A histological and morphometric study on the tissue and cellular distribution of iron in carp Cyprinus carpio L. during chronic waterborne exposure

The effect of long-term (77 day) exposure of carp Cyprinus carpio to low concentrations of waterborne iron (1 mg Fe-dextran l⁻¹) on accumulation and cellular distribution of iron in the liver was assessed using Perl's staining and histological observations and morphometric measurements. Accumulation of iron in the liver occurred after 14 days of exposure, when the majority of the iron was found in the sinusoidal endothelium with lower amounts in the cytoplasm and nuclei of hepatocytes. Upon further treatment the iron was predominantly distributed in the cytoplasm of the hepatocytes either as granules or diffusive iron and in macrophages.     

Quantitative immunolocalization of four immunodominant antigens of Toxoplasma gondii

Ultrastructural localization of four immunodominant antigens of Toxoplasma gondii was investigated quantitatively on thin sections and replicas by an immunogold technique using four monoclonal antibodies (Mab). On immunoblot Mab IV47, GII9, II38 and IE10 identified proteins of 28, 30, 45 and 66-70 kDa, respectively. Use of digital image analyzer and a semi-automatic procedure developed by us, the patterns of label distribution were compared in three cell structures: cell surface, submembrane area and rhoptries. On the whole cell surface, protein P28 and P30 were 2.5 and 4 times more abundant than P66-70 respectively. The protein P28 was essentially concentrated in the submembrane area with a labeling of 195.4 +/- 46.7 gold particles/microns 2 that follows a decreasing gradient from this area to the cell centre. In the rhoptries, all four antigens were detected, P45 and P66-70 being major with a labeling of 97.1 +/- 31.1 gold particles/microns 2 and 155.1 +/- 39.3 gold particles/microns 2 respectively. The results support the hypothesis that rhoptries are the essential site for antigen storage.     

Bacterioplankton interactions with Daphnia and algae in experimental enclosures

Development of bacterioplankton was studied by manipulation of planktivorous fish and/or nutrients in experimental enclosures in a fish pond. Grazing pressure exerted by large zooplankton (Daphnia galeata and Daphnia pulicaria) strongly influenced the counts and size distribution of bacterial populations. Morphometric analyses by scanning electron microscope revealed a shift in size distribution from larger mainly rod-type bacteria under low grazing pressure towards smaller mainly coccus-type under strong grazing pressure. The metabolic activity of bacteria measured as glucose uptake was higher under strong grazing pressure. After removal of large daphnids, the increase in bacterial density was probably the result of two additive factors: low grazing pressure and high level of dissolved organic matter (DOM) due to photosynthetic activity of more abundant algae. Composition of bacterial populations shifted toward larger, rod-type bacteria, and their metabolic efficiency measured by uptake, was lowered. The basic dimensionality of the system and interactions between variables was describe by R-mode factor analysis. The manipulated enclosures were relate with factor score.     

Same species,different population dynamics: Spatio-temporal differences of Undaria pinnatifida (Ochrophyta,Phaeophyceae) in the intertidal of North Patagonia,Argentina

Population dynamics can be influenced by physical and biological factors, particularly in stressful environments. Introduced species usually have great physiological plasticity, resulting in populations with different traits. Undaria pinnatifida, a macroalga originally described from northeast Asia, was introduced in Northern Patagonia, Argentina (San Matías Gulf) around 2010. To describe the spatio-temporal variability in population structure and morphometry of U. pinnatifida, we conducted monthly field samplings for 2 years at the intertidal area of two contrasting sites in the San Matías Gulf. Individuals of U. pinnatifida were classified by developmental stage, and their morpho-gravimetric variables were measured. In both intertidal sites juveniles were found in higher proportion during austral autumn and grew and matured during the autumn-winter months (from May onwards), and individuals senesced during early austral summer (December and January). Conversely, density and biomass were largely different between sites, and individuals showed slight morphological variability between sites. Environmental (e.g., nutrient concentration, available substrate) and biological factors (e.g., facilitation, competition) may explain the observed differences. Since there is not a macroalga with U. pinnatifida morphometrical characteristics in the intertidal environments of San Matías Gulf, studying this recent introduction gives us a better understanding of its potential ecological effects.     

MORPHOLOGICAL EVOLUTION IN MUROID RODENTS II. CRANIOMETRIC FACTOR DIVERGENCE IN SEVEN NEOTROPICAL GENERA,WITH EXPERIMENTAL RESULTS FROM ZYGODONTOMYS

First principal components extracted from covariance matrices of log-transformed craniodental measurements closely approximate general size factors within field-collected samples representing 14 species in seven Neotropical muroid genera; because these samples are mixed-cross-sectional, scores are age-correlated and coefficients reflect postweaning growth allometries. Compared between congeners, sample first principal component coefficients are very similar, an observation that implies a nearly parallel orientation of ontogenetic trajectories in log-measurement space. On the assumption that a common general size factor (estimated as the first principal component of the pooled-within covariance matrix) accounts for most of the observed measurement covariance within samples, size-adjusted differences between congeneric species were estimated variable-by-variable in separate analyses of covariance; these differences reflect developmental adjustments of craniodental morphology that precede the measured interval of postweaning ontogeny. Vectors of size-adjusted difference coefficients are not similar from genus to genus, and a diversity of causal mechanisms is probably responsible. Analyses of captive-bred samples from two “species” of Zygodontomys provide prima facie evidence that size-adjusted differences estimated from field-collected samples have a genetic basis. Postweaning growth allometries in the muroid head skeleton may be conserved due to the biomechanical constraints of masticatory function; the apparent evolutionary plasticity of earlier ontogenetic adjustments may reflect the absence of such constraints in the fetus or suckling pup. The relevance of these results for current theories concerning the developmental genetics of mammalian morphometric evolution is discussed.     

GENETIC CORRELATIONS AMONG MORPHOMETRIC TRAITS AND RATES OF GROWTH AND DIFFERENTIATION IN THE GREEN TREE FROG,HYLA CINEREA

It is often proposed that the morphometric shape of animals often evolves as a correlated response to selection on life-history traits such as whole-body growth and differentiation rates. However, there exists little empirical information on whether selection on rates of growth or differentiation in animals could generate correlated response in morphometric shape beyond that owing to the correlation between these rates and body size. In this study genetic correlations were estimated among growth rate, differentiation rate, and body-size-adjusted head width in the green tree frog, Hyla cinerea. Head width was adjusted for size by using the residuals from log-log regressions of head width on snout-vent length. Size-adjusted head width at metamorphosis was positively genetically correlated with larval period length. Thus, size-independent shape might evolve as a correlated response to selection on a larval life-history trait. Larval growth rate was not significantly genetically correlated with size-adjusted head width. An additional morphometric trait, size-adjusted tibiofibula length, had a nonnormal distribution of breeding values, and so was not included in the analysis of genetic correlations (offspring from one sire had unusually short legs). This result is interesting because, although using genetic covariance matrices to predict long-term multivariate response to selection depends on the assumption that all loci follow a multivariate Gaussian distribution of allelic effects, few data are available on the distribution of breeding values for traits in wild populations. Size at metamorphosis was positively genetically correlated with larval period and larval growth rate. Quickly growing larvae that delay metamorphosis therefore emerge at a large size. The genetic correlation between larval growth rate and juvenile (postmetamorphic) growth rate was near zero. Growth rate may therefore be an example of a fitness-related trait that is free to evolve in one stage of a complex life cycle without pleiotropic constraints on the same trait expressed in the other stage.     

AN ANALYSIS OF SELECTIONAL RESPONSE IN RELATION TO A POPULATION BOTTLENECK

Selection for increased morphometric shape (ratio of wing length to thorax width) was compared between control (nonbottlenecked) populations and bottlenecked populations founded with two male–female pairs of flies. Contrary to neutral expectation, selectional response was not reduced in bottlenecked populations, and the mean realized heritabilities and additive genetic variances were higher for the bottlenecked lines than for the nonbottlenecked lines. Additive genetic variances based on these realized heritabilities were consistent with independent estimates of genetic variances based on parent–offspring covariances. Joint scaling tests applied to the crosses between selected lines and their controls revealed significant nonadditive components of genetic variance in the ancestor, which were not detected in the crosses involving bottlenecked lines. The nonbottlenecked lines responded principally by changes in one trait or the other (wing length or thorax width) but not in both, and regardless of which trait responded, larger trait size was dominant and epistatic to smaller size. Stabilizing selection for morphometric shape in the ancestor likely molded the genetic architecture to include nonadditive genetic effects.     

The significance of morphometric and fecundity differences between the ‘biotypes' of the Brown Planthopper,Nilaparvata lugens

A morphometric analysis of biotypes 1, 2 and 3 from the International Rice Research Institute, Philippines, reared respectively on rice cultivars TN1, Mudgo and ASD7, showed significant differences, but some overlap between them. When the three biotypes were each reared for a single generation on TN1, morphometric differences were very greatly reduced and the distributions widely overlapped.Biotypes 2 and 3 were significantly less fecund than biotype 1 when reared on their normal host varieties. When all were reared on TN1, biotype 3 showed a somewhat lower fecundity than did 1 and 2, but the difference was less than previously reported.It is concluded that the evidence for the association of morphometric differences with virulence characteristics inN. lugens is not proved. Equally there is no evidence that morphometric data may be used to identify field populations with distinct patterns of virulence.

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La signification des différences morphométriques et de fécondité entre des biotypes deNilaparvata lugens

Résumé Ce que l'on a appelé des biotypes deN. lugens sont des populations caractérisées par différents types de virulence à l'égard de différents cultivars résistants de riz, mis en évidence par des essais variétaux systématiques. Différents chercheurs ont tenté de trouver des caractères morphologiques pour identifier ces biotypes.Nous avons fait une analyse morphométrique des biotypes 1, 2 et 3 de l'International Rice Research Institute (IRRI) Philippines. Quand ils sont élevés sur leur propre varieté — biotype 1 sur TN1, 2 sur Mudgo, 3 sur ASD7 — des différences significatives sont observées, bien qu'il y ait un chevauchement considérable. Quand les 3 populations biotypes sont élevées sur la variété sensible TN1, les différences morphométriques sont réduites et le chevauchement fortement augmenté. Nous pourrions alors conclure qu'une part importante de la différenciation morphométrique est due à des facteurs écologiques et non à des différences génétiques entre les populations. Des chercheurs avaient indiqué des différences de fécondité entre les biotypes de l'IRRI, le biotype 3 étant significativement moins fécond; les résultats publiés son contradictoires. Nos observations suggèrent une certaine diminution de la fécondité pour le biotype 3 élevé sur TN1, mais plus limitée que les autres auteurs ne l'avaient envisagée.Nous en concluons qu'il n'y a pas de véritable preuve pour étayer l'hypothèse que les biotypes deN. lugens sont caractérisés par des paramètres morphométriques génétiquement déterminés. Il est alors fallacieux de suggérer que de tels caractères pourraient être utilisés pour identifier des populations avec différents types de virulence. Nous repoussons aussi l'hypothèse que les biotypes représentent une étape dans le processus de spéciation.