Mode of growth and life-history strategies of a Late Ordovician halysitid coral

1991 ◽  
Vol 65 (2) ◽  
pp. 191-199 ◽  
Author(s):  
Dong-Jin Lee ◽  
Robert J. Elias
Keyword(s):  
Life History ◽  
Substrate Surface ◽  
Colony Growth ◽  
High Energy ◽  
Growth Patterns ◽  
Life History Strategies ◽  
Large Area ◽  
Physical Strength ◽  
Passive Flow ◽  
Vertical Growth Rate

The upper surface of the corallum ofCatenipora rubrawas often at or just above the sediment-water interface during life. The vertical growth rate was barely sufficient to keep pace with background sedimentation and possible subsidence of the corallum. Therefore, the colonies were in constant danger of being covered by influxes of sediment, especially during storms. This was compensated by the ability of polyps to respond to sedimentation events and by certain aspects of colony growth. Rapid regeneration following partial mortality involved budding of uninjured polyps and rejuvenation of damaged individuals, in some cases accompanied by a type of axial increase not previously known in tabulate corals. Rapid lateral expansion was possible because small, “immature” polyps could bud and grow in a reptant manner.Interconnected ranks of the cateniform corallum served to dam shifting sediment at the periphery of the colony. Lacunae within the colony were reservoirs for material that breached peripheral ranks and for sediment that settled on the ranks and was rejected by polyps or removed by passive flow. Polyps comprising the colony were distributed over a large area of the substrate surface, thereby decreasing the probability of complete mortality during sedimentation events and increasing the probability that a sufficient number of individuals would survive to ensure optimum regeneration. The corallum, anchored in the substrate and with sediment filling the lacunae, provided a broad, stable base during high-energy events.It remains to be established how widespread these growth patterns and strategies were among other corals with cateniform colonies, a form that appeared in many unrelated stocks. Most previous workers emphasized physical strength when considering functional morphology, following a tacit assumption that the corallum rose high above the substrate and was therefore susceptible to breakage during high-energy events. An understanding of the origin of cateniform patterns and the phylogeny of these corals requires knowledge of their modes of growth and life-history strategies, which were genetically as well as environmentally controlled.

Comparing Early Life History Strategies of Pomatomus saltatrix: a Global Approach

1996 ◽  
Vol 47 (2) ◽  
pp. 365 ◽  
Author(s):  
F Juanes ◽  
JA Hare ◽  
AG Miskiewicz
Keyword(s):  
Life History ◽  
Early Life ◽  
Life History Traits ◽  
Early Life History ◽  
Growth Patterns ◽  
Life History Strategies ◽  
Eastern Coast ◽  
The South ◽  
Pomatomus Saltatrix ◽  
South Eastern

Pomatomus saltatrix (Pisces:Pomatomidae) is a highly migratory, continental-shelf species with a worldwide subtropical distribution including the eastern coast of North America, the Gulf of Mexico, Mediterranean Sea, Black Sea, north-western Africa, the eastern coast of South America, the south-eastern coast of South Africa, and the south-eastern and south-westem coasts of Australia. This paper summarizes available life history information from the different regions where P. saltatrix occurs, with a focus on the early life history. The basic physical oceanography of these regions is also reviewed to elucidate patterns in larval transport. Comparison of these populations suggests that there are commonalties: adults migrate to spawning grounds; eggs and larvae are typically advected along-shore to juvenile nursery habitats; juveniles recruit to inshore habitats at a similar size, and there they grow rapidly and are mainly piscivorous, feeding primarily on atherinids and engraulids. There are also a number of life history traits that are quite variable among populations: the number of annual reproductive peaks, the number of juvenile cohorts, adult growth patterns and reproductive parameters. Comparison of these life history patterns leads to several non-exclusive hypotheses as to the adaptive significance of variations in life history traits. The goal is to identify areas where more research is needed to assess the degree to which populations of a global species are adapted to their local environment.

scholarly journals Growth patterns and life-history strategies in Placodontia (Diapsida: Sauropterygia)

2015 ◽  
Vol 2 (7) ◽  
pp. 140440 ◽  
Author(s):  
Nicole Klein ◽  
James M. Neenan ◽  
Torsten M. Scheyer ◽  
Eva Maria Griebeler
Keyword(s):  
Life History ◽  
Bone Tissue ◽  
Developmental Plasticity ◽  
Growth Models ◽  
Age At Onset ◽  
Growth Curves ◽  
Growth Patterns ◽  
Tissue Type ◽  
Life History Strategies ◽  
Long Bone

Placodontia is a clade of durophagous, near shore marine reptiles from Triassic sediments of modern-day Europe, Middle East and China. Although much is known about their primary anatomy and palaeoecology, relatively little has been published regarding their life history, i.e. ageing, maturation and growth. Here, growth records derived from long bone histological data of placodont individuals are described and modelled to assess placodont growth and life-history strategies. Growth modelling methods are used to confirm traits documented in the growth record (age at onset of sexual maturity, age when asymptotic length was achieved, age at death, maximum longevity) and also to estimate undocumented traits. Based on these growth models, generalized estimates of these traits are established for each taxon. Overall differences in bone tissue types and resulting growth curves indicate different growth patterns and life-history strategies between different taxa of Placodontia. Psephoderma and Paraplacodus grew with lamellar-zonal bone tissue type and show growth patterns as seen in modern reptiles. Placodontia indet. aff. Cyamodus and some Placodontia indet. show a unique combination of fibrolamellar bone tissue regularly stratified by growth marks, a pattern absent in modern sauropsids. The bone tissue type of Placodontia indet. aff. Cyamodus and Placodontia indet. indicates a significantly increased basal metabolic rate when compared with modern reptiles. Double lines of arrested growth, non-annual rest lines in annuli, and subcycles that stratify zones suggest high dependence of placodont growth on endogenous and exogenous factors. Histological and modelled differences within taxa point to high individual developmental plasticity but sexual dimorphism in growth patterns and the presence of different taxa in the sample cannot be ruled out.

scholarly journals A tale of two species: climate-competition tradeoffs shape range limits according to tree life-history strategies

2021 ◽  
Author(s):  
Jonathan Schurman ◽  
Pavel Janda ◽  
Milos Rydval ◽  
Martin Mikolas ◽  
Miroslav Svoboda ◽  
...  
Keyword(s):  
Life History ◽  
Interspecific Competition ◽  
Ring Width ◽  
Empirical Support ◽  
Growth Patterns ◽  
Range Limits ◽  
Life History Strategies ◽  
Range Limit ◽  
Lower Range ◽  
Cold Tolerant

Adapting for competitiveness versus climatic stress tolerance constitutes a primary trade-off differentiating tree life-history strategies. This tradeoff likely influences where species’ range-limits occur, but such links are data-demanding to study and key mechanisms lack empirical support. Using an exceptionally rich dendroecological network, we assessed spatial variation in climate and competition effects on Picea abies and Fagus sylvatica throughout the Carpathian Ecoregion. Ring width synchrony aided in diagnosing how the prevalence of resource-limited (competition) and sink-limited (climate) growth changes with altitude and community composition. Contrasting growth patterns towards respective upper and lower range limits of Fagus and Picea reflected tradeoffs between competitive vs. cold-tolerant strategies. Fagus performance declined with altitudinal increases in climate sensitivity, but improved under interspecific competition. Picea growth increased towards the species’ lower range limit, but declined under interspecific competition. Warmer temperatures likely benefit competitively stronger species at mid elevations and thus imply range reductions for alpine conifers.

Seasonality and colony-size effects on the life-history characteristics of Rhytidoponera metallica in temperate south-eastern Australia

2003 ◽  
Vol 51 (6) ◽  
pp. 551 ◽  
Author(s):  
Melissa L. Thomas
Keyword(s):  
Life History ◽  
Social Insects ◽  
Growth Pattern ◽  
Colony Size ◽  
Colony Growth ◽  
Growth Patterns ◽  
Logistic Growth ◽  
Slow Development ◽  
Eastern Australia ◽  
Laboratory Colonies

In social insects, colony growth is assumed to follow a logistic growth curve, with small, newly founded colonies experiencing exponential growth (ergonomic stage) that slows down with increasing colony size and approaches an asymptote when the colony produces sexuals (reproductive stage). Environmental factors may also influence colony growth, particularly in temperate climates where colder temperatures in winter slow development. However, growth patterns are rarely studied in detail in social insects. In this study, I investigated colony size and seasonality effects on life-history parameters of the ponerine ant Rhytidoponera metallica. I followed the growth of 10 laboratory colonies monthly over two years in conjunction with monthly excavations of 5 field colonies. Colony composition was highly seasonal in both laboratory and field colonies, with pupae and larvae produced only during the warmer months. Males, however, were present in colonies throughout most of the year. An expected logistic growth pattern was found in the majority (4 of 6) of laboratory colonies that had positive growth, one colony followed a Gompertz growth pattern and another a power curve. Two laboratory colonies decreased in size and two colonies didn't change in size. The slowing of growth observed with increasing colony size in the majority of laboratory colonies was related to a decrease in per capita brood production with increasing colony size. Colony size also related to the presence of males: field colonies containing males were significantly larger than field colonies where males were absent. By using a combination of laboratory and field colonies, I was able to obtain information on seasonality of brood and male production, in addition to important demographic data on mortality and natality rates that is difficult to obtain in social insects using only field excavations.

scholarly journals Lifelong divergence of growth patterns in Arctic charr life history strategies: implications for sustainable fisheries in a changing climate

2021 ◽  
Author(s):  
Gabrielle Grenier ◽  
Ross F. Tallman
Keyword(s):  
Life History ◽  
Life Histories ◽  
Salvelinus Alpinus ◽  
Arctic Charr ◽  
Growth Increment ◽  
Linear Increase ◽  
Growth Patterns ◽  
Life History Strategies ◽  
Changing Climate ◽  
Summer Growth

Arctic charr (Salvelinus alpinus Linneaus, 1758) are phenotypically variable with multiple life history strategies including anadromous and freshwater resident individuals. The mechanism determining life history is believed to be set early in life. Anadromous individuals show greater seasonality in growth and feeding after the first seaward migration relative to resident conspecifics. We used otolith growth increment measurements to estimate lifelong growth patterns for 355 individuals with anadromous or resident life history from four populations within Cumberland Sound, Nunavut. Using a general and a generalized linear model, we discovered a linear increase (estimate = 0.006) in growth for both Arctic charr life histories between 1990 and 2016. Resident Arctic charr have lower annual growth (estimate = -0.176) and show a decrease in the annual proportion of summer growth as they age (estimate = -0.042) while their anadromous counterparts maintain a higher seasonality in their growth patterns with age. This suggests that growth is indeed important in life history trajectory for Arctic charr and that seasonal growth patterns differ among life histories. The results highlight the importance of improving our understanding of mechanisms influencing life history trajectory in Arctic charr to ensure sustainability of harvested Arctic charr populations in a changing climate.

P20 phosphor on polyimide as a large area high-resolution transmission screen for slow scan CCD systems

1995 ◽  
Vol 53 ◽  
pp. 20-21
Author(s):  
C. C. Ahn ◽  
S. Karnes ◽  
M. Lvovsky ◽  
C. M. Garland ◽  
H. A. Atwater ◽  
...  
Keyword(s):  
Mechanical Stability ◽  
High Energy ◽  
Practical Implementation ◽  
Line Pair ◽  
Modulation Transfer ◽  
Large Area ◽  
Ccd Imaging ◽  
Transmission Electron ◽  
The One ◽  
Beam Broadening

The bane of CCD imaging systems for transmission electron microscopy at intermediate and high voltages has been their relatively poor modulation transfer function (MTF), or line pair resolution. The problem originates primarily with the phosphor screen. On the one hand, screens should be thick so that as many incident electrons as possible are converted to photons, yielding a high detective quantum efficiency(DQE). The MTF diminishes as a function of scintillator thickness however, and to some extent as a function of fluorescence within the scintillator substrates. Fan has noted that the use of a thin layer of phosphor beneath a self supporting 2μ, thick Al substrate might provide the most appropriate compromise for high DQE and MTF in transmission electron microcscopes which operate at higher voltages. Monte Carlo simulations of high energy electron trajectories reveal that only little beam broadening occurs within this thickness of Al film. Consequently, the MTF is limited predominantly by broadening within the thin phosphor underlayer. There are difficulties however, in the practical implementation of this design, associated mostly with the mechanical stability of the Al support film.

scholarly journals Diffuse γ-ray emission toward the massive star-forming region, W40

2020 ◽  
Vol 639 ◽  
pp. A80
Author(s):  
Xiao-Na Sun ◽  
Rui-Zhi Yang ◽  
Yun-Feng Liang ◽  
Fang-Kun Peng ◽  
Hai-Ming Zhang ◽  
...  
Keyword(s):  
Cosmic Ray ◽  
High Energy ◽  
Young Star ◽  
Gas Content ◽  
Large Area ◽  
Stellar Cluster ◽  
Production Region ◽  
Star Forming ◽  
Photon Index ◽  
Young Star Clusters

We report the detection of high-energy γ-ray signal towards the young star-forming region, W40. Using 10-yr Pass 8 data from the Fermi Large Area Telescope (Fermi-LAT), we extracted an extended γ-ray excess region with a significance of ~18σ. The radiation has a spectrum with a photon index of 2.49 ± 0.01. The spatial correlation with the ionized gas content favors the hadronic origin of the γ-ray emission. The total cosmic-ray (CR) proton energy in the γ-ray production region is estimated to be the order of 1047 erg. However, this could be a small fraction of the total energy released in cosmic rays (CRs) by local accelerators, presumably by massive stars, over the lifetime of the system. If so, W40, together with earlier detections of γ-rays from Cygnus cocoon, Westerlund 1, Westerlund 2, NGC 3603, and 30 Dor C, supports the hypothesis that young star clusters are effective CR factories. The unique aspect of this result is that the γ-ray emission is detected, for the first time, from a stellar cluster itself, rather than from the surrounding “cocoons”.

scholarly journals The Growth of Semiconductor Thin Films Studied by RHEED

1990 ◽  
Vol 43 (5) ◽  
pp. 583
Author(s):  
GL Price
Keyword(s):  
Thin Films ◽  
Surface Science ◽  
High Vacuum ◽  
High Energy ◽  
Ultra High Vacuum ◽  
Large Area ◽  
Growth Modes ◽  
Semiconductor Thin Films ◽  
Wide Range ◽  
Recent Developments

Recent developments in the growth of semiconductor thin films are reviewed. The emphasis is on growth by molecular beam epitaxy (MBE). Results obtained by reflection high energy electron diffraction (RHEED) are employed to describe the different kinds of growth processes and the types of materials which can be constructed. MBE is routinely capable of heterostructure growth to atomic precision with a wide range of materials including III-V, IV, II-VI semiconductors, metals, ceramics such as high Tc materials and organics. As the growth proceeds in ultra high vacuum, MBE can take advantage of surface science techniques such as Auger, RHEED and SIMS. RHEED is the essential in-situ probe since the final crystal quality is strongly dependent on the surface reconstruction during growth. RHEED can also be used to calibrate the growth rate, monitor growth kinetics, and distinguish between various growth modes. A major new area is lattice mismatched growth where attempts are being made to construct heterostructures between materials of different lattice constants such as GaAs on Si. Also described are the new techniques of migration enhanced epitaxy and tilted superlattice growth. Finally some comments are given On the means of preparing large area, thin samples for analysis by other techniques from MBE grown films using capping, etching and liftoff.

Sign in / Sign up

Export Citation Format

Share Document