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PubMed2005

Discrete layers of interacting growing protein seeds: convective and morphological stages of evolution.

The growth of several macromolecular seeds uniformly distributed on the bottom of a protein reactor (i.e., a discrete layer of N crystals embedded within a horizontal layer of liquid with no-slip boundaries) under microgravity conditions is investigated for different values of N and for two values of the geometrical aspect ratio of the container. The fluid dynamics of the growth reactor and the morphological (shape-change) evolution of the crystals are analyzed by means of a recently developed moving boundary method based on differential equations coming from the protein "surface incorporation kinetics." The face growth rates are found to depend on the complex multicellular structure of the convective field and on associated "pluming phenomena." This correspondence is indirect evidence of the fact that mass transport in the bulk and surface attachment kinetics are competitive as rate-limiting steps for growth. Significant adjustments in the roll pattern take place as time passes. The convective field undergoes an interesting sequence of transitions to different values of the mode and to different numbers of rising solutal jets. The structure of the velocity field and the solutal effects, in turn, exhibit sensitivity to the number of interacting crystals if this number is small. In the opposite case, a certain degree of periodicity can be highlighted for a core zone not affected by edge effects. The results with no-slip lateral walls are compared with those for periodic boundary conditions to assess the role played by geometrical constraints in determining edge effects and the wavelength selection process. The numerical method provides "microscopic" and "morphological" details as well as general rules and trends about the macroscopic evolution (i.e., "ensemble behaviors") of the system.

Binding Sites↗
PubMed2003

The evolution of cursorial carnivores in the Tertiary: implications of elbow-joint morphology.

The evolution of cursorial adaptations in Tertiary (65-1.65 Myr ago) carnivores has been a contentious issue. Most such studies have focused on the relationship between hind limb proportions and running speed. Here, we show morphometrically that in extant carnivores, the elbow joint has evolved in two distinct directions with mutually exclusive implications for locomotor ability and prey procurement. Some carnivores retain supinatory ability, allowing them to manipulate prey and other items with the forepaws. Such carnivores can become very large. Other carnivores lose the ability to supinate and become cursors. This allows for only moderate size increase. Modern carnivores above ca. 20 kg body mass are committed to one or other of these strategies. This threshold coincides with a postulated threshold in carnivore physiology. The biaxial pattern mostly follows phylogenetic lines, but a strong selective regime can override this signal, as shown by the extant cheetah. Oligocene (33.7-23.8 Myr ago) and early-middle Miocene (23.8-11.2 Myr ago) carnivores follow the same pattern, though in the Miocene the pattern is shifted towards larger body mass, which may be owing to the extraordinary richness of browsing ungulates at this time.

Adaptation, Biological↗
PubMed2003

Sperm competition and the evolution of gamete morphology in frogs.

Despite detailed knowledge of the ultrastructure of spermatozoa, there is a paucity of information on the selective pressures that influence sperm form and function. Theoretical models for both internal and external fertilizers predict that sperm competition could favour the evolution of longer sperm. Empirical tests of the external-fertilization model have been restricted to just one group, the fishes, and these tests have proved equivocal. We investigated how sperm competition affects sperm morphology in externally fertilizing myobatrachid frogs. We also examined selection acting on egg size, and covariation between sperm and egg morphology. Species were ranked according to probability of group spawning and hence risk of sperm competition. Body size, testis size and oviposition environment may also influence gamete traits and were included in our analyses. After controlling for phylogenetic relationships between the species examined, we found that an increased risk of sperm competition was associated with increased sperm head and tail lengths. Path analysis showed that sperm competition had its greatest direct effect on sperm tail length, as might be expected under selection resulting from competitive fertilization. Sperm competition did not influence egg size. Oviposition location had a strong influence on egg size and a weak influence on sperm length, with terrestrial spawners having larger gametes than aquatic spawners. Our analysis revealed significant correlated evolution between egg morphology and sperm morphology. These data provide a conclusive demonstration that sperm competition selects for increased sperm length in frogs, and evidence for evolutionary covariance between aspects of male and female gamete morphology.

Animals↗
PubMed1996

Application of morphological trends of evolution to phylogenetic interpretation of chemotaxonomic data.

Data on the membranotropic action of triterpene glycosides from sea cucumbers (Holothurioidea, Echinodermata) are used as a model for studying the evolution of biochemical adaptations. Conceptions such as the theory of modes of organogenesis, and the theory of phylembryogeneses developed by the Russian school of evolutionary morphology, and other morphological trends of evolutionary transformations of anatomical structures are applicable to the phylogenetic interpretation of chemotaxonomic data. The processes of ontogenesis and biosynthesis of secondary metabolites are compared within the framework of the theory of phylembryogeneses. The deep inner similarity of these processes are shown. Concurrence of the modes of phyembryogenesis noted by Severtsov and the principles of micromolecular evolution noted by Gottlieb and Harborne are also shown. The biological significance of presence or absence of substances, (or some features of these substances) for the whole organism that produced them is the main criterion we propose as an approach for polarization of a biochemical phylogenetic series. The application of methods of comparative anatomy to the molecular level for purposes of investigation on evolution of biomolecules and their functions could be called "chemical morphology".

Adaptation, Physiological↗
PubMed2003

A hierarchical model of plumage: morphology, development, and evolution.

Plumage is a complex component of the avian phenotype. The plumage of an individual is composed of numerous hierarchically arranged developmental and morphological modules. We present a hierarchical model of plumage that provides an intellectual framework for understanding the development and evolution of feathers. Independence, covariation, and interaction among plumage modules create numerous opportunities for developmental and evolutionary diversification of feather complexity and function. The hierarchical relationships among plumage modules are characterized by both top-down and bottom-up effects in which properties of modules at one level of the hierarchy determine or influence the properties of modules at lower or higher levels of the hierarchy. Plumage metamodules are created by covariation or interaction among modules at different levels of the hierarchy.

Animals↗
PubMed1996

[Ischemic neuronal damage in early recovery. A morphological study on evolution of damage in hyperglycemia and normoglycemia].

The evolution of neuronal damage in various regions during ischemia and in early recovery was investigated morphologically using hyperglycemic and normoglycemic Wistar rats. Hyperglycemia (20-35 mu mol/ml plasma) was achieved with the infusion of glucose (i.v.) prior to ischemia. Forebrain ischemia (10 minutes) was induced by bilateral common carotid artery occlusion and hypotension. Normoglycemic rats were fasted prior to ishcemia. Ischemic changes of neurons were quantified by a five-point scale in the caudoputamen (CPu), globus pallidus (GP), hippocampus CA 1 (CA 1), parietal cortex (Par), and substantia nigra reticulata (SNR) during ishcemia and for 90 minutes after recirculation. In the hyperglycemic group, (1), CPu, CA 1 and Par; severely damaged neurons were seen at 60-90 minutes after recirculation. (2) GP; there was little neuronal damage. (3) SNR; immediately after recirculation damaged neurons were observed, and more damage was observed at 90 minutes post recirculation. In the normoglycemic group, no prominent neuronal damage was observed in any region. Hyperglycemia exacerbated ischemic neuronal damage after reperfusion. The evolution of neuronal damage was similar in the CPu and Par regions, but was different in the GP and SNR regions.

Animals↗
PubMed2004

Phylogeny of Lasius ants based on mitochondrial DNA and morphology, and the evolution of social parasitism in the Lasiini (Hymenoptera: Formicidae).

Phylogeny of ants of the tribe Lasiini (Lasius, Acanthomyops, Prenolepis, Euprenolepis, Paratrechina, Pseudolasius, and Myrmecocystus) was analysed using 81 morphological, ecological, and behavioural characters (for 41 species) and mitochondrial DNA sequences (COI, COII, tRNA-Leu; for 19 species). The free-living subgenus Lasius s. str. is paraphyletic with respect to the rest of genus; the traditional "genus" Acanthomyops should be considered a part of Lasius s. lat.; free-living subgenus Cautolasius is a member of the clade of socially parasitic Lasius ants (=Chtonolasius+Acanthomyops+Austrolasius+Dendrolasius). The tree topology is congruent with two alternative scenarios of origin of the temporary social parasitism: (i) a single origin of the parasitic strategy in a derived subclade of Lasius and a secondary loss of this trait in Cautolasius, (ii) a parallel origin of the social parasitism within the clade of hypogeic Lasius ants (in Chtonolasius, and in Acanthomyops+Dendrolasius+Austrolasius). Emery's rule in the strict sense does not apply to this group because most parasites exploit any ecologically available, even phylogenetically distant host species. The parasitic strategy in Lasius could have originated from the aggressive interactions between cofounding queens during pleometric colony founding and/or from the secondary queen adoption.

Animals↗
PubMed1981

Dysmaturative myopathy. Evolution of the morphological picture in three cases.

In a previous paper we grouped together several myopathic pictures as alterations of muscle maturation and we proposed the term of dysmaturative myopathy for them. In this report we shall describe the follow up on three of the original cases, studied 4 1/2, 7 and 6 years after the first biopsy. These cases demonstrate that the muscular picture is not static and that it evolves towards normality. During this evolution, it changes from one to another of the morphological pictures previously described as myotubular and/or centronuclear myopathy, hypotrophy of type I fibers with or without central nuclei and congenital disproportion of types.

Adolescent↗
PubMedDate not supplied

Hepatic fibrosis in alcoholic steatosis. Morphologic aspects and evolutive tendencies.

Alcoholic hepatic steatosis, considered for a long time as a reversible "harmless" disease, is now re-evaluated according to the concept of cirrhosis without cell necrosis and inflammation. The study of 166 biopsies from alcoholic hepatic steatosis has demonstrated the presence of fibrotic process in 25 (15%) of the cases. Histologic and electron microscopic examination have supplied data on the distribution of this fibrosis (perivenous, perisinusoidal and extensive) as well as on the cells involved in collagen synthesis; myofibroblasts, fat storing cells (Ito cells) and the hepatocyte itself. Peritoneoscopy revealed aspects of incipient portal hypertension in some of the cases. Follow-up in time with reiteration of morphologic exploration at intervals of 2 to 3 years has shown the possible evolution toward cirrhosis in cases of steatosis with fibrosis when ethanol consumption is continued. Detection of early fibrosis, in patients with alcoholic steatosis, by means of morphologic or biochemical methods would be necessary for its therapeutic implication: possible reversibility by abstinence from alcohol and antifibrogenic therapy.

Biopsy↗
PubMed2004

Correlated evolution of floral morphology and mating-type frequencies in a sexually polymorphic plant.

In sexually polymorphic species, reproductive morphology governs mating patterns and the character of negative frequency-dependent selection. If local environmental conditions cause sexual morphs to differ between populations, then frequency-dependent selection should create corresponding geographic variation in morph frequencies. We investigate this relation with a model of morph-ratio evolution and analysis of geographic variation in the heterostylous plant Narcissus triandrus. Unlike other tristylous species, N. triandrus possesses both imperfect reciprocity among morphs in sex-organ position and a self-incompatibility system that permits outcrossing within and between morphs. We sampled 137 populations throughout the Iberian Peninsula for floral-morph ratios, and measured floral morphology in 31 populations. Morph ratios exhibited three atypical features: (1) predominance of the long-styled (L) morph; (2) absence of the mid-styled (M) morph from 17.5% of populations; and (3) a negative relation between the frequencies of the L and M morphs among populations. Morph ratios varied geographically, with decreasing frequency of the M morph from the southeast to the northwest of the species' range. Much of this variation accompanied allometric change in the positions of sex organs, especially the mid-level organs, with the M morph declining in frequency and ultimately being lost in large-flowered populations. Using multivariate multiple regression, we demonstrate that variation in floral morphology among populations predicts this geographic variation in morph frequencies. Our theoretical analysis illustrates that patterns of pollen transfer governed by imperfect sex-organ reciprocity can select for unequal equilibrium morph ratios like those observed for N. triandrus. We interpret the L-biased morph ratios and the unusual morphology of N. triandrus as a consequence of its atypical intramorph compatibility system.

Biological Evolution↗
PubMed2006

Nonlinear evolution of surface morphology in InAs/AlAs superlattices via surface diffusion.

Continuum simulations of self-organized lateral compositional modulation growth in InAs/AlAs short-period superlattices on InP substrate are presented. The results of the simulations correspond quantitatively to the results of synchrotron x-ray diffraction experiments. The time evolution of the compositional modulation during epitaxial growth can be explained only including a nonlinear dependence of the elastic energy of the growing epitaxial layer on its thickness. From the fit of the experimental data to the growth simulations we have determined the parameters of this nonlinear dependence. It was found that the modulation amplitude does not depend on the values of the surface diffusion constants of particular elements.

Journal Article↗
PubMed1981

Morphology of a novel cyanobacterium and characterization of light-harvesting complexes from it: Implications for phycobiliprotein evolution.

The morphology of the marine cyanobacterium DC-2 and two light-harvesting complexes from it have been characterized. DC-2 has an outer cell wall sheath not previously observed, the purified phycoerythrin shows many unusual properties that distinguish it from all phycoerythrins characterized to date, and isolated phycobilisomes have a single absorption band at 640 nm in the phycocyanin-allophycocyanin region of the spectrum. On the basis of these observations we suggest that DC-2, rather than being a member of the Synechococcus group, should be placed in its own taxonomic group. In addition, the particular properties of the isolated phycoerythrin suggest that it may be representative of an early stage in the evolution of the phycoerythrins. These observations are of special interest in light of the contribution DC-2 and related cyanobacteria may make to global primary productivity.

Journal Article↗
PubMed2006

Parallel evolution of larval morphology and habitat in the snail-killing fly genus Tetanocera.

In this study, we sequenced one nuclear and three mitochondrial DNA loci to construct a robust estimate of phylogeny for all available species of Tetanocera. Character optimizations suggested that aquatic habitat was the ancestral condition for Tetanocera larvae, and that there were at least three parallel transitions to terrestrial habitat, with one reversal. Maximum likelihood analyses of character state transformations showed significant correlations between habitat transitions and changes in four larval morphological characteristics (cuticular pigmentation and three characters associated with the posterior spiracular disc). We provide evidence that phylogenetic niche conservatism has been responsible for the maintenance of aquatic-associated larval morphological character states, and that concerted convergence and/or gene linkage was responsible for parallel morphological changes that were derived in conjunction with habitat transitions. These habitat-morphology associations were consistent with the action of natural selection in facilitating the morphological changes that occurred during parallel aquatic to terrestrial habitat transitions in Tetanocera.

Animals↗
PubMed2004

Rapid divergent evolution of sexual morphology: comparative tests of antagonistic coevolution and traditional female choice.

Male structures specialized to contact females during sexual interactions often diverge relatively rapidly over evolutionary time. Previous explanations for this pattern invoked sexual selection by female choice, but new ideas emphasize possible sexually antagonistic coevolution resulting from male-female conflict over control of fertilization. The two types of selection have often not been carefully distinguished. They do not theoretically exclude one another, but they have not necessarily had equally important roles in producing rapid evolutionary divergence. To date, most recent empirical studies of antagonistic coevolution have emphasized only a few taxa. This study uses the abundant but little-used data in the taxonomic literature on morphology to evaluate the roles of antagonistic coevolution and traditional female choice over a wide taxonomic spectrum (61 families of arthropods, mostly insects and spiders). Groups with species-specific male structures that contact females were checked for coevolution of species-specific female structures that are contacted by the male and that have mechanical properties that could potentially defend her against the male. Facultatively deployable, species-specific female defensive structures, a design that would seem likely to evolve frequently under the sexually antagonistic coevolution hypothesis, were completely absent (0% of 106 structures in 84 taxonomic groups). Although likely cases of sexually antagonistic coevolution exist, using conservative criteria, 79.2% of the 106 structures lacked even potentially defensive female coevolution. A common pattern (53.8% of 106) was a nearly complete absence of female change in areas contacted by species-specific male structures. Post-hoc arguments invoking possible coevolution of defensive female behavior instead of morphology, or of female sensitivities and responses to male sensory traps, could enable the sexually antagonistic coevolution hypothesis to explain these data. No case of such coevolution of female behavior or sensitivities has been demonstrated, and there are additional reasons to doubt that they are general explanations for the data presented here. Detailed studies of female resistance behavior could help illuminate several issues. The possibility of a greater role for antagonistic coevolution in reproductive physiology than in morphology and the possibility that female choice and sexually antagonistic coevolution have both been important in some lineages are discussed.

Animals↗
PubMed2000

Evolution of gall morphology and host-plant relationships in willow-feeding sawflies (Hymenoptera: Tenthredinidae).

There are over 200 species of nematine sawflies that induce galls on willows (Salix spp.). Most of the species are mono- or oligophagous, and they can be separated into seven or eight different groups based on the type of gall that they induce. We studied the evolution of different gall types and host plant associations by reconstructing the phylogeny of five outgroup and 31 ingroup species using DNA sequence data from the mitochondrial cytochrome b gene. Maximum-parsimony and maximum-likelihood analyses resulted in essentially the same phylogeny with high support for important branches. The results show that: (1) the galling species probably form a monophyletic group; (2) true closed galls evolved only once, via leaf folders; (3) with the possible exception of leaf rollers, all gall type groups are mono- or paraphyletic; (4) similar gall types are closer on the phylogeny than would be expected by a random process; (5) there is an apparent evolutionary trend in galling site from the leaf edge towards the more central parts of the host plant; and (6) many willow species have been colonized several times, which excludes the possibility of parallel cladogenesis between willows and the gallers; however, there are signs of restrictions in the evolution of host use. Many of the patterns in the evolutionary history of nematine gallers have also been observed in earlier studies on other insect gallers, indicating convergent evolution between the independent radiations.

Animals↗
PubMed1988

Post-transfusional vs. sporadic non-A, non-B chronic hepatitis. A clinico-pathological and evolutive study.

The clinical, morphological and evolutive features of 60 patients with chronic hepatitis, presumably caused by non-A, non-B virus infection, have been retrospectively analyzed. In all the cases the disease began as an acute episode of viral hepatitis that was followed by persistently abnormal liver function tests. No patient had evidence of current or past hepatitis B virus infection and other known causes of chronic liver disease were excluded. Thirty patients had received blood transfusions in the recent past, five were drug addicts and the source of the infection was not identified in the remaining 25, in whom the disease was considered to be sporadic. Clinical or biochemical differences between patients with post-transfusional and sporadic non-A, non-B chronic hepatitis were not observed, but liver histology showed a higher proportion of patients with chronic persistent hepatitis in the sporadic (72%) than in the transfusional group (53%). On follow-up, sustained normalization of liver function tests was observed in 46% of the cases with sporadic hepatitis but only in 13% of the cases with post-transfusion hepatitis. These observations suggest that non-A, non-B chronic hepatitis is more severe in patients with transfusion-related infection than in sporadic cases.

Adult↗