Delayed juvenile behavioural development and prolonged dependence are adaptations to desert life in the grey Falcon

Rapid learning in the young of most endothermic animals can be expected to be favoured by natural selection because early independence reduces the period of vulnerability. Cases of comparatively slow juvenile development continue, therefore, to attract scientific attention. In most species of birds, including raptors, the young depend on their parents for some time after fledging for the provisioning of food and for protection whilst they learn to become nutritionally and otherwise independent. Among raptors, post-fledging dependence periods that exceed six months are exclusive to the largest species and these have reproductive cycles that exceed 12 months. By contrast, young of the medium-sized grey falcon Falco hypoleucos have been reported in close company with their parents up to 12 months after fledging, i.e., at a time when the adults are expected to breed again. We investigated the occurrence and characteristics of prolonged adult-juvenile association relative to other falcons and similar-sized raptors. We found that the behavioural development of grey falcon young is extremely delayed, and that they even depend nutritionally on their parents for up to 12 months after fledging. We suggest that these two distinctive features are, ultimately, adaptations of the grey falcon to its extreme environment, Australia’s arid and semi-arid zone, one of the hottest environments in the world.

Larval metamorphosis is inhibited by methimazole and propylthiouracil that reveals possible hormonal action in the mussel Mytilus coruscus

Larval metamorphosis in bivalves is a key event for the larva-to-juvenile transformation. Previously we have identified a thyroid hormone receptor (TR) gene that is crucial for larvae to acquire “competence” for the metamorphic transition in the mussel Mytilus courscus (Mc). The mechanisms of thyroid signaling in bivalves are still largely unknown. In the present study, we molecularly characterized the full-length of two iodothyronine deiodinase genes (McDx and McDy). Phylogenetic analysis revealed that deiodinases of molluscs (McDy, CgDx and CgDy) and vertebrates (D2 and D3) shared a node representing an immediate common ancestor, which resembled vertebrates D1 and might suggest that McDy acquired specialized function from vertebrates D1. Anti-thyroid compounds, methimazole (MMI) and propylthiouracil (PTU), were used to investigate their effects on larval metamorphosis and juvenile development in M. coruscus. Both MMI and PTU significantly reduced larval metamorphosis in response to the metamorphosis inducer epinephrine. MMI led to shell growth retardation in a concentration-dependent manner in juveniles of M. coruscus after 4 weeks of exposure, whereas PTU had no effect on juvenile growth. It is hypothesized that exposure to MMI and PTU reduced the ability of pediveliger larvae for the metamorphic transition to respond to the inducer. The effect of MMI and PTU on larval metamorphosis and development is most likely through a hormonal signal in the mussel M. coruscus, with the implications for exploring the origins and evolution of metamorphosis.

Essential Fatty Acid Requirements in Tropical and Cold-Water Marine Fish Larvae and Juveniles

To improve survival at early developmental stages (larvae and juveniles) of captive fish species, essential nutrients [i.e., essential fatty acids (EFA)] need to be identified. The physiological needs are likely to be different among species, particularly among those using different thermal habitats, because lipids are largely used to maintain cell membrane integrity (homeoviscous adaptation) in fishes. This review paper will focus on currently published research and the main results from our laboratories regarding optimum qualitative EFA requirements during larval and early juvenile stages in a warm-water marine species, the Florida pompano (Trachinotus carolinus), and a cold-water marine species, the winter flounder (Pseudopleuronectes americanus). To identify the qualitative optimal EFA requirements, we calculated the ratio of certain fatty acids (FA) in larval or early juvenile tissues to total FA present in the diet. This ratio indicates whether a specific FA from prey is selectively incorporated by larvae and juveniles. Overall, we found that young larvae from both cold- and warm-water species have greater demands for n-3 and n-6 highly unsaturated fatty acids (HUFA) than do larvae at weaning stages. However, the qualitative EFA requirements of the cold-water species at all early developmental stages were higher than those of the warm-water species. Enriched rotifer diets provided satisfactory amounts of omega 3 and omega 6 in Florida pompano, with small selective retention for docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (ARA), suggesting a potential minor diet deficiency in these EFA. There were higher deficiencies in the cold-water species fed enriched rotifers, as demonstrated by the higher selective retentions of all EFA (DHA, EPA, and ARA), with the exception of larvae fed with copepods. The physiological needs in EFA for juvenile development seemed to be better met for both species when they were fed micro pellets. From the beginning of settlement and in young juveniles, qualitative values of 12% DHA, 10% EPA, 5% ARA, and 40% PUFA of total FA seem to be required for winter flounder juvenile development. In Florida pompano, these requirements could be met until larger juvenile stages, with 15% DHA, 3% EPA, 2% ARA, 2% DPA, and total PUFA below 30% of total FA. This review was done to aid future research aiming to develop nutritionally balanced microdiets or live-prey enrichment diets to satisfy the physiological requirements of captive tropical and cold-water marine fish species.

Evaluation of Maize Growth Following Early Season Foliar P Supply of Various Fertilizer Formulations and in Relation to Nutritional Status

The efficiency of phosphorus (P) use in agriculture needs to be improved, with farmers being increasingly forced by law to reduce P soil fertilization. Thus, P foliar application might become more important in agriculture. The effect of foliar P fertilization has not been widely studied in maize, despite it being a crop with high P demand during juvenile development. Our aim was to investigate the effect of P foliar application during juvenile development on maize crop growth and yield. We conducted outdoor pot experiments to investigate the effect on P uptake, translocation, and dry matter following three applications of foliar fertilizer of various P formulations and with additional P soil fertilization between the 4th and 6th leaf stage during two growing seasons. To determine direct and possible long-term effects, plants were harvested at various developmental stages. P foliar application resulted in a significant increase in P concentration in all plant parts ten days after the last application, regardless of P form, nutritional status, or year. P concentration remained high only in those parts of the plant that were present during foliar application. Biomass effects were sporadically visible until flowering, but not at maturity. We conclude that foliar P fertilization during juvenile development does not increase yield but might nevertheless be a useful remedy for short-term P deficits.

Eicosanoid Signaling in Insect Immunology: New Genes and Unresolved Issues

This paper is focused on eicosanoid signaling in insect immunology. We begin with eicosanoid biosynthesis through the actions of phospholipase A2, responsible for hydrolyzing the C18 polyunsaturated fatty acid, linoleic acid (18:2n-6), from cellular phospholipids, which is subsequently converted into arachidonic acid (AA; 20:4n-6) via elongases and desaturases. The synthesized AA is then oxygenated into one of three groups of eicosanoids, prostaglandins (PGs), epoxyeicosatrienoic acids (EETs) and lipoxygenase products. We mark the distinction between mammalian cyclooxygenases and insect peroxynectins, both of which convert AA into PGs. One PG, PGI2 (also called prostacyclin), is newly discovered in insects, as a negative regulator of immune reactions and a positive signal in juvenile development. Two new elements of insect PG biology are a PG dehydrogenase and a PG reductase, both of which enact necessary PG catabolism. EETs, which are produced from AA via cytochrome P450s, also act in immune signaling, acting as pro-inflammatory signals. Eicosanoids signal a wide range of cellular immune reactions to infections, invasions and wounding, including nodulation, cell spreading, hemocyte migration and releasing prophenoloxidase from oenocytoids, a class of lepidopteran hemocytes. We briefly review the relatively scant knowledge on insect PG receptors and note PGs also act in gut immunity and in humoral immunity. Detailed new information on PG actions in mosquito immunity against the malarial agent, Plasmodium berghei, has recently emerged and we treat this exciting new work. The new findings on eicosanoid actions in insect immunity have emerged from a very broad range of research at the genetic, cellular and organismal levels, all taking place at the international level.

Manganese exposure in juvenile C57BL/6 mice increases glial inflammatory responses in the substantia nigra following infection with H1N1 influenza virus

Infection with Influenza A virus can lead to the development of encephalitis and subsequent neurological deficits ranging from headaches to neurodegeneration. Post-encephalitic parkinsonism has been reported in surviving patients of H1N1 infections, but not all cases of encephalitic H1N1 infection present with these neurological symptoms, suggesting that interactions with an environmental neurotoxin could promote more severe neurological damage. The heavy metal, manganese (Mn), is a potential interacting factor with H1N1 because excessive exposure early in life can induce long-lasting effects on neurological function through inflammatory activation of glial cells. In the current study, we used a two-hit model of neurotoxin-pathogen exposure to examine whether exposure to Mn during juvenile development would induce a more severe neuropathological response following infection with H1N1 in adulthood. To test this hypothesis, C57BL/6 mice were exposed to MnCl2 in drinking water (50 mg/kg/day) for 30 days from days 21–51 postnatal, then infected intranasally with H1N1 three weeks later. Analyses of dopaminergic neurons, microglia and astrocytes in basal ganglia indicated that although there was no significant loss of dopaminergic neurons within the substantia nigra pars compacta, there was more pronounced activation of microglia and astrocytes in animals sequentially exposed to Mn and H1N1, as well as altered patterns of histone acetylation. Whole transcriptome Next Generation Sequencing (RNASeq) analysis was performed on the substantia nigra and revealed unique patterns of gene expression in the dual-exposed group, including genes involved in antioxidant activation, mitophagy and neurodegeneration. Taken together, these results suggest that exposure to elevated levels of Mn during juvenile development could sensitize glial cells to more severe neuro-immune responses to influenza infection later in life through persistent epigenetic changes.

Application of a novel banding technique and photographic recapture to describe plumage development and behaviour of juvenile Fairy Terns

The Australian Fairy Tern Sternula nereis nereis is a seabird that breeds along the coast and whose small populations are dispersed over vast stretches of the Australian seaboard and nearshore islands. In recent years, citizen science programs have been developed to bolster monitoring efforts to better understand breeding success and identify site threat profiles. The development of protocols that facilitate the collection of consistent measurements is important for long-term monitoring of this threatened (Vulnerable) species. This study describes plumage development and age-related behaviour in juvenile Australian Fairy Terns using direct observations and photographic recapture of individually marked birds. This information may be used as the basis for the development of a field ageing guide, enabling the collection of standardised information on colony demographics and juvenile development. A temporary colour-banding study was trialled by painting nail varnish onto 15 Australian Bird and Bat Banding Scheme (ABBBS) incoloy bands, avoiding the need to band nestlings with additional readable or PVC colour-bands. The varnish remained intact, albeit chipped, on four surviving birds that were resighted ≤80 days after banding, enabling the identification of individuals away from the colony site, without the need for recapture. The temporary marking of ABBBS bands using nail varnish offered an effective short-term solution for identifying individual juvenile Fairy Terns in the field and for describing plumage changes over a period of c. 3 months.