Populational Changes of the Enteric Protozoans Opalina spp. and Nyctotherus cordiformis During the Ontogeny of Anuran Tadpoles

ABSTRACT. We studied ontogenetic population changes of Opalina and Nyctotherus cordiformis in eight species of tadpoles from 10 sites in east-central Mississippi. Most tadpoles acquired Opalina early in development, while the acquisition of N. cordiformis was variable. Developmental stage, species and collection site explained significant amounts of the variation in Opalina density of tadpoles ( F = 11.6; df = 27, 235; P < 0.0001) and metamorphs ( F = 7.31; df = 24, 84; P < 0.0001). Relationships between Opalina density and host stage showed either (1) a gradual decrease or (2) a gradual increase throughout host ontogeny. Opalina densities declined during metamorphosis. Density variations of N. cordiformis were explained by host species of tadpoles ( F = 9.30; df = 7, 142; P < 0.0001) and by host species and stage of metamorphs ( F = 5.85; df = 8, 62; P < 0.0001).
The length of larval period, habitat duration and generation time of the protozoans are suggested as major modifiers of the protozoan densities. Hosts with long larval periods show a decreasing population density and hosts with short developmental periods show a pattern of increasing density. Neither pattern was detected in tadpoles from temporary sites. Metamorphic declines in protozoan density, but not necessarily the loss of protozoans, reflect metamorphic alterations of the gut common to all hosts.     

Lifetime prevalence and age-of-onset distributions of mental disorders in the World Health Organization's World Mental Health Survey Initiative

Data are presented on the lifetime prevalence, projected lifetime risk, and age-of-onset distributions of mental disorders in the World Health Organization (WHO)''s World Mental Health (WMH) Surveys. Face-to-face community surveys were conducted in seventeen countries in Africa, Asia, the Americas, Europe, and the Middle East. The combined numbers of respondents were 85,052. Lifetime prevalence, projected lifetime risk, and age of onset of DSM-IV disorders were assessed with the WHO Composite International Diagnostic Interview (CIDI), a fully-structured lay administered diagnostic interview. Survival analysis was used to estimate lifetime risk. Median and inter-quartile range (IQR) of age of onset is very early for some anxiety disorders (7-14, IQR: 8-11) and impulse control disorders (7-15, IQR: 11-12). The age-of-onset distribution is later for mood disorders (29-43, IQR: 35-40), other anxiety disorders (24-50, IQR: 31-41), and substance use disorders (18-29, IQR: 21-26). Median and IQR lifetime prevalence estimates are: anxiety disorders 4.8-31.0% (IQR: 9.9-16.7%), mood disorders 3.3-21.4% (IQR: 9.8-15.8%), impulse control disorders 0.3-25.0% (IQR: 3.1-5.7%), substance use disorders 1.3-15.0% (IQR: 4.8-9.6%), and any disorder 12.0-47.4% (IQR: 18.1-36.1%). Projected lifetime risk is proportionally between 17% and 69% higher than estimated lifetime prevalence (IQR: 28-44%), with the highest ratios in countries exposed to sectarian violence (Israel, Nigeria, and South Africa), and a general tendency for projected risk to be highest in recent cohorts in all countries. These results document clearly that mental disorders are commonly occurring. As many mental disorders begin in childhood or adolescents, interventions aimed at early detection and treatment might help reduce the persistence or severity of primary disorders and prevent the subsequent onset of secondary disorders.     

The fitness advantage of a high-performance weapon

Weapons used in combat between males are usually attributed to sexual selection, which operates via a fitness advantage for males with weapons of better 'quality'. Because the performance capacity of morphological traits is typically considered the direct target of selection, Darwin's intrasexual selection hypothesis can be modified to predict that variation in reproductive success should be explained by variation in performance traits relevant to combat. Despite such a straightforward prediction, tests of this hypothesis are conspicuously lacking. We show that territorial male collared lizards with greater bite-force capacity sire more offspring than weaker biting rivals but exhibit no survival advantage. We did not detect stabilizing or disruptive selection on bite-force capacity. Taken together, these results support the hypothesis that superior weapon performance provides a fitness advantage through increased success in male contests. Sexual selection on weapon performance therefore appears to be a force driving the evolution and maintenance of sexual dimorphism in head shape.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 840–845.     

Morphological and molecular evidence for phylogeny and classification of South American pitvipers,genera Bothrops,Bothriopsis, and Bothrocophias (Serpentes: Viperidae)

Species in the genus Bothrops s. l. are extraordinarily variable in ecology and geography, compared with other genera in the subfamily Crotalinae. In contrast to the trend of splitting large and variable groups into smaller, more ecologically and phenotypically cohesive genera, the genus Bothrops has remained speciose. In addition, previous phylogenetic analyses have found Bothrops to be paraphyletic with respect to the genus Bothriopsis. Taxonomic arguments exist for synonymizing Bothriopsis with Bothrops, and for splitting Bothrops into smaller genera, but the greatest hindrance to taxonomic revision has been incomplete phylogenetic information. We present a phylogeny of Bothrops, Bothriopsis, and Bothrocophias based on 85 characters of morphology and 2343 bp of four mitochondrial gene regions, and with significantly greater taxonomic coverage than previous studies. The combined data provide improved support over independent datasets, and support the existence of discrete species groups within Bothrops. The monophyly and distinctness of these groups warrant recognition at the generic level, and we propose a new taxonomic arrangement to reflect these findings. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 156 , 617–640.     

Non-Coordinate Genetic Alterations in the Expression of Catalase and other Glyoxysomal Enzymes during Maize Development

In the scutellum of maize during post-germinative development,the primary form of catalase expressed is the product of theCat2 structural gene, CAT-2. The developmental time-course ofCAT-2 protein follows a rapid increase with a peak at approximately4–5 d alter germination and a subsequent decline. An inbredstrain of maize, A337, has been found to exhibit a similar generalizedprofile with the significant exception that the level of CAT-2protein present in the scutellum is far above that in the ‘typical’maize lines exemplified by W64A. Our data suggest that the higherlevels of CAT-2 exhibited in A337 are due to increased synthesisand accumulation of more CAT-2 protein, and not merely to enzymeactivation. A comparison of A337 and W64A showed that the twolines are similar with respect to number of glyoxysomes andwith the exception of catalase, other microbody associated enzymesexhibit similar activity levels and developmental profiles.Thus, the results presented suggest that the catalasc developmentalprogramme characteristic of line A337 is not due to a concurrentincrease and subsequent decline in the number of glyoxysomesformed in the scutellum during this developmental period butis instead due to a greater level of CAT-2 protein. The datafurther support our earlier findings that the genes coding forglyoxysomal enzymes in maize are non-coordinately regulated. Key words: Gene regulation, glyoxysomes, catalase, glyoxysomal enzymes     

Variations of skull-body regressions of the lemming (Dicrostonyx groenlandicus) under laboratory and field conditions

Collared lemmings, Dicrostonyx groenlandicus , maintained in the laboratory under short-day photoperiods (2 h light: 22 h dark) grew faster than their cohorts kept under long-day photoperiods (22 h light: 2 h dark). Significant differences in cranial, visceral and body components were found in both sexes. Linear regressions of skull-body parameters were compared to those of wild lemmings trapped at Eskimo Point, Northwest Territories, Canada, during three consecutive summers from 1973 to 1975. The data support the conclusion that variation in body size and skull development associated with changes in population density are, in part, due to photoperiod influences. The importance of this facultative response is discussed in relation to current theories on thermal regulation and variations in subnivial breeding success observed in this species.     

EFFECTS OF SAMPLE SIZE AND PRIOR MASTICATION ON TEXTURE JUDGMENTS

Two experiments were conducted. In the first, 25 untrained subjects judged the hardness and chewiness of three different food samples following either 0, 60, 120, or 180 s of adaptive chewing on an experimental gum compound. No effect of the adaptive chewing was found, in spite of observable and self-reported masticatory fatigue induced by the experimental procedures. These data fail to support the prevalent use of procedural limits on the number and temporal spacing of samples in sensory texture studies. In the second experiment, six groups of subjects (n = 107) judged the hardness and chewiness of two series of food samples that varied in physical size (volume). The groups differed in the degree to which cues about the true size differences were made available. Results showed both hardness and chewiness judgments to increase as a function of sample size, independently of subject awareness of the size differences. These data support the use of procedural controls on sample size, but fail to provide evidence of a size constancy phenomenon. A rheological explanation is proposed to account for the observed sensory effect.     

Mammalian Metaphase Chromosomes with High Molecular Weight DNA isolated at <Emphasis Type="Italic">p</Emphasis>H 10.5

MAMMALIAN metaphase chromosomes may be isolated either at an acid pH^1–4 or at nearly neutral pH^5–7. The only exception is the method of Corry and Cole⁸, performed at pH 9.5. We used alkaline sucrose velocity gradients to determine the size distributions of DNA (molecular weight) in metaphase chromosomes in an attempt to understand their arrangement. Initial experiments yielded 1 × 10⁶ molecular weight DNA (single stranded) pieces regardless of chromosome size. When metaphase cells are lysed directly on the gradient a high molecular weight (1 × 10⁸ for single stranded) is obtained. We therefore examined a large number of chromosome isolation procedures and cytological conditions to determine their effects on the molecular weight of the DNA.     

Lymphopoietic Tissue and Plasma Cells in Amphibians

SYNOPSIS. Lymphoid tissue and lymphopoiesis in the urodelesand anurans was reviewed. Current information suggests the spleenas the principal site of lymphopoiesis in urodeles. Anuranspresent a more complex situation and the principally spleenicreaction of Rana pipiens to "red-leg" organisms was contrastedwith the kidney intertubular lymphoid reaction of Bufo marinusto bovine serum albumin. Intracisternal accumulations of slightlyelectron dense material, probably immunoglobulins, were morefrequently found in Bufo marinus plasma cells than cells withundistended cisternae suggesting some specialization of thesecells in cold-bloodedvertebrates. The superficial nature ofour current knowledge of lymphoid tissue function and immunityin this groups was emphasized.     

WALL STRUCTURE AND ACANTHOPORES IN THE BRYOZOAN LEIOCLEMA ASPERUM

Leioclema asperum (Hall), a typical trepostomatous bryozoan, shows well developed acanthopores which are modified parts of orthodox zooecial walls and not separate skeletal entities. They resulted from locally accelerated forward growth of the wall, hence their distinctive cone-in-cone structure. The comparative absence of growth lines in the axial region of each acanthopore suggests that deposition of calcite in that situation was virtually continuous. There is no reason to believe that the acanthopores were originally hollow and they cannot have housed kenozooids, as is commonly supposed.