Photoluminescence in the bill of the Atlantic Puffin Fratercula arctica

We report the discovery of photoluminescence in the ornamental bill of the Atlantic Puffin Fratercula arctica. The excitation and emission properties of the ceres of one dead and three live individuals were similar.     

Using energy dispersive x-ray fluorescence microchemistry to infer migratory life history of Atlantic sturgeon

Atlantic sturgeon migrate between ocean and freshwater habitats to spawn, and juveniles spend several years in fresh/brackish water before returning to the ocean. Because strontium/calcium (Sr/Ca) ratios are diagnostic for freshwater and marine environments, we examined the utility of energy-dispersive x-ray fluorescence (EDXRF) to quantify Sr/Ca ratios of Atlantic sturgeon pectoral fin spines. Atlantic sturgeon spines from wild adults and experimental juveniles were analyzed along a linear transect from the primordium to the outermost point. To verify the technique hatchery juvenile Atlantic sturgeon were held in experimental tanks at <0.5, 13?C15, or 33?C35?? and sampled after 5?months. Sr/Ca ratios of experimental hatchery fish increased with salinity, and Sr/Ca ratios in wild adults varied predictably along the measurement transect. However, the ratio decreased in the outermost region of the spine in mature fish collected during a return to freshwater for spawning. Therefore EDXRF is a useful tool to track individual movements of Atlantic sturgeons and other diadromous fish.     

Cell migration in the rostral migratory stream

Adult neurogenesis in the olfactory bulb of rodents is provided by cells which migrate tangentially from their site of genesis into the forebrain subependymal layer (SEL). This migration involves 'chains' of neuroblasts sliding into a meshwork of astrocytic cells and processes (glial tubes). The analysis of this process in postnatal rodents and in adult rabbits reveals different types of relationships occurring both among the migrating cells and between these cells and the glial structures of the SEL.     

Atlantic leatherback migratory paths and temporary residence areas

Background

Sea turtles are long-distance migrants with considerable behavioural plasticity in terms of migratory patterns, habitat use and foraging sites within and among populations. However, for the most widely migrating turtle, the leatherback turtle Dermochelys coriacea, studies combining data from individuals of different populations are uncommon. Such studies are however critical to better understand intra- and inter-population variability and take it into account in the implementation of conservation strategies of this critically endangered species. Here, we investigated the movements and diving behaviour of 16 Atlantic leatherback turtles from three different nesting sites and one foraging site during their post-breeding migration to assess the potential determinants of intra- and inter-population variability in migratory patterns.

Methodology/Principal Findings

Using satellite-derived behavioural and oceanographic data, we show that turtles used Temporary Residence Areas (TRAs) distributed all around the Atlantic Ocean: 9 in the neritic domain and 13 in the oceanic domain. These TRAs did not share a common oceanographic determinant but on the contrary were associated with mesoscale surface oceanographic features of different types (i.e., altimetric features and/or surface chlorophyll a concentration). Conversely, turtles exhibited relatively similar horizontal and vertical behaviours when in TRAs (i.e., slow swimming velocity/sinuous path/shallow dives) suggesting foraging activity in these productive regions. Migratory paths and TRAs distribution showed interesting similarities with the trajectories of passive satellite-tracked drifters, suggesting that the general dispersion pattern of adults from the nesting sites may reflect the extent of passive dispersion initially experienced by hatchlings.

Conclusions/Significance

Intra- and inter-population behavioural variability may therefore be linked with initial hatchling drift scenarios and be highly influenced by environmental conditions. This high degree of behavioural plasticity in Atlantic leatherback turtles makes species-targeted conservation strategies challenging and stresses the need for a larger dataset (>100 individuals) for providing general recommendations in terms of conservation.     

A size-dependent migration strategy in Atlantic salmon smolts: Small smolts favour nocturnal migration

Migration theory states that migration behavioural strategies should be optimised to maximise fitness. Many studies have shown that in downstream migrating Atlantic salmon Salmo salar L. smolts, mortality from predation is high and negatively size dependent. The most common predators are birds and piscivorous fish that are mainly daylight feeders. Given the high mortality during this stage we should expect to observe smolts to follow predator avoidance strategies that may be affected by body size. We tested the hypothesis that small smolts have a higher tendency to exhibit predator avoidance strategies (i.e. nocturnal versus diurnal migration) than larger smolts. The number and size of out-migrating/downstream-migrating wild Atlantic salmon smolts was recorded as they passed through a glass-sided channel during April-May, 1996–1999. In all years, the mean size of nocturnal migrating smolts was significantly lower than the mean size of diurnal migrating smolts. Analysis of the size of smolts, during early and late stages of the migration period showed size-dependent nocturnal migration behaviour up to the end of April. After this, no such size dependent migration pattern was observed. However, small smolts (<100 mm) were absent during this period. We suggest that nocturnal migration is an adaptive behaviour that small Atlantic salmon smolts have to avoid predation by large daylight feeding visual piscivorous predators (e.g. pike Esox Lucius L. and fish eating birds).     

Rapid altitudinal migration of mountain plants in Taiwan and its implications for high altitude biodiversity

Mountain systems throughout the globe are characterized by high levels of species richness and species endemism. Biodiversity, however, is not distributed evenly with altitude, but often declines from mid to high altitudes. Conversely, endemic species may be over‐represented at high altitudes. Upward elevational range shifts of mountain species have been reported in response to ongoing changes in climate, yet the reports are dominated by studies on woody species and mountains at high latitudes. We investigated spatial and temporal changes in the mountain biodiversity in the subtropical island of Taiwan, based on historical survey and resurvey data during the period 1906–2006. We found that upper altitudinal limits of mountain plant distributions have risen by ca 3.6 m yr^?1 during the last century, in parallel with rising temperatures in the region. Although species, genus, and family richness decline with altitude, ca 55% of species at the highest altitudes are endemic to the island. Given the steep decline in land area with increasing elevation, these high altitude areas are disproportionately important for plant biodiversity when richness and endemism are standardized by available land area. We argue that the distributional shift that we report, in combination with the altitudinal distribution of plant diversity, is likely to pose a major threat to high mountain species of this highly biodiverse island, a threat that is becoming increasingly evident for high mountain plants throughout the globe.     

Biocomplexity in a highly migratory pelagic marine fish, Atlantic herring

The existence of biologically differentiated populations has been credited with a major role in conferring sustainability and in buffering overall productivity of anadromous fish population complexes where evidence for spatial structure is uncontroversial. Here, we describe evidence of correlated genetic and life history (spawning season linked to spawning location) differentiation in an abundant and highly migratory pelagic fish, Atlantic herring, Clupea harengus, in the North Sea (NS) and adjacent areas. The existence of genetically and phenotypically diverse stocks in this region despite intense seasonal mixing strongly implicates natal homing in this species. Based on information from genetic markers and otolith morphology, we estimate the proportional contribution by NS, Skagerrak (SKG) and Kattegat and western Baltic (WBS) fish to mixed aggregations targeted by the NS fishery. We use these estimates to identify spatial and temporal differences in life history (migratory behaviour) and habitat use among genetically differentiated migratory populations that mix seasonally. Our study suggests the existence of more complex patterns of intraspecific diversity than was previously recognized. Sustainability may be compromised if such complex patterns are reduced through generalized management (e.g. area closures) that overlooks population differences in spatial use throughout the life cycle.     

Diel vertical migration of zooplankton in the Northeast Atlantic

Acoustic Doppler current profiler (ADCP) data collected duringAugust–September 1991 reveal the diel migration of zooplanktonin the northeast Atlantic (50–60     

Sacral neural crest cell migration to the gut is dependent upon the migratory environment and not cell-autonomous migratory properties

Avian neural crest cells from the vagal (somite level 1-7) and the sacral (somite level 28 and posterior) axial levels migrate into the gut and differentiate into the neurons and glial cells of the enteric nervous system. Neural crest cells that emigrate from the cervical and thoracic levels stop short of the dorsal mesentery and do not enter the gut. In this study we tested the hypothesis that neural crest cells derived from the sacral level have cell-autonomous migratory properties that allow them to reach and invade the gut mesenchyme. We heterotopically grafted neural crest cells from the sacral axial level to the thoracic level and vice versa and observed that the neural crest cells behaved according to their new position, rather than their site of origin. Our results show that the environment at the sacral level is sufficient to allow neural crest cells from other axial levels to enter the mesentery and gut mesenchyme. Our study further suggests that at least two environmental conditions at the sacral level enhance ventral migration. First, sacral neural crest cells take a ventral rather than a medial-to-lateral path through the somites and consequently arrive near the gut mesenchyme many hours earlier than their counterparts at the thoracic level. Our experimental evidence reveals only a narrow window of opportunity to invade the mesenchyme of the mesentery and the gut, so that earlier arrival assures the sacral neural crest of gaining access to the gut. Second, the gut endoderm is more dorsally situated at the sacral level than at the thoracic level. Thus, sacral neural crest cells take a more direct path to the gut than the thoracic neural crest, and also their target is closer to the site from which they initiate migration. In addition, there appears to be a barrier to migration at the thoracic level that prevents neural crest cells at that axial level from migrating ventral to the dorsal aorta and into the mesentery, which is the portal to the gut.     

Migratory connectivity and population-specific migration routes in a long-distance migratory bird

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.     

Summer temperature variation and implications for juvenile Atlantic salmon

Temperature is important to fish in determining their geographic distribution. For cool- and cold-water fish, thermal regimes are especially critical at the southern end of a species’ range. Although temperature is an easy variable to measure, biological interpretation is difficult. Thus, how to determine what temperatures are meaningful to fish in the field is a challenge. Herein, we used the Connecticut River as a model system and Atlantic salmon (Salmo salar) as a model species with which to assess the effects of summer temperatures on the density of age 0 parr. Specifically, we asked: (1) What are the spatial and temporal temperature patterns in the Connecticut River during summer? (2) What metrics might detect effects of high temperatures? and (3) How is temperature variability related to density of Atlantic salmon during their first summer? Although the most southern site was the warmest, some northern sites were also warm, and some southern sites were moderately cool. This suggests localized, within basin variation in temperature. Daily and hourly means showed extreme values not apparent in the seasonal means. We observed significant relationships between age 0 parr density and days at potentially stressful, warm temperatures (≥23°C). Based on these results, we propose that useful field reference points need to incorporate the synergistic effect of other stressors that fish encounter in the field as well as the complexity associated with cycling temperatures and thermal refuges. Understanding the effects of temperature may aid conservation efforts for Atlantic salmon in the Connecticut River and other North Atlantic systems.     

Global navigation in migratory birds: tracks, strategies, and interactions between mechanisms

The advancing development of tracking techniques has led to fascinating new insights into avian migration, documenting the immense diversity, complexity, and flexibility of this phenomenon. Tracking studies so far have confirmed many findings from ringing recoveries and cage studies, for example, the change from flying innate compass courses in the first migration to true navigation, as experienced migrants head toward familiar goals. First attempts to analyze the navigational mechanisms by tracking manipulated migrants indicate strong parallels to those of homing pigeons. Findings suggesting that the magnetic compass of migrants is regularly calibrated by the pattern of polarized light could not be replicated with a number of other birds, pointing out differences between species and possibly region and phases of migration. Tracking has become a valuable tool, complimenting traditional methods by documenting migration behavior in the wild; whether it can be used to further unveil the navigational mechanisms of migrants and the factor used remains an open question.     

Biology and survival of the immature Puffin Fratercula arctica

The biology and survival of Puffins were studied in northeast Scotland. Puffins usually bred first when aged four or five years but returned for several seasons prior to this. Young birds were probably prevented from returning earlier in the season because they moult their primaries in the spring and early summer. As they got older, they came to the colony earlier in the year, displayed and tried to get a burrow. Younger immatures may summer in specific areas away from the colonies.
Many immatures visited colonies other than where they were hatched. This was particularly marked in July of their third year. Up to 23% of Puffins of both sexes permanently emigrated and it is suggested that such behaviour is widespread among auks.
About 60 % of fledglings returned to the natal colonies and 30% of fledglings appeared to reach breeding age (although the true figure will be higher as this does not include birds which emigrated). Adult survival was c. 96% per annum. The population could theoretically increase by c. 7% but the observed rate of increase was c. 9% per annum.     

A possible heterotic threshold in the potato and its implications for breeding

Summary Complex hybrids containing genomes from three different Solanum tuberosum Groups were synthesized (3-way hybrids), utilizing 2n gametes in 4x–2x crosses. Ten such families were compared to nine analogous two-Group (2-way) hybrid families and nine (1-way) families representing conventional Gp. Tuberosum breeding materials. The three types of crosses, representing three descending levels of heterozygosity, were placed in four field trials.The 3-way hybrids were never significantly superior to the 2-way hybrids for vigor, yield, or tuber type. When yields were adjusted for maturity differences, the 3-way hybrids tended to be inferior to the 2-way hybrids for yield. This suggests that there may be a heterotic threshold in the cultivated potato, beyond which point more heterozygosity does not result in greater vigor or more yield.While the 2-way and 3-way hybrids did not significantly differ from each other, they both dramatically surpassed the conventional 1-way crosses for vigor and yield (42%). The evidence of a possible heterotic threshold indicates that more sophisticated methods such as cell fusion and bilateral sexual polyploidization may not be necessary to exploit the full potential of the hybrid approach in the potato. A simple and direct 2-way hybridization approach may be optimal, or at least would seem comparable with other hybrid approaches, and is a technology ready for immediate and widespread implementation.     

A model and its implications for denitrification in soil environment

We analyzed the mechanisms of a soil nitrogen (N) sub-model, which is a subroutine of the Crop-Environment Resources Synthesis (CERES)-maize; a model which was originally designed to simulate crop yield and has been calibrated and validated in Taiwan. Some experiments designed specifically for testing the N sub-model proved the capability of the model in reflecting field observations. With the mechanisms, we could write computer programs for calculating the relative sensitivities of major parameters in the model, and for simulating different treatments of organic matter. The purposes were to find how they affected N transformations, especially the processes of denitrification, which are considered to be responsible for N losses in upland soils and are an important environmental issue related to human disturbance of the N cycle. The results implied that soil water content and temperature were, respectively, the first and second dominant factors. They were much more sensitive than any other parameters, such as the decomposition rate coefficients, soil pH and bulk density. Decomposition of organic matter could slow down if organic matter with different carbon/nitrogen (C/N) ratios were treated in fractions. This treatment could also decrease the process of denitrification unless the organic matter was extremely large in quantity and has a high C/N ratio.     

Partial migration: growth varies between resident and migratory fish

Partial migration occurs in many taxa and ecosystems and may confer survival benefits. Here, we use otolith chemistry data to determine whether fish from a large estuarine system were resident or migratory, and then examine whether contingents display differences in modelled growth based on changes in width of otolith growth increments. Sixty-three per cent of fish were resident based on Ba : Ca of otoliths, with the remainder categorized as migratory, with both contingents distributed across most age/size classes and both sexes, suggesting population-level bet hedging. Migrant fish were in slightly better condition than resident fish based on Fulton''s K condition index. Migration type (resident versus migratory) was 56 times more likely to explain variation in growth than a model just incorporating year- and age-related growth trends. While average growth only varied slightly between resident and migratory fish, year-to-year variation was significant. Such dynamism in growth rates likely drives persistence of both life-history types. The complex relationships in growth between contingents suggest that management of species exhibiting partial migration is challenging, especially in a world subject to a changing climate.     

Diversity and geneflow in a migratory frugivorous fish: implications for Amazonian habitat connectivity

Colossoma macropomum is an ecologically and economically important fish distributed throughout the major tributaries of the Amazon River. C. macropomum require a suite of habitat types for different life stages making them potentially susceptible to the impacts of habitat fragmentation and alteration. As a means of better understanding the potential impacts of development, baseline data on connectivity and patterns of gene flow in species from relatively undisturbed habitat will be of value to monitor potential ecosystem impacts of anthropogenic habitat alteration on native fish communities. We used 13 single sequence repeat markers to determine if fine-scale structuring could be detected at the landscape scale at the Pacaya Samiria National Reserve, Perú. We also applied a model testing approach to evaluate the strength of different migration models, including panmixia, stepping stone and isolation models. Bayesian clustering detected a single genetic grouping across 131 fish. However, a comparison of marginal likelihoods for alternative migration models across PSNR supported a stepping stone model, rather than panmixia (Probability ~1.0). These results demonstrate that even in highly migratory fish with limited genetic structure, the effects of anthropogenic aquatic habitat alterations can be explored using genetic data.     

O chromosome inversion polymorphism in Northern and Atlantic Europe and its implications in the American colonization by Drosophila subobscura

The Western Mediterranean populations of D. subobscura have a very similar chromosomal inversion polymorphism to the American colonizing populations, with the exception of the O₅ inversion. This inversion, which is found in appreciable frequencies in colonizing populations and is distributed according to a significant latitudinal cline, both in North and South America, has never been reported in that Palearctic region. Therefore, an analysis of the distribution of this inversion, along a latitudinal cline, has been carried out in Europe. The O Chromosome inversion polymorphism has been studied in seven populations: Gävle and Lilla Edet (Sweden), Gesten (Denmark), Ter-Apel (Holland) and Crézy, Aizenay and Taulé (France). The O₅ inversion was only detected in three populations and in low frequencies: Gävle (3.7%), Lilla Edet (1.8 %) and Taulé (1.2 %). However, none of these three populations has all the inversions found in the American populations. The clinal distribution of some O chromosomal arrangements has also been studied according to latitude and the temporal changes of this polymorphism.