Juvenile Development Research Articles

Does zircon geochemistry record global sediment subduction?

Abstract Global compilations of zircon geochemistry have been used as evidence for changes in plate tectonic styles and surface environments. In particular, zircon δ18O has been used as a proxy for global sediment subduction and incorporation into igneous melts. However, research employing such compilations commonly ignores geologic and geographic context. We analyze a newly georeferenced zircon δ18O database from 1000 Ma to present. The compilation shows positive and negative isotopic excursions, both of which have been interpreted in the context of global phenomena. Sensitivity testing demonstrates that these excursions are the product of regional tectonic environments. Specifically, low Tonian–Cryogenian δ18O, previously interpreted as a climate signal of snowball Earth glacial meltwater, is isolated to ultra-high-pressure rocks of the Dabie Sulu orogen in central Asia, ophiolites in Egypt, and juvenile arc development in Madagascar, predating Cryogenian glaciation. Positive anomalies in the Ediacaran–Cambrian and Devonian, previously interpreted to record snowball Earth erosion and the rise of land plants, are the result of upper-plate, supracrustal sources of Gondwana. A Neogene anomaly is the result of volcanic rocks associated with Yellowstone and Iceland. Sampling bias in zircon geochemical compilations is analogous to that of Lagerstätten (sites of exquisite fossil preservation) and the “monograph effect” (large contributions from individual researchers) in paleontology, which both result in artifacts of over-representation. Long-term zircon δ18O trends broadly track the generation of collisional granites and continental arcs through time, recording the melting of sediments and sedimentary rocks in individual orogens, and not variations in sediment subduction globally.

Characterization and evaluation of the morphological attributes of Ethiopian mustard (Brassica carinata A. Braun) landraces

Ethiopian mustard (Brassica carinata A. Braun) is one of the Brassica leafy vegetables and oilseed crops, which can withstand adverse environmental conditions. This study was conducted to characterize and evaluate the leaf attributes of 313 Ethiopian mustard accessions grown in the greenhouse and field in 2018/19 in Beijing, China. Data on 18 different leaf morphological attributes were collected based on the IBPGR for Brassica and Raphanus descriptor format and Fiji Image J. The collected data were subjected to descriptive statistics using JMP version 14 software. Results indicate that the majority of the accessions had serrated leaf margin, intermediate juvenile development, rounded apex leaf shape, absence of leaf pubescence, number of lobes > 5 and had intermediate number of leaves per plant with frequencies of 101, 213, 223, 244, 183 and 289, respectively. The accessions had also white midrib color, light green leaf color, purple petiole color, purple stem color and purple apex leaf color pigments with frequencies of 168, 165, 104, 113 and 122, respectively. Significant differences were observed among the accessions for leaf size attributes (p < 0.001) indicating their potential as leafy vegetables. Furthermore, there were significant accession × environment effects for the laminal length, total leaf length, leaf area, leaf weight and petiole length. Notably, 71% of the accessions had an average of 81 days flowering time. The multivariate cluster and principal component analyses divided the 313 accessions into eight groups with distinctive information; consisting of 81, 37, 79, 38, 14, 11, 6 and 47 accessions. Thus, this study provides important information about Ethiopian mustard germplasms that is vital for further advancement and genetic improvement of the crop.

In Vitro Culture of Glochidia and Morphological Changes in Juveniles of the Endangered Freshwater Mussel Solenaia oleivora

The artificial propagation of the endangered Solenaia oleivora, with unknown fish hosts, was performed via in vitro culture with bighead carp, grass carp, common carp, bovine, and rabbit sera. The effects of glochidium density on transformation rates were evaluated, and the development of juveniles that metamorphosed successfully was documented. The control group had a transformation rate of 0 and a contamination rate of 0. No significant differences were found in the transformation and contamination rates of the bighead carp, grass carp, and common carp serum groups, and their transformation rates were significantly higher, and contamination rates were significantly lower than those of the bovine and rabbit serum groups. Moreover, no significant differences were observed in the transformation rates of glochidia (culture density, 2000–5000 glochidia/dish) in contamination-free conditions. Specimen shell length/height increased from 1.08 ± 0.01 on the first day to 3.08 ± 0.29 during the 13th week. On the basis of anterior and posterior growth differences, juvenile growth was divided into the following three phases: the rapid anterior growth period, distinct anterior and posterior idiophase, and rapid posterior growth period. This study not only provides technological support for the artificial propagation of S. oleivora but also lays a foundation for resource recovery.

Variation in temperature of peak trait performance constrains adaptation of arthropod populations to climatic warming

The capacity of arthropod populations to adapt to long-term climatic warming is currently uncertain. Here we combine theory and extensive data to show that the rate of their thermal adaptation to climatic warming will be constrained in two fundamental ways. First, the rate of thermal adaptation of an arthropod population is predicted to be limited by changes in the temperatures at which the performance of four key life-history traits can peak, in a specific order of declining importance: juvenile development, adult fecundity, juvenile mortality and adult mortality. Second, directional thermal adaptation is constrained due to differences in the temperature of the peak performance of these four traits, with these differences expected to persist because of energetic allocation and life-history trade-offs. We compile a new global dataset of 61 diverse arthropod species which provides strong empirical evidence to support these predictions, demonstrating that contemporary populations have indeed evolved under these constraints. Our results provide a basis for using relatively feasible trait measurements to predict the adaptive capacity of diverse arthropod populations to geographic temperature gradients, as well as ongoing and future climatic warming.

Hypothalamic tanycytes as mediators of maternally programmed seasonal plasticity

In mammals, maternal photoperiodic programming (MPP) provides a means whereby juvenile development can be matched to forthcoming seasonal environmental conditions.1,2,3,4 This phenomenon is driven by in utero effects of maternal melatonin5,6,7 on the production of thyrotropin (TSH) in the fetal pars tuberalis (PT) and consequent TSH receptor-mediated effects on tanycytes lining the 3rd ventricle of the mediobasal hypothalamus (MBH).8,9,10 Here we use LASER capture microdissection and transcriptomic profiling to show that TSH-dependent MPP controls the attributes of the ependymal region of the MBH in juvenile animals. In Siberian hamster pups gestated and raised on a long photoperiod (LP) and thereby committed to a fast trajectory for growth and reproductive maturation, the ependymal region is enriched for tanycytes bearing sensory cilia and receptors implicated in metabolic sensing. Contrastingly, in pups gestated and raised on short photoperiod (SP) and therefore following an over-wintering developmental trajectory with delayed sexual maturation, the ependymal region has fewer sensory tanycytes. Post-weaning transfer of SP-gestated pups to an intermediate photoperiod (IP), which accelerates reproductive maturation, results in a pronounced shift toward a ciliated tanycytic profile and formation of tanycytic processes. We suggest that tanycytic plasticity constitutes a mechanism to tailor metabolic development for extended survival in variable overwintering environments.

Characterization of genetic and molecular tools for studying the endogenous expression of Lactate dehydrogenase in Drosophila melanogaster.

Drosophila melanogaster larval development relies on a specialized metabolic state that utilizes carbohydrates and other dietary nutrients to promote rapid growth. One unique feature of the larval metabolic program is that Lactate Dehydrogenase (Ldh) activity is highly elevated during this growth phase when compared to other stages of the fly life cycle, indicating that Ldh serves a key role in promoting juvenile development. Previous studies of larval Ldh activity have largely focused on the function of this enzyme at the whole animal level, however, Ldh expression varies significantly among larval tissues, raising the question of how this enzyme promotes tissue-specific growth programs. Here we characterize two transgene reporters and an antibody that can be used to study Ldh expression in vivo. We find that all three tools produce similar Ldh expression patterns. Moreover, these reagents demonstrate that the larval Ldh expression pattern is complex, suggesting the purpose of this enzyme varies across cell types. Overall, our studies validate a series of genetic and molecular reagents that can be used to study glycolytic metabolism in the fly.

Juvenile exposure to low-level 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alters behavior and longitudinal morphometrics in zebrafish and F1 offspring.

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an environmental endocrine disruptor and model AhR agonist, is linked to skeletal abnormalities, cardiac edema, stunted growth rate, altered metabolism, and neurobehavioral deficits. We have previously reported transgenerational reproductive outcomes of developmental TCDD exposure in adult zebrafish (Danio rerio), an NIH-validated model for developmental and generational toxicology. Using the same paradigm of sublethal TCDD exposure (50 pg/ml) at both 3 and 7 weeks post fertilization (wpf), we investigated several novel endpoints, including longitudinal morphometrics and anxiety-linked behavior, in fish exposed as juveniles. We also assessed developmental abnormalities and neurobehavior in their F1 larval offspring. TCDD exposure induced timepoint-dependent decreases in several craniofacial and trunk morphometrics across juvenile development. In early adulthood, however, only exposed males underwent a transient period of compensatory growth, ending between 7 and 12 months post fertilization (mpf). At 12 mpf, exposed adult fish of both sexes displayed increased exploratory behaviors in a novel tank test. The F1 offspring of parents exposed at both 3 and 7 wpf were hyperactive, but neurobehavioral outcomes diverged depending on parental exposure window. F1 exposure-lineage larvae had increased rates of edema and skeletal abnormalities, but fewer unhatched larvae compared to controls. Parent- and timepoint-specific effects of exposure on abnormality rate were also evaluated; these outcomes were considerably less severe. Our novel behavioral findings expand current knowledge of the long-term and intergenerational consequences of early-life TCDD exposure in a zebrafish model, in addition to delineating minor longitudinal morphometric changes in exposed fish and abnormalities in larval offspring.

Husbandry conditions of spotted ratfish (Hydrolagus colliei, Chimaeriformes) in aquaria for successful embryonic development and long-term survival of juveniles.

The spotted ratfish Hydrolagus colliei is the most common holocephalan species exhibited in aquaria worldwide for introducing deep-sea environments and raising awareness of their conservation. However, little is known about the biology of H. colliei. Current practices in aquaria allow long-term survival of sexually mature H. colliei specimens; however, this species struggles to complete a reproductive cycle in captivity mostly because embryos do not reach the hatchling stage. The aquarists of Planet Ocean Montpellier (POM, France) have bred H. colliei for 15 years and recorded parameters suitable for this species' successful embryonic and post-embryonic development. POM aquarists now regularly record egg-laying events of H. colliei and use four tanks to incubate eggs and raise neonates, late hatchlings, early and intermediate juveniles, subadults, and sexually mature specimens. In this work we provide the first long-term biometric data on H. colliei from the hatchling to the subadult stage. We also report the biotic and abiotic parameters sufficient to breed H. colliei in aquaria. We finally describe the methods used to facilitate individual monitoring of specimens along the ontogeny and several pathologies identified in this species, their putative causes, and the corresponding treatments. This work highlights the importance of ex situ research and points to the valuable outcomes of collaborative efforts between aquaria and academia in deciphering the biology of species whose study in the wild remains challenging.

In Constant Search for Affection: Untold Narratives of Juvenile Delinquents or “SUKARAP” in Davao Region

“Sukarap,” derived from “stagger,” reflects uncontrolled movements while walking. This qualitative-phenomenological study focuses on the challenges faced by Sukarap members in the Davao Region. Examining their involvement, reasons, challenges, and coping mechanisms, the research engaged 14 Sukarap members through interviews and discussions. Participants revealed experiences of painful initiation, exposure to vices, street riots, and life-threatening situations. Coping strategies included diversion, peer support, and ignoring challenges. Insights from Sukarap members highlighted belongingness, learning, and opportunities for change. In conclusion, the study emphasizes the importance of education and affection in nurturing the optimal development of delinquent juveniles seeking attention and affection outside their families. Keywords: gang, gangsterism, plight, Sukarap, stories to tell

The effects of dietary amino acid balance on post-embryonic development in a lubber grasshopper

Effects of dietary protein quality on insect development (not just growth) are unclear. Dietary amino acid blends matching yolk proteins support reproduction and juvenile development in Drosophila melanogaster. We matched amino acids to vitellogenin and tested development of juvenile male lubber grasshoppers, which do not produce vitellogenin. Last instars were fed classic dry diets with amino acids substituted for proteins. Matching amino acids to vitellogenin allowed molting to adulthood, while an unmatched isonitrogenous diet did not. Health on dry diets was poor, so we developed wet diets with agar, horse feed, and amino acids. Juveniles fed these diets matched to vitellogenin developed comparably to juveniles fed lettuce. However, wet diets with amino acids dissimilar to vitellogenin (low-quality) slowed development but maintained size at adulthood. We observed no compensatory feeding on low-quality diets. Theory suggests accumulation of proteins permits development. To detect a threshold, we started last juvenile instars on high-quality diets, then abruptly switched them to low-qualities diets. When switched to the poor-quality diet at 6d, grasshoppers molted at a similar age (∼17d) to grasshoppers continuously on the high-quality diet. Total hemolymph proteins levels were unaffected by the timing of diet switches. Last, methionine is essential but can be noxious at high levels. Diets with low-quality protein except for methionine slowed growth early but did not alter the time or size at molt. Overall, the feeding threshold is solely due to essential amino acids, and low-quality protein diets slowed development but did not affect adult size.

Mosquito larvae exposed to a sublethal dose of photosensitive insecticides have altered juvenile development but unaffected adult life history traits

BackgroundLarvicides are critical for the control of mosquito-borne diseases. However, even sublethal exposure to a larvicide can alter development and life history traits, which can then affect population density and disease transmission dynamics. Photosensitive insecticides (PSIs) are a promising class of larvicide that are toxic when ingested and activated by light. We investigated whether the time of day when exposure occurs, or the process of pupation, affects larval susceptibility to PSI phototoxicity in the mosquito Anopheles gambiae, and whether sublethal exposure to PSIs alters life history traits.MethodsLarvae were treated with lethal concentrations of the PSIs methylene blue (MB) and rose bengal (RB), and larval survival was measured at various times of day. Additionally, larvae were exposed to two concentrations of each PSI that resulted in low and medium mortality, and the life history traits of the surviving larvae were measured.ResultsPupation, which predominantly occurs in the evening, protected larvae from PSI toxicity, but the toxicity of PSIs against larvae that had yet to pupate was unaffected by time of day. Larval exposure to a sublethal concentration of MB, but not RB, shortened the time to pupation. However, larval exposure to a sublethal concentration of RB, but not MB, increased pupal mortality. Neither PSI had a meaningful effect on the time to eclosion, adult longevity, or adult melanization potential.ConclusionsPSIs are lethal larvicides. Sublethal PSI exposure alters mosquito development, but does not affect adult life history traits.Graphical

24 Effects of Gestational and Postweaning Nutrition on Brain Development and Puberty in Beef Heifers

Abstract Approximately 5 million beef heifers enter the U.S. cow herd annually, and their lifetime productivity is largely dependent upon their ability to attain puberty and produce a calf by 24 mo of age. However, a considerable proportion of heifers within existing U.S. production systems fail to achieve these goals, particularly in southern regions where Bos indicus-influenced cattle predominate. Consequently, managerial approaches are needed that employ nutritional programming of the reproductive neuroendocrine axis, while minimizing feeding costs and optimizing the consistent attainment of puberty by approximately 14 mo of age. Our previous research has clearly demonstrated that increased BW gain between 4 and 8 mo of age facilitates pubertal development by programming hypothalamic centers that regulate gonadotropin releasing-hormone (GnRH) secretion. Among the different metabolic hormones, leptin has a critical role in conveying nutritional information to the hypothalamus and controlling puberty. Two hypothalamic neuronal populations that express the orexigenic peptide neuropeptide Y (NPY) and the anorexigenic peptide alpha melanocyte-stimulating hormone (αMSH; a product of the POMC gene) are key components of afferent pathways that convey inhibitory (NPY) and excitatory (αMSH) inputs to GnRH and kisspeptin neurons. Our studies have demonstrated that short-term increases in dietary energy intake after early weaning at 4 mo of age result in epigenetic, structural, and functional modifications in these hypothalamic pathways to promote high-frequency, episodic release of GnRH and luteinizing hormone. However, integrating the foundational knowledge of metabolic imprinting of the brain for early puberty with issues related to lifetime performance is complex. One approach has been to employ a novel stair-step nutritional regimen involving alternating periods of dietary energy-restriction and re-feeding during juvenile development. This approach is designed to support early onset of puberty by imprinting functional alterations in the hypothalamus during key periods of brain development while optimizing other aspects of growth and performance. Finally, while several key processes of fetal brain development occur during late gestation, neither maternal undernutrition (BCS 3.0-3.5) nor maternal obesity (BCS 7.5-8.0) during the last two trimesters of gestation impacted the organization of hypothalamic neurocircuitries controlling GnRH/LH secretion or age at puberty in the heifer offspring. Collectively, these results indicate that the adult reproductive phenotype in Bos indicus-influenced females is resilient to significant degrees of nutritional stress imposed during prenatal development, particularly if early gestation (first trimester) is avoided. These findings are in contrast with reports in Bos taurus females in which late gestation nutritional extremes result in delayed puberty in heifer offspring, suggesting that potential genotype-specific differences may exist. Research support: USDA-NIFA-AFRI (2018-67015-27595 and 2021-67015-33676).

Potential of a new phytoseiid species Neoseiulus setarius (Acari: Phytoseiidae) as a biocontrol agent: Biological and demographic parameters on prey and non-prey foods

Neoseiulus setarius Ma, Meng & Fan is a newly described phytoseiid species found in Inner Mongolia of China. To evaluate the potential of N. setarius as a biocontrol agent, we studied life table parameters of N. setarius reared on four food resources, including western flower thrips Frankliniella occidentalis Pergande, eriophyoid mite Aceria pallida Keifer, cattail pollen Typha latifolia L. and poplar pollen Populus alba L. Neoseiulus setarius fed on two prey species developed faster and produced more eggs than those fed with two kinds of pollen. Neoseiulus setarius had the shortest juvenile development time on A. pallida (5.38 days), and the highest daily fecundity on F. occidentalis (2.43 eggs/female/day). The juvenile development time of N. setarius was similar on cattail pollen and poplar pollen, but the fecundity of N. setarius was significantly higher on cattail pollen. There were significant differences in the demographic parameters of N. setarius reared on the four different diets. The highest intrinsic rate of increase (rm) was on F. occidentalis (0.178 day−1), followed by A. pallida (0.159 day−1), cattail pollen (0.127 day−1) and poplar pollen (0.092 day−1). Neoseiulus setarius showed higher fitness in development and reproduction on prey (F. occidentalis and A. pallida) and cattail pollen. These results suggest that N. setarius could be a promising biocontrol agent for the management of thrips and gall mites.

Phenotypic plasticity of male calls in two populations of the katydid Neoconocephalus triops (Insecta: Tettigoniidae)

The ability to respond to environmental changes plays a crucial role for coping with environmental stressors related to climate change. Substantial changes in environmental conditions can overcome developmental homeostasis, exposing cryptic genetic variation. The katydid Neoconocephalus triops is a tropical species that extended its range to the more seasonal environment of North America where it has two reproductive generations per year. The harsher winter conditions required adults to diapause which resulted in substantially different mating calls of the diapausing winter animals compared to the non-overwintering summer animals in northern Florida. The summer call corresponds to that of tropical populations, whereas the winter call represents the alternative call phenotype. We quantified call plasticity in a tropical (Puerto Rico) and a temperate population of N. triops (Florida) that differ in experiencing winter conditions in their geographic regions. We hypothesized that the plastic call traits, i.e., double-pulse rate and call structure, are regulated independently. Further, we hypothesized that phenotypic plasticity of double-pulse rate results in quantitative changes, whereas that of call structure in qualitative changes. We varied the photoperiod and duration of diapause during male juvenile and adult development during rearing and analyzed the double-pulse rate and call structure of the animals. Double-pulse rate changed in a quantitative fashion in both populations and significant changes appeared at different developmental points, i.e., the double-pulse rate slowed down during juvenile development in Florida, whereas during adult diapause in Puerto Rico. In the Florida population, both the number of males producing and the proportion of total call time covered by the alternative call structure (= continuous calls) increased with duration spent in diapause. In the Puerto Rico population, expression of the alternative call structure was extremely rare. Our results suggest that the expression of both pulse rate and call structure was quantitative and not categorical. Our systematic variation of environmental variables demonstrated a wide range of phenotypic variation that can be induced during development. Our study highlights the evolutionary potential of hidden genetic variation and phenotypic plasticity when confronted with rapidly changing environments and their potential role in providing variation necessary for communication systems to evolve.

Artificial reproduction and description of the embryonic, larval, and juvenile development of sea cucumber (Holothuria inornata Semper 1868) with three different microalgae diets

Artificial reproduction and description of the embryonic, larval, and juvenile development of sea cucumber (Holothuria inornata Semper 1868) with three different microalgae diets

Transcriptome profiling of banana shrimp (Fenneropenaeus merguiensis) ovaries and testes: Insights into FoxL2.

The banana shrimp is found in the Pacific and Indian Oceans. Female shrimp are preferred for consumption because they are larger than males. Understanding the mechanism of sex differentiation is important for developing techniques to increase the number of female shrimp for economic benefits. This study investigates the reproductive development of F. merguiensis using transcriptome analysis. Sxl2, dsx, AGH, FEM-1, and Nrg-X2 were classified as essential genes for testes development during the juvenile stage. Several genes were required for both juvenile and adult male development. Additionally, the expression of several genes was shown to be required for juvenile and adult ovarian development, including SOP1, SOP2, Ptgr1, EST, Vgr, Vmol1, and TR-beta A. Interestingly, high levels of FoxL2 expression were observed in the testes, in contrast to previous studies in humans and other mammals. The binding of FoxL2 to the Vtg promoter was demonstrated in silico with the highest relative binding score (RS = 0.89) using the JASPAR program. Knock-down of the FoxL2 gene with dsRNA significantly suppressed FoxL2 at 2, 4, and 6 d. As a result, Vtg expression increased when compared with the control at 2, 4, and 6 d, indicating that FoxL2 plays an important role in Vtg expression in the ovary. Our findings highlight the role of FoxL2 in banana shrimp reproduction and provide valuable information on the genes associated with the F. merguiensis reproductive system.

Fostering a Sense of Belonging among Pakistani Youth: An Exploration of Cultural Heritage and Identity in the Reluctant Fundamentalist

This paper explores the complex relationship between Pakistani identity and cultural legacy in the framework of Mohsin Hamid's "The Reluctant Fundamentalist," with an emphasis on helping young people feel like they belong. The research tries to explore the manner in which the story navigates the challenges of cultural identity in a globalized society by drawing on sociocultural theories, especially Stuart Hall's encoding/decoding model and Homi K. Bhabha's notions of hybridity and third space. Through the protagonist's trip, we are able to study the conflict between tradition and modernity, as well as East and West, and get insights into the processes that shape Pakistani identity today. This study compiles the body of research on juvenile development and cultural identity. The research aims to shed light on methods for promoting a sense of belonging among Pakistani youth, encouraging cross-cultural understanding, and building a more inclusive and interconnected global society by examining how the protagonist's cultural heritage affects how they perceive themselves and others.

A non-adaptationist hypothesis of play behaviour.

Play is a suite of apparently non-functional, pleasurable behaviours observed in human and non-human animals. Although the phenomenon has been studied extensively, no adaptationist behavioural theory of how play evolved can be supported by the available evidence. However, the advancement of the extended evolutionary synthesis and developments in systems biology offer alternative avenues for non-adaptationist physiological hypotheses. I therefore propose a hypothesis of play, based upon a complex ACh activity that is under agential control of the organism, whereby play initiates ACh-mediated feedforward and feedback processes which act to: (i) regulate metabolic processes; (ii) form new ACh receptors via ACh mRNA activity; (iii) mediate attention, memory consolidation and learning; and (iv) mediate social behaviours, reproduction and embryonic development. However, play occurs across taxa, but does not occur across all taxonomic groups or within all species of a taxonomic group. Thus, to support the validity of the proposed hypothesis, I further propose potential explanations for this anomaly, which include sampling and observer biases, altricial versus precocial juvenile development, and the influence of habitat niche and environmental conditions on behaviour. The proposed hypothesis thus offers new avenues for study in both the biological and social sciences, in addition to having potential applications in applied sciences, such as animal welfare and biomedical research. Crucially, it is hoped that this hypothesis will promote further study of a valid and behaviourally significant, yet currently enigmatic, biological phenomenon.

Sublethal effects of nine insecticides on Drosophila suzukii and its major pupal parasitoid Trichopria drosophilae.

Although the pupal parasitoid Trichopria drosophilae is employed in conservative and augmentative biocontrol of Drosophila suzukii infestations, current pest management strategies mostly rely on multiple insecticide applications. In this context, the aim of the study was to investigate the baseline toxicity of nine insecticides on D. suzukii larvae and their multiple sublethal effects (LC10 ) on immature stages of the pest feeding on contaminated diet and T. drosophilae developing within the intoxicated host. Chlorpyriphos and azadirachtin showed the lowest and the highest LC10 , which values were 9.78×1013 and 1.46×103 times lower than their recommended label field rate, respectively. Among tested insecticides, imidacloprid, malathion and dimethoate were the only treatments that did not affect the juvenile development time of D. suzukii, while spinosad and the organophosphates chlorpyriphos and dimethoate did not influence fly pupal size. No sublethal effects were recorded on T. drosophilae degree of infestation (DI) and juvenile development time. On the contrary, cyazypyr and dimethoate negatively affected the success of parasitism (SP) and the number of progeny of the pupal parasitoid, in association with malathion for the first parameter and spinosad for the fertility. Compared to the untreated control, more female progeny emerged following azadirachtin exposure, while dimethoate caused the opposite effect. Imidacloprid, lambda-cyhalothrin and spinetoram decreased hind tibia length of emerged parasitoids. This study provides new insights on the (eco)toxicological profile of nine insecticides and new information needed to support the deployment of T. drosophilae in the field within the sustainable management techniques against D. suzukii. This article is protected by copyright. All rights reserved.

Relationships between juvenile tree survival and tree density, shrub cover and temperature vary by size class based on ratios of abundance

Global change drivers are altering forest dynamics, yet how these factors influence tree survival across early developmental stages (i.e., seedling to recruited sapling) over large geographies is not well understood. We developed a novel approach to evaluate controls on seedling and sapling survival. This approach was demonstrated on a set of systematic forest inventory plots across the northeastern USA in which seedlings were tallied within six height classes, allowing for a detailed assessment of the stages at which demographic bottlenecks in juvenile tree development are often observed. Forest inventory subplots containing a study species were divided into overlapping bins along an environmental or ecological gradient, and ratios of abundance between successive size classes were used to infer relative survival rates. Relationships between 10 common tree species and tree density, shrub cover, and mean annual temperature were assessed. As seedling height class increased, we observed shifts from positive to negative associations with shrub cover and large tree density. Our results suggest that observed patterns of sapling and tree abundance may belie complex and sometimes opposing influences on seedling survival that are important to quantify when predicting and managing for successful tree recruitment and future canopy tree composition.