Naïve individuals promote collective exploration in homing pigeons

Group-living animals that rely on stable foraging or migratory routes can develop behavioural traditions to pass route information down to inexperienced individuals. Striking a balance between exploitation of social information and exploration for better alternatives is essential to prevent the spread of maladaptive traditions. We investigated this balance during cumulative route development in the homing pigeon Columba livia. We quantified information transfer within pairs of birds in a transmission-chain experiment and determined how birds with different levels of experience contributed to the exploration–exploitation trade-off. Newly introduced naïve individuals were initially more likely to initiate exploration than experienced birds, but the pair soon settled into a pattern of alternating leadership with both birds contributing equally. Experimental pairs showed an oscillating pattern of exploration over generations that might facilitate the discovery of more efficient routes. Our results introduce a new perspective on the roles of leadership and information pooling in the context of collective learning.

Novel Perspectives on the Development of the Amygdala in Rodents

The amygdala is a hyperspecialized brain region composed of strongly inter- and intraconnected nuclei involved in emotional learning and behavior. The cellular heterogeneity of the amygdalar nuclei has complicated straightforward conclusions on their developmental origin, and even resulted in contradictory data. Recently, the concentric ring theory of the pallium and the radial histogenetic model of the pallial amygdala have cleared up several uncertainties that plagued previous models of amygdalar development. Here, we provide an extensive overview on the developmental origin of the nuclei of the amygdaloid complex. Starting from older gene expression data, transplantation and lineage tracing studies, we systematically summarize and reinterpret previous findings in light of the novel perspectives on amygdalar development. In addition, migratory routes that these cells take on their way to the amygdala are explored, and known transcription factors and guidance cues that seemingly drive these cells toward the amygdala are emphasized. We propose some future directions for research on amygdalar development and highlight that a better understanding of its development could prove critical for the treatment of several neurodevelopmental and neuropsychiatric disorders.

A Karyological Study of Tenualosa Ilisha (Hamilton, 1822) From the Confluence of Padma and Meghna River of Bangladesh

Tenualosa ilisha (Hamilton, 1822), commonly known as Hilsha shad is a valuable and highly acceptable species in terms of their high flavored properties. Hilsha shad has striking morpho-genetical adaptation to heterogeneous habitats across their migratory routes. Cytogenetic analysis demonstrates the changes in chromosomes. But none was focused on the cytogenetic analysis of T. ilisha in Bangladesh. T. ilisha was found to possess 2n = 42 number of chromosomes along with a karyotype formula: 1M + 31m + 8sm + 2st using giemsa staining technique. The results demonstrated ‘diffuse type of interphase nuclei, co-existence of continuous type and interstitial type of prophase chromosomes respectively. No heteromorphic sex chromosomes were determined cytologically. The presence of diverse types of chromosomes based on centromeric position, gradual decrease in total haploid chromosome complement, mean centromeric asymmetry, coefficient of variation of chromosome length and Stebbins’s classification highlighted its asymmetry in karyotype with advance nature. Therefore, the elemental karyological data will offer information for the proper identification, cytotaxonomical classification, expanding productivity and preservation of genetic resources ofT. ilisha. Bangladesh J. Zool. 49 (2): 243-255, 2021

Involvement of mechanical cues in the migration of Cajal-Retzius cells in the marginal zone during neocortical development

Emerging evidence points to coordinated action of chemical and mechanical cues during brain development. At early stages of neocortical development, angiogenic factors and chemokines such as CXCL12, ephrins, and semaphorins assume crucial roles in orchestrating neuronal migration and axon elongation of postmitotic neurons. Here we explore the intrinsic mechanical properties of the developing marginal zone of the pallium in the migratory pathways and brain distribution of the pioneer Cajal-Retzius cells. These pioneer neurons are generated in several proliferative regions in the developing brain (e.g., the cortical hem and the pallial subpallial boundary) and migrate tangentially in the preplate/marginal zone covering the upper portion of the neocortex. These cells play crucial roles in correct neocortical layer formation by secreting several molecules such as Reelin. Our results indicate that the motogenic properties of Cajal-Retzius cells and their perinatal distribution in the marginal zone are also modulated by both chemical and mechanical factors, by the specific mechanical properties of Cajal-Retzius cells, and by the differential stiffness of the migratory routes. Indeed, cells originating in the cortical hem display higher migratory capacities than those generated in the pallial subpallial boundary which may be involved in the differential distribution of these cells in the dorsal-lateral axis in the developing marginal zone.

Counterterrorism and Immigration in Hungary

The European migration crisis beginning in 2014 served as a turning point in Hungarian politics where immigration issues effectively altered the nation’s security environment. The migratory routes as a pathway for illegal border crossings positioned Hungary on the frontline as a transit country for migrants seeking asylum in Western Europe. A critical analysis of Orbán's rhetoric and Hungary’s behavior in the realm of immigration and counterterrorism (CT) policy during and after the immigration crisis is relevant in understanding the state’s security environment. Anti-immigrant sentiments reflected in the population and Prime Minister Viktor Orbán's rhetoric aims to tie refugee migration to terrorist acitvity. Migrants were targeted as a risk to the traditional European identity and survival of the state with a specific emphasis on Muslim migration from the Middle East and North Africa. This study seeks to understand Hungary’s regional and global security role and how CT activity is used by the government to legitimize government actions, particularly on immigration via securitization theory from the Copenhagen School. Hungary has heightened its role on the international stage through transnational CT cooperation and capitalized on anti-immigrant sentiments through speech acts to further exercise its influence in border control and the international fight against global terrorism. By examining a total of 36 speeches presented by Orbán from 2015 to 2020, the study is able to examine how immigration issues were securitized to develop pathways for extraordinary actions and authoritarian reforms performed by securitizing actors.

The Arid Coastal Wetlands of Northern Chile: Towards an Integrated Management of Highly Threatened Systems

The ecological value of coastal wetlands is globally recognized, particularly as biodiversity hotspots, but also as buffer areas because of their role in the fight against climate change in recent years. Most of Chile’s coastal wetlands are concentrated in the central and southern part of the country due to climate conditions. However, northern coastal wetlands go unnoticed despite being located in areas of high water deficit (desert areas) and their role in bird migratory routes along the north–south coastal cordon of South America. This study reviews the current environmental status of the arid coastal wetlands of northern Chile (Lluta, Camarones, Loa, La Chimba, Copiapó, Totoral, Carrizal Bajo) in terms of regulations, management, and future aims. The main natural and anthropogenic threats to these coastal wetlands are identified, as well as the main management tools applied for their protection, e.g., the Nature Sanctuary designation, which allows for the protection of both privately and publicly owned property; and the Urban Wetland, a recently created protection category.

Current status of Great Bustard Otis tarda in Turkey: population size, distribution, movements, and threats

Summary The Great Bustard Otis tarda is a globally threatened species with populations inhabiting the steppe zones of Turkey. In recent decades, its populations in Turkey have suffered severe declines in range and size. Although the remaining populations are in urgent need of protection, there has been no national-scale study on the species since 2009, and huge information gaps remain concerning its range, abundance, and movements in the country. Here, we combined data from five years of fieldwork together with all available sight and literature records to present up-to-date estimates of distribution and population size in Turkey, to better understand its movement patterns, to reveal its recent and historical population changes, and to assess its national extinction risk and threats. We find that the species’ breeding population has shrunk by 20–29% over the last five years, and there are only 559–780 breeding Great Bustards in Turkey distributed in two discrete subpopulations. Comparison with historical records shows that the species’ range has shrunk by at least 60% since the beginning of the 20th century. We suggest possible migratory routes within and through Turkey and that Turkey might have a higher regional importance for the species than previously thought. Illegal hunting, agricultural intensification, shift to irrigated crops, overgrazing, collision with powerlines, and disturbance are the most severe threats to the species in Turkey. Our national Red List assessment yields an Endangered categorisation. Further studies are needed to understand the metapopulation structure and movements of the species and to conserve its remaining populations in Turkey.

A Guide for Using Flight Simulators to Study the Sensory Basis of Long-Distance Migration in Insects

Studying the routes flown by long-distance migratory insects comes with the obvious challenge that the animal’s body size and weight is comparably low. This makes it difficult to attach relatively heavy transmitters to these insects in order to monitor their migratory routes (as has been done for instance in several species of migratory birds. However, the rather delicate anatomy of insects can be advantageous for testing their capacity to orient with respect to putative compass cues during indoor experiments under controlled conditions. Almost 20 years ago, Barrie Frost and Henrik Mouritsen developed a flight simulator which enabled them to monitor the heading directions of tethered migratory Monarch butterflies, both indoors and outdoors. The design described in the original paper has been used in many follow-up studies to describe the orientation capacities of mainly diurnal lepidopteran species. Here we present a modification of this flight simulator design that enables studies of nocturnal long-distance migration in moths while allowing controlled magnetic, visual and mechanosensory stimulation. This modified flight simulator has so far been successfully used to study the sensory basis of migration in two European and one Australian migratory noctuid species.