverse class of Crustacea. The phylogenetic position of one order within this class, the Euphausiacea ("krill," subclass Eumalacostraca) was investigated using 28S rDNA sequences from representatives of several malacostracan orders. Phylogenies for these sequences were estimated by maximum-likelihood and maximum-parsimony analysis. The results of these analyses produced a new scheme for evolution within the Eumalacostraca. The new phylogenies suggested that Euphausiacea are most closely related to the Mysida and not the Decapoda, as is generally thought. Furthermore, the Mysida were found not to be closely related to the Lophogastrida, which are often considered their sister taxon. These hypotheses were tested against the hypotheses of monophyly for the Eucarida, Mysidacea, and Peracarida and found to be significantly better on the basis of the 28S rDNA data.

Animals↗
PubMed1991

Molecular evolutionary history of ancient aquatic angiosperms.

Aquatic plants are notoriously difficult to study systematically due to convergent evolution and reductionary processes that result in confusing arrays of morphological features. Plant systematists have frequently focused their attention on the "water lilies," putative descendants of the most archaic angiosperms. Classification of these 10 plant genera varies from recognition of one to three orders containing three to six families. We have used DNA sequence analysis as a means of overcoming many problems inherent in morphologically based studies of the group. Phylogenetic analyses of sequence data obtained from a 1.2-kilobase portion of the chloroplast gene rbcL provide compelling evidence for the recognition of three distinct lineages of "water lily" plants. Molecular phylogenies including woody Magnoliidae sequences and sequences of these aquatic plants depict Ceratophyllum as an early diverging genus. Our results support hypotheses that most taxonomic concepts of the order Nymphaeales reflect polyphyletic groups and that the unusual genus Ceratophyllum represents descendants of some of the earliest angiosperms.

Base Sequence↗
PubMed1995

Assessment of normal testis growth by quantitative texture analysis of 2-D echo images.

Six phases summarize the evolution of the healthy male gonad. Qualitative examination of two-dimensional echograms detects tonal differences at different ages of the testes. However, routine qualitative evaluation of the echograms is too subjective and dependent upon the scanner controls; on the other hand, simple morphology reports are not sufficient to establish the correct histologic and physiologic evolution. So far computer-assisted quantitative analysis of ultrasonic images has been successful in the characterization of tissues based on their echographic properties; thus this approach could be suitable for an accurate identification of the age of healthy testis. Sixty-two normal subjects, ranked in six groups according to age, underwent echographic examination in standard conditions. Echograms were digitized and analysed by means of well-established algorithms for first and second order statistics. Significant differences in tonal features were found able to discriminate among different ages, in agreement with the qualitative analysis and the histologic reports. Furthermore, some second order analysis features exhibit statistically significant alterations of the micro-structural organisation of the echo patterns consequent to changes of the configuration of the ultrasonic targets, that is, of the gonad's histology. In conclusion, quantitative analysis of echograms can provide a tool for a better assessment of normal testis evolution than the qualitative approach.

Adult↗
PubMed1982

Meconium peritonitis. Pathology, evolution, and diagnosis.

The diagnosis of meconium peritonitis has received little attention in the pathology literature. Morphologic features of meconium peritonitis can be confusing to the pathologist unfamiliar with this specific entity, especially in case of extraperitoneal lesions presenting clinically as tumor nodules in the tunica vaginalis. Unfamiliarity with this entity can lead to unnecessary removal of the testis. This paper describes four cases of meconium peritonitis and reviews the literature on the pathology, evolution and diagnostic features of the disease, with emphasis on the healed stage, presenting as a tumor mass in the inguinal canal or tunica vaginalis.

Calcinosis↗
PubMed1990

Origin of tetrapods inferred from their mitochondrial DNA affiliation to lungfish.

This paper shows that questions of an unexpected phylogenetic depth can be addressed by the study of mitochondrial DNA (mtDNA) sequences. For decades, it has been unclear whether coelacanth fishes or lungfishes are the closest living relatives of land vertebrates (Tetrapoda). Segments of mtDNA from a lungfish, the coelacanth, and a ray-finned fish were sequenced and compared to the published sequence of a frog mtDNA. A tree based on inferred amino acid replacements, silent transversions, and ribosomal RNA (rRNA) substitutions showed with statistical confidence that the lungfish mtDNA is more closely related to that of the frog than is the mtDNA of the coelacanth. This result appears to rule out the possibility that the coelacanth lineage gave rise to land vertebrates; hence, morphological characters that link the latter two groups are possibly due to convergent evolution or reversals and not to common descent. Besides supporting the theory that land vertebrates arose from an offshoot of the lineage leading to lungfishes, the molecular tree facilitates an evolutionary interpretation of the morphological differences among the living forms. It would appear that the common ancestor of lungfishes and tetrapods already possessed multiple morphological traits preadapting their locomotion, circulation, and respiration for life on land.

Animals↗
PubMed2006

Genetic architecture of the cryptic species complex of Acanthocyclops vernalis (Crustacea: Copepoda). II. Crossbreeding experiments, cytogenetics, and a model of chromosomal evolution.

Collectively, populations of Acanthocyclops vernalis, a species complex of freshwater copepods, are remarkably similar as to morphology and DNA content, despite variability in chromosome number. Reproductive isolation had been reported among some populations, but with each new investigation the species boundaries and factors that may influence them appeared less clear. To clarify the pattern of biological species within this group of populations, we adopted a comprehensive approach and examined patterns of reproductive isolation in populations for which morphology, chromosome number, DNA content, and 18S rDNA sequences are known. In this study we established nine isofemale lines from four sites in Wisconsin and performed 266 crosses. Crosses within and among these lines were used to relate the degree of reproductive isolation to chromosome differences and to construct a model to explain the origin and maintenance of chromosome number variability. Different gametic and somatic chromosome numbers were observed among specimens within some isofemale lines. In a few cases, gametes with different haploid numbers were produced by a single female. Matings within isofemale lines always produced at least some reproductively successful replicate crosses (produced viable, fertile offspring). Crosses between lines from the same site showed reduced success relative to within-line crosses. Crosses between populations from distant sites showed limited genetic compatibility, producing viable, fertile F1 offspring but infertile F2 adults. One cross between lines with different chromosome numbers (one with 2n = 8 and one with 2n = 10) produced fertile viable offspring, which reproduced for at least 60 generations. These hybrids had either eight or nine chromosomes in the third generation of inbreeding, and eight chromosomes after 20 generations. These hybrids also had reduced nuclear DNA contents at the third generation, a level that persisted through the 20th generation. Successful backcrosses between some hybrids and their parental lines further demonstrated the potential for genetic compatibility among forms with different chromosome numbers. We propose a model in which alterations due to Robertsonian fusions, translocations, and/or loss of chromosomal fragments generate heritable variation, only some of which leads to reproductive isolation. Hence, some of the criteria traditionally used to recognize species boundaries in animals (morphology, DNA content, chromosome number) may not apply to this species complex.

Animals↗
PubMed1997

Distribution of highly repeated DNA sequences in species of the genus Secale.

The presence and distribution of the most important highly repetitive DNA sequences of rye in cultivated and wild species of the genus Secale were investigated using fluorescence in situ hybridization. Accurate identification of individual chromosomes in the most commonly recognized species or subspecies of the genus Secale (S. cereale, S. ancestrale, S. segetale, S. afghanicum, S. dighoricum, S. montanum, S. montanum ssp. kuprijanovii, S. africanum, S. anatolicum, S. vavilovii, and S. silvestre) was achieved using three highly repetitive rye DNA sequences (probes pSc119.2, pSc74, and pSc34) and the 5S ribosomal DNA sequence pTa794. It is difficult to superimpose trends in the complexity of repetitive DNA during the evolution of the genus on conclusions from other cytogenetic and morphological assays. However, there are two clear groups. The first comprises the self-pollinated annuals S. silvestre and S. vavilovii that have few repeated nucleotide sequences of the main families of 120 and 480 bp. The second group presents amplification and interstitialization of the repeated nucleotide sequences and includes the perennials S. montanum, S. anatolicum, S. africanum, and S. kuprijanovii, as well as the annual and open-pollinated species S. cereale and its related weedy forms. The appearance of a new locus for 5S rRNA in S. cereale and S. ancestrale suggests that cultivated ryes evolved from this wild weedy species.

Biological Evolution↗
PubMed2003

The evolution of floral homeotic gene function.

Plant MADS-box genes encode transcriptional regulators that are critical for a number of developmental processes. In the angiosperms (the flowering plants), these include the specification of floral organ identities, flowering time and fruit development. It appears that the MADS box gene family has undergone considerable gene duplication and sequence divergence within the angiosperms. Here I discuss the possibility that these events have allowed the recruitment of these genes to new developmental pathways in particular angiosperm lineages. Recent analyses of sequence changes, expression patterns and, in a few cases, gene function are beginning to provide tantalizing evidence for deciphering when and how such genetic diversification has led to particular morphological innovations. In the future, comparative studies of large numbers of species will be required to assess the extent of such variation as well as to fully understand the mechanisms by which evolution of these developmental regulators has played a role in shaping new morphologies.

Evolution, Molecular↗
PubMed1996

Neuroethological and morphological (Neo-Timm staining) correlates of limbic recruitment during the development of audiogenic kindling in seizure susceptible Wistar rats.

Acute audiogenic seizures are a model of generalized tonic-clonic seizures, induced by high intensity acoustic stimulation in genetically susceptible rodents. The neural substrate are sensory motor brainstem nuclei. Recruitment of forebrain structures takes places upon repetition of acoustically evoked seizures. The term audiogenic kindling means forebrain kindling evoked by repeated brainstem seizures and has been described in several strains of genetically epilepsy-prone rats. Thus, the present work was conducted in order to test the hypothesis that audiogenic kindling recruits the forebrain, which may be behaviorally evaluated and associated with morphological changes as well. The behavioral sequences observed during the development of audiogenic kindling were assessed by neuroethological methods (cluster analysis), with the ETHOMATIC program. Seizure severity indexes (brainstem and limbic seizures) and latencies of wild running and tonic-clonic seizures were measured to quantify seizure evolution. Densitometric analysis of Neo-Timm staining was used for assessing morphological changes associated with audiogenic kindling. In group I, II resistant (R) and 16 susceptible (S) animals were stimulated (120 dB) 21 times, and allowed a 10 day recovery period prior to retesting. In group II, 22 R and 20 S were stimulated 60 times, and allowed a 2 month recovery period prior to retesting. Repetition of the acoustic stimulation in group I and group II susceptible animals led to a progressive and statistically significant attenuation of the behaviors associated with brainstem seizures and a concomitant increased expression of the behaviors associated with limbic seizures. After either a 10 day (group I) or 2 month (group II) recovery period, acoustic stimulation preferentially evoked brainstem-associated behaviors and seizures rather than limbic ones in the audiogenic susceptible animals, although in some animals overlapped brainstem and limbic seizures were detected. Latencies for the wild running and tonic seizures after acoustic stimulation significantly increased during audiogenic kindling for both group I and group II susceptible animals. The quantitative ethological evaluation in both group I and group II, illustrated by flowcharts, showed the evolution of the kindling installation by the presence of limbic seizure clusters, competing in time with the original tonic-clonic clusters. Expression of limbic seizures by group I animals, after acoustic stimulation, was not associated with changes in the mossy fiber Neo-Timm staining pattern of these animals. In group II however, Neo-Timm staining revealed mossy fiber sprouting in the ventral hippocampus (but not in the dorsal), and a significant change in the optical density of amygdaloid nuclei and perirhinal cortex in susceptible animals as compared to resistant ones. In conclusion, audiogenic kindling effectively recruits forebrain structures, responsible for the appearance of limbic seizures. It is possible that the paradigm used in group I was subthreshold for the development of clear-cut synaptic reorganization in the hippocampal mossy fiber system, since the behavioral patterns reverted ten days after the last seizure induction. In group II, however, an increased number of evoked seizures and a more prolonged time after the last chronic seizure showed structural re-arrangements in amygdala, perirhinal cortex and hippocampus, associated with permanence in terms of behavioral data (lack of regression of limbic seizures to control values).

Acoustic Stimulation↗
PubMed2004

Detecting interregionally diversifying natural selection on modern human cranial form by using matched molecular and morphometric data.

This comparison of morphological and neutral genetic variation in 10 human populations was designed to test a neutral hypothesis of cranial evolution in living and recent humans and to explain deviations from neutrality where detected. Overall, among-population differences in extant Homo sapiens cranial morphology are proportional to among-population differences in neutral molecular characteristics. For most of the populations studied, cranial morphology varies among regions in a manner consistent with neutral expectations. Removal of the effects of shared population history and structure by using the partial Mantel's test, however, does not remove the correlation between some aspects of cranial morphology and a measure of coldness of climate. The excess differentiation is most apparent in those population comparisons that involve a Siberian population living in an extremely cold environment. This finding suggests the action of natural selection, associated with regional variation in temperature, leading to among-population differentiation in excess of neutral expectations for some cranial dimensions. Those dimensions reflect the breadth of the skull, cranial vault size and shape, and aspects of nasal morphology. Although morphology for most of the world appears to vary among populations in accordance with neutral expectations in the context of population structure and history, morphology of the Siberian population appears to have undergone adaptation by natural selection.

Data Interpretation, Statistical↗
PubMed2004

The phylogeny of the social wasp subfamily Polistinae: evidence from microsatellite flanking sequences, mitochondrial COI sequence, and morphological characters.

BACKGROUND: Social wasps in the subfamily Polistinae (Hymenoptera: Vespidae) have been important in studies of the evolution of sociality, kin selection, and within colony conflicts of interest. These studies have generally been conducted within species, because a resolved phylogeny among species is lacking. We used nuclear DNA microsatellite flanking sequences, mitochondrial COI sequence, and morphological characters to generate a phylogeny for the Polistinae (Hymenoptera) using 69 species. RESULTS: Our phylogeny is largely concordant with previous phylogenies at higher levels, and is more resolved at the species level. Our results support the monophyly of the New World subgenera of Polistini, while the Old World subgenera are a paraphyletic group. All genera for which we had more than one exemplar were supported as monophyletic except Polybia which is not resolved, and may be paraphyletic. CONCLUSION: The combination of DNA sequences from flanks of microsatellite repeats with mtCOI sequences and morphological characters proved to be useful characters establishing relationships among the different subgenera and species of the Polistini. This is the first detailed hypothesis for the species of this important group.

Animals↗
PubMed2003

Evolution of placental specializations in viviparous African and South American lizards.

Phylogenetic information offers an important resource in analyses of reproductive diversity, including interpretations of fetal membrane evolution. In this paper, we draw upon ongoing studies of South American and African lizards to consider the value of combining phylogenetic and reproductive evidence in the construction of evolutionary interpretations. South American lizards of the genus Mabuya exhibit several reproductive specializations that are convergent on those of eutherian mammals, including viviparity, long gestation periods, ovulation of tiny eggs, and placental supply of the nutrients for development. Studies of placental morphology and development indicate that New World Mabuya share several other derived features, including chorionic areolae and a "Type IV" epitheliochorial placenta with a villous, mesometrial placentome. Some characteristics of these lizards are shared by two African skinks, M. ivensii and Eumecia anchietae, including minuscule eggs, placentotrophy, an absorptive chorioallantois, and features of the yolk sac. Available evidence is consistent with two explanations: (1) placentotrophy originated in Africa, predating a trans-Atlantic colonization by Mabuya of the New World; and (2) placentotrophy arose two or three separate times among these closely related skinks. As illustrated by analysis of these animals, not only can data on fetal membrane morphology yield phylogenetic information, but phylogenetic evidence in turn provides a valuable way to reconstruct the evolution of fetal membranes in a biogeographic context. When appropriately interpreted, morphological and phylogenetic evidence can be combined to yield robust evolutionary conclusions that avoid the pitfalls of circular reasoning.

Allantois↗