Statistical structure of lateral connections in the primary visual cortex

The statistical structure of the visual world offers many useful clues for understanding how biological visual systems may understand natural scenes. One particularly important early process in visual object recognition is that of grouping together edges which belong to the same contour. The layout of edges in natural scenes have strong statistical structure. One such statistical property is that edges tend to lie on a common circle, and this 'co-circularity' can predict human performance at contour grouping. We therefore tested the hypothesis that long-range excitatory lateral connections in the primary visual cortex, which are believed to be involved in contour grouping, display a similar co-circular structure.By analyzing data from tree shrews, where information on both lateral connectivity and the overall structure of the orientation map was available, we found a surprising diversity in the relevant statistical structure of the connections. In particular, the extent to which co-circularity was displayed varied significantly.Overall, these data suggest the intriguing possibility that V1 may contain both co-circular and anti-cocircular connections

Factors Affecting the Recruitment of Juvenile Caribbean Spiny Lobsters Dwelling in Macroalgae

In south Florida, Caribbean spiny lobsters (Panulirus argus) settle and spend their first few months in macroalgae or seagrass. After a few months, these \u27\u27algal-phase\u27\u27 juveniles emerge from vegetation and, as \u27\u27postalgal-phase\u27\u27 juveniles, seek refuge in crevices, often dwelling in groups. The importance of crevice shelters in determining the abundance of postalgal-phase juvenile spiny lobsters has been studied but we know little about the processes affecting lobster distribution and survival during their cryptic algal-dwelling phase. We found that postlarval supply varied independently of changes in the structure of macroalgal settlement habitat. For this reason, postlarval supply alone can not reliably predict local settlement density. Changes in the size of macroalgal patches in particular tend to increase the variability in settlement density among locations and times. Field and mesocosm experiments indicate that social interactions and individual movements are unlikely to alter the general distribution of algal-phase lobsters established at settlement. But if algal-phase lobsters are aggregated at scales \u3c1 \u3em(2) (e.g., due to patchy settlement), they experience higher mortality than non-aggregated lobsters, as revealed in field experiments where lobsters were tethered alone or in pairs and at varying inter-individual distances. Field manipulations of settlement density indicate that recapture (survival) of microwire tagged algal-phase juveniles is positively associated with features of the habitat that affect lobster density (e.g., site area, macroalgal patch size), but survival and growth of lobsters are unrelated to artificially manipulated settlement density. Collectively, these results imply that the population dynamics of juvenile P. argus dwelling in macroalgae are not typically regulated by density-dependent processes, although density-dependent predation may be locally important in patches when settlement is episodically high

Setting the foundation for renewal: restoring sponge communities aids the ecological recovery of Florida Bay

Coastal ecosystems are constantly buffeted by anthropogenic forces that degrade habitats and alter ecological processes and functions; in turn, this habitat degradation diminishes the ecosystem goods and services on which humans rely. Within the last few decades, the field of restoration ecology has burgeoned into a discipline that marries scientific rigor with functional restoration practice—an idea championed by Pete Peterson and his research. Here, we describe our efforts to restore the hard-bottom sponge communities of Florida Bay, FL (USA)—a once-diverse subtropical lagoon severely degraded by cyanobacteria blooms—and the scientific and practical lessons learned from those efforts. Sponge community restoration yielded insights into basic sponge biology and ecology (e.g., density-dependent growth rates) and hastened the recovery of ecological processes (e.g., rates of sedimentation, structuring of water column characteristics, soundscape productions). Because the results of our initial restoration efforts were promising, our collaboration among academic researchers, natural resource managers, and non-governmental organizations has begun scaling up restoration efforts to re-establish the sponge communities over large areas of degraded hard-bottom to “jump start” the ecological recovery of Florida Bay. Though our efforts show promise for ecological recovery, restoration will require a concerted effort by scientists, resource managers, and citizens to stem the anthropogenic drivers of ecological degradation of this unique South Florida ecosystem

Atmospheric Beacons of Life from Exoplanets Around G and K Stars

The current explosion in detection and characterization of thousands of extrasolar planets from the Kepler mission, the Hubble Space Telescope, and large ground-based telescopes opens a new era in searches for Earth-analog exoplanets with conditions suitable for sustaining life. As more Earth-sized exoplanets are detected in the near future, we will soon have an opportunity to identify habitable worlds. Which atmospheric biosignature gases from habitable planets can be detected with our current capabilities? The detection of the common biosignatures from nitrogen-oxygen rich terrestrial-type exoplanets including molecular oxygen (O2), ozone (O3), water vapor (H2O), carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) requires days of integration time with largest space telescopes, and thus are very challenging for current instruments. In this paper we propose to use the powerful emission from rotational-vibrational bands of nitric oxide, hydroxyl and molecular oxygen as signatures of nitrogen, oxygen, and water rich atmospheres of terrestrial type exoplanets highlighted by the magnetic activity from young G and K main-sequence stars. The signals from these fundamental chemical prerequisites of life we call atmospheric beacons of life create a unique opportunity to perform direct imaging observations of Earth-sized exoplanets with high signal-to-noise and low spectral resolution with the upcoming NASA missions.Comment: 9 pages, published online in Nature Scientific Reports, November 2, 201

Regional Characterisation of Hard-Bottom Nursery Habitat for Juvenile Caribbean Spiny Lobster (Panulirus argus) Using Rapid Assessment Techniques

Shallow, hard-bottom habitat constitutes approximately 30% of the coastal waters of south Florida, United States, yet it is a chronically understudied feature of the marine seascape in this region. In this study, we characterised the general biogeographic and structural features of shallow benthic hard-bottom communities in the Florida Keys, and related those to the abundance of juvenile Caribbean spiny lobster (Panulirus argus), the target of one of Florida\u27s most economically valuable fisheries. We used rapid assessment techniques to survey more than 100 hard-bottom sites in the Florida Keys to estimate the percentage bottom coverage of vegetation (seagrass and macroalgae) and the abundance of sponges, octocorals, hard corals, and other crevice-bearing structures, as well as the abundance of juvenile lobsters. Using a multivariate statistical approach, we evaluated the relationship between habitat and size-specific juvenile lobster abundance and quantitatively verified the existence of six generally accepted biogeographic subregions. Although the types of hard-bottom shelters used by juvenile lobsters varied somewhat among these subregions, in all regions, branching-candle sponges and octocorals were under-used by lobsters, whereas loggerhead sponges, coral heads, and solution holes were over-used (i.e., used more frequently than expected based on their availability). There was also an ontogenetic transition in the shelter preference of juvenile lobsters; small juveniles tended to occupy a variety of sponges, whereas large juveniles preferred hard structures such as coral heads and solution holes. This study yields the first quantitative biogeographic description of hard-bottom communities of the Florida Keys, and confirms the suspected relationship between the structural features of hard-bottom habitat and the value of these communities as nurseries for juvenile spiny lobster

Exploratory fishing for tunas and tuna tagging in the Marquesas, Tuamotu, Society, Pitcairn, and Gambier Islands

The Marquesas Islands are located in the Pacific Ocean at about 9 degrees south latitude and 140 degrees west longitude (Figure 1). It has been demonstrated by tagging (Anonymous, 1980b) that skipjack tuna, Katsuwonus pelamis, which occur in the northeastern Pacific Ocean have migrated to the Hawaiian Islands and Christmas Island in the central Pacific and also to the area between the Marshall and Mariana islands in the western Pacific. The Tuamotu, Society, Pitcairn, and Gambier islands, though the first two are not as close to the principal fishing areas of the eastern Pacific Ocean as are the Marquesas Islands, and the last two are small and isolated, are of interest for the same reasons that the Marquesas Islands are of interest, and thus skipjack should be tagged in those islands for the same reason that they should be tagged in the Marquesas Islands. The organizations which participated in the Marquesas Islands tagging and other scientific activities were the Inter-American Tropical Tuna Commission (IATTC), the South Pacific Commission (SPC), the Centre National pour l'Exploitation des Oceans (CNEXO), the Office de la Recherche Scientifique et Technique Outre-Mer (ORSTOM), the Service de la Peche de la Polynesie Francaise (SPPF), and the Service de l'Economie Rural (SER)

Is Seagrass an Important Nursery Habitat for the Caribbean Spiny Lobster, Panulirus argus, in Florida?

Caribbean spiny lobster (Panulirus argus) settle preferentially in macroalgal-covered hard-bottom habitat, but seagrass is more prevalent in Florida (United States) and the Caribbean, so even low settlement of lobsters within seagrass could contribute substantially to recruitment if post-settlement survival and growth were high. We tested the role of seagrass and hard-bottom habitats for P. argus recruitment in three ways. We first explored possible density-dependent regulation of early benthic juvenile lobster survival within cages deployed in seagrass and hard-bottom habitats. Second, we compared settlement and survival of P. argus in both habitats, by comparing the recovery of microwire-tagged early benthic juveniles from patches of seagrass and hard-bottom. Finally, we assessed the relative abundance of juvenile lobsters in each habitat by deploying artificial structures in seagrass sites and compared these data with data from similar deployments of artificial structures in hard-bottom habitat in other years. More early benthic juvenile lobsters were recovered from cages placed in hard-bottom than in seagrass, but mortality of the early benthic life stage was high in both habitats. In regional surveys, the mean number of lobsters recovered from artificial shelters deployed within seagrass was lower than in any year that we sampled hard-bottom, indicating that fewer lobsters reside naturally in seagrass, particularly large juveniles \u3e40 mm carapace length. The greater abundance (and likely survival) of juvenile P argus that we observed in hard-bottom habitat as opposed to seagrass, combined with previous studies demonstrating that postlarval P. argus are attracted to, settle in, and metamorphose more quickly in red macroalgae, confirm that macroalgae-dominated hard-bottom habitat appears to be the preferred and more optimal nursery for Caribbean spiny lobster

Sulfur dioxide and particles in quiescent volcanic plumes from Poás, Arenal, and Colima Volcanos, Costa Rica and Mexico

Measurements of SO2 emission rates and concentrations and of particle distribution, size, shape, and composition were made in quiescent volcanic plumes emitted into the troposphere from Poás and Arenal volcanos, Costa Rica, and Colima volcano, Mexico. SO2 emission rates were 700±180 metric tons per day (t/d) for Poás, 210±30 t/d for Arenal, and 320±50 t/d for Colima. The concentrations of SO2 calculated from the COSPEC/lidar data were 5–380 ppb. Concentrations of SO2measured directly by flame photometry were 10–250 ppb. Particles collected in the plumes with a quartz crystal microbalance impactor were mostly less than 3 μm in diameter and consisted of droplets of dilute sulfur-bearing solutions and minor amounts of larger silicate particles coated with a sulfur-bearing film or crust. Total particle concentrations were 4.7 μg/m3 for Poás and 18.8 μg/m3for Colima. Comparison of concentrations of SO2 in the plumes with gas samples collected at fumaroles on the ground suggests that the plumes are diluted by the atmosphere by factors of up to 105