Academic literature on the topic 'Migratory routes'

Migration can be costly with consequences that can influence population trajectories. These costs and consequences are especially heightened during over-water travels, which can be high-risk events for birds. We created spatial models to evaluate potential migratory responses of “oceanic”, island-hopping grey-faced buzzards that encounter variation in landscape parameters and weather as they move through and out of the Philippine archipelago. We constrained the modeled routes to enter the island chain at Basco and to use one of four potential exit points in the south of the country, either Balabac, Bongao, Balut Island, or Cape San Agustin. We used all possible combinations of our three external parameters (stopover sites, water crossings and wind direction) to model alternative migratory routes for each of the four exit points (n = 20 migratory routes). Modeled grey-faced buzzard routes were between 1,582 and 2,970 km. Routes overlapped over eastern and central Luzon, along a leading line created by the Sierra Madre Mountains. Routes also overlapped and suggested unavoidable over-water crossings between Mindoro and Palawan, Negros and Zamboanga del Norte, and Leyte and Surigao. Our models suggest that the optimal migratory strategy for these birds is to find the shortest route to an exit point with the greatest possible access to stopover habitats and fewest open-water crossings under wind resistance. Understanding how each of these external factors affected the geography and characteristics of the migratory routes helps us to understand the context for different migratory strategies of birds that face dangerous open-water crossings on migration.

Abstract Satellite-tracking technology has allowed scientists to make a quantum leap in the field of migration ecology. Nowadays, the basic description of migratory routes of many species of birds has been reported. However, the investigation of bird migration at individual level (i.e. repeatability in migratory routes and timing) still remains seldom explored. Here, we investigated repeated migratory trips of a trans-Saharan endangered migratory raptor, the Egyptian Vulture Neophron percnopterus, tracked by GPS satellite telemetry. We compared between- and within-individual variation in migratory routes and timing in order to assess the degree of repeatability (or conversely, the flexibility) in migration. To this end, we analysed a dataset of 48 trips (23 springs and 25 autumns) recorded for six adult birds during 2007-2013. Our results showed consistent migration timing at the individual level, both in spring and autumn. Interestingly, there was a high degree of flexibility in the routes followed by the same individual in different years, probably due to variations in meteorological conditions. Contrary to expectations of a faster migration in spring than in autumn owing to a time-minimization strategy for breeding, birds spent less time in autumn migration (13 ± 2 days, range = 9–18 d) than in spring migration (19 ± 3 days, range = 13–26 d), which can be explained by differences in environmental conditions en route. Egyptian vultures showed a consistent clockwise loop migration through western Africa, following more easterly routes in autumn than in spring. Finally, our results provide supporting evidence of low phenotypic plasticity in timing of migration (i.e. strong endogenous control of migration) and high flexibility in routes.

Knowledge about migratory connectivity, the degree to which individuals from the same breeding site migrate to the same wintering site, is essential to understand processes affecting populations of migrants throughout the annual cycle. Here, we study the migration system of a long-distance migratory bird, the Montagu's harrier Circus pygargus , by tracking individuals from different breeding populations throughout northern Europe. We identified three main migration routes towards wintering areas in sub-Saharan Africa. Wintering areas and migration routes of different breeding populations overlapped, a pattern best described by ‘weak (diffuse) connectivity’. Migratory performance, i.e. timing, duration, distance and speed of migration, was surprisingly similar for the three routes despite differences in habitat characteristics. This study provides, to our knowledge, a first comprehensive overview of the migration system of a Palaearctic-African long-distance migrant. We emphasize the importance of spatial scale (e.g. distances between breeding populations) in defining patterns of connectivity and suggest that knowledge about fundamental aspects determining distribution patterns, such as the among-individual variation in mean migration directions, is required to ultimately understand migratory connectivity. Furthermore, we stress that for conservation purposes it is pivotal to consider wintering areas as well as migration routes and in particular stopover sites.

Tha-kha Floating Market is a famous tourist attraction in Tha Kha sub-district, Amphawa district, Samut Songkram Province, Thailand. There are Thai paddle-boats for tourists to get close to nature and local people lifestyle along the canals. The objectives of this research were (1) to study species diversity, feeding behavior and status of birds in the research area. (2) to analyze abundance and similarity of birds in the research area. The data was carried out by field survey of species of birds and their behaviors sighted directly and from their calls by using line transect method then classify species, feeding behavior and status of birds, analyze their abundance and similarity in three routes. Three boat touring routes were surveyed; route 1 (Tha Kha floating market—homestay), route 2 (Tha Kha floating market—Thai traditional sugar making kiln), and route 3 (Thai traditional sugar making kiln—resort). The survey was conducted in the morning from 7 a.m. to 10 a.m. and in the afternoon from 3 p.m. to 6 p.m. One survey was made each month from April 2017–March 2018. The result of this research found that there were 15 orders, 37 families and 74 species of birds. The highest number of bird species in 3 routes was 49 species in December and 47 species in November accordingly because it was migratory season of migratory birds in the research area. According to bird feeding behavior, the maximum insectivorous bird species of 35 were found in 3 routes. According to status of birds, 52 resident birds, 9 migratory birds, 13 resident and migratory birds were found in 3 routes. According to bird abundance, 21 bird species were in level 5, 7 bird species in level 4, 20 bird species in level 3, 9 bird species in level 2 and 17 bird species in level 1. According to bird similarity index, the similarity index between route 1 and route 3 was 0.814. The community also organized eco-touring activities by using Thai paddle-boats. So the birds are as indicators of natural balance of local ecosystem.

The Arctic tern is an iconic seabird, famous for its annual migrations between the Arctic and the Antarctic. Its wide geographical range has impeded knowledge of potential population bottlenecks during its annual bi-hemispheric movements. Although Arctic terns breed in the Pacific, Atlantic, and Arctic coasts of North America, few tracking studies have been conducted on North American Arctic terns, and none in Canada, which represents a significant proportion of their circumpolar breeding range. Using light-level geolocators, we tracked 53 Arctic terns from 5 breeding colonies across a wide latitudinal and longitudinal range within North America. We compared the routes taken by birds in our study and migration timing to those previously tracked from Greenland, Iceland, The Netherlands, Sweden, Norway, Maine (USA), and S. Alaska (USA). Most Arctic terns tracked globally used one of 3 southbound migration routes: (1) Atlantic West Africa; (2) Atlantic Brazil; and (3) Pacific coastal, and one of 2 northbound migration routes: (1) Mid-ocean Atlantic and (2) Mid-ocean Pacific. Some other trans-equatorial seabirds also used these migration routes, suggesting that Arctic tern routes may be important for other species. The migration timing for southbound and northbound migrations was generally different between tracked tern colonies worldwide but generally fell within a 1-2 mo window. Our research suggests that conservation management of Arctic terns during their migration should dynamically adapt with the times of the year that terns use parts of their route. Future identification of common multi-species seabird flyways could aid the international negotiations required to conserve pelagic seabirds such as Arctic terns.

Migratory birds can be adversely affected by climate change as they encounter its geographically uneven impacts in various stages of their life cycle. While a wealth of research is devoted to the impacts of climate change on distribution range and phenology of migratory birds, the indirect effects of climate change on optimal migratory routes and flyways, through changes in air movements, are poorly understood. Here, we predict the influence of climate change on the migratory route of a long-distant migrant using an ensemble of correlative modelling approaches, and present and future atmospheric data obtained from a regional climate model. We show that changes in wind conditions by mid-century will result in a slight shift and reduction in the suitable areas for migration of the study species, the Oriental honey-buzzard, over a critical section of its autumn journey, followed by a complete loss of this section of the traditional route by late century. Our results highlight the need for investigating the consequences of climate change-induced disturbance in wind support for long-distance migratory birds, particularly species that depend on the wind to cross ecological barriers, and those that will be exposed to longer journeys due to future range shifts.

The Upland Goose (Chloephaga picta picta) is a migratory species of South America, which breeds from September to April in Patagonia (Argentina and Chile) and winters from May to September in the southern Pampas (Argentina). Despite some protection in both countries, this species is still persecuted and large numbers are killed by unregulated hunting. Therefore, precise knowledge of their migratory routes is vital to ensure protection of necessary resources and sites throughout the year. We deployed five miniaturised satellite transmitters on adult Upland Geese to gather data about breeding, wintering and stopover sites all along their migratory routes. We aimed to identify important areas in the wintering and breeding grounds through kernel density analyses, and to match these sites along the migration routes with protected areas. Tracked birds exhibited different migration routes and reached different breeding grounds. Two individuals travelled from their wintering grounds in Buenos Aires province to their presumed breeding areas in southern Patagonia. However, we also found different stopover sites from another bird in northern Patagonia, from the ones postulated before, and evidence that some Upland Geese are not large-scale migrants. Our results highlight a considerable amount of plasticity in Upland Geese migratory behaviour. This study represents an essential first step towards identifying important stopover sites along the Upland Geese flyways and it also highlights the lack of protected habitats along most of their migration routes.

We studied the habitat selection of pronghorn (Antilocapra americana) during seasonal migration; an important period in an animal’s annual cycle associated with broad-scale movements. We further decompose our understanding of migration habitat itself as the product of both broad- and fine-scale behavioral decisions and take a multi-scale approach to assess pronghorn spring and fall migration across the transboundary Northern Sagebrush Steppe region. We used a hierarchical habitat selection framework to assess a suite of natural and anthropogenic features that have been shown to influence selection patterns of pronghorn at both broad (migratory neighborhood) and fine (migratory pathway) scales. We then combined single-scale predictions into a scale-integrated step selection function (ISSF) map to assess its effectiveness in predicting migration route habitat. During spring, pronghorn selected for native grasslands, areas of high forage productivity (NDVI), and avoided human activity (i.e., roads and oil and natural gas wells). During fall, pronghorn selected for native grasslands, larger streams and rivers, and avoided roads. We detected avoidance of paved roads, unpaved roads, and wells at broad spatial scales, but no response to these features at fine scales. In other words, migratory pronghorn responded more strongly to anthropogenic features when selecting a broad neighborhood through which to migrate than when selecting individual steps along their migratory pathway. Our results demonstrate that scales of migratory route selection are hierarchically nested within each other from broader (second-order) to finer scales (third-order). In addition, we found other variables during particular migratory periods (i.e., native grasslands in spring) were selected for across scales indicating their importance for pronghorn. The mapping of ungulate migration habitat is a topic of high conservation relevance. In some applications, corridors are mapped according to telemetry location data from a sample of animals, with the assumption that the sample adequately represents habitat for the entire population. Our use of multi-scale modelling to predict resource selection during migration shows promise and may offer another relevant alternative for use in future conservation planning and land management decisions where telemetry-based sampling is unavailable or incomplete.

AbstractKnowledge of migratory connectivity is critical to understanding the consequences of habitat loss and climate change on migratory species. We used light-level geolocators to determine breeding locations and migratory routes of wintering Golden-crowned Sparrows (Zonotrichia atricapilla) in two regions of California, USA. Eight out of 9 birds tagged at coastal-wintering sites in Marin County went to breeding sites along the Gulf Coast of Alaska, while 7 out of 8 inland-wintering birds in Placer County migrated to interior sites in the Yukon, Northwest Territories, and British Columbia, Canada. Our estimate of the strength of migratory connectivity was relatively high (rm = 0.66). Coastal-wintering birds followed a coastal migration route while inland-wintering birds migrated inland. Coastalwintering birds migrated significantly farther than inland birds (3,624 km versus 2,442 km). Coastal birds traveled at a greater rate during spring migration (179 km/d) than did inland birds (118 km/d), but there was no statistical difference in the rate of fall migration (167 km/d and 111 km/d, respectively). Dates of arrival and departure, and duration of spring and fall migration, did not differ between groups, nor did return rates. Rates of return also did not differ between tagged and control birds. The distinct migration routes and breeding areas suggests that there may be more structuring in the migratory geography of the Golden-crowned Sparrow than in a simple panmictic population.

Migratory birds, some small and light weight as matchboxes, engage in seasonal inter-continental journeys in order to take advantage of the long summer days and abundance of food at northern latitudes to breed and raise their young, and then escape the harsh winters by migrating to lower latitudes. This thesis deals with two important aspects of migration, the routes taken during migration and the birds’ behaviour at stopovers. The migratory routes are for many species unknown, whole or in part, and this is especially true for species that migrate nocturnally. At stopovers birds replenish fuel reserves that powers migratory flight, and studying how birds utilise stopovers is important in order to understand how migration is organised. In this thesis I have used modern tracking technology to study both continental wide movements of thrush nightingales (Luscinia luscinia) and common rosefinches (Carpodacus erythrinus) using small light-level geolocators, and smaller scale movements at a single stopover site of garden warblers (Sylvia borin) using miniature radio-transmitters. I have also studied the fuelling behaviour of garden warblers during autumn migration in the field and in the lab, and great reed warblers (Acrocephalus arundinaceus) at a stopover site on Crete during spring migration after the Sahara crossing. The thesis discusses the significance of several aspects of migration shown by the birds that would have been very difficult to detect without the aid of modern tracking technology, such as loop migration, prolonged stops during migration, multiple wintering sites, and nocturnal relocations at stopover sites. Studies carried out at stopover sites also show that garden warblers and great reed warblers can attain large fuel loads even at sites where they have no barrier to cross and this might be a result of good foraging conditions. The thesis also highlights the importance of combining different techniques when studying stopover behaviour to get reliable estimates on stopover durations and fuel deposition rates as well as the importance of choosing sites preferred by birds when planning stopover studies.<br><p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.</p>

En adoptant une approche qualitative et pluridisciplinaire, basée sur l’étude longitudinale des circulations de la population de Deir Mqaren - un village syrien situé entre Damas et la frontière libanaise - cette thèse interroge la dimension réticulaire des mobilités humaines. A travers les récits de vie des réfugiés de cette bourgade et l’analyse de leurs parcours migratoires vers la Jordanie et l’Allemagne, elle décrypte la mécanique des flux au départ de Syrie. Cette recherche invite ainsi le lecteur à déplacer son regard vers des réseaux de lieux et d’acteurs souvent considérés comme marginaux, mais formant pourtant l’ossature des routes de l’exil reliant la Syrie au reste du globe. En plaçant la focale sur les conditions du mouvement des individus, l’intention de cette étude est à la fois de mettre en exergue les imbrications entre les migrations économiques antérieures au conflit et la logique des mouvements actuels de réfugiés ; mais aussi de montrer de manière tangible l’évolution des mécanismes relationnels permettant aux exilés d’accéder à des ressources (informations, mobilité, logement, emploi) en dépit des contraintes structurelles auxquelles ils ne cessent d’être confrontés. Les représentations (carto)graphiques élaborées dans le cadre de cette thèse visent pour leur part à mieux rendre compte du caractère mobile, instable et particulièrement labile de ces dynamiques socio-spatiales<br>In adopting a qualitative and multidisciplinary approach, based on the longitudinal study of the Deir Mqaren’s inhabitants’ circulations – a Syrian village located between Damascus and the Lebanese border – this thesis questions the “reticular” dimension of human mobility. Through refugees’ narratives and the analysis of their migration journeys to Jordan and Germany, its aims to understand the mechanics of refugee flows from Syria. Thus, this research invites the reader to move his focus towards networks of places and actors often considered as being marginal, despite the fact that they form the “backbone” of the roads of exile liking Syria to the rest of the world. By placing the focal point on individuals’ conditions of movement, the intention of this study is to both highlight the continuum existing between pre-conflict economic migration and the logic of the current refugee movements; and show in a tangible way the evolution of the relational mechanisms allowing exiles to access resources (such as information, mobility, housing, employment) despite the structural constraints they are constantly facing on their way towards safe destinations. The graphic representations developed in the framework of this thesis aim to better reflect the mobile, unstable and particularly labile nature of these socio-spatial dynamics

Les migrations africaines en Amérique latine s'inscrivent dans un processus de reconfiguration du phénomène migratoire. Les parcours se déploient et se recomposent au gré non seulement de l'histoire des politiques migratoires, des crises et des opportunités économiques mais aussi en fonction des histoires de groupes et d'individus. La complexification des procédures de contrôle au Nord et la mondialisation des Suds engendrent un certain éclatement des destinations. Dès les années 1990, mais surtout depuis les années 2000, des migrants, en provenance surtout d'Afrique de l'Ouest, tissent les contours d'un dispositif migratoire transatlantique Sud-Sud.À Buenos Aires, les Africains s'inscrivent sur le territoire selon des modalités distinctes. Si la grande majorité développe une activité de commerce de rue sous l'impulsion notamment de la communauté mouride sénégalaise, d'autres essaient d'exploiter une demande d'africanité, ou encore de se frayer une voie dans le football et dans les affaires. De ces inscriptions multiples, naissent des liens cosmopolites avec les différents segments de population la société d'accueil. Ces interactions qui peuvent donner lieu à des processus de négociation, produisent des recompositions sociales et identitaires à caractère ethnique, religieux ou encore de genre<br>African migration in Latin America is part of a process of reconfiguration of global migration. Paths unfold and recompose by the way of not only the history of migration policies, crises and economic opportunities but also by the groups and individuals stories. The rising complexity of the control procedures in the North, joint to the South globalization, results in bursting of destinations. By the 1990s, but especially since the 2000s, especially migrants from West Africa, weave the contours of a transatlantic migration South-South device. In Buenos Aires, the Africans try to be part of the territory in different ways. While the vast majority develops a street trading activity, driven mainly by the Murid Senegalese Community, others try to exploit a desire of Africanness, or maybe to find their way in football and in business. From these multiple origins, cosmopolitan links with the various segments of the host society population are born. These interactions, which can lead to negotiation processes, produce social and identity changes in ethnic, religious or gender dimensions<br>Las migraciones africanas en América Latina hacen parte de un processo de reconfiguración global del fenómeno migratorio. Los recorridos se despliegan y se recomponenal ritmo, no solo de la historia de las politicas migratorias, las crisis y las oportunidades ecónomicas, sino también en función de las historias de grupos e individuos. Los procedimientos de control cada vez más complejos en los países del Norte y la globalización de los países del Sur generan cierta diversificación en los destinos. Desde la década de los 90, pero especialmente desde al año 2000, los immigrantes procedentes principalmente de Africa occidental,han tejido los contornos de un dispositivo transatlántico de migración Sur-Sur. En Buenos Aires, los Africanos se inscriben sobreel territorio según diversas modalidades. Si bien la gran mayoría desarrolla una actividad de comercia callejero, iniciada principalmentepor la comunidad mora senegalesa, otros tratan de explotar un deseo de africanidad, o aún, forjarse un camino en el fútbol y en los negocios. De estas inscripciones múltiples,nacen vinculos cosmopolitas con diversos segmentos de población de la sociedad de acogidad. Esta interraciones, que pueden dar lugar a procesos de negociación, producen recomposiciones sociales e identitarias de carácter étnico, religioso y hasta de género religioso

O estudo apresentado está inserido num projeto mais amplo, de nível nacional denominado de Trajetórias de Vida de Reclusas de Nacionalidade Estrangeira em Portugal1, cujo objetivo é explorar as trajetórias de vida destas mulheres reclusas de nacionalidade estrangeira detidas em dois estabelecimentos prisionais em Portugal. Este estudo tem por isso o objetivo de explorar e analisar as trajetórias destas mulheres reclusas, no que respeita aos seus percursos migratórios, envolvimento no crime, e perspetivações de futuro, construídos nas suas narrativas. Para seleção da amostra constituída por 41 mulheres, utilizou-se uma metodologia qualitativa partindo da análise de dados recolhidos no estudo Trajetórias de Vida de Reclusas de Nacionalidade Estrangeira em Portugal. A partir da análise dos dados, foi possível perceber as motivações destas mulheres no que respeita à decisão da migração, e envolvimento no crime. Sucintamente percebemos que estas mulheres procuram sobretudo uma melhoria das suas condições de vida. No entanto e, não encontrando a curto prazo propostas de trabalho ou alternativas, vêm-se forçadas a recorrer a atividades ilícitas, que lhes oferecem grandes propostas a curto prazo de obtenção de dinheiro. Assim, a realização deste estudo revelou-se pertinente para a compreensão das migrações femininas, e do modo como estas se entrecruzam com a reclusão de mulheres.<br>The present study is part of a wider project of national called Life Trajectories of prisoners of foreign nationality in Portugal21, whose goal is to explore the life trajectories of these women prisoners are foreign nationals detained in two prisons in Portugal. This study is therefore the purpose of exploring and analyzing the trajectories of these women prisoners, in respect to their migratory pathways, involvement in crime, and perspectivations future, built in their narratives. To select the sample of 41 women, we used a qualitative methodology based on an analysis of data collected in the study of life trajectories of prisoners of foreign nationality in Portugal. From the data analysis, it was possible to perceive the motivations of these women with regard to the decision of migration, and involvement in crime. Succinctly realize that these women look particularly an improvement in their living conditions. However, and not finding short-term work proposals or alternatives have been forced to resort to illegal activities, they offer great short term proposals to raise money. Thus, this study proved to be relevant for the understanding of female migration, and how these intersect with the seclusion of women.

A República Bolivariana da Venezuela, país que dispõe das maiores reservas de petróleo do mundo, que já teve os mais elevados índices de produção petrolífera da América Latina e que detém uma variedade de recursos naturais capaz de o tornar autossuficiente, acabou por se distanciar de um caminho focado no desenvolvimento e entrou numa fervilhante ebulição social, política e económica. Um cenário improvável de antever, tendo em conta a dimensão do seu impacto, mas que retrata apenas uma pequena fração de uma realidade retratada como degradante e desumana, desmentindo as afirmações do próprio governo venezuelano. A inabilidade das políticas empreendidas, sobretudo, após a morte do precursor da Revolução Bolivariana, Hugo Chávez Frias, pelo atual presidente da Venezuela, Nicolás Maduro Moros, e a sua administração, contribuiu para a emergência de uma crescente vaga migratória no subcontinente americano e provocou um desastre humanitário, que se considera ser exacerbado pela polarização política (intensificada pela afirmação de um novo interveniente político, Juan Gerardo Guaidó), pelas sanções económicas impostas, maioritariamente, pelos Estados Unidos e pela mais recente pandemia mundial. Desta forma, o principal objetivo que se impõe neste estudo é: compreender o alcance, a natureza e as repercussões da crise venezuelana, que, por diversas vezes, passa despercebida aos olhos do mundo e da atual agenda mediática internacional. Para tal, a análise documental de fontes oficiais e a realização de um estudo de caso sobre um grupo particular de emigrantes foram essenciais para perceber as adversidades por que passam os venezuelanos.<br>The Bolivarian Republic of Venezuela, a country with the largest oil reserves in the world, which has had the highest oil production rates in Latin America and has a variety of natural resources capable of making it self-sufficient, has distanced itself from a path focused on development and has entered in a social, political and economic boiling. An unlikely scenario to predict, given the scale of its impact, but one that portrays only a small fraction of a reality portrayed as degrading and inhuman, disproving the statements of the Venezuelan government itself. The inability of the policies undertaken, especially, after the death of the forerunner of the Bolivarian Revolution, Hugo Chávez Frias, by the current president of Venezuela, Nicolás Maduro Moros, and his administration, contributed to the emergence of a growing wave of migration in the American subcontinent and caused a humanitarian disaster, considered to be exacerbated by political polarization (intensified by the affirmation of a new political actor, Juan Gerardo Guaidó), economic sanctions imposed, mainly, by the United States and the most recent global pandemic. In this sense, the main objective that is imposed in this study is: to understand the dimension, nature, and repercussions of the Venezuelan crisis, which, on several occasions, goes unnoticed in the eyes of the world and the current international media agenda. To achieve this purpose, the documentary analysis from official sources and the realization of a case study on a particular group of emigrants were essential to understanding the adversities faced by Venezuelans.

Tese de mestrado. Biologia (Biologia Evolutiva e do Desenvolvimento). Universidade de Lisboa, Faculdade de Ciências, 2011<br>Primordial germ cells (PGCs) are the founders of the gametes. They are one of the first discernible embryonic cell types which are set aside very early in the developing embryo. As it happens in other organisms, in chicken embryos, PGCs migrate from their extraembryonic location to combine with the somatic component of the gonad. An ingression of PGCs from the hypoblast into the vascular system, around stage HH8-10, was previously addressed using SSEA-1 as a marker for PGCs. Nonetheless, the isolation of the chicken vasa homolog (cvh), which is known to play a role in chicken germline, and the production of an antibody against VASA protein, permitted its use as a reliable marker to analyze the migration process of PGCs in chicken embryos. In this work we compared the specificity of VASA antibody with the specificity of SSEA-1 antibody for PGCs at different developmental stages. We concluded that SSEA-1 is not a specific marker for PGCs. Therefore we decided to characterize the position of PGCs, in different developmental stages, using VASA antibody. We identified the presence of PGCs in one structure that was not related with their migration in chicken embryos, or even in other animal model: the amnion/chorion. Taking advantage of the easiness of chicken embryos manipulation, we preformed a functional study to understand if amnion/chorion is having a role on PGCs migration. Our experiments demonstrated that embryos cultured with a modified “cornish pasty” method have a normal development, regarding the body structures and also the extra and intraembryonic vascular system. However the development of somatopleure is affected, and there is no separation between chorion and amnion or development of the amnion/chorion fold. The absence of PGCs in the genital ridges at stage HH17 and their presence in the somatopleure, allowed us to conclude that the developing amnion/chorion is involved in the migration process of PGCs.<br>A formação de órgãos durante o desenvolvimento embrionário baseia-se na cooperação de diferentes tipos celulares. Algumas células são definidas a alguma distância do local onde o futuro órgão se formará. A migração celular é um fenómeno central em vários momentos do desenvolvimento embrionário permitindo que estas células se desloquem até à estrutura onde virão, mais tarde, a desempenhar o seu papel biológico correctamente. As células germinais primordiais (CGPs) são um dos primeiros tipos celulares a distinguirem-se no embrião. As CGPs constitutem as progenitoras dos gâmetas desempenhando, por isso, uma função fundamental nos organismos sexuados. Depois de especificadas as CGPs são mantidas longe da gónada, até ao momento em que os movimentos celulares embrionários estabilizam, o que permite que mantenham a sua identidade. Mais tarde, as células iniciam a sua migração em direcção às gónadas, onde encontrarão as células somáticas ali presentes que lhes servirão de suporte nutritivo, o que permitirá seu correcto desenvolvimento. Ao atingirem a gónada esta fica apta a produzir gâmetas femininos ou masculinos, processo que se completará na puberdade. Os gâmetas são responsáveis por uma parte da variabilidade dos organismos sexuados, sendo por isso células com um papel muito importante tanto ao nível biológico individual como ao nível evolutivo. No caso da ave, a migração das CGPs ocorre da parte anterior extraembrionária para uma parte posterior do embrião, as cristas genitais, local onde se formará a futura gónada. Inicialmente, no estádio X (Eyal-Giladi and Kochav), as CGPs encontram-se no epiblasto, mais precisamente no centro da zona pelúcida. As células são deslocadas até ao hipoblasto. Durante a formação da linha primitiva as CGPs são transferidas para uma região extraembrionária, anterior à linha primitiva em desenvolvimento, denominada crescente germinal. É na zona do crescente germinal que estas células se incorporam na rede vascular aí formada, durante os estádios HH8-10, migrando pelo sistema vascular do embrião, até atingirem as futuras gónadas entre os estádios HH15-19. No entanto alguns destes estudos foram realizados usando marcadores não específicos para esta linha celular, nomeadamente o stage specific embryonic antigen 1 (SSEA-1). Neste trabalho avaliámos a especificidade do marcador SSEA-1 nestas células. Usámos como marcador mais fidedigno o anticorpo contra VASA, proteína que sabemos estar envolvida na identificação destas células em diferentes grupos taxonómicos ao longo da evolução (incluíndo o grupo Gallus gallus). Ao longo nosso trabalho, o marcador SSEA-1 não se revelou específico desta linha celular, sobretudo em estádios mais precoces. Esta observação levou-nos à necessidade de caracterizar a posição destas células no embrião de galinha, em diferentes estruturas embrionárias ao longo de vários estádios de desenvolvimento, a fim de perceber melhor o seu processo de migração. Ao analisar imunohistoquimicamente embriões entre os estádios de desenvolvimento HH5-19, deparámos com a presença destas células, em estádios HH8-13, numa estrutura nunca antes referida no seu processo de migração: o âmnio/córion. Para compreender se o âmnio e o córion têm um papel na migração das CGPs, cultivámos embriões de galinha pelo método de cultura “cornish pasty”. Este método de cultura in vitro, permite o correcto desenvolvimento do embrião com excepção do desenvolvimento da somatopleura e da prega amniótica, que devido à ausência de pressão da cabeça sobre os tecidos adjacentes, não consegue elevar-se sobre o embrião. Desta forma, a somatopleura continua o seu desenvolvimento à volta da área extraembrionária. A análise imunohistoquímica destes embriões, permitiu concluir que as CGPs no estádio HH10 se encontram no local onde seriam encontradas num embrião com desenvolvimento in ovo (localizadas numa posição anterior à cabeça, e na qual, num embrião com desenvolvimento in ovo se elevaria a prega amniótica). No entanto em estádios intermédios (HH13) estas células encontram-se na somatopleura. Verificámos também que a presença destas células nesta estrutura se mantêm em estádios mais avançados (HH17), nos quais é de esperar a presença das CGPs nas futuras gónadas. A partir destas observações concluímos que estas células estão a usar esta estrutura numa parte inicial da sua migração. Ao longo deste trabalho deparámo-nos com lacunas na literatura à cerca do âmnio que, desta forma, encontrámos algumas lacunas na literatura relativamente aos mecanismos inerentes ao seu desenvolvimento. Assim, usando técnicas histológicas tradicionais aliadas a técnicas de live imaging, procedemos à análise do desenvolvimento desta estrutura que pensamos ter um papel importante na migração das CGPs. Concluímos dessa forma que esta estrutura extraembrionária parece ter um desenvolvimento dependente da formação da cabeça embrionária e do proamnio. O proamnion, estrutura diblástica anterior à cabeça, estará a servir de “clip”, possibilitanto que a cabeça “mergulhe” sobre os tecidos subjacentes à mesma, ajudando ao correcto desenvolvimento da prega amniótica mediana pre-axial sobre a cabeça. A integração dos dados obtidos neste trabalho, levou-nos a propor um novo mecanismo de migração para estas células com uma fase transitória de migração através do âmnio/córion. As CGPs, inicialmente presentes no epiblasto e mais tarde deslocadas para o hipoblasto, são depois incorporadas na mesoderme. A mesoderme, que ingressa pela linha primitiva, dará origem à espancnopleura e somatopleura. Estas duas estruturas estão envolvidas na formação do sistema vascular extraembrionário e do âmnio/córion, respectivamente. Assim o nosso modelo considera que as CGPs, presentes na mesoderme, durante a formação da somatopleura e da esplancnopleura, são incorporadas na somatopleura. O nosso modelo não exclui o facto de que algumas destas células poderão ficar na mesoderme que, em conjunto com a endoderme, formará a esplancnopleura e que por essa razão tenham sido identificadas nas ilhas sanguíneas, em estádios precoces do desenvolvimento (HH1O). O facto de as CGPs usarem o âmnio/córion como estrutura transitória na sua migração poderá estar relacionado com o facto de as CGPs, apesar de mais tarde usarem o sistema vascular para se deslocarem até à futura gónada, estarem a evitar os processos envolvidos na vasculogénese e angiogénese que estão a ocorrer ao nível das ilhas sanguíneas. Durante o processo de vasculogénese e angiogénese são recrutados inúmeros sinais químicos e parácrinos que poderiam conduzir a uma alteração da linhagem das CGPs. O âmnio e o córion foram uma das novidades evolutivas mais importantes no decurso da evolução, permitindo a independência de ambientes aquáticos para a reprodução. Permitiram a exploração de uma enorme variabilidade de nichos terrestres. No entanto, parece-nos que além da sua função como protector da dissecação em amniotas, esta estrutura poderá estar a ser usada em outros processos embrionários. Este trabalho veio assim redefinir o papel do âmnio/córion na migração das CGPs. Esta estrutura extra-embrionária, constitui um suporte com características que permitem a manutenção da estaminidade celular, como tem sido descrito recentemente. Este trabalho demonstra assim a necessidade de um estudo mais aprofundado deste anexo embrionário que poderá ter mais aplicações, na área das células estaminais, do que inicialmente se esperava, sendo o facto de as CGPs estarem a usá-lo no seu processo de migração um indicador revelador dessa capacidade de manutenção da estaminidade celular.

This chapter highlights the multiple ways in which Burgos's legacy extends into visual culture and El Barrio neighborhood in East Harlem. In the act of remembering Julia de Burgos, visual artists are less concerned with finding the “true” Julia; rather, they create sites of memory that are at once collective and individual. As Burgos emerged as an icon specific to New York Latino/a culture, remembering her became one of the memory circuits mapping the migratory routes of New York Latino/a cosmopolitan networks. The chapter then charts the course of Burgos's iconography, mapping the migratory trajectories and circulation of her influence from New York to Puerto Rico and the Dominican Republic and consequently offering insight into New York Latino/a cultural production.

During the nineteenth century, Britain maintained a complex network of garrisons to manage its global empire. While these bases helped the British project power and secure trade routes, they served more than just a strategic purpose. During their tours abroad, many British officers engaged in formal and informal scientific research. In this ambitious history of ornithology and empire, Red Coats and Wild Birds tracks British officers as they moved around the world, just as migratory birds traversed borders from season to season. The book examines the lives, writings, and collections of a number of ornithologist-officers, arguing that the transnational encounters between military men and birds simultaneously shaped military strategy, ideas about race and masculinity, and conceptions of the British Empire. Collecting specimens and tracking migratory bird patterns enabled these men to map the British Empire and the world and therefore to exert imagined control over it. Through its examination of the influence of bird watching on military science and soldiers' contributions to ornithology, Red Coats and Wild Birds remaps empire, nature, and scientific inquiry in the nineteenth-century world.

This chapter examines Burgos's migratory routes from Puerto Rico to Havana and New York by looking at her second and third poetry collections—Canción de la verdad sencilla (Song of the Simple Truth, 1939) and El mar y tú (The Sea and You, 1954)—as well as her little-studied letters to her sister. The poetry collections and letters reveal her conflicted relationship to Puerto Rico. Despite her patriotism, home and nation became limiting, restrictive, and repressive spaces. As such, Burgos attempted to create a home and a life for herself beyond the boundaries of the nation. The chapter then discusses and extends the term sexile, usually used to describe queer migration, to heterosexual women whose sexuality appears excessive in Caribbean morality, contributing to their departure from the island.

Abstract Satellite-linked platform terminal transmitters (PTTs) are important tools for conducting research of sea turtles in their marine habitats. Appropriate conservation actions can be identified using PTTs, mounted to the top of sea turtles’ shells, to collect information about migratory routes and habitat usage. However, there is concern that PTTs introduce hydrodynamic drag that may bias natural sea turtle behavior, making the migratory and habitat data inaccurate representations of the “untagged” population. PTTs also have limited attachment durations, hypothesized to be caused by hydrodynamic loading and shell expansion during growth. The aim of this research is to investigate the hydrodynamic drag induced by PTTs on juvenile hard-shelled sea turtles, with the broader goal of increasing deployment duration and minimizing behavioral effects. A computational fluid dynamics (CFD) model was created to simulate the hydrodynamics of juvenile sea turtles. The drag and lift coefficients for five PTTs, virtually attached to the sea turtle model, were calculated using numerical methods. A comparison table of PTT performance is presented. The results will be used to explore PTT form factor design trades-offs that reduce hydrodynamic loading, while still meeting operational requirements. This research could enable biologists to collect data that more accurately represents the untagged sea turtle population.

Background: The role of B cells in multiple sclerosis (MS) is increasingly recognized. B cells undergo compartmentalized redistribution in blood and cerebrospinal fluid (CSF) during active MS, whereby memory B cells accumulate in the CSF. While B-cell trafficking across the blood– brain barrier has been intensely investigated, cellular diapedesis through the blood–CSF barrier (BCSFB) is incompletely understood. Objectives: To investigate how B cells interact with the choroid plexus to transmigrate into the CSF, we isolated circulating B cells from healthy donors (HC) and MS patients, utilized an inverted cell culture filter system of human choroid plexus papilloma (HIBCPP) cells to determine transmigration rates of B-cell subsets, immunofluorescence, and electron microscopy to analyze migration routes, and qRT-PCR to determine cytokines/chemokines mediating B-cell diapedesis. We also screened the transcriptome of intrathecal B cells from MS patients. Results: We found that spontaneous transmigration of HC- and MS-derived B cells was scant yet increased significantly in response to B-cell specific chemokines CXCL-12/CXCL-13, was further boosted upon pre-activation and occurred via paracellular and transcellular pathways. Migrating cells exhibited upregulation of several genes involved in B-cell activation/migration and enhanced expression of chemokine receptors CXCR4/CXCR5 and were predominantly of isotype class switched memory phenotype. This antigen-experienced migratory subset displayed more pronounced chemotactic activities in MS than in HC and was retrieved in intrathecal B cells from patients with active MS. Trafficking of class-switched memory B cells was downscaled in a small cohort of natalizumab-exposed MS patients and the proportions of these phenotypes were reduced in peripheral blood yet were enriched intrathecally in patients who experienced recurrence of disease activity after withdrawal of natalizumab. Conclusion: Our findings highlight the relevance of the BCSFB as an important gate for the entry of potentially harmful activated B cells into the CSF.