Changing light levels induce photo-oxidative stress and alterations in shell density of Amphistegina lobifera (Foraminifera)

2016 ◽  
Vol 549 ◽  
pp. 69-78 ◽  
Author(s):  
M Prazeres ◽  
S Uthicke ◽  
JM Pandolfi
Keyword(s):  
Oxidative Stress ◽  
Light Levels ◽  
Changing Light

Interspecific variation in the response of growth, crown morphology, and survivorship to light of six tree species in the conifer belt of the Bhutan Himalayas

2004 ◽  
Vol 34 (5) ◽  
pp. 1093-1107 ◽  
Author(s):  
Georg Gratzer ◽  
Andras Darabant ◽  
Purna B Chhetri ◽  
Prem Bahadur Rai ◽  
Otto Eckmüllner
Keyword(s):  
Tree Species ◽  
Radial Growth ◽  
Interspecific Variation ◽  
Low Light ◽  
Continuous Growth ◽  
Light Levels ◽  
Shade Tolerant Species ◽  
Lower Light ◽  
Crown Morphology ◽  
Changing Light

The responses of radial and height growth, plant architecture, and the probability of mortality of saplings to varying light levels were quantified for six tree species in temperate conifer forests of the Bhutan Himalayas. Increases in growth with increasing light were comparable with those of high latitude tree species but lower than those of tropical tree species and temperate species in North America. The shade-tolerant species Tsuga dumosa (D. Don.) Eichler showed the strongest increase in radial growth at low light and reached asymptotic growth early. It had the deepest crowns in low light and a low decrease of leader growth with decreasing light. It represents a continuous growth type, which invests in height rather than lateral growth under low light conditions. Betula utilis D. Don. showed greater increases in radial growth and a higher mortality at low light than the more shade-tolerant Abies densa Griff., in keeping with the trade-off between survivorship and growth at low light. Picea spinulosa Griff, Larix griffithiana Carriére, and Pinus wallichiana A.B. Jackson showed small increases in growth at low light levels. The latter two species showed no capacity to adapt their morphology in response to changing light levels, which resulted in higher probabilities of mortality at lower light levels. Differences in the probability of mortality at different light levels were more pronounced than differences in the light-growth response, underlining the importance of survivorship at low light for successional dynamics.

scholarly journals Light-regulated collective contractility in a multicellular choanoflagellate

2019 ◽  
Author(s):  
Thibaut Brunet ◽  
Ben T. Larson ◽  
Tess A. Linden ◽  
Mark J. A. Vermeij ◽  
Kent McDonald ◽  
...  
Keyword(s):  
Animal Movement ◽  
Swimming Behavior ◽  
Undescribed Species ◽  
Caribbean Island ◽  
Sensory Inputs ◽  
Light Levels ◽  
Cgmp Pathway ◽  
The Caribbean ◽  
Tissue Deformations ◽  
Changing Light

AbstractCollective cell contractions that generate global tissue deformations are a signature feature of animal movement and morphogenesis. Nonetheless, the ancestry of collective contractility in animals remains mysterious. While surveying the Caribbean island of Curaçao for choanoflagellates, the closest living relatives of animals, we isolated a previously undescribed species (here namedChoanoeca flexasp. nov.), that forms multicellular cup-shaped colonies. The colonies rapidly invert their curvature in response to changing light levels, which they detect through a rhodopsin-cGMP pathway. Inversion requires actomyosin-mediated apical contractility and allows alternation between feeding and swimming behavior.C. flexathus rapidly converts sensory inputs directly into multicellular contractions. In this respect, it may inform reconstructions of hypothesized animal ancestors that existed before the evolution of specialized sensory and contractile cells.One Sentence SummaryA newly described choanoflagellate species forms cup-shaped colonies that reversibly invert their curvature in response to light.

scholarly journals Convergent Phenotypic Evolution of Rhodopsin for Dim-Light Sensing across Deep-Diving Vertebrates

2021 ◽  
Author(s):  
Yu Xia ◽  
Yimeng Cui ◽  
Aishan Wang ◽  
Fangnan Liu ◽  
Hai Chi ◽  
...  
Keyword(s):  
Release Rate ◽  
Light Level ◽  
Emperor Penguin ◽  
Light Sensing ◽  
Deep Diving ◽  
Light Levels ◽  
Critical Residue ◽  
Retinal Chromophore ◽  
Dim Light ◽  
Changing Light

Abstract Rhodopsin comprises an opsin attached to a retinal chromophore and is the only visual pigment conferring dim-light vision in vertebrates. On activation by photons, the retinal group becomes detached from the opsin, which is then inactive until it is recharged. Of all vertebrate species, those that dive face unique visual challenges, experiencing rapid decreases in light level and hunting in near darkness. Here, we combine sequence analyses with functional assays to show that the rhodopsin pigments of four divergent lineages of deep-diving vertebrates have undergone convergent increases in their retinal release rate. We compare gene sequences and detect parallel amino acids between penguins and diving mammals and perform mutagenesis to show that a single critical residue fully explains the observed increases in retinal release rate in both the emperor penguin and beaked whale. At the same time, we find that other shared sites have no significant effect on retinal release, implying that convergence does not always signify adaptive significance. We propose that accelerated retinal release confers rapid rhodopsin recharging, enabling the visual systems of diving species to adjust quickly to changing light levels as they descend through the water column. This contrasts with nocturnal species, where adaptation to darkness has been attributed to slower retinal release rates.

Phytoplankton community adaptation to changing light levels in the southern Beaufort Sea, Canadian Arctic

2009 ◽  
Vol 82 (3) ◽  
pp. 537-546 ◽  
Author(s):  
Atsushi Matsuoka ◽  
Pierre Larouche ◽  
Michel Poulin ◽  
Warwick Vincent ◽  
Hiroshi Hattori
Keyword(s):  
Phytoplankton Community ◽  
Canadian Arctic ◽  
Beaufort Sea ◽  
Community Adaptation ◽  
Light Levels ◽  
Changing Light

scholarly journals Interactive Effects of Elevated CO2 Concentration and Light on the Picophytoplankton Synechococcus

2021 ◽  
Vol 8 ◽  
Author(s):  
Nanou Bao ◽  
Kunshan Gao
Keyword(s):  
Growth Rate ◽  
Electron Transport ◽  
Specific Growth Rate ◽  
Specific Growth ◽  
North Atlantic Ocean ◽  
Light Condition ◽  
Interactive Effects ◽  
Global Changes ◽  
Light Levels ◽  
Changing Light

Synechococcus is a major contributor to the primary production in tropic and subtropical oceans worldwide. Responses of this picophytoplankton to changing light and CO2 levels is of general concern to understand its ecophysiology in the context of ocean global changes. We grew Synechococcus sp. (WH7803), originally isolated from subtropic North Atlantic Ocean, under different PAR levels for about 15 generations and examined its growth, photochemical performance and the response of these parameters to elevated CO2 (1,000 μatm). The specific growth rate increased from 6 μmol m–2 s–1 to reach a maximum (0.547 ± 0.026) at 25 μmol m–2 s–1, and then became inhibited at PAR levels over 50 μmol m–2 s–1, with light use efficiency (α) and photoinhibition coefficient (β) being 0.093 and 0.002, respectively. When the cells were grown at ambient and elevated CO2 concentration (400 vs. 1,000 μatm), the high-CO2 grown cells showed significantly enhanced rates of electron transport and quantum yield as well as significant increase in specific growth rate at the limiting and inhibiting PAR levels. While the electron transport rate significantly increased at the elevated CO2 concentration under all tested light levels, the specific growth did not exhibit significant changes under the optimal growth light condition. Our results indicate that Synechococcus WH7803 grew faster under the ocean acidification (OA) treatment induced by CO2 enrichment only under limiting and inhibiting light levels, indicating the interactive effects and implying that the picophytoplankton respond differentially at different depths while exposing changing light conditions.

Diel vertical migration in the Lake Superior pelagic community. I. Changes in vertical migration of coregonids in response to varying predation risk

2006 ◽  
Vol 63 (10) ◽  
pp. 2286-2295 ◽  
Author(s):  
Thomas R Hrabik ◽  
Olaf P Jensen ◽  
Steven J.D. Martell ◽  
Carl J Walters ◽  
James F Kitchell
Keyword(s):  
Predation Risk ◽  
Vertical Migration ◽  
Lake Superior ◽  
Light Levels ◽  
Biological Variables ◽  
Physico Chemical ◽  
Prey Resources ◽  
Diel Variability ◽  
The Vertical Distribution ◽  
Changing Light

The distribution of fishes is influenced by a host of physico-chemical and biological variables, including temperature and oxygen, prey abundance, feeding or assimilation rates, and predation risk. We used hydroacoustics and midwater trawls to measure the vertical distribution of pelagic fishes during a series of research cruises on Lake Superior's western arm in 2001 and 2004. Our objective was to assess vertical structuring in the fish assemblage over varying light levels. We observed variability in vertical structuring of both ciscoes (Coregonus spp.) and their primary predator, the siscowet (Salvelinus namaycush siscowet). Our results indicate that deepwater predators and prey migrate extensively over a diel cycle. This migration pattern is most consistent with changes in the distribution of prey resources for siscowet and diel variability in predation risk controlled by changing light levels for ciscoes. The magnitude of vertical migration in ciscoes increased with higher abundance of siscowets, supporting predation risk as a driver of cisco distribution. This study describes the extent of vertical migration in each group of fish, provides a statistical description of the pattern, and discusses the implications for trophic interactions in the Lake Superior food web.

Null By Morse: Historical Optical Communication to Smartphones

Leonardo ◽  
2013 ◽  
Vol 46 (4) ◽  
pp. 344-352
Author(s):  
Tom Schofield
Keyword(s):  
Optical Communication ◽  
Media Art ◽  
Signal Lamp ◽  
Light Levels ◽  
Camera Image ◽  
History Of ◽  
Slow Technology ◽  
Changing Light

Null By Morse is an installation artwork that incorporates a military signaling lamp and smartphones. A series of Morse messages is transmitted automatically by the signal lamp. The messages are drawn from the history of Morse and telegraphy. A custom app for iPhone and Android uses the phone's camera to identify the changing light levels of the lamp and the associated timings. The app then decodes the Morse and displays the message on the screen on top of the camera image. This paper discusses the artwork in relation to the following theoretical aspects: It contextualizes the position of smartphones in the history of optical communication. It proposes an approach to smartphones in media art that moves away from futurist perspectives whose fundamental approach is to seek to creatively exploit the latest features. Lastly, it discusses the interaction with the phone in the exhibition context in terms of slow technology.

Diel Distribution and Activity of American Eels (Anguilla rostrata) in a Cave-Spring

1986 ◽  
Vol 43 (8) ◽  
pp. 1595-1605 ◽  
Author(s):  
Gene S. Helfman
Keyword(s):  
Total Population ◽  
Activity Patterns ◽  
Food Concentration ◽  
Anguilla Rostrata ◽  
Considerable Variability ◽  
High Food ◽  
Light Levels ◽  
American Eels ◽  
Changing Light ◽  
Inhibitory Threshold

American eels (Anguilla rostrata) in a Florida cave-spring (total population [Formula: see text] 142 eels, density [Formula: see text] 0.03 eels/m2) showed distinctive day versus night differences in distribution and activity. Larger eels occurred deeper at all times. Eels were diurnally quiescent, nocturnally active, and changed over between behavior modes roughly at dusk and dawn, although considerable variability existed in timing of changeover. Changeover at dusk involved movement from deeper regions of low food to shallower regions of high food concentration, with smaller eels more likely to migrate. Changing light levels apparently determined onset and cessation of activity, with an inhibitory threshold of 10–100 lx influencing movement between deep and shallow regions. An endogenous rhythm and hunger may have also affected activity patterns.

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