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Hatch
Kinds of Hatch Terms modified by Hatch Selected AbstractsHatch and Sumner's Textbook of Paediatric AnaesthesiaANAESTHESIA, Issue 5 2010J A Davies No abstract is available for this article. [source] Mapping the organizational culture research in nursing: a literature reviewJOURNAL OF ADVANCED NURSING, Issue 5 2006Shannon Scott-Findlay PhD RN Aim., This paper reports a critical review of nursing organizational culture research studies with the objectives of: (1) reviewing theoretical and methodological characteristics of the studies and (2) drawing inferences specific to the state of knowledge in this field. Background., Organizational culture is regarded as significant in influencing research use in clinical practice yet it is not understood how culture shapes practitioners' behaviours. Only one review of this empirical literature in nursing has been completed. Method., Using selected computerized databases, published nursing research studies in English that examine organizational culture were accessed. Organizational culture studies were categorized using Hatch's three perspectives on organizational culture: (1) modern, (2) symbolic-interpretive and (3) postmodern. The review was conducted in 2005. Results., Twenty-nine studies were in the final data set. Results pointed to variations in cultural definitions and incorporation of organizational sciences theory. In classifying the studies, modern perspectives dominated (n = 22), symbolic-interpretive approaches were an emerging group (n = 6) and one study was unclassifiable. Our results expand current cultural instrument reviews by pinpointing tools that have been previously overlooked and by identifying ongoing theoretical and methodological challenges for researchers. Conclusion., An exclusive reliance on modernistic approaches in organizational culture research cannot yield a complete understanding of the phenomenon. Rather, the field could benefit from a variety of cultural approaches. In a similar vein, researchers need to be mindful of the terminology and the unit of analysis they use in their research, as these are the two largest research challenges. [source] Postembryonic development of the cranial lateral line canals and neuromasts in zebrafishDEVELOPMENTAL DYNAMICS, Issue 3 2003Jacqueline F. Webb Abstract The development of the cranial lateral line canals and neuromast organs are described in postembryonic zebrafish (0,80 days postfertilization). Cranial canal development commences several weeks after hatch, is initiated in the vicinity of individual neuromasts, and occurs in four discrete stages that are described histologically. Neuromasts remain in open canal grooves for several weeks during which they dramatically change shape and increase in size by adding hair cells at a rate one-tenth that in the zebrafish inner ear. Scanning electron microscopy demonstrates that neuromasts elongate perpendicular to the canal axis and the axis of hair cell polarization and that they lack a prominent nonsensory cell population surrounding the hair cells,features that make zebrafish neuromasts unusual among fishes. These results demand a reassessment of neuromast and lateral line canal diversity among fishes and highlight the utility of the lateral line system of postembryonic zebrafish for experimental and genetic studies of the development and growth of hair cell epithelia. Developmental Dynamics, 2003. © 2003 Wiley-Liss, Inc. [source] Toxicity of dispersed weathered crude oil to early life stages of Atlantic herring (Clupea harengus)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2010Stephen McIntosh Abstract Reports of the chronic toxicity of dispersed crude oil to early life stages of fish perpetuate uncertainty about dispersant use. However, realistic exposures to dispersed oil in the water column are thought to be much briefer than exposures associated with chronic toxicity testing. To address this issue, the toxicity of dispersed weathered oil to early life stages of Atlantic herring (Clupea harengus) was tested for short exposure durations, ranging from 1 to 144,h. Toxicity was a function of concentration and duration of exposure, as well as of the life stage exposed. Medium South American crude oil dispersed with Corexit 9500 caused blue sac disease in embryos, but not in free-swimming embryos. The age of embryos was negatively correlated with their sensitivity to oil; those freshly fertilized were most sensitive. Sensitivity increased after hatch, with free-swimming embryos showing signs of narcosis. Gametes were also tested; dispersed oil dramatically impaired fertilization success. For exposures of less than 24,h, gametes and free-swimming embryos were the most sensitive life stages. For those of more than 24,h, young embryos (<1 d old) were most sensitive. The results are presented as statistical models that could assist decisions about dispersant use in the vicinity of fish spawning habitats. Environ. Toxicol. Chem. 2010;29:1160,1167. © 2010 SETAC [source] Chronic effects of silver exposure on ion levels, survival, and silver distribution within developing rainbow trout (Oncorhynchus mykiss) embryosENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2001Christine M. Guadagnolo Abstract Rainbow trout embryos were chronically exposed to silver (as AgNO3) in moderately hard water (120 mg CaCO3/L, 0.70 mM Cl,, 1.3 mg/L dissolved organic matter, 12.3 ± 0.1 °C) at nominal concentrations of 0.1, 1, and 10 ,g/L (measured = 0.117 ± 0.008, 1.22 ± 0.16, and 13.51 ± 1.58 ,g/L, respectively) to investigate the effects on mortality, ionoregulation, and silver uptake and distribution of the embryo. Mortalities in the low concentrations (0.1 and 1.2 ,g/L) were not significantly different from controls throughout embryonic development (days 1,32 postfertilization). Mortalities of embryos in the 13.5-,g/L treatment reached 56% by day 32 postfertilization (33% when accounting for control mortality), by which time more than 50% of surviving embryos had hatched. Accumulation of silver in whole embryos of 1.2- and 13.5-,g/L treatments reached the highest concentrations of 0.13 and 0.24 ,g/g total silver, respectively, by day 32, but whole embryo silver burden was not correlated with mortality. Silver concentrations in different compartments of the whole embryo (chorion, dissected embryo, and yolk) were greatest just before hatch and were higher in the chorion for all experimental treatments. Up to 85% of total whole embryo silver content was bound to the chorion, which acts as a protective barrier during silver exposure. Whole embryo Na+ concentration in the 13.5-,g/L treatment was significantly reduced relative to controls from days 23 to 32 postfertilization, and levels in the embryo were reduced by 40% at day 32 postfertilization, indicating that silver toxicity in the whole embryo is associated with an ion regulatory disturbance that is similar to the acute effect of AgNO3 in juvenile and adult trout. [source] Reproductive and transgenerational effects of methylmercury or Aroclor 1268 on Fundulus heteroclitusENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2001Mary Baker Matta Abstract This research determined the potential for methylmercury or Aroclor 1268 to disrupt reproduction and sexual differentiation in Fundulus heteroclitus. The research determined whether fish that are exposed to mercury or Aroclor 1268 survive and successfully reproduce; whether offspring of exposed fish hatch, survive, produce eggs, and fertilize them; and whether the secondgeneration offspring of exposed fish hatch and survive. Fundulus heteroclitus were exposed to mercury or Aroclor 1268 via contaminated food. Endpoints evaluated included survival, growth, fecundity, fertilization success, hatch success, larval survival, sex ratios, and the prevalence of gonadal abnormalities. In general, polychlorinated biphenyls were highly bioavailable and accumulated well through feeding. The only statistically significant effect observed as a result of treatment with Aroclor 1268 was an increase in growth in the offspring of exposed fish. Mercury was accumulated in a dose-dependent fashion via food exposures. Exposure to mercury in food increased mortality in male F. heteroclitus, which possibly occurred as a result of behavioral alterations. Increased mortality was observed at body burdens of 0.2 to 0.47 ,g/g. Offspring of F. heteroclitus fed mercury-contaminated food were less able to successfully reproduce, with reduced fertilization success observed at egg concentrations of 0.01 to 0.63 ,g/g, which corresponds with parent whole-body concentrations of 1.1 to 1.2 ,g/g. Offspring of exposed fish also had altered sex ratios, with treatment at moderate concentrations producing fewer females and treatment at the highest concentration producing more females than expected. Alterations in sex ratios were observed at concentrations of less than 0.01 ,g/g in eggs or between 0.44 and 1.1 ,g/g in parents. Offspring of mercury-exposed fish also had increased growth in moderate treatments, when egg concentrations were less than 0.02 ,g/g, or when parent whole bodies contained 0.2 to 0.47 ,g/g. In summary, exposure to mercury reduced male survival, reduced the ability of offspring to successfully reproduce, and altered sex ratios in offspring. Both direct effects on exposed fish and transgenerational effects were observed. [source] Toxic responses of medaka, D-rR strain, to polychlorinatednaphthalene mixtures after embryonic exposure by in ovo nanoinjection: A partial life-cycle assessmentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2000Sergio A. Villalobos Abstract Polychlorinated naphthalenes (PCNs) are organic compounds with some chemical properties and uses similar to polychlo-rinated biphenyls. Polychlorinated naphthalenes have been detected in biota from certain aquatic environments. The toxicities of several PCN technical mixtures (Halowax) to medaka (Oryzias latipes) were determined by use of an embryo nanoinjection method. Medaka eggs (early gastrula) were injected with 0.5 nl of triolein (vehicle control) or 0.5 nl of four to five graded doses (0.3,30 ng/egg) of Halowax 1014, Halowax 1013, or Halowax 1051 in triolein. Following exposure, embryos developed, and fry were reared to sexual maturity (4 months), at which time they were euthanized. Responses were evaluated as early life stage (ELS) and early adult life stage (EALS) assessments. For ELS, lethality and sublethal alterations in embryos and larvae (<16 d old), such as craniofacial, cardiovascular, and myoskeletal deformities and abnormal or delayed hatch, were monitored for the first 9 d, and a dose severity index was computed. The EALS assessment examined the survival of 16-d-old larvae until early adulthood (123 ± 3 d old), including gonadosomatic index (GSI) and morphometry. Halowax 1014 was found to be the most toxic mixture (LD50 4.2 ng/egg), whereas Halowax 1013 and 1051 were significantly less toxic (LD50s could not be determined). The gonadosomatic index of females was significantly less in fish dosed with Halowax 1014 or 1051. The LD50 for medaka embryos nanoinjected with 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) is about 0.75 pg/egg. Thus, Halowax 1014 was 5,585-fold less potent than TCDD. For Halowax 1014, ELS assessments accurately predicted the results of EALS assessments. [source] Effects of Ultraviolet Radiation on Locomotion and Orientation in Roughskin Newts (Taricha granulosa)ETHOLOGY, Issue 3 2000Andrew R. Blaustein Environmental changes, including those associated with the atmosphere may significantly affect individual animals and ultimately populations. Ultraviolet (UV) radiation, perhaps increasing due to stratospheric ozone depletion, has been linked to mortality in a number of organisms, including amphibians. The eggs and larvae of certain amphibian species hatch at significantly lower rates when exposed to ambient ultraviolet light. Yet little is known about the sublethal effects of UV radiation. For example, UV radiation may affect specific behaviors of an animal that could alter its ability to survive. To examine if UV radiation affects amphibian behavior, we used roughskin newts (Taricha granulosa) as a model. Newts were exposed to low-level doses of UV in the laboratory and then tested in the field to examine if UV-exposed and control (no UV) newts differed in orientation towards water or in locomotor activity levels. UV-exposed and control newts both exhibited a significant orientation towards water in field tests but there was no significant difference in orientation between treatments. However, UV-exposed newts were significantly more active than control newts. Our results suggest that exposure to short-term low levels of UV radiation alters certain behaviors. Environmentally induced changes in behavior may have significant ecological and evolutionary consequences. [source] EVOLUTION OF INCOMPATIBILITY-INDUCING MICROBES IN SUBDIVIDED HOST POPULATIONSEVOLUTION, Issue 2 2009Ralph Haygood Many insects, other arthropods, and nematodes harbor maternally inherited bacteria inducing "cytoplasmic incompatibility" (CI), reduced egg hatch when infected males mate with uninfected females. Although CI drives the spread of these microbes, selection on alternative, mutually compatible strains in panmictic host populations does not act directly on CI intensity but favors higher "effective fecundity," the number of infected progeny an infected female produces. We analyze the consequences of host population subdivision using deterministic and stochastic models. In subdivided populations, effective fecundity remains the primary target of selection. For strains of equal effective fecundity, if population density is regulated locally (i.e., "soft selection"), variation among patches in infection frequencies may induce change in the relative frequencies of the strains. However, whether this change favors stronger incompatibility depends on initial frequencies. Demographic fluctuations maintain frequency variation that tends to favor stronger incompatibility. However, this effect is weak; even with small patches, minute increases in effective fecundity can offset substantial decreases in CI intensity. These results are insensitive to many details of host life cycle and migration and to systematic outbreeding or inbreeding within patches. Selection acting through transfer between host species may be required to explain the prevalence of CI. [source] Characterization and gene cloning of a novel serine protease with nematicidal activity from Trichoderma pseudokoningii SMF2FEMS MICROBIOLOGY LETTERS, Issue 2 2009Lei-Lei Chen Abstract Trichoderma pseudokoningii SMF2 is a biocontrol fungus with inhibitory ability against phytopathogenic fungi. Here, a crude extract of strain SMF2 in a solid ferment exhibited strong nematicidal activity against Meloidogyne incognita, and a novel serine protease SprT with nematicidal activity was purified from the crude extract. Protease SprT has a molecular mass of 31 kDa, a pH optimum of 8.5, and a temperature optimum of 60,65 °C. It had good thermostability, and was stable in an alkaline environment. SprT could degrade bovine serum albumin, lysozyme, and gelatin, and its activity was enhanced by many metal ions. The cuticles of nematodes treated by protease SprT obviously crimpled. Purified protease SprT could kill juveniles of M. incognita and inhibit egg hatch, suggesting that it is involved in the nematicidal process of T. pseudokoningii SMF2. The full-length cDNA gene-encoding protease SprT was cloned by rapid amplification of cDNA ends. Sequence analysis showed that SprT is a monodomain subtilase containing 284 amino acid residues. It had higher identities and a closer relation to the nematicidal serine proteases (59,69%) from nematode parasitic fungi than to the serine proteases (<50%) from Trichoderma. Protease SprT represents the first well-characterized subtilase with nematicidal activity from Trichoderma. [source] The possible adaptive advantages of terrestrial egg deposition in some fluvial diadromous galaxiid fishes (Teleostei: Galaxiidae)FISH AND FISHERIES, Issue 3 2006RM McDowall Abstract Several diadromous New Zealand and Australian species of Galaxias are now known, or suspected, to deposit their eggs amongst riparian vegetation or substrates either supratidally in estuaries or in forested streams in locations that are only temporarily submerged by elevated water levels. The eggs develop in a humid atmosphere and hatch when the egg deposition sites are resubmerged; a significant role for agitation in stimulating hatching seeming likely. There are risks from the eggs becoming dehydrated, and also from a failure by water to resubmerge the eggs before they have exhausted their energy resources. Hatching is triggered by elevated flows, perhaps being an outcome of agitation of the eggs. Elevated flows may also increase the rate of downstream transport of the larvae, facilitating survival during dispersal to sea from spawning sites in streams that may be long distances inland. Hatching during flood events may favour survival of the larvae because turbid flows may provide ,cover' for the larvae as they emigrate to sea. Risks from egg predation by aquatic predators may be replaced by risks from terrestrial predators. [source] Effects of ontogeny, temperature, and light on vertical movements of larval Pacific cod (Gadus macrocephalus)FISHERIES OCEANOGRAPHY, Issue 5 2009THOMAS P. HURST Abstract The role of behavior, especially vertical migration, is recognized as a critical component of realistic models of larval fish dispersion. Unfortunately, our understanding of these behaviors lags well behind our ability to construct three-dimensional flow-field models. Previous field studies of vertical behavior of larval Pacific cod (Gadus macrocephalus) were limited to small, preflexion stages (,11 mm SL) in a narrow range of thermal conditions. To develop a more complete picture of larval behavior, we examined the effects of ontogeny, temperature, and light on vertical responses of larval Pacific cod in experimental columns. While eggs were strictly demersal, yolk-sac larvae displayed a strong surface orientation as early as 1 day post hatch (, 5 mm SL). Consistent with field observations, small preflexion larvae (<10 mm SL) showed no response to varying light levels. However, there was a direct effect of temperature on larval behavior: Pacific cod larvae exhibited a stronger surface orientation at 4°C than at 8°C. The behavior of larger, postflexion larvae (>15 mm SL) in experimental columns was consistent with a diel vertical migration and independent of water temperature: fish were more widely distributed in the column, and median positions were consistently deeper at higher light levels. These laboratory observations are combined with observations from discrete-depth (MOCNESS) sampling in the Gulf of Alaska to characterize the vertical distribution of larval Pacific cod and contrast ontogenetic patterns with walleye pollock (Theragra chalcogramma). The vertical movements of larval Pacific cod described here will be applied in the development of dispersal projections from Gulf of Alaska spawning grounds. [source] Larval lobster (Homarus americanus) distribution and drift in the vicinity of the Gulf of Maine offshore banks and their probable originsFISHERIES OCEANOGRAPHY, Issue 2 2005G. C. HARDING Abstract Surveys for lobster larvae in offshore waters of the north-eastern Gulf of Maine in 1983, 1987 and 1989 confirm that local hatching occurs mainly at depths <100 m over the banks, including Georges and Browns Banks. Detailed studies in the vicinity of Georges Bank in late July of both 1987 and 1989 indicate that the first and second moult stages were located primarily over the bank whereas stages III and IV lobster were collected both over and off the bank. At times stage IV lobster were more abundant off the bank than over it. The condition of stage III and IV lobster, as measured by a lipid index, was better off than over Georges Bank in 1988 and 1989 indicating a possible physiological advantage to being off the bank. In addition, the higher surface temperatures off Georges Bank would shorten larval development time to settlement. To determine the probable hatch sites of stage IV lobster collected off of Browns Bank in 1983 and off of Georges in 1987 and 1989, a 3-D circulation model of the Gulf of Maine was used to simulate larval lobster drift backwards in time. In all cases, areas off Cape Cod, MA, and off Penobscot Bay, ME were suggested as the source of the larvae, although most of the larval trajectories never reached these near-shore waters that are well-known, larval hatching areas. The model-projected larval release times match most closely the observed inshore hatch off Massachusetts but model uncertainties mean that coastal Maine cannot be ruled out as a source. Georges Bank is also a potential source because the present model does not take into account short-term wind events, off-bank eddy transport or the possibility of directed off-bank larval swimming. Examination of weather records prior to and during our 1988 and 1989 sampling periods indicates that winds were not of sufficient intensity and duration to induce larval transport off Georges Bank. The shedding of eddies from the northern flank of Georges Bank into the Gulf of Maine are a relatively common phenomenon during summer but not enough is known about them to evaluate their contribution to possible cross-bank transport of lobster larvae. Directed larval swimming is another possible source for the stage IV lobster found near Georges Bank. Plankton distributions across the northern frontal zone of Georges Bank in 1988 were used as proxies for the scarce larval lobsters. The more surface distribution of the microplankton, in particular, supports the possibility that wind and eddy events may be important in the transport of stage III and IV lobsters off of Georges Bank. Further studies are needed to evaluate these possible additional sources of advanced stage lobster larvae found off of the offshore banks. [source] The chicken B-cell receptor complex and its role in avian B-cell developmentIMMUNOLOGICAL REVIEWS, Issue 1 2000Camil E. Sayegh Summary: The bursa of Fabricius is critical to normal B-lymphocyte development in birds. During embryonic life, B-cell precursors migrate to the bursal rudiment and those which have undergone productive V(D)J recombination colonize lymphoid follicles and undergo immunoglobulin V gene diversification by gene conversion. The chicken surface IgM complex appears structurally and functionally equivalent to its mammalian counterpart, with homologs to CD79a and CD79b. Expression of a truncated Ig chain is sufficient to drive the early stages of B-cell development in the embryo bursa. Bursal cells expressing the truncated receptor complex proliferate in bursal follicles, and those which contain V gene rearrangements undergo V gene diversification by gene conversion. The bursa is a gut-associated organ and antigen is focused to bursal lymphoid follicles after hatch. While expression of the truncated chain is sufficient to support B-cell development in the embryo, B cells expressing this receptor are rapidly eliminated after hatch. We suggest the possibility that B-cell development in the bursa after hatch is driven by encounter with antigen leading to redistribution of B cells within the lymphoid follicle, B-cell proliferation and V gene repertoire development by gene conversion. [source] A teratocyte gene from a parasitic wasp that is associated with inhibition of insect growth and development inhibits host protein synthesisINSECT MOLECULAR BIOLOGY, Issue 5 2003D. L. Dahlman Abstract After parasitization, some wasps induce hosts prematurely to initiate metamorphic development that is then suspended in a postwandering, prepupal state. Following egression of the parasite larva, the host remains in this developmentally arrested state until death. Teratocytes, cells released at egg hatch from extra-embryonic serosal membranes of some wasp parasites, inhibit growth and development when injected into host larvae independent of other parasite factors (e.g. venom, polydnavirus). Synthesis of some developmentally regulated, abundantly expressed Heliothis virescens host proteins is inhibited in hosts parasitized by Microplitis croceipes and by teratocyte injection. A cDNA encoding a 13.9 kDa protein (TSP14) that inhibited protein synthesis, growth and development was isolated from a protein fraction secreted by teratocytes. TSP14 appears to be responsible, in part, for the teratocyte-mediated inhibition of host growth and development. Interestingly, this cDNA encoded a cysteine-rich amino acid motif similar to that described from Campoletis sonorensis polydnavirus, a mutualistic virus that enables wasp parasitization of lepidopteran larvae. Moreover, TSP14 inhibited protein synthesis in a dose-dependent manner in rabbit reticulocyte lysate and wheat germ extract translation systems. We hypothesize that some wasp parasites inhibit translation as a general means to regulate and redirect lepidopteran host physiology to support endoparasite development. [source] Constructing life-tables for the invasive maize pest Diabrotica virgifera virgifera (Col.; Chrysomelidae) in EuropeJOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2006S. Toepfer Abstract:, The western corn rootworm (Diabrotica virgifera virgifera LeConte, Col.; Chrysomelidae) is an alien invasive species in Europe. It is a univoltine species with eggs that overwinter in the soil and larvae that hatch in spring. Three larval instars feed on maize roots, which can cause plant lodging and yield loss of economic importance. Adults emerge between mid-June and early August and can reduce yields through intensive silk feeding. In order to provide a thorough understanding of the population dynamics of this invasive pest species in the invaded European region, complete age specific life-tables were constructed in two maize fields in southern Hungary assessing the significance of natural mortality factors acting on D. v. virgifera populations. This information provides a rational basis for devising sustainable integrated pest management programmes, in particular, by enabling the identification of vulnerable pest age intervals for the timely application of various management tools. The life-table for D. v. virgifera in Europe resulted in a total mortality of about 99% from the egg stage in the autumn to the emergence of adult females in the following year (KTotal = 2.48), which is comparable with North America. The highest reduction of D. v. virgifera numbers resulted from the mortality in first instar larvae (94% marginal death rate) and from the unrealized fecundity (80%). However, only the variation in mortality between years can change the generational mortality and thus influence population growth. High variation in the marginal death rate between fields and years was found in the second and third instar larval stages, and in the overwintering egg stage. These mortality factors therefore have the potential to cause changes in the total generational mortality. Furthermore, the life-table suggested that a high fecundity could compensate for a high generational mortality and would lead to population increase. [source] A guide to the embryonic development of the shovelnose sturgeon (Scaphirhynchus platorynchus), reared at a constant temperatureJOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2007R. E. Colombo Summary Described is the sequence and timing of embryologic development of shovelnose sturgeon, (Scaphirhynchus platorynchus) reared at a constant temperature 20 ± 0.5°C. Artificially spawned, fertilized eggs were held in a recirculating system. Embryos were sampled hourly during the first 48 h of development and every 3 h thereafter. Embryos were viewed and imaged at 35× magnification. The first cleavage furrow appeared 2 h post-fertilization; early (synchronous) cleavage was completed after 7 h. Blastulation concluded at 16 h when the dorsal blastopore lip formed. The slitlike blastopore appeared at 29 h, signifying the completion of gastrulation. At 33 h, the rudiments of the excretory system emerged, followed by closing of the neural tube at 36 h and formation of the s-shaped heart at 60 h. The body continued to elongate with mass hatch occurring at 102 h. After hatch, larvae swam into the water column and drifted in the flow for approximately 2 days after which the larvae became positively rheotaxic. After expulsion of the pigment plug, the larvae began exogenous feeding and other structures continued to develop. Metamorphosis was completed after 26 days of development. Because the shovelnose sturgeon possesses developmental patterns similar to those of other sturgeon, we can use this species as a model for the closely related pallid and Alabama sturgeon. [source] Direct and correlated responses to selection for larval ethanol tolerance in Drosophila melanogasterJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2001J. D. Fry Ethanol is an important larval resource and toxin for natural Drosophila melanogaster populations, and ethanol tolerance is genetically variable within and among populations. If ethanol-tolerant genotypes have relatively low fitness in the absence of ethanol, as suggested by the results of an earlier study, genetic variation for ethanol tolerance could be maintained by variation in ethanol levels among breeding sites. I selected for ethanol tolerance in large laboratory populations by maintaining flies on ethanol-supplemented media. After 90 generations, the populations were compared with control populations in egg-to-adult survival and development rate on ethanol-supplemented and unsupplemented food. When compared on ethanol-supplemented food, the ethanol-selected populations had higher survival and faster development than the control populations, but on unsupplemented food, the populations did not differ in either trait. These results give no evidence for a ,trade-off' between the ability to survive and develop rapidly in the presence of ethanol and the ability to do so in its absence. The effect of physiological induction of ethanol tolerance by exposing eggs to ethanol was also investigated; exposing eggs to ethanol strongly increased subsequent larval survival on ethanol-supplemented food, but did not affect survival on regular food, and slowed development on both ethanol-supplemented and regular food, partly by delaying egg hatch. [source] The influence of first-feeding diet on the Atlantic cod Gadus morhua phenotype: survival, development and long-term consequences for growthJOURNAL OF FISH BIOLOGY, Issue 1 2010R. M. Koedijk Atlantic cod Gadus morhua larvae reached four-fold (at low larval density) to 11 fold higher body mass (high larval density) at 50 days post hatch (dph) when fed zooplankton rather than enriched rotifers. A short period (22,36 dph) of dietary change affected larval growth positively if changed from enriched rotifers to natural zooplankton and negatively if prey type changed vice versa. Overall survival did not differ between the two larval groups at low larval density, but at high density the rotifer group had a higher overall survival (10·8% v. 8·9%). Long-term growth was affected significantly by larval diet in favour of the zooplankton diet; juveniles reached a 23% higher mass in a 12 week growth period. No difference in growth performance was found between juveniles fed natural zooplankton during the larval period for 36, 22 or 14 days, but all these juveniles performed significantly better compared with the rotifer-fed group. These findings suggest that optimal diet during a short period in the larval period can result in improved growth in both the larval and juvenile period. Improved rotifer quality may, therefore, hold a large potential for growth improvement in this species. [source] Photoresponse in allis shad larvaeJOURNAL OF FISH BIOLOGY, Issue 3 2008P. Jatteau Allis shad Alosa alosa photoresponse was investigated in 3 day-old to 1 month-old larvae. Regardless of age, larvae strongly preferred the lit compartment in aquaria experiments. Such response was consistent with other experimental studies which have suggested a pelagic behaviour of allis shad larvae from the time of hatch. [source] Growth of organ systems of Dentex dentex(L) and Psetta maxima(L) during larval developmentJOURNAL OF FISH BIOLOGY, Issue 2 2005R. Sala Growth in volume of common dentex Dentex dentex and turbot Psetta maxima during larval development was studied by means of a quantitative histological method. A two-phase pattern of volume increase was recorded for both species, turbot volume being always higher than dentex volume. During the first phase, the increase was small but during the second phase volume rose sharply from 22 days post hatch (dph) and 17 dph onwards in dentex and turbot, respectively. In dentex, the specific growth rate (G) of the whole larva as well as that of all the structures studied (nervous tissue, trunk musculature, digestive tract, liver, pancreas, spleen and thymus) was always higher during the second phase, whereas in turbot, only total volume of the larva, trunk musculature and nervous tissue had a higher G during the same period. The pattern of allometric growth of digestive organs was similar for both species. These organs showed an initial positive allometric growth that later became near-isometric (digestive tract and liver) or negative (pancreas). In dentex, nervous tissue and trunk musculature showed near-isometry throughout the period studied. In turbot, nervous tissue exhibited negative allometry and trunk musculature changed from negative to positive allometry. In both species studied, the highest allometry coefficients were recorded for digestive organs before the larva switched to strict exotrophy. This would indicate the importance of the development of these organs for survival. [source] Relating the ontogeny of functional morphology and prey selection with larval mortality in Amphiprion frenatusJOURNAL OF MORPHOLOGY, Issue 6 2010Justin Anto Abstract Survival during the pelagic larval phase of marine fish is highly variable and is subject to numerous factors. A sharp decline in the number of surviving larvae usually occurs during the transition from endogenous to exogenous feeding known as the first feeding stage in fish larvae. The present study was designed to evaluate the link between functional morphology and prey selection in an attempt to understand how the relationship influences mortality of a marine fish larva, Amphiprion frenatus, through ontogeny. Larvae were reared from hatch to 14 days post hatch (DPH) with one of four diets [rotifers and newly hatched Artemia sp. nauplii (RA); rotifers and wild plankton (RP); rotifers, wild plankton, and newly hatched Artemia nauplii (RPA); wild plankton and newly hatched Artemia nauplii (PA)]. Survival did not differ among diets. Larvae from all diets experienced mass mortality from 1 to 5 DPH followed by decreased mortality from 6 to 14 DPH; individuals fed RA were the exception, exhibiting continuous mortality from 6 to 14 DPH. Larvae consumed progressively larger prey with growth and age, likely due to age related increase in gape. During the mass mortality event, larvae selected small prey items and exhibited few ossified elements. Cessation of mass mortality coincided with consumption of large prey and ossification of key elements of the feeding apparatus. Mass mortality did not appear to be solely influenced by inability to establish first feeding. We hypothesize the interaction of reduced feeding capacities (i.e., complexity of the feeding apparatus) and larval physiology such as digestion or absorption efficiency contributed to the mortality event during the first feeding period. J. Morphol., 2010. © 2010 Wiley-Liss, Inc. [source] Surface topology and structural integrity of the Theromyzon tessulatum (Annelida: Hirudinea: Glossiphoniidae) cocoonJOURNAL OF MORPHOLOGY, Issue 7 2008Jon'elle Coleman Abstract Cocoons secreted by the aquatic leech Theromyzon tessulatum comprise a tubular, membranous ovoid, sealed at each end by a glue-like substance, called an operculum. Scanning electron microscopy showed surface features of the T. tessulatum cocoon that included a circuitous bulge, cups that conformed to the shape of embryos, relief folds that radiated from opercula, and asymmetric distributions of protuberances on the upper aspect of the cocoon surface. The structural integrity of the T. tessulatum cocoon was assessed after exposure to a variety of denaturing conditions (e.g., extreme heat, detergents, acids). Although both the fibrous cocoon membrane and opercula were strikingly resilient, the membrane/operculum boundary appeared to be the weakest structural component of the cocoon, consistent with its functional role as an escape hatch for juvenile leeches. The operculum itself was more sensitive to denaturation than the cocoon membrane, and thus was probably the source of a major protein component isolated from the T. tessulatum cocoon (i.e., Tcp; Theromyzon cocoon protein). J. Morphol., 2008. © 2008 Wiley-Liss, Inc. [source] Intestinal function and body growth of broiler chickens on maize-based diets supplemented with mimosa tannins and a microbial enzymeJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 12 2004Paul A Iji Abstract A study was conducted to evaluate the effects of tannin (0, 5, 15, 20 and 25 g kg,1 diet) and a microbial enzyme supplement (MES) on the feed consumption, body growth and digestive physiology of broiler chickens between hatch and 22 days of age. Feed intake, body weight and body weight gain declined (p < 0.001) with an increase in dietary tannin content. Feed conversion efficiency was increased (p < 0.001) in line with dietary tannin level, up to 15 g kg,1 diet. There were no significant effects of dietary treatment on the protein content of pancreatic tissue or activities of pancreatic and jejunal enzymes. The ileal digestibilities of energy, protein, arginine, alanine and leucine were reduced (p < 0.001) as dietary tannin level rose to 20 g kg,1 diet and beyond. The digestibilities of methionine and phenylalanine were also negatively affected (p < 0.01) at the highest level of dietary tannins, while phosphorus digestion was improved (p < 0.05) on diets containing tannin. Apart from an increase (p < 0.01) in the protein content of the jejunal mucosa of birds on the diet with 20 g tannin kg,1 diet, there were no significant effects of the MES on most of the variables assessed. The results demonstrate the negative effects of tannin, especially at high levels of inclusion in the diet. However, neither tannins nor MES influenced the activities of digestive enzymes assessed, suggesting that a wider range of factors may be involved in regulating the effects of tannins on poultry. Copyright © 2004 Society of Chemical Industry [source] The Effects of Temperature and Salinity on Early Life Stages of Black Sea Bass Centropristis striataJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 3 2004David L. Berlinsky Along the Atlantic coast black sea bass occur from the Gulf of Maine to Florida and support important commercial and recreational fisheries. Interest in commercial production of black sea bass has increased in recent years due to high demand and limited seasonable availability. Efforts towards large-scale production have been hampered by a high incidence of early larval mortality. Two of the most important environmental variables affecting hatchery production of marine finfish larvae are temperature and salinity. In the wild, larval black sea bass are found in waters with temperatures of 12,24 C and salinity levels of 30,35 ppt. Studies were conducted to define the temperature and salinity ranges that support growth and development of black sea bass during early life stages. Three developmental phases were investigated: 1) fertilization to hatch: 2) hatch through yolk sac absorption: and 3) during the initial exogenous feeding stage (5,14 days post hatch: DPH). Fertilized eggs were obtained by manual spawning of fish following administration of LHRHa. Fertilized eggs were transferred to 300-mL glass Petri dishes or 500-mL beakers to assess the effects of salinity and temperature through hatch and yolk sac absorption, respectively. To determine environmental effects on growth and survival during initial exogenous feeding 400 actively feeding larvae were cultured in green water and fed enriched rotifers for a 9-d period. For investigation of the effect of salinity, sea water (35 ppt) was diluted gradually to 15, 20, 25, and 30 ppt and maintained at 21 C. For examination of the effect of temperature, seawater was adjusted from 21 C to 12, 15, 21, 27, or 30 C at a rate of 3 C/h. No eggs hatched at 12 C or when salinity was maintained at 0 or 5 ppt. Hatching was uniformly high (, 85%) at temperatures between 15 and 27 C and at salinities , 15 ppt. Survival through yolk sac absorption was greatest at temperatures between 18 and 27 C and at salinities , 20 ppt. Survival through first feeding stage was highest at temperatures , 18 C and 30 ppt salinity. Larval growth through first feeding was not significantly affected by salinity level but did increase with rearing temperature. The results indicate that survival and development of black sea bass during early life stages are most favorable at temperatures >18 C with salinity levels approaching full strength seawater. [source] The Effect of Temperature on First Feeding, Growth, and Survival of Larval Witch Flounder Glyptocephalus cynoglossusJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 4 2001Deborah A. Bidwell Witch flounder Glyptocephalus cynoglossus has recently been identified as a candidate species for aquaculture in the northeastern United States and the Canadian Atlantic Provinces. This study investigated the optimal temperatures for witch flounder larval first feeding and for long term larval culture from hatching through metamorphosis. Maximum first feeding occurred between 15.0 and 16.2 C. Larvae did not survive beyond first feeding when reared at mean temperatures of 5.1, 10.4, or 19.5 C and were unable to initiate feeding at mean rearing temperatures below 6.0 C. At a rearing temperature of 15.0 C in 16-L tanks, mean larval survival to 60 days post hatch (dph) was 14.1%. Mean overall length-specific growth rate for larvae reared to 60 dph at 15.0 C was 3.5%/d and mean absolute growth was 0.62 mm/d. Subsequent larval growth at 15.6 C began to taper off towards 70 dph at the onset of weaning which overlapped with larval metamorphosis. Growth plateaued at 85 dph, followed by a rebound between 90 and 95 dph. Survival was 100% when weaning onto a dry, pelleted diet was initiated at 70 dph with a 10-d live diet co-feeding period. These results are favorable and encourage the further pursuit of commercial witch flounder culture. [source] Effects of Larval Stocking Density on Laboratory-Scale and Commercial-Scale Production of Summer Flounder Paraliehthys dentatusJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 3 2000Nicholas J. King Experiments 1 and 2 at commercial scale tested the densities of 10 and 60 larvae/L, and 10, 20, and 30/L, respectively. The laboratory scale experiment tested the densities of 10, 20, 30, and 40 larvae/L. Experiments were carried out in two separate filtered, flow-through seawater systems at URI Narragansett Bay Campus (laboratory-scale), and at GreatBay Aquafarms, Inc. (commercial-scale). At both locations, the larvae were raised in a "greenwater" culture environment, and fed rotifers and brine shrimp nauplii according to feeding regimes established for each location. Water temperature was maintained at 21C (± 2) and 19C (± 1) for the duration of laboratory and commercial experiments, respectively. Experiments 1 and 2 at the commercial location were terminated at 42 and 37 d post hatch (dph), respectively, and the laboratory experiment lasted 34 DPH. Larvae initially stocked at 10/L grew to an average length of 14.3 and 14.4 mm, and were significantly larger (P < 0.05) than those stocked at 30/L (13.1 mm) and 60/L (11.7 mm) in commercial scale experiments I and 2, respectively. At laboratory scale, no significant differences in length were detected, although mean total length tended to decrease with increasing stocking density (average length of 14.2, 13.3, 12.7, and 12.7 mm for treatments of 10, 20, 30, and 40/L, respectively). Final survival percentage was not affected by stocking density in either commercial experiment, and was 61 and 40% for treatments of 10 and 60/L in Experiment 1, respectively, and 62, 59, and 56% for Experiment 2, respectively. Similarly, there was no significant difference in final survival percentage among treatments in the laboratory experiment, which averaged 59, 55, 56, and 37% for treatments of 10, 20, 30, and 40L. respectively. Since larval length was not different between the intermediate densities (20 and 30 Iarvae/L), and because high-density rearing can produce a much greater numerical yield per tank, we recommend a density of 30 larvaen as an optimal stocking density for the hatchery production of summer flounder. [source] Production, Quality, and Low Temperature Incubation of Eggs of Atlantic Cod Gadus morhua and Haddock Melanogrammus aeglefinus in CaptivityJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2000Lawrence J. Buckley Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinus broodstock maintained under altered regimens of temperature and photoperiod spawned up to 8 mo per year. The cod broodstock produced viable embryos from October through June. The haddock broodstock produced viable embryos from December through May. Egg diameters were largest during the middle of the spawning season when water temperature was at a minimum, resulting in an inverse relationship between egg diameter and water temperature in both species. Egg quality was high, as evaluated by buoyancy, fertilization rate, regularity of early cleavage, and percent viable hatch. Low temperature incubation of cod and haddock eggs extended the embryonic period. Cod embryos tolerated a wider range of temperatures than haddock. High mortality (1 90%) was observed before hatching in haddock embryos incubated at 1 C. Atlantic cod embryos hatched at temperatures as low as ,1 C, extending the embryonic period to 59 d. At 8 C Atlantic cod and haddock embryos hatched in 11,12 d. To determine if extending the embryo incubation time by using low temperatures had a detrimental effect, embryos were incubated through hatch at either 1 C or 6 C, and the larvae from both groups reared at 6 C. Growth and early survival of larvae were comparable in both treatments. [source] Life history of amphibians in the seasonal tropics: habitat, community and population ecology of a caecilian (genus Ichthyophis)JOURNAL OF ZOOLOGY, Issue 3 2005Alexander Kupfer Abstract Fundamental information on the ecology of the limbless tropical caecilians is needed for a well-founded conservation assessment. Here, essential life-history characters are presented for the oviparous caecilian Ichthyophis cf. kohtaoensis from a field site in South-east Asia (Mekong valley, north-eastern Thailand). Ichthyophis cf. kohtaoensis was found in a range of terrestrial macrohabitats including open scrubs, gallery forests and open secondary dipterocarp forests. In the dry season, caecilians were found mainly in soil but in the rainy season they were also detected in epigeic microhabitats (leaf litter or rotten vegetation). Ichthyophis cf. kohtaoensis were recorded in low densities (median 0.08 individuals/m2) and they share their habitat with a range of other terrestrial amphibians and reptiles. The population structure of I. cf. kohtaoensis varied seasonally. Records of late metamorphs were restricted to the cold dry season and occasionally to the onset of the rainy season. Females with clutches were only found in the rainy season. A life-history scenario of I. cf. kohtaoensis in north-eastern Thailand was set up. Reproduction and larval development is related to the rainy season. Mating and oviposition may start at the onset of the monsoon. Larvae hatch at the peak until the end of the rainy season and metamorphose until the end of the dry season. In the light of amphibian decline, this study may encourage further baseline work on the ecology of other caecilian species. [source] Effect of pyriproxyfen, a juvenile hormone mimic, on egg hatch, nymph development, adult emergence and reproduction of the Asian citrus psyllid, Diaphorina citri KuwayamaPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 4 2010Dhana Raj Boina Abstract BACKGROUND: The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is a vector of bacteria presumably responsible for huanglongbing (HLB) disease in citrus. In this laboratory study, an investigation was made of the activity of pyriproxyfen, a juvenile hormone mimic, on ACP eggs, nymphs and adults to evaluate its potential as a biorational insecticide for inclusion in an integrated pest management (IPM) program for ACP. RESULTS: Irrespective of egg age, timing or method of treatment, a significantly lower percentage of eggs (5,29%) hatched after exposure to 64 and 128 µg mL,1 of pyriproxyfen. Only 0,36% of early instars (first, second and third) and 25,74% of late instars (fourth and fifth) survived to adults following exposure to 16, 32 and 64 µg mL,1 of pyriproxyfen. However, 15,20% of adults that emerged following treatment as late instars exhibited morphological abnormalities. Furthermore, pyriproxyfen adversely affected reproduction (fecundity and fertility) of adults that emerged from treated fifth instars or that were treated topically with 0.04 µg as adults. CONCLUSIONS: Application of pyriproxyfen at 64 µg mL,1 resulted in greater inhibition of egg hatch and suppression of adult emergence compared with lower rates. Pyriproxyfen also markedly reduced female fecundity and egg viability for adults that were exposed either as fifth instars or as newly emerged adults. The ovicidal, larvicidal and reproductive effects against ACP suggest that pyriproxyfen is suitable for integration into an IPM program for ACP. Copyright © 2009 Society of Chemical Industry [source] | |||||||||||||||||||