Effects of density and food limitation on size variation and mortality of larval Hexagenia rigida (Ephemeroptera: Ephemeridae)

1992 ◽  
Vol 70 (9) ◽  
pp. 1824-1832 ◽  
Author(s):  
Elizabeth C. Hanes ◽  
Jan J. H. Ciborowski
Keyword(s):  
Food Limitation ◽  
Larval Growth ◽  
Natural Populations ◽  
Size Variation ◽  
Food Level ◽  
Larval Size ◽  
Detroit River ◽  
Frequency Distributions ◽  
Exogenous Factors ◽  
Growth Differences

Natural populations of the burrowing mayfly belonging to the genus Hexagenia are characterized by unusually broad size-frequency distributions. Environmental features are often invoked to explain among-populations growth differences. We used a 4 × 4 factorial design to investigate differences in mean larval size and mortality of Hexagenia reared at different densities and food levels over four time intervals (30, 60, 90, and 120 d) in the laboratory. Larvae were hatched from eggs collected from imagoes at the Detroit River near Windsor, Ontario. Although neither density nor food limitation influenced larval growth at either 30 or 60 d growth, the number of days required for eggs to hatch did significantly influence larval growth at this time. At 30 d growth, larvae that hatched after 6 d incubation were significantly smaller than larvae that required an additional day to hatch (7 d). At both 30 and 60 d, larvae that hatched after 6 d incubation had lower mortality than larvae that hatched after 7 d. At 90 and 120 d growth, density and food significantly influenced larval size and mortality. Larvae reared at low density and with a high food level attained the largest size. Mortality increased under stressed conditions (high density and (or) low food level). Since endogenous features (day of hatch) can be important early in larval development (at 30 or 60 d), such features may contribute to the outcome of competitive events that occur later in development (at 90 or 120 d), when exogenous factors (density and food) become significant.

Effects of temperature and photoperiod on larval size and survivorship of a burrowing mayfly (Ephemeroptera, Ephemeridae)

1992 ◽  
Vol 70 (2) ◽  
pp. 256-263 ◽  
Author(s):  
Lynda D. Corkum ◽  
Elizabeth C. Hanes
Keyword(s):  
Size Variation ◽  
Larval Survival ◽  
Time Intervals ◽  
Larval Size ◽  
Detroit River ◽  
Naturally Occurring ◽  
Different Temperatures ◽  
Effects Of Temperature ◽  
D 12 ◽  
Hexagenia Limbata

There is great size variation in naturally occurring and laboratory-reared populations of larvae of Hexagenia species. We investigated differences in mean larval size and survivorship of Hexagenia limbata and Hexagenia rigida reared at different temperatures (12, 17, and 22 °C) and photoperiods (24 h L, 24 h D, 12 h L: 12 h D) over two time intervals (60 and 120 d) in the laboratory. Owing to space limitations, two sets of replicates (3 replicates per set) were conducted in sequence for the 60-d trial. Larvae were hatched from eggs collected from imagoes at the Detroit River near Windsor, Ontario, and stored at 8 °C. Of the factors examined, temperature alone influenced larval size after 60 d of growth. None of the factors had any significant effect on larval survival after 60 d. Larvae from the second 60-d replicate set (hatched from eggs incubated for 75 d longer than the first set) were larger and exhibited lower survivorship than larvae in the first set. This finding suggests that larval size may not be a good indicator of larval age, especially if eggs have been exposed to low temperatures for varying periods. Temperature and its interaction with photoperiod significantly affected both size and survivorship of larvae reared for 120 d. At 22 °C, larvae reared under the 12 h L: 12 h D regime were larger than those reared under either constant light or dark conditions; no discernible trend in photoperiod was evident at the lower temperatures. Larval survivorship was lowest for treatments exhibiting conflicting environmental cues (12 °C and 24 h L, and 22 °C and 24 h D).

scholarly journals Independent evolution towards larger body size in the distinctive Faroe Island mice

2021 ◽  
Author(s):  
Ricardo Wilches ◽  
William H Beluch ◽  
Ellen McConnell ◽  
Diethard Tautz ◽  
Yingguang Frank Chan
Keyword(s):  
Body Size ◽  
Meta Analysis ◽  
Small Body ◽  
Laboratory Mouse ◽  
Large Body ◽  
Natural Populations ◽  
Size Variation ◽  
Phenotypic Traits ◽  
Island Population ◽  
Multiple Loci

Abstract Most phenotypic traits in nature involve the collective action of many genes. Traits that evolve repeatedly are particularly useful for understanding how selection may act on changing trait values. In mice, large body size has evolved repeatedly on islands and under artificial selection in the laboratory. Identifying the loci and genes involved in this process may shed light on the evolution of complex, polygenic traits. Here, we have mapped the genetic basis of body size variation by making a genetic cross between mice from the Faroe Islands, which are among the largest and most distinctive natural populations of mice in the world, and a laboratory mouse strain selected for small body size, SM/J. Using this F2 intercross of 841 animals, we have identified 111 loci controlling various aspects of body size, weight and growth hormone levels. By comparing against other studies, including the use of a joint meta-analysis, we found that the loci involved in the evolution of large size in the Faroese mice were largely independent from those of a different island population or other laboratory strains. We hypothesize that colonization bottleneck, historical hybridization, or the redundancy between multiple loci have resulted in the Faroese mice achieving an outwardly similar phenotype through a distinct evolutionary path.

Growth of four species of juvenile fish associated with the Seagrass Zostera capricorni, in Botany Bay, NSW

1992 ◽  
Vol 43 (5) ◽  
pp. 1189 ◽  
Author(s):  
DG Worthington ◽  
DJ Ferrell ◽  
SE NcNeill ◽  
JD Bell
Keyword(s):  
Sea Water ◽  
New South ◽  
Juvenile Fish ◽  
Natural Populations ◽  
Length Frequency ◽  
Frequency Distributions ◽  
South Wales ◽  
Time Period ◽  
Flow Through ◽  
Sampling Programme

Populations of four species of juvenile fish- Rhabdosargus sarba, Acanthopagrus australis, Achoerodus viridis and Girella tricuspidata-were sampled from a seagrass bed in Botany Bay, New South Wales. Fish were collected eight times between 22 March 1990 and 22 February 1991, using a small seine-net. Growth rates were calculated from the progression of cohorts in length-frequency distributions. Cohorts of R. sarba, A. australis and A. viridis grew most slowly during winter (0.02, 0.04 and 0.21 mm day-1, respectively); growth then increased, peaking just prior to the loss of the cohort from the habitat (0.3 1, 0.24 and 0.39 mm day-1). Populations of R. sarba, A. australis and A. viridis were comprised of one or two cohorts that remained in the habitat for at least 3-4 months. Conversely, up to seven cohorts of G. tricuspidata were found between October and February, and most cohorts did not remain in the habitat for more than 2 months. As a result, there were only two confident estimates of growth for G. tricuspidata: 0.23 mm day-1 between October and November, and 0.34 mm day-1 between January and February. Individuals of each species were also kept in a flow-through 4000-L tank of sea water. Growth of cohorts of fish kept in the tank was very similar to that found in natural populations during the same time period. The rates of recruitment and loss of cohorts from seagrass can be rapid and these factors must be considered in designing a sampling programme to assess growth by analysis of length-frequency distributions.

An individual-based analysis of the variability of eggs and their newly hatched larvae of Atlantic cod (Gadus morhua) on the Scotian Shelf

1995 ◽  
Vol 52 (5) ◽  
pp. 1083-1093 ◽  
Author(s):  
Thomas J. Miller ◽  
Tomasz Herra ◽  
William C. Leggett
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Seasonal Pattern ◽  
Size Variation ◽  
Seasonal Temperature ◽  
Scotian Shelf ◽  
Larval Size ◽  
Newly Hatched Larvae ◽  
Shelf Region ◽  
Egg Diameter

We assessed the seasonal pattern of size variation in cod eggs on the Scotian Shelf region of the Northwest Atlantic during the period March 1991–May 1993. Cod eggs were present from October to May during the surveys. Spawning was not strongly bimodal. There was a dominant autumn peak, in contrast to the historically dominant spring spawning. Egg diameter varied seasonally. Seasonal temperature patterns explained 52% of the variation in egg diameter. By incubating the eggs on-board ship, we also assessed the seasonality of the standard length (SL) of larvae that hatched from these eggs. Larval SL also varied seasonally. Egg diameter and SL were significantly correlated, but the correlation was weak (r2 = 0.3). However, the strength of correlation was consistent with laboratory estimates based on individual data. The results suggest that previous estimates of the egg size – larval size correlations are inflated. Temperature exerted a significant effect on both egg diameter and larval size, and is hypothesized to be the agent responsible for the observed seasonal variation.

scholarly journals Sex‐dependent and sex‐independent regulatory systems of size variation in natural populations

2019 ◽  
Vol 15 (11) ◽  
Author(s):  
Hirokazu Okada ◽  
Ryohei Yagi ◽  
Vincent Gardeux ◽  
Bart Deplancke ◽  
Ernst Hafen
Keyword(s):  
Natural Populations ◽  
Size Variation ◽  
Regulatory Systems

Dry weight and resource allocation patterns among individuals in populations of Plantago major and P. rugelii

1982 ◽  
Vol 60 (11) ◽  
pp. 2424-2439 ◽  
Author(s):  
W. R. Hawthorn ◽  
P. B. Cavers
Keyword(s):  
Frequency Distribution ◽  
Reproductive Effort ◽  
Natural Populations ◽  
Dry Weight ◽  
Life History Trait ◽  
Plantago Major ◽  
Allocation Pattern ◽  
Plant Weight ◽  
Frequency Distributions ◽  
Allocation Patterns

The frequency distributions of log plant weight in 1st-year plants of Plantago major L. and P. rugelii Decne. were studied in greenhouse experiments, including an investigation of associated differences in allocation patterns to plant parts between individuals in various weight classes. The frequency distributions of log plant weight of both plantains were strongly negatively skewed (many large plants and few small ones) at the lowest sowing density, where little or no mortality occurred during the course of the study. At two higher sowing densities significant mortality was noted and the frequency distributions tended to "log normality" or to a significant platykurtosis. The presence of bromegrass (Bromus inermis Leyss.) reduced the weight of individual plantains and resulted in frequency distributions that were essentially "log normal." Growing the two plantains together did not alter the shapes of the frequency distributions achieved in monocultures with and without grass. A possible pattern of changes in the frequency distribution of log plant weight with the passage of time is briefly discussed. Significant differences were observed in the allocation patterns of individuals of P. major within a population to roots, caudices, leaves, supporting reproductive structures, and seeds. The allocation patterns were not normally distributed according to plant weight; thus the use of average values of allocation pattern for the population as a whole should be viewed with caution. The proportional allocation to seeds (reproductive effort) by individuals of P. major from increasingly larger weight classes generally increased at an exponential rate, and more rapidly than simultaneous decreases in root and caudex allocation. The greatest reproductive effort and the greatest number of seeds per plant of P. major were associated with the strongest negative skewness of frequency distribution of log plant weight. First-year plants of P. rugelii exhibited a different response. Very few flowered during the study. However, in a variety of treatments the allocation to root and caudex by individuals which differed in biomass by as much as two orders of magnitude was remarkably constant at about 23%. In contrast, the allocation to belowground structures was much more variable among individuals of P. major, ranging from 50% or more by the smallest individuals to less than 5% by the largest plants. This life-history trait could partly account for the greater survival over winter and longevity observed in natural populations of P. rugelii compared with those of P. major.

scholarly journals Embryonic and larval development is conditioned by water temperature and maternal origin of eggs in the sea urchin Arbacia dufresnii (Echinodermata: Echinoidea)

2021 ◽  
Vol 69 (Suppl.1) ◽  
pp. 452-463
Author(s):  
Jimena Pía-Fernández ◽  
Florencia Belén-Chaar ◽  
Lucía Epherra ◽  
Jorge-Marcelo González-Aravena ◽  
Tamara Rubilar
Keyword(s):  
Larval Development ◽  
Embryo Development ◽  
Linear Models ◽  
Sea Urchins ◽  
Seawater Temperature ◽  
Larval Growth ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Larval Size ◽  
Embryonic And Larval Development

Introduction: Embryonic and larval development in sea urchins is highly dependent on maternal nutritional status and on the environmental conditions of the seawater. Objective: To compare the development of Arbacia dufresnii in two different water temperatures and in progeny with varying maternal origins. Methods: We induced A. dufresnii females and males from Nuevo Gulf to spawn, collected the eggs of each female individually (progeny), separated them into two seawater temperatures (12 and 17 °C), and fertilized them. We recorded the percentage of fertilized eggs and embryos per developmental stage according to time, temperature and progeny. We measured larval growth by total length (TL) and midline body length (M) according to time post fecundation (DPF), temperature, and progeny. Results: Temperature did not affect fertilization, but embryo development was faster and more synchronized in the high temperature treatment. The generalized linear models indicate that embryo development depends on a quadruple interaction between the embryonic stage, time (h), seawater temperature and progeny. Larval growth was faster, producing larger larvae at the highest temperature. Larval growth depends on a triple interaction between time (DPF), seawater temperature and progeny. Conclusions: We found a temperature and progeny impact during embryonic and larval development and, in both cases, these factors generate a synergistic effect on developmental timing and larval size. This probably provides a survival advantage as a more rapid speed of development implies a decrease in the time spent in the water column, where the sea urchins are vulnerable to biotic and abiotic stressors.

scholarly journals Nano-CT characterization reveals coordinated growth of a rudimentary organ necessary for soldier development in the antPheidole hyatti

2021 ◽  
Author(s):  
Sophie Koch ◽  
Rui Tahara ◽  
Angelly Vasquez-Correa ◽  
Ehab Abouheif
Keyword(s):  
Imaginal Disc ◽  
Larval Growth ◽  
Three Dimensional ◽  
Imaginal Discs ◽  
Minor Worker ◽  
Differential Growth ◽  
Larval Size ◽  
Worker Caste ◽  
Regulatory Functions ◽  
Coordination Patterns

AbstractThe growth of imaginal discs in holometabolous insects is coordinated with larval growth to ensure the symmetrical and proportional development of the adult appendages. In ants, the differential growth of these discs generates distinct castes – the winged male and queen castes and the wingless worker caste. In the hyperdiverse ant genusPheidole, the worker caste is composed of two morphologically distinct subcastes: small minor workers and larger, big-headed soldiers. Although these worker subcastes are completely wingless, soldier larvae develop rudimentary forewing discs that are necessary for generating the disproportionate head-to-body scaling of the big-headed soldier subcaste. However, it remains unclear whether rudimentary forewing discs in soldier larvae are coordinated with other imaginal discs, and whether disc growth and coordination patterns vary between the minor worker and soldier subcastes. Here we show, using quantitative nano-CT three-dimensional analyses, that growth of the soldier rudimentary forewing discs is coordinated with the increase in volume of the leg and eye-antennal (head) discs as well as with larval size. We found that the growth rate of the rudimentary forewing discs differs from the leg discs but is similar to the growth of the head (eye-antennal) discs relative to larval size, suggesting that growth of each type of imaginal disc may be differentially regulated. In addition to their larger size, the soldier eye-antennal discs increase in width as they undergo morphogenesis to generate the characteristic shape of the large soldier head, suggesting that the rudimentary forewing discs may regulate their patterning in addition to their growth. Finally, we observe little growth of the leg and eye-antennal discs during the bipotential stage, while in minor worker development these discs grow at similar rates to one another in coordination with larval size to generate the smaller minor worker subcaste. Our results suggest that rudimentary organs with regulatory functions may participate in new patterns of inter-organ coordination and regulation to produce novel phenotypes and complex worker caste systems. We provide characterization of larval development and imaginal disc growth and morphogenesis with the aim of highlighting this as an emerging system for the study of rudimentary organs during development and evolution.

Genome size variation in natural populations of wild potato species from west Argentina

Botany ◽  
2020 ◽  
Author(s):  
Perla Carolina Kozub ◽  
Ricardo Masuelli ◽  
Carlos Federico Marfil
Keyword(s):  
Genome Size ◽  
Natural Populations ◽  
Size Variation ◽  
Solanum Species ◽  
Wild Potato ◽  
Genome Size Variation ◽  
Wild Potato Species ◽  
Ecological Adaptability ◽  
Potato Species ◽  
Bioclimatic Variables

Wild potato species (Solanum, section Petota) have great ecological adaptability and represent essential genetic resources for the improvement of the third most important food crop worldwide. From more than one-hundred species described in this section, the genome size has been established for 12. The aims of this work were to: contribute data on the C-values for Solanum species; assess the degree of interspecific and intraspecific genome size variation; investigate correlations between genome size and bioclimatic variables; and determine whether genome size data are helpful in taxa delineation. The DNA contents of 97 genotypes from 28 populations and two accessions of seven wild potato species, including diploids, triploids and tetraploids, were measured by flow cytometry. Statistical genome size differences within and among species were found. The natural interploidal hybrid Solanum x rechei had the highest intraspecific genome size variation. The tetraploid S. acaule presented the smallest monoploid genome size (0.72 pg), while the triploid cytotype of S. microdontum the largest one (0.82 pg). Correlations among bioclimatic and geographic variables and genome size were found in most species. The roles of hybridisation and polyploidisation events on genome size variability are discussed.

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