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PubMed2004

Evaluation of prey-stage preference as an indicator of life-style type in phytoseiid mites.

Discriminant analysis (DA) models were developed and applied to examine the use of prey-stage preference (Tetranychus urticae Koch egg versus larval prey) in the classification of phytoseiid mites into life-style types. Prey-stage preferences and developmental times when preying on T. urticae, and relative ovipositional rates on six food categories were determined for four phytoseiid species occurring on apple in central and eastern Oregon, USA: Galendromus flumenis (Chant), Galendromus occidentalis (Nesbitt), Metaseiulus citri (Garman and McGregor) and Typhlodromus caudiglans Schuster. In terms of all three aspects studied, the phytoseiid species showed a consistent polarization of G. occidentalis < or = G. flumenis < or = T. caudiglans < M. citri. Specifically, G. occidentalis ('The Dalles' strain) had a significant preference for eggs, G. flumenis had no preference, and T. caudiglans and M. citri had significant preferences for larvae; G. occidentalis had the shortest developmental time, followed by G. flumenis and T. caudiglans, while M. citri had the longest developmental time; and diet breadth was most narrow for G. occidentalis and progressively broader from G. flumenis, T. caudiglans through M. citri, which was able to sustain oviposition on the broadest range of prey and pollens. Species were classified somewhat differently depending on which traits were considered in a given DA. Prey-stage preference was not included as an indicator in the parsimonious DA model when all species and all traits were considered, but in general this trait performed well as an indicator alone (single-trait DA) and somewhat improved the classifications of multitrait discriminant analyses.

Animals↗
PubMed1995

Heterochrony and the phylotypic period.

There has been a resurgence of interest in comparative embryology. It is now important to be able to compare gene expression in different species at similar developmental stages. One phenomenon which may make it difficult to compare embryos in this way is heterochrony--a change in developmental timing during evolution. It is not clear whether heterochrony can affect the intermediate stages of embryonic development, when many important genes involved in pattern formation are expressed. A prevalent view is that these so-called phylotypic stages are resistant to evolutionary change because they are when the body plan is laid down. Haeckel's famous drawings, which show different vertebrates developing from virtually identical somite-stage embryos, are still used to support this idea. I have reexamined the morphological data relating to developmental timing in somite-stage embryos. The data reveal striking patterns of heterochrony during vertebrate evolution. These shifts in developmental timing have strongly affected the phylotypic stage, which is therefore poorly conserved and is more appropriately described as the phylotypic period. This is contrary to the impression created by Haeckel's drawings, which I show to be inaccurate and misleading. The study of gene expression in embryos which show heterochrony could give important insights into evolutionary and developmental mechanisms.

Animals↗
PubMed2001

Identifying body residues of HCBP associated with 10-d mortality and partial life cycle effects in the midge, Chironomus riparius.

The relationship between the body residue of 2,2',4,4',5,5'-hexachlorobiphenyl (HCBP) and its effects, including 10-d mortality and chronic sublethal effects on the midge, Chironomus riparius, are examined in a partial life cycle assessment. The alga, Chlorella vulgaris, was loaded with 14C-labeled HCBP and fed to midges as the method for delivery of the toxicant. In a 10-d bioassay, median lethal body residue (LR50) was 0.57 (95% CI: 0.49-0.66) mmol/kg. In the partial life cycle test, midges were fed a mixture of 12C- and 14C-HCBP-laden algae and exposed in four separate tests to assess the different developmental stages representing 2nd to 3rd instar, 2nd to 4th, 2nd to pupa, and 2nd to adult stages. A variety of sublethal endpoints were monitored, including developmental time within a stadium, body concentration at the end of each stadium, body weight, and fecundity (the number of ova) for the female pupae and adults. Overall, midge body concentrations of HCBP increased with increasing exposure concentration. Body weight was not significantly affected by HCBP except during the 4th instar. Body residue also increased with each successive stadium. Developmental time increased significantly with increasing body concentration in 2nd to 4th, 2nd to pupa, and 2nd to adult tests, while there was no statistical significance in developmental time for the 2nd to 3rd instar test. The number of ova decreased significantly in adults with increasing body concentration of HCBP, with an average of 345 ova in controls, 289 ova at 0.028 mmol/kg of HCBP, and 258 ova at 0.250 mmol/kg. These data, which relate chronic endpoints to body residues, suggest that sublethal endpoints in invertebrates are useful for defining sublethal hazards of PCBs. These data also suggest that ecological consequences may result from relatively low body burdens of PCBs.

Animals↗
PubMed2000

Effects of transgenic Bacillus thuringiensis maize grain on B. thuringiensis-susceptible Plodia interpunctella (Lepidoptera: Pyralidae).

Percentage survivorship, developmental time, adult body length, and sex ratio of Plodia interpunctella (Hübner) reared on field-produced grain from sixteen cultivars of maize, Zea mays L., including several transgenic Bacillus thuringiensis (Bt) Berliner hybrids and selected non-Bt isolines, were evaluated under laboratory conditions. Compared with isolines, development was delayed and survivorship reduced for P. interpunctella reared on grain from transgenic hybrids with the CaMV/35s promoter that express Cry1Ab protein. Similarly, compared with non-Bt hybrids, a transgenic hybrid with the CaMV/35s promoter that expresses Cry9C protein delayed development, decreased survivorship, and caused reductions in adult body length of P. interpunctella. In contrast, no significant differences in P. interpunctella developmental times or survivorship were observed between transgenic hybrids with the PEPC promoter expressing Cry1Ab and their isolines. Additionally, developmental time, survivorship, and adult body length were similar between P. interpunctella reared on a transgenic hybrid with the CaMV/35s promoter expressing Cry1Ac and non-Bt hybrids. Our data demonstrate that transgenic Bt maize grain, especially grain from hybrids with the CaMV/35s promoter expressing Cry1Ab or Cry9C, can significantly affect B. thuringiensis-susceptible P. interpunctella populations up to 4 or 5 mo after harvest.

Animals↗
PubMed2001

Whole-genome effects of ethyl methanesulfonate-induced mutation on nine quantitative traits in outbred Drosophila melanogaster.

We induced mutations in Drosophila melanogaster males by treating them with 21.2 mm ethyl methanesulfonate (EMS). Nine quantitative traits (developmental time, viability, fecundity, longevity, metabolic rate, motility, body weight, and abdominal and sternopleural bristle numbers) were measured in outbred heterozygous F3 (viability) or F2 (all other traits) offspring from the treated males. The mean values of the first four traits, which are all directly related to the life history, were substantially affected by EMS mutagenesis: the developmental time increased while viability, fecundity, and longevity declined. In contrast, the mean values of the other five traits were not significantly affected. Rates of recessive X-linked lethals and of recessive mutations at several loci affecting eye color imply that our EMS treatment was equivalent to approximately 100 generations of spontaneous mutation. If so, our data imply that one generation of spontaneous mutation increases the developmental time by 0.09% at 20 degrees and by 0.04% at 25 degrees, and reduces viability under harsh conditions, fecundity, and longevity by 1.35, 0.21, and 0.08%, respectively. Comparison of flies with none, one, and two grandfathers (or greatgrandfathers, in the case of viability) treated with EMS did not reveal any significant epistasis among the induced mutations.

Alleles↗
PubMed1991

The amniotic sac as scaffolding: prenatal ontogeny of an action pattern.

Intraoral lemon infusion elicits facial wiping behavior in fetal rats on Days 20 and 21 of gestation. On Day 19, fetuses tested in a warm saline bath respond to infusion but do not express the wiping response. In contrast, fetuses tested within the amniotic sac exhibit wiping. Fetal movements after infusion were analyzed on Days 19 and 20 in both the bath and amnion environments. Facial wiping is assembled from simpler components in both real time (during the 15 s after infusion) and developmental time (over Days 19-20 of gestation). In real time, the wiping response occurs following a brief period of fetal activity comprising head and forelimb movements. After the wiping bout is initiated, strokes by left and right forelimbs increase in duration and become synchronized. In developmental time, components of the wiping response (forelimb strokes) are consistently expressed on Day 19, but other components (head stabilization) are lacking when fetuses are tested in bath. The amniotic sac appears to provide scaffolding that reduces head movement and promotes paw-face contact, thus facilitating facial wiping.

Amnion↗
PubMed2004

Sex differences in voice onset time: a developmental study of phonetic context effects in British English.

Voice onset time (VOT) data for the plosives /p b t d k g/ in two vowel contexts (/i a/) for 5 groups of 46 boys and girls aged 5; 8 (5 years, 8 months) to 13;2 years were investigated to examine patterns of sex differences. Results indicated that there was some evidence of females displaying longer VOT values than the males. In addition, these were found to be most marked for the data of the 13;2-year olds. Furthermore, the sex differences in the VOT values displayed phonetic context effects. For example, the greatest sex differences were observed for the voiceless plosives, and within the context of the vowel /i/.

Adolescent↗
PubMed2000

Involvement of the period gene in developmental time-memory: effect of the perShort mutation on phase shifts induced by light pulses delivered to Drosophila larvae.

Phases of circadian locomotor activity rhythms of adult Drosophila reared in constant darkness have been shown to be set by a light stimulus delivered as early as the first-instar larval stage. This implies that a circadian clock functions continuously throughout postembryonic development. The clock genes period (per) and timeless (tim) are expressed cyclically in the larval central nervous system of Drosophila, and daily oscillations of per expression persist throughout metamorphosis in a group of cells, which gives rise to the pacemaker cells underlying locomotor activity rhythms of adults. Therefore, PER and TIM cyclings in these neurons may be responsible for the phenomenon of "larval time-memory." In the absence of any evidence for the involvement of these genes in such a developmental clock, and because circadian-pacemaker functions are underanalyzed in terms of the functions during development, the authors tested the time-memory of a fast-clock period mutant. They show that dark-reared perS mutant individuals as well as wild-type flies can be entrained as larvae and that a brief light pulse given to such entrained larvae can induce phase shifts in animals of either genotype. However, the direction and magnitude of phase shifts were different between wild type and perS, suggesting that a clock under the control of period gene participates in the regulation of developmental time-memory. The authors show that the relevant clock can be entrained by two light input pathways, one involving the phospholipase C encoded by the norpA gene, the other mediated by the blue-light receptor cryptochrome. Phase shifts of molecular oscillations during the larval stage were smaller than those measured by adult behavior, suggesting molecularly transient responses during development.

Animals↗
PubMed2002

Effect of low stressful temperature on genetic variation of five quantitative traits in Drosophila melanogaster.

A half-sib analysis was used to investigate genetic variation for three morphological traits (thorax length, wing length and sternopleural bristle number) and two life-history traits (developmental time and larva-to-adult viability) in Drosophila melanogaster reared at a standard (25 degrees C) and a low stressful (13 degrees C) temperature. Both phenotypic and environmental variation showed a significant increase under stressful conditions in all traits. For estimates of genetic variation, no statistically significant differences were found between the two environments. Narrow heritabilities tended to be higher at 13 degrees C for sternopleural bristle number and viability and at 25 degrees C for wing length and developmental time, whereas thorax length did not show any trend. However, the pattern of genetic variances and evolvability indices (coefficient of genetic variation and evolvability), considered in the context of literature evidence, indicated the possibility of an increase in additive genetic variation for the morphological traits and viability and in nonadditive genetic variation for developmental time. The data suggest that the effect of stressful temperature may be trait-specific and this warns against generalizations about the behaviour of genetic variation under extreme conditions.

Analysis of Variance↗
PubMed2000

Stochastic variation in food availability influences weight and age at maturity.

Variation in mean food availability, and in the variance around the mean, affects the growth rate during development. Previous theoretical work on the influence of environmental quality or growth rates on the phenotypic traits age and size at maturation assumed that there is no variation in growth rate or food availability within a generation. We develop a stochastic dynamic programming (SDP) model of the foraging behaviour of aphidophagous syrphids, and use this model to predict when syrphids should pupate (mature) when average food availability changes, or varies stochastically, during development. The optimal strategy takes into account not only the availability of food, but also the timing of its availability. Food availability, when small, influences developmental time, but not weight at pupation. Food availability, when large, influences weight at pupation, but not developmental time. When the food supply is low, the optimal strategy adjusts the size at pupation downwards for stochastic as opposed to deterministic availability of food. The conclusions reinforce the need for life-history studies to consider state dependence and short-term variability in growth rates.

Animals↗
PubMed1992

Laboratory colonization and maintenance of Toxorhynchites moctezuma.

A colony of Toxorhynchites moctezuma was established at the Caribbean Epidemiology Centre in Trinidad in 1984. Toxorhynchites moctezuma was maintained in cages with high humidities. Eggs were deposited most frequently in a cut bicycle tire containing water. A minimum of 42 h was required for hatching, but 94% hatched between 43 and 51 h. Aedes aegypti larvae were supplied as prey. Larval development times varied with the quantity of prey offered, but when fed ad lib, peak developmental time was 18 days. Mean pupal developmental time was 5.5 days. Although only 12% of larvae survived to pupation in 3 years of production, our experience indicates this species would be a likely candidate for mass production and release.

Animals↗
PubMed2001

Winter biology of Aedes albifasciatus (Diptera: Culicidae) from Córdoba, Argentina.

Host-seeking females of Aedes albifasciatus (Macquart) were collected from April to September 1997, kept under seminatural conditions, and offered sugar solution and blood. Daily survival of females ranged from 0.91 to 0.96, with blood fed females living longer than sugar fed females. Overall, 43% of engorged females completed a gonotrophic cycle, and 15% of them refed and completed a second gonotrophic cycle. The life expectancy of females emerging at the end of summer was longer than those that emerged during winter. Immature developmental time and the developmental threshold were estimated by regression. Embryo development was recorded during autumn, winter, and spring, with a duration of 5-9 d. The developmental threshold for eggs was estimated to be 2.28 degrees C. Egg mortality varied from 0.51 to 0.74. The development time for larva and pupa was between 16 and 29 d and was significantly correlated with temperature. The developmental threshold for larvae and pupae was estimated to be 4.75 degrees C. A greater proportion of females than males emerged when temperatures averaged < or = 18 degrees C. Larval and pupal mortality was high at temperatures below the developmental threshold. Aedes albifasciatus females remained gonotrophically active and immature development continued during winter in Córdoba (10 degrees C isotherm).

Aedes↗
PubMedDate not supplied

Developmental regulation of skull morphology. I. Ontogenetic dynamics of variance.

In the absence of processes regulating morphogenesis and growth, phenotypic variance of a population experiencing no selective mortality should increase throughout ontogeny. To determine whether it does, we measure variance of skull shape using geometric morphometrics and examine its ontogenetic dynamics in the precocial cotton rat (Sigmodon fulviventer) and the altricial house mouse (Mus musculus domesticus). In both species, variance of shape halves between the two youngest samples measured (between 1 and 10 days postnatal and 10 and 15 days postnatal, respectively) and thereafter is nearly constant. The reduction in variance did not appear to result from a general regulation of skull size or developmental timing, although skull size may also be regulated and developmental timing is an important component of the variation in skull shape of young house mice. The ontogenetic dynamics of variance suggest two possible scenarios. First, variation generated during fetal or early postnatal growth is not immediately compensated and therefore accumulates, whereas later in growth, variation is continually generated and rapidly compensated. Second, variation generated during fetal and early postnatal growth is rapidly compensated, after which no new variance is produced. Based on a general model for bone growth, we hypothesize that variance is generated when bone grows under the direction of disorganized muscular movements and decreases with increasing neuromuscular control. Additionally, increasing coherence of signals transmitted by the growing brain and sensory organs, which exert tensile forces on bone, may also canalize skull shape.

Anatomy↗
PubMed1999

Effects and timing of developmental peer appraisals in self-managing work groups.

This study used a repeated measures time-series design to examine the immediate and longer term impact of a structured, face-to-face developmental peer appraisal on 294 undergraduates in 44 self-managing work groups (SMWGs) and 217 MBA students in 36 SMWGs. Results revealed an immediate positive impact on perceptions of open communication, task motivation, social loafing, group viability, cohesion, and satisfaction. Also, the effects of the peer appraisal were not dependent on the perceived ratio of positive to negative feedback, and the enduring impact of the appraisal was influenced by its timing relative to task deadline. Overall, results emphasized that peer appraisals can have a positive effect on relationships and task focus, are influenced by temporal context, and have great potential for work teams.

Adult↗
PubMed1997

Timing of paternal substance use disorder cessation and effects on problem behaviors in sons.

The developmental timing of paternal substance use disorder (SUD) offset on internalizing and externalizing problem behaviors was examined in prepubertal sons. Analyses revealed a significant main effect of the developmental timing of SUD offset on both internalizing and externalizing problems. No differences were found between sons of control-subject fathers and SUD+ fathers whose offsets occurred before the son's sixth birthday. However, when paternal SUD extended beyond the boys' sixth year, significant increases in internalizing and externalizing problem behaviors were found. The results suggest the importance of early parental SUD intervention in prevention of the intergenerational transmission of behavioral problems.

Age Factors↗
PubMed2003

Patterns of variability in voice onset time: a developmental study of motor speech skills in humans.

This study investigated the developmental patterns of variability in the speech parameter voice onset time (VOT) in 46 children. Five groups of children participated in the study as follows: (i) Group 1, aged 5 years 8 months (n=6); (ii) Group 2, 7 years 10 months (n=10); (iii) Group 3, 9 years 10 months (n=10); (iv) Group 4, 11 years 10 months (n=10); and (v) Group 5, 13 years 2 months (n=10). Coefficient of variation values were examined for the VOT values of both 'voiceless' (/p t k/) and 'voiced' (/b d g/) plosives to determine patterns of variability. Significant effects of age were revealed for both the voiceless and voiced plosives, and levels of variability levelled off for Group 4. The data suggest that although variability in VOT decreases with age, the presence of residual variability may be a prerequisite for the further refinement of motor speech skills.

Adolescent↗
PubMed1999

Rearing stable fly larvae (Diptera: Muscidae) on an egg yolk medium.

The growth and survival of Stomoxys calcitrans (L.) larvae on egg yolk medium inoculated with bacteria isolated from a colony of stable flies was evaluated. Five species of bacteria--Acinetobacter sp., Aeromonas sp., Empedobacter breve (Holmes & Owen), Flavobacterium odoratum Stutzer, and Serratia marcescens Bizio--were identified according to fatty acid profiles using a microbial identification system. Larvae failed to develop on uninoculated plates, confirming that bacteria are required to complete development. Larvae also failed to complete development on plates inoculated with Aeromonas sp. and S. marcescens, and died during the 1st instar. Larvae completed development on the remaining 3 bacterial species as well as on Escherichia coli (Migula). Survival was generally higher when larvae were reared on Acinetobacter sp. and F. odoratum compared with E. coli and E. breve. Egg density did not influence larval survival, although the variability in survival was lowest using 20 and 40 eggs per plate. Larval survival in mixed cultures of Acinetobacter and Flavobacterium averaged 22.7% lower than survival in the pure cultures, and averaged 21.6% higher in mixed cultures of Empedobacter and Flavobacterium compared with pure cultures. Larval survival in mixed cultures did not differ significantly from mean survival in pure cultures for combinations of Acinetobacter and E. coli, Acinetobacter and Empedobacter, E. coli and Empedobacter, and E. coli and Flavobacterium. Larval developmental time was faster on all mixed bacterial cultures compared with developmental time on pure bacterial cultures. Optimal sample sizes and egg numbers are presented for detecting specified differences in larval survival. This rearing procedure will be useful for studying insect-microbe interactions and evaluating mortality using bacterial agents.

Animals↗
PubMed2004

Studying the dynamics of problem behavior across multiple time scales: prospects and challenges.

As a commentary on the Special Issue, this paper discusses recent advances in the study of change across several time scales. It points out the importance of specifying time scales and putative patterns of change when characterizing problem behavior over developmental time scales. Methods for studying risk and protective mechanisms through observation of social interaction are also discussed as a way to study influences that operate in real time. Methods for studying episode-level interaction patterns that result from such real-time influences are also discussed, along with ways to integrate these with longitudinal assessments to study the effects of social interaction on problem behavior across developmental time scales.

Behavioral Research↗