Population size structure, growth, arm number and damage in the sea star Archaster angulatus Müller and Troschel, 1842 (Echinodermata: Asteroidea)

2017 ◽  
Vol 61 (2) ◽  
pp. 119-127 ◽  
Author(s):  
John K. Keesing
Keyword(s):  
Population Size ◽  
Size Structure ◽  
Sea Star ◽  
Population Size Structure

scholarly journals Ochre star mortality during the 2014 wasting disease epizootic: role of population size structure and temperature

2016 ◽  
Vol 371 (1689) ◽  
pp. 20150212 ◽  
Author(s):  
Morgan E. Eisenlord ◽  
Maya L. Groner ◽  
Reyn M. Yoshioka ◽  
Joel Elliott ◽  
Jeffrey Maynard ◽  
...  
Keyword(s):  
Population Size ◽  
Size Structure ◽  
Disease Risk ◽  
Puget Sound ◽  
Mortality Rates ◽  
Adult Mortality ◽  
Disease Spread ◽  
Sea Star ◽  
Wasting Disease ◽  
Population Size Structure

Over 20 species of asteroids were devastated by a sea star wasting disease (SSWD) epizootic, linked to a densovirus, from Mexico to Alaska in 2013 and 2014. For Pisaster ochraceus from the San Juan Islands, South Puget Sound and Washington outer coast, time-series monitoring showed rapid disease spread, high mortality rates in 2014, and continuing levels of wasting in the survivors in 2015. Peak prevalence of disease at 16 sites ranged to 100%, with an overall mean of 61%. Analysis of longitudinal data showed disease risk was correlated with both size and temperature and resulted in shifts in population size structure; adult populations fell to one quarter of pre-outbreak abundances. In laboratory experiments, time between development of disease signs and death was influenced by temperature in adults but not juveniles and adult mortality was 18% higher in the 19°C treatment compared to the lower temperature treatments. While larger ochre stars developed disease signs sooner than juveniles, diseased juveniles died more quickly than diseased adults. Unusual 2–3°C warm temperature anomalies were coincident with the summer 2014 mortalities. We suggest these warm waters could have increased the disease progression and mortality rates of SSWD in Washington State.

Population size structure and sex ratios in some woodlice (Crustacea: Oniscidae) from southern Africa

1994 ◽  
Vol 10 (2) ◽  
pp. 261-271 ◽  
Author(s):  
J. M. Dangerfield ◽  
S. R. Telford
Keyword(s):  
Population Size ◽  
Southern Africa ◽  
Life Histories ◽  
Mating Systems ◽  
Size Structure ◽  
Sex Ratios ◽  
Interspecific Variation ◽  
Sexual Competition ◽  
Population Size Structure ◽  
Adult Sex Ratio

ABSTRACTThe population size structure and adult sex ratio were recorded for four indigenous and one introduced species of terrestrial isopod from southern Africa. Interspecific variation was considerable with either discrete or continuous distributions indicative of the production of separate cohorts or continuous recruitment. Intraspecific variation was also considerable particularly in species such as Aphiloscia vilis which can be found in diverse habitats. Sex ratios were consistently female biased, a result consistent with observations made on temperate species. These observations, and a consideration of sexual dimorphism based on body mass, suggest that phenotypic plasticity may be an important tactic in the life histories of tropical woodlice and that in some populations the potential exists for strong sexual competition and complex mating systems.

Growth, reproduction, and population structure in four alpine lichens during 240 years of primary colonization

2004 ◽  
Vol 82 (9) ◽  
pp. 1356-1362 ◽  
Author(s):  
Geir Hestmark ◽  
Olav Skogesal ◽  
Øystein Skullerud
Keyword(s):  
Population Size ◽  
Life Histories ◽  
Size Structure ◽  
Growth Period ◽  
Maximum Size ◽  
Strongly Correlated ◽  
Interspecific Differences ◽  
Population Size Structure ◽  
The Relationship ◽  
Plant Life Histories

The increase in thallus diameter and apothecium production, and the population size structure of the saxicolous lichens Umbilicaria cylindrica (L.) Del., Umbilicaria hyperborea (Ach.) Hoffm., Umbilicaria proboscidea (L.) Schrad, and Umbilicaria torrefacta (Lightf.) Schrad, were measured in a chronosequence of 240 years in a glacier foreland in the alpine Jotunheimen National Park in Norway. All four species exhibited a pattern of fast growth in the early decades of their life history, followed by a rapid decrease in growth, slowly approaching a maximum body size. There were clear interspecific differences in initial estimated growth rate, growth period, and maximum size. In all species, apothecium production is strongly correlated with thallus size, but in U. hyperborea the relationship approximates an exponential function, while in the other species the trend is more linear. In U. proboscidea, the slowest to mature, a fairly high proportion of sterile individuals also occur in the higher size classes. There was no observed trade off between growth and reproduction. Quite the contrary: the species that grow faster also start to reproduce abundantly and early. The relatively slow growth and reproductive maturation of the species implies that a population of 40- to 50-year-old individual thalli is still a population consisting mainly of immigrants. The population size structure of all four species remains strongly skewed during the entire chronosequence, with a predominance of small thalli.Key words: plant life histories, lichen growth rates, size structure, Umbilicaria.

Efficacy of population size structure as a bioassessment tool in freshwaters

2013 ◽  
Vol 34 ◽  
pp. 571-579 ◽  
Author(s):  
Christina A. Murphy ◽  
Frederic Casals ◽  
Carolina Solà ◽  
Nuno Caiola ◽  
Adolf de Sostoa ◽  
...  
Keyword(s):  
Population Size ◽  
Size Structure ◽  
Population Size Structure
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