Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Juveniles

  • early juvenile
  • infective juvenile
  • second-stage juvenile
  • small juvenile
  • vannamei juvenile
  • young juvenile

  • Terms modified by Juveniles

  • juvenile Litopenaeu vannamei
  • juvenile animals
  • juvenile atlantic salmon
  • juvenile bird
  • juvenile black sea bream
  • juvenile brown trout
  • juvenile channel catfish
  • juvenile chinese sucker
  • juvenile cod
  • juvenile court
  • juvenile court judge
  • juvenile crime
  • juvenile delinquency
  • juvenile density
  • juvenile dermatomyositis
  • juvenile development
  • juvenile dispersal
  • juvenile female
  • juvenile fish
  • juvenile form
  • juvenile growth
  • juvenile habitat
  • juvenile halibut
  • juvenile herring
  • juvenile hormone
  • juvenile hormone analog
  • juvenile huntington's disease
  • juvenile hybrid tilapia
  • juvenile idiopathic arthritis
  • juvenile jian carp
  • juvenile justice
  • juvenile justice policy
  • juvenile justice system
  • juvenile male
  • juvenile mortality
  • juvenile murray cod
  • juvenile myelomonocytic leukaemia
  • juvenile myelomonocytic leukemia
  • juvenile myoclonic epilepsy
  • juvenile nile tilapia
  • juvenile offender
  • juvenile onset
  • juvenile parkinsonism
  • juvenile patient
  • juvenile period
  • juvenile periodontitis
  • juvenile phase
  • juvenile pig
  • juvenile pink salmon
  • juvenile plant
  • juvenile population
  • juvenile rainbow trout
  • juvenile rat
  • juvenile recruitment
  • juvenile rheumatoid arthritis
  • juvenile salmon
  • juvenile salmonid
  • juvenile sex offender
  • juvenile size
  • juvenile specimen
  • juvenile stage
  • juvenile survival
  • juvenile survivorship
  • juvenile tilapia
  • juvenile tree

  • Selected Abstracts


    JOURNAL OF PHYCOLOGY, Issue 3 2004
    Brianne E. Henry
    Diminishing levels of atmospheric ozone are increasing UV stress on intertidal algae. Early developmental stages tend to be more susceptible to environmental stresses; however, little research has examined how these stages are protected from UV radiation (UVR). Many brown algae contain high levels of phlorotannins, which are thought to function in screening UVR. In this study, we tested the effects of ambient levels of UV-B and UV-A on growth and phlorotannin production in 1- to 2-cm juvenile and microscopic postsettlement embryos of the intertidal alga Fucus gardneri Silva. Algae were grown in four light treatments: 1) ambient light; 2) under cellulose acetate, which lowered light quantity but did not affect light quality; 3) under MylarTM, which filtered UV-B; and 4) under PlexiglasTM, which blocked UV-A and UV-B. Over a 3-week period, UV-B inhibited and UV-A enhanced the growth of F. gardneri embryos, whereas the growth of juveniles was not affected. Phlorotannin concentrations of both embryos and juveniles did not differ in any of the light treatments. Our results suggest that embryos of F. gardneri are susceptible to UV light but develop a tolerance to it as they mature. This tolerance may result from increases in phlorotannin concentrations that occur during maturation; however, phlorotannin production in embryonic or juvenile stages is either not induced by UV light or takes more than 3 weeks to occur. [source]


    FAMILY COURT REVIEW, Issue 4 2005
    Hon. Leonard Edwards
    The William H. Rehnquist Award is one of the most celebrated judicial honors in the country.1 It is given each year to a state court judge who demonstrates the "highest level of judicial excellence, integrity, fairness, and professional ethics."2 The 2004 recipient, Judge Leonard Edwards, is the Supervising Judge of the Santa Clara County, California juvenile dependency court.3 He is the first juvenile court judge to receive this prestigious award. During the 24 years he has held his position, Judge Edwards has worked extremely hard to improve how the juvenile court system serves troubled families. He has founded two organizations to achieve this end, the Juvenile Court Judges of California and the Santa Clara County Domestic Violence Council.4 Judge Edwards serves as a lead judge in San Jose's Model Court, which is one of twenty-five jurisdictions in the country which utilizes new ideas and techniques to improve adoption rates for children in foster care.5 Moreover, he has worked as president of the National Council of Juvenile and Family Court Judges.6 Below is the speech he gave after accepting the award from U.S. Supreme Court Justice Anthony M. Kennedy. The speech notes the importance of the award to everyone working in America's juvenile courts. [source]


    FAMILY COURT REVIEW, Issue 2 2000
    Improving Court Practice for the Millennium
    Chief Judge Judith S. Kaye of New York delivered the following address to the Millennium Conference of the National Council of Juvenile and Family Court Judges in Washington, D.C., on November 15, 1999. In it, she describes the development of the philosophy of the family court in the past century. Judge Kaye describes the family court's transition from reliance on social science to the incorporation of procedural due process guarantees in the Gault decision. She suggests that a further transformation is required to meet the needs of children and families in the 21st century. Judge Kaye proposes that in the next millennium the family court abandon the "remote adjudicator" judge who evolved after Gault to a "problem-solving model of judging, a judge who looks at the issues that are driving the caseload, who looks at the results that are being achieved, and who uses a hands-on style to figure out how we might do better both in individual cases and on a systemic level." The New York Times described Chief Justice Kaye as, "A dedicated and effective reformer of the state's sprawling court system. Each of her hard won changes has had a positive impact." Chief Judge Kaye recently received the National Center for State Courts' William H. Rhenquist Award for Judicial Excellence in November 1999. On the occasion of the award, Roger K. Warren, president of the National Center, observed about her,"There are many who are working hard to better process the many cases that come before the state courts, but there are few working an harder or more successfully to better serve the people who use the state courts." [source]

    Molt and growth of an estuarine crab, Chasmagnathus granulatus (Brachyura: Varunidae), in Mar Chiquita coastal lagoon, Argentina

    T. A. Luppi
    Summary Juvenile and adult growth of Chasmagnathus granulatus was studied in the laboratory in terms of molt increment in size (MI) and the intermolt period (IP), comparing data obtained from short-term (STE) and long-term (LTE) laboratory experiments. Crabs in a pre-molt condition were collected for STE, including the entire size range of the species. Larger crabs remained in the laboratory no more than 14 days; the average time to molt was 5.8 ± 3.1 days. We registered the molt of 94 females, 64 males and 34 undifferentiated juveniles and calculated their MI. Moreover, 24 males and four females were reared in the laboratory over 3 years (LTE). Hiatt diagrams did not show sex-specific differences between juveniles of both sexes, but revealed differences between juveniles and adults in each sex as well as between adults of both sexes. The MI decreased gradually with size; this pattern was described with a quadratic model. The IP increased exponentially with size. The presence of regenerating limbs diminished the MI. The abdomen of females reached its final shape and maximum relative width at functional maturity. Growth curves for both sexes were calculated using the von Bertalanffy model, but this model yielded an underestimation of the actual maximum size of this crab. [source]

    Physiological effects in juvenile three-spined sticklebacks feeding on toxic cyanobacterium Nodularia spumigena -exposed zooplankton

    J.-P. Pääkkönen
    Feeding rate, growth and nutritional condition as well as nodularin concentration of juvenile three-spined sticklebacks Gasterosteus aculeatus were assessed in an experimental study where field-collected fish were given a diet of zooplankton fed with toxic Nodularia spumigena for 15 days. Food consumption was higher in N. spumigena bloom conditions compared with the cyanobacterium-free control, but despite this the growth rate of exposed fish did not improve. Control fish and fish fed N. spumigena -exposed zooplankton had higher RNA:DNA ratios and protein content than fish grown in cyanobacterial bloom conditions indicating good nutritional condition and recent growth of fish, whereas in bloom conditions metabolic transformation of nodularin to less toxic compounds may cause an energetic cost to the fish affecting the growth rate of the whole organism. Juvenile three-spined sticklebacks collected from the field contained higher concentrations of nodularin at the beginning of the experiment (mean 503·1 ,g kg,1). After 15 days, the lowest nodularin concentrations in fish were measured in the control treatment, suggesting that fish fed with non-toxic food are able to detoxify nodularin from their tissues more effectively than fish in continuing exposure. [source]

    An Empirical Analysis of 30 Years of U.S. Juvenile and Adult Sexual Homicide Offender Data: Race and Age Differences in the Victim,Offender Relationship

    Heng Choon (Oliver) Chan M.A.
    Abstract:, Little is known about the racial patterns of crimes committed by sexual homicide offenders (SHOs). This study examined race and age influences on victim,offender relationship for juvenile and adult SHOs. A large sample (N = 3868) from the Supplemental Homicide Reports (1976,2005) was used. Analyses of victim,offender patterns included examining victim age effects (child, adolescent, adult, and elderly). The findings revealed several race- and age-based differences. Black offenders were significantly overrepresented in the SHO population. This finding held for juveniles and adults independently. White SHOs were highly likely to kill within their race, "intra-racially" (range 91,100%) across four victim age categories, whereas Black SHOs killed both intra-racially (range 24,82%) and inter-racially (18,76%), with the likelihood of their killing inter-racially increasing as the age of the victim increased. This study underscores the importance of considering victim,offender racial patterns in sexual murder investigations, and it offers practical implications for offender profiling. [source]

    "Juvenile stress" alters maturation-related changes in expression of the neural cell adhesion molecule L1 in the limbic system: Relevance for stress-related psychopathologies

    M.M. Tsoory
    Abstract L1 is critically involved in neural development and maturation, activity-dependent synaptic plasticity, and learning processes. Among adult rats, chronic stress protocols that affect L1 functioning also induce impaired cognitive and neural functioning and heightened anxiety reminiscent of stress-induced mood and anxiety disorders. Epidemiological studies indicate that childhood trauma is related predominantly to higher rates of both mood and anxiety disorders in adulthood and is associated with altered limbic system functioning. Exposing rats to stress during the juvenile period ("juvenile stress") has comparable effects and was suggested as a model of induced predisposition for these disorders. This study examined the effects of juvenile stress on rats aversive learning and on L1 expression soon after exposure and in adulthood, both following additional exposure to acute stress and in its absence. Adult juvenile-stressed rats exhibited enhanced cued fear conditioning, reduced novel-setting exploration, and impaired avoidance learning. Furthermore, juvenile stress increased L1 expression in the BLA, CA1, DG, and EC both soon after the stressful experience and during adulthood. It appears that juvenile stress affects the normative maturational decrease in L1 expression. The results support previous indications that juvenile stress alters the maturation of the limbic system and further support a role for L1 regulation in the mechanisms that underlie the predisposition to exhibit mood and/or anxiety disorders in adulthood. Furthermore, the findings support the "network hypothesis," which postulates that information-processing problems within relevant neural networks might underlie stress-induced mood and anxiety disorders. © 2009 Wiley-Liss, Inc. [source]

    Mortality of Northern Bluefin Tuna Thunnus thynnus Due to Trauma Caused by Collision During Growout Culture

    Shigeru Miyashita
    Collisions with the walls of tanks or nets caused mass mortality that occurs during growout. The period when collisions frequently occur and the types of injury caused by collision were examined in this study. Juveniles were reared in indoor tanks from 30 to 120 d after hatching, and in an open sea net cage from 42 to 150 d after hatching. Dead fish were collected and counted daily in both of the experiments. In the indoor experiment, the sampled fish were preserved in 10% formalin solution, and each of 10 specimens of about 30, 50, 70, 85, 100, 130, 160 and 225 mm in body length (BL) were examined using x-rays to detect injury of the bones. Juvenile and young adult bluefin tuna showed a reduction in numbers caused by collision with the tank or the net wall during the experiments. In the indoor tank, there were 1,200 fish on day 30 but only eight on day 120. The daily mortality increased from day 30 after hatching, when juveniles reached 50-mm BL and remained over 4%/d until day 60 when juveniles grew to 300-mm BL. The proportion of dead fish with injuries of bone, especially of the vertebral column and the parasphenoid, increased after fish reached 50-mm BL, and exceeded 60% in fish with BL 85 mm or greater. In the open sea net cage, there were 3,841 fish at the start of the experiment on day 42 and only 65 on day 150. In this experiment, the reduction was greatest from the start of the experiment until day 80, when fish grew to approximately 25 cm in total length. Significant bacterial, viral or parasitic diseases were not observed in these fish; the only findings were dislocations of the vertebral column and injuries to the upper and lower jaws. These results show that the loss of juvenile and young adult bluefin tuna was caused by collision with the tank or net wall that fatally damaged the bones of the vertebral columns and the parasphenoid. [source]

    Targeting Underage Drinking and Driving in Juvenile and Domestic Relations Courts: The Reinforcing Alcohol Prevention (RAP) Program

    Kelli England Will
    ABSTRACT Alcohol use is a concern among our nation's least experienced drivers, and underage drinking contributes to the overall burden of traffic injury and mortality. The goal of the Reinforcing Alcohol Prevention (RAP) Program was to develop a court-based program targeting underage drinking and driving among teens. An advisory board created the program which included changes to the drivers' licensing ceremonies and traffic dockets conducted in Juvenile and Domestic Relations Courts. Additions included 5-minute videos of individuals in alcohol-related crashes and a crash-photo display. Exit evaluations garnering impressions/opinions of the program indicated 84% of teenagers felt every teen should view the presentation and 96% would be less likely to drive after drinking. The RAP Program has been well-received by judges and participants and could be easily implemented by other jurisdictions. [source]

    Asking the Right Questions: Utilizing a Judicial Checklist to Track the Educational Success of Youth in Foster Care

    ABSTRACT Asking about the educational objectives for children in foster care has not been a priority in most juvenile and family courts. Research has shown that compared to the general school population, children in foster care have lower grade point averages, change schools more frequently, earn fewer credits toward graduation, and are more likely to be placed in special education programs. In response, Casey Family Programs, in collaboration with the National Council of Juvenile and Family Court Judges' Permanency Planning for Children Department, developed a Judicial Checklist with key educational questions to be asked from the bench. The Checklist has become a useful tool for juvenile and family court judges when assessing the effectiveness of current educational placements of the children who come before their courts, tracking their performance, and in making a positive future impact on their educational outcomes. [source]

    Pathways from Traumatic Child Victimization to Delinquency: Implications for Juvenile and Permanency Court Proceedings and Decisions

    ABSTRACT Research studies and observations by mental health and judicial professionals suggest that childhood traumatic victimization may contribute to the development of juvenile delinquency. Based on this evidence, we describe a chronological pathway that runs from: (a) early childhood victimization, to (b) escalating dysregulation of emotion and social information processing ("survival coping," which takes the form of depression, anxiety, social isolation, peer rejection, and conflicted relationships), to (c) severe and persistent problems with oppositional-defiance and overt or covert aggression compounded by post-traumatic reactivity and hypervigilance ("victim coping"). A case vignette is provided, and implications for judicial review and decisions are discussed. [source]

    Juvenile Delinquency Guidelines: Improving Court Practice in Juvenile Delinquency Cases SIXTEEN KEY PRINCIPLES

    Article first published online: 14 JUL 200
    ABSTRACT This article is excerpted from the National Council of Juvenile and Family Court Judges' landmark JUVENILE DELINQUENCY GUIDELINES: Improving Court Practice in Juvenile Delinquency Cases, Chapter I, Foundations for Excellence, published in 2005. Beginning with a basic discussion of why separate courts for juveniles and adults continue to be necessary, the article describes the goals and key principles of a juvenile delinquency court of excellence. [source]

    Faith-Based Programs for Reentry Courts: A Summary of Issues and Recommendations

    ABSTRACT In 2002, the Bush Administration directed the Department of Justice to include faith-based organizations in its distribution of funds earmarked for programs targeting the prevention and treatment of juvenile delinquency and substance abuse. Among the initiatives most likely to be affected by this new policy are reentry court programs that endeavor to reintegrate juvenile delinquents into their communities by placing them within local neighborhood-based programs. However, reentry court personnel and leaders of faith-based organizations are likely to encounter numerous challenges as they try to establish appropriate programming. In this article, we discuss the current understanding of First Amendment jurisprudence governing the federal funding of faith-based organizations and summarize key issues identified by a National Council of Juvenile and Family Court Judges' workgroup on faith-based programming that are necessary for including faith-based organizations within a reentry court's continuum of care. We also discuss several concerns that reentry court personnel and faith-based organizations should consider as they seek to maximize the impact of their programs. [source]

    Zero to Three: Critical Issues for the Juvenile and Family Court

    ABSTRACT Infants are the fastest growing population in foster care. Without intervention they are at great risk of poor developmental outcomes. Juvenile and family courts have a unique opportunity to make a positive difference in the lives of the babies in their care. This article outlines six critical issues that impact the development of very young children in the child welfare system and recommends strategies that juvenile and family courts can use to address the needs of this most vulnerable population. [source]

    The Nature of Exocytosis in the Yolk Trophoblastic Layer of Silver Arowana (Osteoglossum bicirrhosum) Juvenile, the Representative of Ancient Teleost Fishes

    Marta Jaroszewska
    Abstract We have chosen the silver arowana (Osteoglossum bicirrhosum), a representative of the most ancient teleost family Osteoglossidae, to address the question of yolk nutrients utilization. Silver arowana have particularly large eggs (1,1.5 cm of diameter) and a unique morphology of the yolk. We present evidence that the yolk cytoplasmic zone (ycz) in the "yolksac juveniles" is a very complex structure involved in sequential processes of yolk hydrolysis, lipoprotein particles synthesis, their transport, and exocytosis. Vacuoles filled with yolk granules in different stages of digestion move from the vitellolysis zone through the ycz to be emptied into the microvillar interspace in the process of exocytosis. The area of the ycz with the abundance of the mitochondria must play an important role in providing energy for both the transport of vacuoles and the release of their contents. Therefore, we postulate that the function of yolk syncytial layer (ysl) as the "early embryonic patterning center" transforms in fish larvae or yolksac juveniles into a predominantly specialized role as the yolk trophoblastic layer (ytl) involved in yolk nutrients utilization. In addition to discovering the mechanism of transformation of the ysl function into ytl function, we suggest that the machinery involved in nutrient mobilization and exocytosis in yolk of arowana yolksac juveniles can be very attractive system for studies of regulatory processes in almost all secretory pathways in animal cells. Anat Rec, 2009. © 2009 Wiley-Liss, Inc. [source]

    Analysis of Testosterone Effects on Sonic Hedgehog Signaling in Juvenile, Adolescent and Adult Sprague Dawley Rat Penis

    Christopher W. Bond MS
    ABSTRACT Introduction., Smooth muscle apoptosis is a major contributing factor to erectile dysfunction (ED) development in prostatectomy and diabetic patients and animal models. A critical regulator of penile smooth muscle and apoptosis is Sonic hedgehog (SHH). The SHH protein is decreased in ED models and SHH treatment of cavernous nerve (CN) injured rats prevents smooth muscle apoptosis. A close association between androgen deficiency and ED has been suggested in the literature, but few studies have examined the molecular effects on penile smooth muscle and on known signaling mechanisms that regulate morphology. Aim., Examine testosterone and SHH interaction in eugonadal adult, adolescent and juvenile rats by performing castration studies and treatment with supraphysiological testosterone. Methods., The eugonadal adult Sprague Dawley rats were either treated with testosterone for 7 or 14 days (N = 14) or were castrated for 4 or 7 days (N = 12). The juvenile rats were treated with testosterone for 8 days (N = 7). The adolescent rats were castrated and sacrificed at P88 (N = 8). The control rats had empty vehicle (N = 22) or sham surgery (N = 20). Main Outcome Measures., The active form of SHH protein and mRNA were quantified by semi-quantitative immunohistochemical analysis and real-time reverse transcriptase polymerase chain reaction (RT-PCR). Results., Testosterone treatment did not alter SHH signaling in juvenile rats. Shh mRNA increased 3.2-fold and SHH protein increased 1.2-fold in rats castrated during puberty. In adult rats, castration decreased Shh mRNA 3.2-fold but did not alter SHH protein. Testosterone supplement in adult rats increased Shh mRNA 2.3-fold and decreased SHH protein 1.3-fold. Conclusions., SHH signaling is independent of testosterone in normal juvenile rats and is sensitive to testosterone during adolescence, while testosterone supplement in the adult adversely impacts SHH signaling in a very similar manner to that observed with CN injury. Bond CW, Angeloni NL, and Podlasek CA. Analysis of testosterone effects on sonic hedgehog signaling in juvenile, adolescent and adult Sprague Dawley rat penis. J Sex Med 2010;7:1116,1125. [source]

    Demography of an Afrotropical passerine in a highly fragmented landscape

    M. Githiru
    Abstract Demographic attributes of discrete subpopulations of animals and plants that constitute a larger (meta)population network may affect the strength and direction of local population responses to habitat loss or degradation. To address this question in an Afrotropical context, we studied survival rates, population densities, sex ratios and age distributions in seven white-starred robin Pogonocichla stellata populations inhabiting differently sized forest remnants in a highly fragmented Kenyan landscape. Sex ratios were strongly male biased, especially during the non-breeding season, but the level of bias did not differ between age groups nor fragment sizes. Juvenile to adult ratios were smallest in the medium-sized fragment, but did not differ between the largest and smallest fragments. Low population density combined with a skewed sex ratio in the medium-sized fragment pointed towards a local scarcity of females, which was supported by the presence of unmated territorial males. Based on capture,recapture analysis, all populations were considered stable on average. When combining demographic patterns with those emerging from a recent population genetic study and removal experiment, our results support the notion that small populations inhabiting tiny habitat remnants may play an important role in augmenting the long-term survival of spatially structured populations. [source]

    Effects of dietary zinc levels on growth, serum zinc, haematological parameters and tissue trace elements of soft-shelled turtles, Pelodiscus sinensis

    S.-C. HUANG
    Abstract A 10-week feeding trial was conducted to evaluate the effects of dietary zinc (Zn) contents on the growth, tissue trace element contents and serum Zn levels in soft-shelled turtles, Pelodiscus sinensis. Juvenile soft-shelled turtles approximately 4.8 g in body weight were fed casein-based diets containing seven levels of Zn (14, 23, 32, 43, 58, 87 and 100 mg kg,1) for 10 weeks. There were no significant differences (P > 0.05) in weight gain (WG), feed conversion ratio (FCR) or protein efficiency ratio (PER) among the dietary treatments. However, Zn concentrations in the liver, serum and carapace of turtles fed the basal diet containing 14 mg Zn kg,1 were the lowest among all groups. Zn contents in the liver, serum and carapace increased when dietary Zn increased up to a dietary Zn level of approximately 43 mg kg,1. Beyond this dietary level, tissue Zn contents were relatively constant. Carapace iron (Fe), selenium (Se) in hard tissues and haemoglobin concentrations decreased when dietary Zn increased. Dietary Zn requirements of juvenile soft-shelled turtles derived from regression modelling using the liver, serum, carapace and bone Zn contents as indicators were 42, 39, 35 and 46 mg Zn kg,1, respectively. [source]

    Eugenol as an efficacious anaesthetic for tambaqui, Colossoma macropomum (Cuvier)

    Rodrigo Roubach
    Abstract Anaesthetics are important in fish culture to reduce handling stress and mortality. Eugenol is a promising anaesthetic because of its low cost, efficacy, safety margin for fish and lack of toxicity to humans. The goal of this study was to establish a protocol using eugenol as a fish anaesthetic for tambaqui Colossoma macropomum (Cuvier), and provide information for regulating authorities on establishing safety dosage protocols for its use. Juvenile and sub-adult tambaqui were first individually exposed to doses of 35, 50, 65, 85, 100 or 135 mg L,1 eugenol for 10 min. A second experiment examined the effect of the duration of exposure to eugenol on the time required for recovery and survival of tambaqui. A eugenol dose of 65 mg L,1 was adequate to induce fish of both sizes into a surgical anaesthetic state, and recovery time was similar for dosages up to 100 mg L,1. Exposure to the ideal dose (65 mg L,1) for up to 30 min did not cause fish mortality. Fish blood glucose values were similar for all the tested eugenol doses as well as with the benzocaine control. The results show that eugenol is an efficient and safe anaesthetic for tambaqui. [source]

    An Experimental Investigation of Landscape Resistance of Forest versus Old-Field Habitats to Emigrating Juvenile Amphibians

    Betsie B. Rothermel
    Larval amphibians,spotted salamander (Ambystoma maculatum), small-mouthed salamander (A. texanum), and American toad ( Bufo americanus ),were added to artificial pools in four dispersal arrays on forest edges. Each array consisted of a pool surrounded by a circular drift fence with pitfall traps and two 2.5 × 50 m enclosures (runs) extending into forest and old-field habitat. Juveniles captured at the circular fences were individually marked and released into either field or forest runs. We determined initial distance, initial rate, total distance, and net distance moved by juveniles in the field versus forest from recaptures in the runs. We also conducted 24-hour dehydration trials to compare the rates of evaporative water loss by spotted and small-mouthed salamanders in field and forest. Initial orientation of spotted salamanders and toads was significantly biased toward forest. Orientation of small-mouthed salamanders did not differ significantly from random expectations. The avoidance of open-canopy habitat by juvenile American toads in particular indicates that predictions of dispersal behavior based on adult habitat use may be misleading. Spotted salamanders moved almost four times farther and toads more than three times farther into the forest than into the field, and recapture rates of both species were much lower in the field. We attribute the lower recapture rates and shorter distances moved in the field to higher mortality due to desiccation or an abundance of predators. Juvenile spotted and small-mouthed salamanders experienced greater evaporative water loss in the field. Our data on movement behavior and dehydration rates suggest that old-field habitats offer greater landscape resistance to dispersing juveniles of some species. Thus, forest fragmentation is likely to reduce dispersal rates between local populations of these three species, with potentially negative consequences for population persistence in altered landscapes. Resumen: Utilizamos un enfoque experimental para investigar los efectos de la composición del paisaje sobre el éxito inicial de dispersión de anfibios juveniles. Colcamos larvas de anfibios (salamandras manchadas [Ambystoma maculatum] y A. texanum y sapo americano [Bufo americanus] ) en estanques artificiales en cuatro secuencias de dispersión en bordes de bosque. Cada secuencia consistió de un estanque rodeado por un cerco circular con trampas de fosa y dos encierros (corridas) de 2.5 × 50 m que se extendían hacia el hábitat de bosque y de campo viejo. Los juveniles capturados en los cercos circulares fueron marcados individualmente y liberados en las corridas de bosque o de campo. A partir de recapturas en las corridas, determinamos la distancia inicial, la tasa inicial, las distancia total y la distancia neta recorrida por juveniles en el campo versus el bosque. También realizamos pruebas de deshidratación de 24 horas para comparar las tasas de pérdida de agua por evaporación en salamandras en el campo y el bosque. La orientación inicial de Ambystoma maculatum y Bufo americanus estuvo significativamente sesgada hacia el bosque. La orientación inicial de A. texanum no fue significativamente diferente de las expectativas aleatorias. La evasión del hábitat abierto en particular por juveniles de sapo americano indica que las predicciones del comportamiento de dispersión basadas en el uso del hábitat por adultos pueden llevar a conclusiones erróneas. Las salamandras manchadas se movieron cuatro veces mas lejos y los sapos más de tres veces más lejos dentro del bosque que dentro del campo, y las tasas de recaptura de ambas especies fueron mucho menores en el campo. Atribuimos las bajas tasas de recaptura y las distancias menores a la mayor mortalidad debido a la desecación o a la abundancia de depredadores. Los juveniles de las dos especies de salamandras experimentaron mayor pérdida de agua por evaporación en los campos. Nuestros datos del comportamiento de movimiento y las tasas de deshidratación sugieren que los hábitats de campo viejo ofrecen mayor resistencia de paisaje para los juveniles dispersantes de algunas especies. Por tanto, es probable que la fragmentación de bosques reduce las tasas de dispersión entre poblaciones locales de estas tres especies, con consecuencias potencialmente negativas para la persistencia de la población en paisajes alterados. [source]


    CRIMINOLOGY, Issue 3 2006
    Juveniles in secure confinement allegedly suffer from more mental health problems than their peers. This may reflect background and behavioral characteristics commonly found in clients of both mental health and juvenile justice systems. Another explanation is that mental disorders increase the risk of arrest. These interpretations were tested on a sample of Pittsburgh boys (n = 736). Findings indicate that arrested youth exhibit more attention deficit hyperactivity (ADH) problems, oppositional defiant (OD) problems, and nondelinquent externalizing symptoms prior to their first arrests compared to their never-arrested peers. However, arrested and nonarrested youth score similarly on prior affective and anxiety problems and internalizing symptoms. Net of delinquency, substance use, and other selection factors, internalizing problems lower the risk of subsequent arrest, whereas OD problems and nondelinquent externalizing symptoms increase it. ADH problems have no effect on arrest net of delinquency and substance use. These findings lend only partial support to the criminalization hypothesis. Whereas some mental health symptoms increase the risk of arrest, others elicit more cautious or compassionate official responses. [source]

    Prolonged maturation of auditory perception and learning in gerbils

    Emma C. Sarro
    Abstract In humans, auditory perception reaches maturity over a broad age range, extending through adolescence. Despite this slow maturation, children are considered to be outstanding learners, suggesting that immature perceptual skills might actually be advantageous to improvement on an acoustic task as a result of training (perceptual learning). Previous non-human studies have not employed an identical task when comparing perceptual performance of young and mature subjects, making it difficult to assess learning. Here, we used an identical procedure on juvenile and adult gerbils to examine the perception of amplitude modulation (AM), a stimulus feature that is an important component of most natural sounds. On average, Adult animals could detect smaller fluctuations in amplitude (i.e., smaller modulation depths) than Juveniles, indicating immature perceptual skills in Juveniles. However, the population variance was much greater for Juveniles, a few animals displaying adult-like AM detection. To determine whether immature perceptual skills facilitated learning, we compared naďve performance on the AM detection task with the amount of improvement following additional training. The amount of improvement in Adults correlated with naďve performance: those with the poorest naďve performance improved the most. In contrast, the naďve performance of Juveniles did not predict the amount of learning. Those Juveniles with immature AM detection thresholds did not display greater learning than Adults. Furthermore, for several of the Juveniles with adult-like thresholds, AM detection deteriorated with repeated testing. Thus, immature perceptual skills in young animals were not associated with greater learning. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 70: 636,648, 2010 [source]

    The development of "roughness" in the play fighting of rats: A Laban Movement Analysis perspective

    Afra Foroud
    Abstract With increasing age, rats, when play fighting, become rougher. In part, this change can be accounted for by the increasing likelihood of using adult-typical fighting tactics. However, even when using the same tactics, adults appear rougher than juveniles in their play. In this study, videotaped sequences of play fighting in rats from the juvenile (30 days) to the post-pubertal (70 days) period were analyzed using Laban Movement Analysis (LMA). Movement qualities called Effort Factors in LMA captured the character of some of this change. Juveniles tended to use Indulging Efforts, whereas older rats tended to use Condensing Efforts. The latter are related to performing movements that are more controlled. This greater level of control was also evident in the way older rats maintained postural support during play fights. When standing over supine partners, juveniles are more likely to stand on the partner with all four paws, reducing their postural stability, and hence ability to control their partner's movements. Older rats are more likely to place their hind paws on the ground, thus providing a firmer anchor for movements with their upper bodies and forepaws. These age-related changes in behavior were found for both males and females. The findings lend support to a growing body of evidence that play fighting in the juvenile phase of rats is not just a more frequently occurring version of that present in adults, but rather, has unique organizational properties. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 42: 35,43, 2003. [source]

    Atlantic salmon Salmo salar L., brown trout Salmo trutta L. and Arctic charr Salvelinus alpinus (L.): a review of aspects of their life histories

    A. Klemetsen
    Abstract ,,,Among the species in the family Salmonidae, those represented by the genera Salmo, Salvelinus, and Oncorhynchus (subfamily Salmoninae) are the most studied. Here, various aspects of phenotypic and life-history variation of Atlantic salmon Salmo salar L., brown trout Salmo trutta L., and Arctic charr Salvelinus alpinus (L.) are reviewed. While many strategies and tactics are commonly used by these species, there are also differences in their ecology and population dynamics that result in a variety of interesting and diverse topics that are challenging for future research. Atlantic salmon display considerable phenotypic plasticity and variability in life-history characters ranging from fully freshwater resident forms, where females can mature at approximately 10 cm in length, to anadromous populations characterised by 3,5 sea-winter (5SW) salmon. Even within simple 1SW populations, 20 or more spawning life-history types can be identified. Juveniles in freshwater can use both fluvial and lacustrine habitats for rearing, and while most smolts migrate to sea during the spring, fall migrations occur in some populations. At sea, some salmon undertake extensive oceanic migrations while other populations stay within the geographical confines of areas such as the Baltic Sea. At the other extreme are those that reside in estuaries and return to freshwater to spawn after spending only a few months at sea. The review of information on the diversity of life-history forms is related to conservation aspects associated with Atlantic salmon populations and current trends in abundance and survival. Brown trout is indigenous to Europe, North Africa and western Asia, but was introduced into at least 24 countries outside Europe and now has a world-wide distribution. It exploits both fresh and salt waters for feeding and spawning (brackish), and populations are often partially migratory. One part of the population leaves and feeds elsewhere, while another part stays as residents. In large, complex systems, the species is polymorphic with different size morphs in the various parts of the habitat. Brown trout feed close to the surface and near shore, but large individuals may move far offshore. The species exhibits ontogenetic niche shifts partly related to size and partly to developmental rate. They switch when the amount of surplus energy available for growth becomes small with fast growers being younger and smaller fish than slow growers. Brown trout is an opportunistic carnivore, but individuals specialise at least temporarily on particular food items; insect larvae are important for the young in streams, while littoral epibenthos in lakes and fish are most important for large trout. The sexes differ in resource use and size. Females are more inclined than males to become migratory and feed in pelagic waters. Males exploit running water, near-shore and surface waters more than females. Therefore, females feed more on zooplankton and exhibit a more uniform phenotype than males. The Arctic charr is the northernmost freshwater fish on earth, with a circumpolar distribution in the Holarctic that matches the last glaciation. Recent mtDNA studies indicate that there are five phylogeographic lineages (Atlantic, Arctic, Bering, Siberian and Acadian) that may be of Pleistocene origin. Phenotypic expression and ecology are more variable in charr than in most fish. Weights at maturation range from 3 g to 12 kg. Population differences in morphology and coloration are large and can have some genetic basis. Charr live in streams, at sea and in all habitats of oligotrophic lakes, including very deep areas. Ontogenetic habitat shifts between lacustrine habitats are common. The charr feed on all major prey types of streams, lakes and near-shore marine habitats, but has high niche flexibility in competition. Cannibalism is expressed in several cases, and can be important for developing and maintaining bimodal size distributions. Anadromy is found in the northern part of its range and involves about 40, but sometimes more days in the sea. All charr overwinter in freshwater. Partial migration is common, but the degree of anadromy varies greatly among populations. The food at sea includes zooplankton and pelagic fish, but also epibenthos. Polymorphism and sympatric morphs are much studied. As a prominent fish of glaciated lakes, charr is an important species for studying ecological speciation by the combination of field studies and experiments, particularly in the fields of morphometric heterochrony and comparative behaviour. [source]

    Extended Mother,Offspring Relationships in Crayfish: The Return Behaviour of Juvenile Procambarus Clarkii

    ETHOLOGY, Issue 10 2008
    Laura Aquiloni
    Crayfish shows a relatively complex parental behaviour compared with other invertebrates, but the literature provides only anecdotal accounts of this phenomenon. In Procambarus clarkii, we described the ,return' behaviour of third-stage juveniles when offered four types of adults: biological mothers, foster mothers, non-brooding females and males. Then, we analysed the posture and behaviour of the adults to understand the role played by the putative mother in attracting the juveniles. Contrary to non-brooding individuals, both biological and foster mothers displayed a relatively rare locomotion, executed few cleaning and feeding acts, and never attempted to prey on juveniles. They often assumed a ,spoon-like telson posture' that seemed to facilitate offspring's approaches. Juveniles increased the frequency of tail-flips away in the presence of non-brooding adults; conversely, they accepted foster mothers, along with biological mothers, but not as fast as the latter. Taken together, these results suggest that mother,offspring relationships in P. clarkii are more refined than previously thought, being possibly a key factor enabling this species to thrive in harsh environmental conditions. [source]

    Fruit Colour Preferences of Redwings (Turdus iliacus): Experiments with Hand-Raised Juveniles and Wild-Caught Adults

    ETHOLOGY, Issue 6 2004
    Johanna Honkavaara
    Certain fruit colours and their contrast with the background coloration are suggested to attract frugivorous birds. To test the attractiveness of different colours, we performed three experiments in laboratory with controlled light conditions. In the first two experiments, we studied the fruit colour preferences of naive juvenile redwings. In the third experiment, we continued to investigate whether the contrast of the fruit colour with the background coloration affects the preference of both naive juveniles and experienced adult redwings. In the first experiment, juvenile birds preferred black, UV-blue and red berries, to white ones. In pairwise trials, a new set of juveniles still preferred red berries to white ones. When testing the effect of contrasts on their choice, juveniles preferred UV-blue berries to red ones on a UV-blue background. However, no preference was found, when the background was either red or green. Adult redwings preferred UV-blue berries to red ones on all backgrounds. According to these results, juveniles seem to have an innate avoidance of white berries. Furthermore, the foraging decisions of fruit-eating birds are affected more by fruit colour than its contrast with background coloration, at least when contrasting displays are encountered from relatively short distances. Differences in preferences of adult and juvenile birds also indicate that learning seems to play a role in fruit choices. [source]

    Chemosensory Recognition of Familiar and Unfamiliar Conspecifics by Juveniles of the Iberian Wall Lizard Podarcis hispanica

    ETHOLOGY, Issue 4 2002
    Enrique Font
    Chemosensory recognition of familiar conspecifics has been reported in studies with members of several lizard families and may be advantageous to distinguish between intruders and neighbors or group members. However, few species have been studied and information on the ability to discriminate between familiar and unfamiliar conspecifics by chemosensory means is lacking for most lizard families. In this paper we ask whether juveniles of the Iberian wall lizard Podarcis hispanica (Lacertidae), can discriminate between chemical signals from familiar conspecifics with whom they have shared a terrarium for several months and those from unfamiliar conspecifics housed in a different terrarium. Experimental trials were conducted by transferring juveniles to a test terrarium with a filter paper substrate. We tested the responses of lizards to paper substrates labeled by familiar cage-mates, unfamiliar conspecifics, or unlabeled. Tongue-flicks and other behaviors in response to pheromonal stimuli were recorded for 10 min Juveniles directed more chemosensory behavior towards paper substrates bearing chemicals from familiar conspecifics than towards similar paper substrates labeled by unfamiliar conspecifics. These results indicate that juveniles in this lizard species can recognize familiar conspecifics and discriminate between familiar and unfamiliar individuals using only chemical stimuli. We discuss the role of habituation in familiar conspecific recognition and review possible explanations of the functional significance of this type of discrimination in lizards. [source]

    Opening the Social Gateway: Early Vocal and Social Sensitivities in Brown-Headed Cowbirds (Molothrus ater)

    ETHOLOGY, Issue 1 2002
    David J. White
    The organization of cowbird (Molothrus ater) social groups affords individuals living in the groups different opportunities for learning and also structures trajectories of social development. Here, we studied the influence of adults on social organization of very young cowbirds. In three experiments, we housed juvenile birds in large, seminatural environments that either contained or did not contain adult conspecifics. We then observed the social associations and vocalizations of juveniles in each environment. The presence of adults in the social environment influenced the assortment and singing patterns of juveniles, although throughout the three experiments adults rarely interacted physically with juveniles. Juveniles housed with adults interacted with other juveniles more often and sang significantly less often than juveniles housed without adults. Effects of adult presence or absence on social organization and singing patterns emerged extremely rapidly and could be reversed quickly. Taken as a whole, the experiments revealed that very young cowbirds, in the first days of independence from their hosts, were sensitive to, and reacted rapidly to, the composition of their social environment. Specifically, presence of other age classes of individuals within the group increased juvenile associations and delayed production of vocalizations by juvenile males. Self-organization within the social group produced different social environments, which could in turn create different gateways for social learning and vocal development. [source]

    Shrinking baseline: the growth in juvenile fisheries, with the Hong Kong grouper fishery as a case study

    FISH AND FISHERIES, Issue 4 2009
    Allen W L To
    Abstract Historic and current information on the grouper fishery from Hong Kong and adjacent waters reveals significant changes in species composition and fish sizes over the past 50 years in this important Asian centre for seafood consumption. Once dominant, large groupers are now rare and small species and sizes prevail in the present-day fishery. Juveniles comprise over 80% of marketed fish by number among the most commonly retailed groupers, and reproductive-sized fish are absent among larger species. Current fishery practices and the lack of management in Hong Kong and adjacent waters pose a significant threat to large species with limited geographic distribution such as Epinephelus akaara and Epinephelus bruneus, both now listed as threatened by the IUCN. The heavy reliance on juveniles, not only for groupers, but for an increasing diversity of desired fishes within Asia, potentially reduces stock spawning potential. The ,shrinking baseline' in terms of a progressive reduction in fish sizes being marketed in the region can seriously undermine fishery sustainability and recoverability of depleted fish stocks. Fishing pressure on groupers and other valuable food fishes within the Asia-Pacific is intensifying, the declining long-term trend of grouper landings in Hong Kong and the increasing focus on juveniles for immediate sale or for mariculture ,grow-out' signal a worrying direction for regional fisheries. Moreover, the common appearance of small groupers for sale will influence public perception regarding what are ,normal-sized' fish. Management attention is needed if these fisheries are to remain viable. [source]

    Eco-phenotypic growth in juvenile smooth marron, Cherax cainii (Decapoda: Parastacidae)

    Abstract, The smooth marron, Cherax cainii Austin, now occurs in regions of Western Australia that are warmer and drier than those of the natural distribution. Animals sourced along a south to north geographical axis decrease in body mass per unit length. Juveniles reared from gravid females sourced from four sites along this axis were raised in common laboratory conditions for 14 weeks. No differences between sites were observed in body mass, standardised for length, indicating that in situ differences are a phenotypic response to local conditions. [source]