Causes of decoupling between larval supply and settlement and consequences for understanding recruitment and population connectivity

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Experimental Marine Biology and Ecology 392 (2010): 9-21, doi:10.1016/j.jembe.2010.04.008.Marine broadcast spawners have two-phase life cycles, with pelagic larvae and benthic adults. Larval supply and settlement link these two phases and are crucial for the persistence of marine populations. Mainly due to the complexity in sampling larval supply accurately, many researchers use settlement as a proxy for larval supply. Larval supply is a constraining variable for settlement because, without larval supply, there is no settlement. Larval supply and settlement may not be well correlated, however, and settlement may not consistently estimate larval supply. This paper explores the argument that larval supply (i.e., larval abundance near settlement sites) may not relate linearly to settlement. We review the relationship between larval supply and settlement, from estimates and biases in larval supply sampling, to non-behavioral and behavioral components, including small-scale hydrodynamics, competency, gregarious behavior, intensification of settlement, lunar periodicity, predation and cannibalism. Physical and structural processes coupled with behavior, such as small-scale hydrodynamics and intensification of settlement, sometimes result in under- or overestimation of larval supply, where it is predicted from a linear relationship with settlement. Although settlement is a function of larval supply, spatial and temporal processes interact with larval behavior to distort the relationship between larval supply and settlement, and when these distortions act consistently in time and space, they cause biased estimates of larval supply from settlement data. Most of the examples discussed here suggest that behavior is the main source of the decoupling between larval supply and settlement because larval behavior affects the vertical distribution of larvae, the response of larvae to hydrodynamics, intensification of settlement, gregariousness, predation and cannibalism. Thus, larval behavior seems to limit broad generalizations on the regulation of settlement by larval supply. Knowledge of the relationship is further hindered by the lack of a well founded theoretical relationship between the two variables. The larval supply- settlement transition may have strong general consequences for population connectivity, since larval supply is a result of larval transport, and settlement constrains recruitment. Thus, measuring larval supply and settlement effectively allows more accurate quantification and understanding of larval transport, recruitment and population connectivity.JP would like to thank WHOI Ocean Life Institute for partial funding. FP’s contribution is based upon research supported by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation

Preliminary Evidence of “Other-Race Effect”-Like Behavior Induced by Cathodal-tDCS over the Right Occipital Cortex, in the Absence of Overall Effects on Face/Object Processing

Neuromodulation techniques such as tDCS have provided important insight into the neurophysiological mechanisms that mediate cognition. Albeit anodal tDCS (a-tDCS) often enhances cognitive skills, the role of cathodal tDCS (c-tDCS) in visual cognition is largely unexplored and inconclusive. Here, in a single-blind, sham-controlled study, we investigated the offline effects of 1.5 mA c-tDCS over the right occipital cortex of 86 participants on four tasks assessing perception and memory of both faces and objects. Results demonstrated that c-tDCS does not overall affect performance on the four tasks. However, post-hoc exploratory analysis on participants' race (Caucasian vs. non-Caucasians), showed a “face-specific” performance decrease (≈10%) in non-Caucasian participants only. This preliminary evidence suggests that c-tDCS can induce “other-race effect (ORE)-like” behavior in non-Caucasian participants that did not show any ORE before stimulation (and in case of sham stimulation). Our results add relevant information about the breadth of cognitive processes and visual stimuli that can be modulated by c-tDCS, about the design of effective neuromodulation protocols, and have important implications for the potential neurophysiological bases of ORE

Functional significance of the taper of vertebrate cone photoreceptors

© The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of General Physiology 139 (2012): 159-187, doi:10.1085/jgp.201110692.Vertebrate photoreceptors are commonly distinguished based on the shape of their outer segments: those of cones taper, whereas the ones from rods do not. The functional advantages of cone taper, a common occurrence in vertebrate retinas, remain elusive. In this study, we investigate this topic using theoretical analyses aimed at revealing structure–function relationships in photoreceptors. Geometrical optics combined with spectrophotometric and morphological data are used to support the analyses and to test predictions. Three functions are considered for correlations between taper and functionality. The first function proposes that outer segment taper serves to compensate for self-screening of the visual pigment contained within. The second function links outer segment taper to compensation for a signal-to-noise ratio decline along the longitudinal dimension. Both functions are supported by the data: real cones taper more than required for these compensatory roles. The third function relates outer segment taper to the optical properties of the inner compartment whereby the primary determinant is the inner segment’s ability to concentrate light via its ellipsoid. In support of this idea, the rod/cone ratios of primarily diurnal animals are predicted based on a principle of equal light flux gathering between photoreceptors. In addition, ellipsoid concentration factor, a measure of ellipsoid ability to concentrate light onto the outer segment, correlates positively with outer segment taper expressed as a ratio of characteristic lengths, where critical taper is the yardstick. Depending on a light-funneling property and the presence of focusing organelles such as oil droplets, cone outer segments can be reduced in size to various degrees. We conclude that outer segment taper is but one component of a miniaturization process that reduces metabolic costs while improving signal detection. Compromise solutions in the various retinas and retinal regions occur between ellipsoid size and acuity, on the one hand, and faster response time and reduced light sensitivity, on the other.This work was funded by the Natural Sciences and Engineering Research Council of Canada Discovery Grant 238886 and a Grass-Marine Biological Laboratory Sabbatical Fellowship in Neurosciences to I. Novales Flamarique.2012-07-1

Culture of estuarine benthic and nectonic first trophic level feeders

The paper deals with some base trophic factors in relation to two herbivores, namely oysters and mullets, which derive their energy directly from the first trophic level of an estuarine ecosystem. The analysis of the gut contents of both organisms has shown that they feed mostly on micro-organisms, especially planktonic and benthic diatoms, and a significant percentage of detritus materials, including inorganic particles, is always present. Their dietary components are very much related to seasonal abundance of food production of the estuary. Current yields of oysters and mullets are far too low and food source is not a limiting factor for their production on large scale. Tidal flows, particularly in relation to salinity, have profound effect on culture grounds. Mortality is largely due to predation

April 2018 critical care case of the month

No abstract available. Article truncated after 150 words. History of Present Illness: A 70-year-old man was admitted for shortness of breath (SOB) secondary to a “COPD exacerbation/ILD”. A pulmonary consult was placed for possible interstitial lung disease (ILD). A thoracic CT scan for pulmonary embolism showed no embolism and no obvious ILD. He was treated for a COPD exacerbation with the usual therapy of antibiotics, steroids, nebulized bronchodilators and oxygen. He started to improve. A few days later as he was preparing for discharge, the patient suddenly decompensated becoming more SOB (once more proving that this a dangerous time for patients in hospital). There were reports that this began after he choked and perhaps aspirated on some food and drink. His blood pressure remained stable, but he became tachycardic to 130 beats/min, hypoxic on 100% non-rebreathing mask with saturations of 92%. Obvious clinical acute respiratory failure was present. The patient was started on non-invasive ventilation but continued

The hands of a healer

No abstract available. Article truncated after 150 words. The article in this month’s SWJPCC - "Physical Examination in the Intensive Care Unit. Opinions of Physicians at Three Teaching Hospitals" (1), is a fascinating insight to medical practice and how it has changed with the advent of new technology. The study at three large teaching facilities addressed the questions of how often a physical exam was performed in the ICU, what the perceived utility of the physical exam was, who examines patients most, and an interesting question pertaining to what exactly constitutes a physical exam. Participants were given theoretical scenarios and answered questions pertaining to the role of a physical exam. Even though the format was a questionnaire and not direct observation, the results support what I see in clinical practice. The results show that the physical exam, at least in the ICU, is not deemed a critical tool in our armamentarium and that reliance on technology has supplanted ..

Critical care review: the high price of sugar

The intensive control of blood glucose had been proposed to be important in increasing survival in the intensive care unit (ICU) despite only one positive randomized trial. The concept was supported by guidelines released by several regulatory organizations including the Joint Commission of Healthcare Organizations and the Institute of Healthcare Improvement. However, the large, randomized, multi-center NICE-SUGAR trial published in 2009 showed tight control of glucose in the ICU is actually hazardous with a 14% increase in mortality. The historical basis and data used to support intense control of glucose in the ICU are reviewed and illustrate the harm that can result when guidelines are based on weak evidence