Juvenile Behavior Research Articles

Are antipredator behaviours of hatchery Salmo salar juveniles similar to wild juveniles?

This study explores how antipredator behaviour of juvenile Atlantic salmon Salmo salar developed during conventional hatchery rearing of eggs from wild brood stock, compared with the behaviour of wild-caught juveniles from the same population. Juveniles aged 1+ years were tested in two unfamiliar environments; in one S. salar were presented with simulated predator attacks and in the other they were given the opportunity to explore an open-field arena. No difference was found in their spontaneous escape responses or ventilation rate (reflex responses) after simulated predator attacks. Hatchery-reared juveniles were more risk-prone in their behaviours than wild-caught individuals. Hatchery juveniles stayed less time in association with shelter. In the open-field arena, hatchery juveniles were more active than wild juveniles. Hatchery juveniles were also immobile for less time and spent a shorter amount of time than wild juveniles in the fringe of the open-field arena. Salmo salar size had no effect on the observed behaviour. Overall, this study provides empirical evidence that one generation of hatchery rearing does not change reflex responses associated with threats, whereas antipredator behaviour, typically associated with prior experience, was less developed in hatchery-reared than in wild individuals.

Efecto de microorganismos probióticos aislados de Hypostomus plecostomus en juveniles de Oreochromis sp

Objetivo. El objetivo del estudio fue evaluar el comportamiento de juveniles de tilapia roja (Oreochromis sp.) frente a los posibles microorganismos probióticos aislados del tracto gastrointestinal del pez panche (Hypostomus plecostomus). Materiales y métodos. En la fase de evaluación del probiótico, se seleccionaron 120 juveniles de Tilapia roja (Oreochromis sp) con un peso promedio de 1.28±0.22 g y una longitud promedio de 2.99±0.27 cm. Se formularon tres tratamientos experimentales teniendo en cuenta las necesidades nutricionales de la tilapia roja (Oreochromis sp.). El modelo estadístico que se empleó fue un diseño completamente al azar. Resultados. Las tres cepas del género Lactobacillus (Lactobacillus plantarum, Lactobacillus pentosus, Lactobacillus rhamnosus) aisladas del tracto digestivo del H. plecostomus, dieron resultados diversos en las variables biométricas consideradas, así como en la TCE, TEP, EA y CA. Conclusiones. Los mejores reportes en cuanto a ganancia en longitud fueron para el tratamiento con el probiótico nativo y se deduce que se establecieron con facilidad en el intestino del pez (Oreochromis sp.) se determinó que si existen diferencias significativas en los resultados de ganancia de longitud, para Concentrado Control (CC) vs., Concentrado más Probiótico Nativo (CPN) para Tilapia roja (Oreochromis sp.) en la etapa de juveniles por un período de 30 días.

Behavioural differences of Heterodera glycines and Meloidogyne incognita infective juveniles exposed to root extracts in vitro

In vitro behaviour of infective second-stage juveniles (J2) of Heterodera glycines and Meloidogyne incognita was compared in the presence and absence of plant root extracts. In an agar plate attraction-retention assay, with samples applied by agar disc infused with water (control) or aqueous test solutions, H. glycines was 15-fold more responsive to a chemical attractant (CaCl2) than was M. incognita. Control discs retained H. glycines at a rate 2.9-fold greater than M. incognita. Crude extracts (slurries; 40 mg dry root (ml water)−1) from roots of six plant species (corn, Zea mays; cucumber, Cucumis sativus; marigold, Tagetes patula; mustard, Sinapis alba; pepper, Capsicum annuum; soybean, Glycine max) differentially affected the two nematodes. Cucumber, marigold, pepper and soybean each attracted H. glycines at rates between 2.2- and 3.6-fold greater than controls. No root preparations were attractive to M. incognita, which were significantly repelled by corn, cucumber, mustard and pepper, relative to controls. Preparation of selected root extract supernatants, which involved vacuum drying, decreased the attractiveness of marigold and soybean to H. glycines by 38 and 82%, respectively, but the effect of pepper was unchanged. Supernatant processing had no effect on M. incognita behaviour. In a liquid-based J2 movement assay, root supernatants from marigold, pepper and soybean at 1 mg dry root ml−1 each decreased the frequency of head movement in H. glycines and M. incognita relative to controls. However, dose responses were detected only with marigold, with maximum decreases in activity at 16 mg dry root ml−1 for each species. These decreases were significantly different at 46 and 66%, respectively, for H. glycines and M. incognita. The behaviour of the two nematodes was qualitatively different in assays that required detection of signals across a short distance (agar assay), whereas qualitative responses were similar when juveniles were immersed in treatment solution (liquid assay). In the latter, quantitative responses to marigold differed significantly between H. glycines and M. incognita J2.

Divergent migratory behaviours associated with body size and ocean entry phenology in juvenile sockeye salmon

Survival during early marine life stages is hypothesized to contribute disproportionately to variation in salmonid recruitment, yet estimates of cumulative mortality are constrained by knowledge of how long juveniles reside in specific regions. We used otolith microstructure techniques to examine the relationship between migratory rate and ocean entry characteristics of juvenile sockeye salmon (Oncorhynchus nerka). We observed differences in migratory rate between catch locations that are consistent with divergent migratory behaviours. Individuals captured in northern regions were typically older, larger at ocean entry, and migrated more rapidly. Migratory rate was also correlated with entry size, phenology, population group, and year. Next, we compared “lingering” individuals captured nearshore during fall surveys to juveniles from the same populations captured during the peak summer migratory period. We determined that individuals that entered after 24 May and at smaller sizes (<85 mm) had a greater probability of being captured late in the year. Our findings demonstrate that the entry characteristics of sockeye salmon are strongly correlated with migratory variation within populations and suggest these traits may directly influence juvenile behaviour.

Parentally acquired differences in resource acquisition ability between brown trout from alternative life history parentage

AbstractDominance hierarchies, where they exist, affect individual food acquisition ability and fitness, both of which have the potential to influence life history pathways. Juvenile salmonids exhibit clear dominance hierarchies in early life. As one of the drivers for the adoption of alternative life histories in salmonids is the relative rate of resource acquisition, there is potential for juvenile behaviour to influence the subsequent life history strategy of the individual. Lacustrine brown trout, Salmo trutta, exhibit a multitude of life histories which includes among others the piscivorous (ferox) life history where individuals grow to large size and have delayed maturity and benthivorous and pelagic life histories where individuals grow to much smaller sizes, however mature earlier. Using a number of observable characteristics of dominance, this study compared differences in behaviour between size‐matched pairs of progeny, reared under common garden conditions which are derived from alternative, co‐existing life history strategy parents. We found that first‐generation progeny of ferox trout were more aggressive, acquired more food, had lighter skin pigmentation and held more desirable positions than the progeny of benthivorous brown trout in an experimental stream system. Ferox trout progeny were dominant over benthivorous brown trout progeny in 90% of trials in dyadic contests. Given such clear differences in dominance, this study indicates that parentally acquired dominance‐related differences, passed through either, or both, of genetic and nongenetic (e.g. maternal effects) means, are likely a contributing factor to the continued maintenance of distinct life history strategies of brown trout.

Characterization of stress coping style in Senegalese sole (Solea senegalensis) juveniles and breeders for aquaculture.

The aim of this work was to characterize stress coping styles of Senegalese sole (Solea senegalensis) juveniles and breeders and to select an operational behavioural screening test (OBST) that can be used by the aquaculture industry to classify and select between behavioural phenotypes in order to improve production indicators. A total of 61 juveniles and 59 breeders were subjected to five individual behavioural tests and two grouping tests. At the end of the individual tests, all animals were blood sampled in order to measure cortisol, glucose and lactate. Three tests (restraining, new environment and confinement) characterized the stress coping style behaviour of Senegalese sole juveniles and breeders and demonstrated inter-individual consistency. Further, the tests when incorporated into a principal components analysis (PCA) (i) identified two principal axes of personality traits: ‘fearfulness-reactivity’ and ‘activity-exploration’, (ii) were representative of the physiological axis of stress coping style, and (iii) were validated by established group tests. This study proposed for the first time three individual coping style tests that reliably represented proactive and reactive personalities of Senegalese sole juveniles and breeders. In addition, the three proposed tests met some basic operational criteria (rapid testing, no special equipment and easy to apply and interpret) that could prove attractive for fish farmers to identify fish with a specific behaviour that gives advantages in the culture system and that could be used to establish selection-based breeding programmes to improve domestication and production.

Exploring the behavior of juveniles and young adults raised by custodial grandmothers

The present study compares behaviors of youth raised by a custodial grandmother, biological mother, or other female caregiver from adolescence to young adulthood using data from Waves I, II, and III of the National Longitudinal Study of Adolescent Health (Add Health) data set. Caregiver type was not significantly related to antisocial behavior. However, respondents who were raised by a custodial grandmother reported being stopped by police more times than those respondents raised by their biological mothers. The effect of parenting characteristics such as warmth, control, and involvement by a custodial grandmother may operate differently than in a biological mother-headed household.

Early life low intensity stress experience modifies acute stress effects on juvenile brain cell proliferation of European sea bass (D. Labrax)

Early life adversity may be critical for the brain structural plasticity that in turn would influence juvenile behaviour. To address this, we questioned whether early life environment has an impact on stress responses latter in life, using European sea bass, Dicentrarchus labrax, as a model organism. Unpredictable chronic low intensity stress (UCLIS), using a variety of moderate intensity stressors, was applied during two early ontogenetic stages, flexion or formation all fins. At juvenile stage, fish were exposed to acute stress and plasma cortisol, brain mRNA expression of corticosteroid receptors’ genes (gr1, gr2, mr) and brain cell proliferation (using BrdU immunohistochemistry) were determined in experimental and matched controls. UCLIS treatment specifically decreased brain gr1 expression in juveniles, but had no effect on the juvenile brain cell proliferation pattern within the major neurogenic zones studied of dorsal (Dm, Dld) and ventral (Vv) telencephalic, preoptic (NPO) areas, periventricular tectum gray zone (PGZ) and valvula cerebellum (VCe). In contrast, exposure to acute stress induced significant plasma cortisol rise, decreases of cerebral cell proliferation in juveniles, not previously exposed to UCLIS, but no effect detected on the expression levels of gr1, gr2 and mr in all groups of different early life history. Interestingly, juveniles with UCLIS history showed modified responses to acute stress, attenuating acute stress-induced cell proliferation decreases, indicating a long-lasting effect of early life treatment. Taken together, early life mild stress experience influences an acute stress plasticity end-point, cerebral cell proliferation, independently of the stress-axis activation, possibly leading to more effective coping styles.

Impulsivity Mediates the Relationship between Future Orientation and Juvenile Deviancy

ABSTRACTBoth future orientation and impulsivity are intrinsic parts of an adolescent’s self-control, and empirical evidence clearly establishes them as crucial features on the origin of juvenile deviant behavior. However, we do not yet fully understand how these variables relate in explaining deviant conduct. In the present study, we tested a mediation model between these variables among 126 Portuguese adolescents. Findings support the mediation model in analysis, namely that impulsivity fully mediates the effect of future orientation on deviant behavior. In conclusion, our results suggest that lesser future orientated youth develop impulsive behavior which, in turn, explains their higher deviant conduct.

Changes in behavior and feeding habits of hatchery-reared tiger puffer Takifugu rubripes juveniles

Changes in behavior and feeding habits of hatchery-reared tiger puffer Takifugu rubripes juveniles

Morphological and behavioral ontogeny in larval and early juvenile discus fish Symphysodon aequifasciatus

We observed the growth, morphological changes, and behavior of larvae and juveniles of the Amazonian substrate-brooding cichlid discus fish Symphysodon aequifasciatus under laboratory conditions. The mean body length (BL) of newly hatched larvae was 3.4–3.5 mm, and the yolksac extended to approximately 42 % of their BL. Larvae detached from the substrate on day 4 began swimming and immediately displayed biting behavior on the body surface of the parents. Larvae had completely consumed their yolksacs by day 7. They began swimming at an earlier developmental stage compared with other cichlid species. Their thick lips may be advantageous for removing mucus from the bodies of the parent fish. Juveniles actively fed on Artemia spp. by day 30, and the frequency of biting behavior toward the parents decreased between days 20 and 35. Bone ossification was essentially complete in juveniles by day 32. Juveniles reached 16.0 ± 1.1 mm BL by day 35. These results indicate that the morphology and behavior of larval and early juvenile S. aequifasciatus exhibit adaptations for mucus provisioning.

Addicted to the Thrill of the Virtual Hunt: Examining the Effects of Internet Addiction on the Cyberstalking Behaviors of Juveniles

ABSTRACTThe rapid advancement of technology has produced several substantial benefits that enrich individuals’ lives, but some also note that technology has provided new methods to engage in crime—particularly stalking. This investigation was one of the first to explore whether a relationship existed between cyberstalking and a new phenomenon becoming a pressing issue in the lives of adolescents: Internet Addiction. High school students in a rural North Carolina country were surveyed about their Internet behaviors and experiences. After analysis, the results indicated there is a significant relationship between Internet Addiction and cyberstalking in adolescents.

English

Conilon coffee is a highly heterozygous diploid plant that is also allogamous, producing seeds through cross-fertilisation. Due to their allogamy, plants of seminiferous origin are highly heterogeneous, exhibiting high morphological and genetic diversity. However, propagation through cutting guarantees the maximum homogeneity of fields, particularly in grain maturation, among other desirable characteristics. Currently, the majority of commercial Conilon coffee is planted using seedlings propagated by cuttings. Studying the juvenile behaviour of different clonal genotypes of the Conilon coffee plant represents an important tool to assist with the establishment of this crop. The objective of this study was to assess the growth, development and genetic diversit y in several promising genotypes of the Conilon coffee plant based on the morphological characteristics of seedlings propagated by cutting. We used seedlings Conilon coffee of 33 genotypes selected by coffee growers, and with great productive potential, and genotype 02 of the Emcapa 8111 variety. Based on morphological characteristics linked to the growth and development of the aboveground and root systems of the genotypes, their phenotypic correlations were estimated, along with the genetic diversity among genotypes, using Tocher’s optimisation method and the unweighted peer group method with arithmetic mean. Genotypes A1, P2, Z39, Ouro Negro, Tardio C, Cheique, and Z29 exhibited a higher Dickson quality index (between 0.40 and 0.56). Genetic variability exists among the seedlings of the 34 genotypes of Conilon coffee studied. The most dissimilar genotypes were CHR, 18, and Z39, which remained in isolated groups in all experiments.

Martial arts participation and externalizing behavior in juveniles: A meta-analytic review

Martial arts are very popular among juveniles all over the world, but the relation between martial arts and externalizing behavior in juveniles remains unclear. The current multilevel meta-analysis of 12 studies, including 94 effect sizes and N = 5949 juveniles, was conducted to examine the relation between martial arts participation and externalizing behavior in juveniles, and to examine factors with a possible moderating effect. Results showed that there was no overall relation between martial arts participation and externalizing behavior in juveniles. However, a trim-and-fill procedure implicated publication bias of studies reporting that juvenile martial artist showed more externalizing behavior than non-martial artists, suggesting that the current overall outcomes might underestimate externalizing behavior in martial artists. Moderator analyses showed that studies published in higher impact factor journals, and studies with a higher training intensity in martial arts found more externalizing behavior in martial artists. Furthermore, karate was found to be less related to externalizing behavior than judo. Finally, in comparison with non-athletes and team sport athletes, martial artists showed similar levels of externalizing behavior, but they showed more externalizing behavior when compared to individual sport athletes. Implications for future policy and research are discussed.

Artificial Spawning Behavior and Development of Eggs, Larvae and Juveniles of the Red Spotted Grouper, Epinephelus akaara in Korea.

This study was conducted in order to examine the egg development in red spotted grouper, Epinephelus akaaraand the morphological development of its larvae and juveniles, and to obtain data for taxonomic research. This study was conducted in June 2013, and 50 male and female fish were used for the study. One hundred μg/kg of LHRHa was injected into the body of the fish for inducing spawning, and the fish were kept in a small-sized fish holder (2×2×2 m). Eggs were colorless transparent free pelagic eggs, 0.71–0.77 mm large (mean 0.74±0.02 mm, n=30), and had an oil globule. Hatching started within 27 h after fertilization. Pre-larvae that emerged just after hatching were 2.02–2.17 mm in total length (mean 2.10±0.11 mm), their mouth and anus were not opened yet, and the whole body was covered with a membrane fin. Post-larvae that emerged 15 days post hatching were 3.88–4.07 mm in total length (mean 3.98±0.13 mm), and had a ventral fin with two rays and a caudal fin with eight rays. Juveniles that were formed at 55 d post hatching, were 31.9–35.2 mm in total length (mean 33.6±2.33 mm), with red color deposited over the entire body, and black chromophores deposited in a spotted pattern. The number of fin rays, body color, and shape were the same as that in the adult fish.

Climate-driven coral reorganisation influences aggressive behaviour in juvenile coral-reef fishes

Globally, habitat degradation is altering the abundance and diversity of species in a variety of ecosystems. This study aimed to determine how habitat degradation, in terms of changing coral composition under climate change, affected abundance, species richness and aggressive behaviour of juveniles of three damselfishes (Pomacentrus moluccensis, P. amboinensis and Dischistodus perspicillatus, in order of decreasing reliance on coral). Patch reefs were constructed to simulate two types of reefs: present-day reefs that are vulnerable to climate-induced coral bleaching, and reefs with more bleaching-robust coral taxa, thereby simulating the likely future of coral reefs under a warming climate. Fish communities were allowed to establish naturally on the reefs during the summer recruitment period. Climate-robust reefs had lower total species richness of coral-reef fishes than climate-vulnerable reefs, but total fish abundance was not significantly different between reef types (pooled across all species and life-history stages). The nature of aggressive interactions, measured as the number of aggressive chases, varied according to coral composition; on climate-robust reefs, juveniles used the substratum less often to avoid aggression from competitors, and interspecific aggression became relatively more frequent than intraspecific aggression for juveniles of the coral-obligate P. moluccensis. This study highlights the importance of coral composition as a determinant of behaviour and diversity of coral-reef fishes.

Sustained Effects of Developmental Exposure to Ethanol on Zebrafish Anxiety-Like Behaviour.

In zebrafish developmentally exposed to ambient ethanol (20mM-50mM) 1–9 days post fertilization (dpf), the cortisol response to stress has been shown to be significantly attenuated in larvae, juveniles and 6 month old adults. These data are somewhat at variance with similar studies in mammals, which often show heightened stress responses. To test whether these cortisol data correlate with behavioural changes in treated animals, anxiety-like behaviour of zebrafish larvae (9dpf and 10dpf) and juveniles (23dpf) was tested in locomotor assays designed to this end. In open field tests treated animals were more exploratory, spending significantly less time at the periphery of the arena. Behavioural effects of developmental exposure to ethanol were sustained in 6-month-old adults, as judged by assessment of thigmotaxis, novel tank diving and scototaxis. Like larvae and juveniles, developmentally treated adults were generally more exploratory, and spent less time at the periphery of the arena in thigmotaxis tests, less time at the bottom of the tank in the novel tank diving tests, and less time in the dark area in scototaxis tests. The conclusion that ethanol-exposed animals showed less anxiety-like behaviour was validated by comparison with the effects of diazepam treatment, which in thigmotaxis and novel tank diving tests had similar effects to ethanol pretreatment. There is thus a possible link between the hypophyseal-pituitary-interrenal axis and the behavioural actions of developmental ethanol exposure. The mechanisms require further elucidation.

Behavioral Thermoregulation and Trade-Offs in Juvenile Lobster Homarus americanus.

Water temperature influences the behavior and distribution patterns of both larval and adult American lobster Homarus americanus. However, very little is known about the responses of juvenile lobsters. The juvenile life stage is a critical period; high levels of mortality, combined with specific behavioral responses, can disconnect larval settlement from patterns of abundance of adults. We assessed behavioral thermoregulation in juvenile lobsters, and determined how thermal preferences can be altered by the presence of shelter and food. Juvenile lobsters avoided temperatures higher than 20 °C and lower than 8 °C, and had a mean temperature preference of 16.2 ± 1 °C. This preference was unaffected by prior acclimation, origin (laboratory-raised or wild), or size. When the animals were subjected to a temperature change (5-20 °C), activity rates peaked at 15 °C, and remained stable thereafter. Activity rates did not change when a shelter was added. The addition of food resulted in an increase in activity associated with food handling. When juvenile lobsters were offered a choice between temperature, shelter, and food, they always chose the environment with a shelter, even when it was in a thermally unfavorable temperature. Juveniles also spent more time in a thermally unfavorable environment when food was present; however, acquisition of a shelter was prioritized over food. Although juveniles had a similar thermal preference to adults, they are more vulnerable to predation; the innate shelter-seeking behavior of juveniles overrode their thermal preference. While temperature is an important environmental factor affecting the physiology, distribution, and growth of aquatic ectotherms, our findings suggest that trade-off behaviors occur in order to maintain optimal fitness and survival of the individual.

It rhymes with lust? Matt Baker and the ironic politics of race, sex and gender in the golden age

In Seduction of the Innocent, Dr Frederic Wertham famously described Golden Age comics as pornography that fostered juvenile sexual deviance, anti-social behaviour, misogyny and racism. In singling out Phantom Lady #17 as an example, Wertham ironically implicated one of Golden Age comics’ only African-American artists, Matt Baker. This study considers the roles that Baker’s race and sexual orientation played in his work. Contextualising Baker’s life experience within the general sweep of African-American history and gender studies, this essay asserts that Baker’s contribution to Good Girl Art were shaped by the unique African-American expressive and visual culture of 1930–50s Harlem. This, in turn, affected his representation of the female form and his attention to drawing racial minorities. It further suggests that recent scholarly models interrogating gay writers and readers’ engagement with superheroines provide intriguing insight into aspects of Baker’s art.

Figure of juveniles in the media children as victims and observers of violence

The paper representation of children in the media and the impact of mass media on the behavior of juveniles. This hot topic is gaining in importance and the fact that juvenile delinquency in our country is increasing. Be sure that the sad fact that influenced the economic crisis, growing poverty, the transition in society and state, but the main causes must be sought in the family. In the struggle for economic existence, parents have no time to take care of their children, so that education, as one of its core functions, left to the media, which again is an existential survival and race of sensations and negative circulation model offers education and a distorted image of moral values. Negative selection, most children are observers of violence in the media or write about them only when they become victims of violence.