Density-dependent growth in cockles (Cerastoderma edule): evidence from interannual comparisons

1993 ◽  
Vol 73 (2) ◽  
pp. 333-342 ◽  
Author(s):  
K. Thomas Jensen
Keyword(s):  
Growth Rates ◽  
Dry Weight ◽  
Growing Season ◽  
Intertidal Mudflat ◽  
Low Density ◽  
Cerastoderma Edule ◽  
Density Dependent ◽  
The Difference ◽  
Dependent Growth ◽  
Growth Differences

To examine density-dependent effects on growth in Cerastoderma edule (L.) (Bivalvia), growth rates of individual cockles established by chance at high and low densities on the same intertidal mudflat in two different years (1984 and 1989) were compared. Two-year-old cockles occurring at high densities (>2000 individuals m-2 in 1984) attained mean lengths from 16.1 to 18.8 mm on the lower shore at the end of their third growing season, while low-density cockles (<50 individuals m-2 in 1989) of the same age reached mean lengths in the range of26.5 to 30.3mm. In terms of individual weight the difference between cockles from the two periods was even more striking, as the flesh ash-free dry-weight of a cockle from 1984 constituted only 7% of that from a 1989 cockle. During both periods growth in cockles increased with the duration of tidal submersion, but the interannual growth differences exceeded by far the effect of differences in submersion time.

Do abiotic mechanisms determine interannual variability in length-at-age of juvenile Arcto-Norwegian cod?

2002 ◽  
Vol 59 (1) ◽  
pp. 57-65 ◽  
Author(s):  
Geir Ottersen ◽  
Kristin Helle ◽  
Bjarte Bogstad
Keyword(s):  
Growth Rates ◽  
Gadus Morhua ◽  
Barents Sea ◽  
Water Masses ◽  
Inverse Relation ◽  
Lower Growth ◽  
Density Dependent ◽  
The Barents Sea ◽  
The Mean ◽  
Dependent Growth

For the large Arcto-Norwegian stock of cod (Gadus morhua L.) in the Barents Sea, year-to-year variability in growth is well documented. Here three hypotheses for the observed inverse relation between abundance and the mean length-at-age of juveniles (ages 1–4) are suggested and evaluated. Based on comprehensive data, we conclude that year-to-year differences in length-at-age are mainly determined by density-independent mechanisms during the pelagic first half year of the fishes' life. Enhanced inflow from the southwest leads to an abundant cohort at the 0-group stage being distributed farther east into colder water masses, causing lower postsettlement growth rates. We can not reject density-dependent growth effects related to variability in food rations, but our data do not suggest this to be the main mechanism. Another hypothesis suggests that lower growth rates during periods of high abundance are a result of density-dependent mechanisms causing the geographic range of juveniles to extend eastwards into colder water masses. This is rejected mainly because year-to-year differences in mean length are established by age 2, which is too early for movements over large distances.

MORPHOLOGICAL DEVELOPMENT OF TWO ALFALFA CULTIVARS UNDER VARIOUS HARVESTING SCHEDULES

1974 ◽  
Vol 54 (1) ◽  
pp. 79-87 ◽  
Author(s):  
Y. SINGH ◽  
J. E. WINCH
Keyword(s):  
Growth Rates ◽  
Dry Weight ◽  
Growing Season ◽  
Field Conditions ◽  
Morphological Development

Two alfalfa cultivars grown under field conditions were harvested at different stages of maturity during the growing season of 1969. The number of buds and stems that originated from various locations on the plant and the dry weight of the stems were recorded periodically. The pattern of regrowth was the same for both cultivars. During regrowth, following all stages of harvest, many buds that developed early failed to produce mature stems. Uncut alfalfa produced a second crop of regrowth stems from the bases of stems that formed the first growth. After each harvest regrowth stems originated mainly from the stubble of the most recently harvested stems. Yield reductions occurring in successive regrowths of each harvest schedule were due mainly to the production of smaller stems. Increased growth rates following more mature stages of cutting resulted mainly from faster elongation of stems developing from larger buds. The implications of these findings with respect to the breeding of alfalfa are discussed.

Biology of Fire Ephemerals of the Sandplains of the Kwongan of South-Western Australia

1985 ◽  
Vol 12 (6) ◽  
pp. 641 ◽  
Author(s):  
JS Pate ◽  
NE Casson ◽  
J Rullo ◽  
J Kuo
Keyword(s):  
Life Cycle ◽  
Reproductive Biology ◽  
Seedling Growth ◽  
Western Australia ◽  
Growth Rates ◽  
Dry Matter ◽  
Dry Weight ◽  
Growing Season ◽  
Adaptive Significance ◽  
Sexually Dimorphic

The growth, longevity, mineral relationships and reproductive biology of 18 species of fire ephemerals were examined in sclerophyllous shrubland, located mainly within the Jurien : Badgingarra region of the Northern Sandplains of the kwongan of SW. Australia. Ten of the species were monocarpic, completing their life cycle within the 6-8 month winter growing season after a summer or autumn fire. The remaining species were polycarpic, commencing reproduction in their second season and surviving and reproducing for a further two to eight seasons (depending on species). Detailed study was made of growth and dry matter allocation in the dioecious, sexually dimorphic, polycarpic species Tersonia brevipes (Gyrostemonaceae). Monocarpic species tended to produce smaller seeds, and exhibited greater seed output per unit biomass and higher harvest indices for dry matter and minerals than polycarpic species. Certain monocarpic species showed great plasticity in final dry weight, e.g. a 2700-fold difference between largest and smallest individuals in a sample of 250 plants of Stipa elegantissima (Poaceae), and a 180-fold range in a similarly sized sample of Macarthuria apetala (Aizoaceae). The fire ephemerals studied generally exhibited faster seedling growth rates, greater concentrations of P and N (but not of Ca, Mg and K) in seedling dry matter, but usually lesser concentrations of P and N (but not of Ca, Mg and K) in seed dry matter than in cohabiting obligate seeder or sprouter species with potential life spans exceeding 15 years. The above-mentioned features of fire ephemerals are suggested to be of special adaptive significance within the context of exploitation of transiently non-limiting habitat resources immediately following fire.

Growth rates of black caiman (Melanosuchus niger) and spectacled caiman (Caiman crocodilus) from two different Amazonian flooded habitats

2013 ◽  
Vol 34 (4) ◽  
pp. 437-449 ◽  
Author(s):  
Ronis Da Silveira ◽  
Zilca Campos ◽  
John Thorbjarnarson ◽  
William E. Magnusson
Keyword(s):  
Growth Rates ◽  
Biotic Interactions ◽  
Alligator Mississippiensis ◽  
Growth And Survival ◽  
Density Dependent ◽  
Demographic Models ◽  
Caiman Crocodilus ◽  
Dependent Growth ◽  
Rates Of Growth ◽  
Dependent Processes

Rates of growth and survival in wild populations are affected by the physical environment, biotic interactions, and density-dependent processes, such as growth and fecundity. However, the relative importance of these factors in long-lived reptiles is poorly understood. We analyzed growth rates of Melanosuchus niger and Caiman crocodilus coexisting in two areas of the Brazilian Amazon with very different environmental characteristics. Growth rates of Caiman crocodilus at the two sites were similar, but M. niger grew more slowly in the area with higher productivity and higher density of caimans. Growth rates of the same species from other sites and of the temperate-zone Alligator mississippiensis indicate large differences among sites, but little evidence that these differences are primarily due to differences in productivity or temperature. Demographic models used to estimate sustained yields from caiman harvests should take into account the likely importance of density-dependent growth.

Reevaluating evidence of density-dependent growth in northern fur seals (Callorhinus ursinus) based on measurements of archived skeletal specimens

2004 ◽  
Vol 61 (9) ◽  
pp. 1616-1626 ◽  
Author(s):  
Michael A Etnier
Keyword(s):  
Growth Rates ◽  
Environmental Conditions ◽  
Somatic Growth ◽  
Callorhinus Ursinus ◽  
Density Dependent ◽  
Fur Seals ◽  
Time Period ◽  
Northern Fur Seals ◽  
Time Periods ◽  
Dependent Growth

Analysis of length-at-age measurements of archived skeletal material shows that somatic growth rates of male northern fur seals (Callorhinus ursinus) vary inversely with population density. Von Bertalanffy growth curves were estimated for two series of known-age mandibles collected 1911–1920 (n = 156) and 1940–1953 (n = 151), time periods representing the historic population minimum and maximum, respectively. Mandibles from the former time period are larger than mandibles from the latter time period, suggesting a density-dependent response in somatic growth. Although density-dependent growth in northern fur seals has been suggested before, previous studies have been hampered by the potentially confounding factors of fisheries interactions, variable environmental conditions, and harvest of adult female northern fur seals. The material analyzed here pre-dates the substantial development of the Bering Sea groundfish fishery and the period of heaviest culling of females. Likewise, the two time periods examined are characterized by broadly similar climatic and environmental conditions. Therefore, the results support the hypothesis that measurements of somatic growth rates provide an index of population levels relative to carrying capacity. Growth rate studies could therefore be used to evaluate the current population status of northern fur seals.

scholarly journals 594 Effect of Water Stress during the Harvest Period on the Carbohydrate Reserves of Mature Almond Trees

HortScience ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 549C-549
Author(s):  
Gaston Esparza ◽  
Ted M. DeJong ◽  
Steve A. Weinbaum
Keyword(s):  
Water Stress ◽  
Dry Weight ◽  
Growing Season ◽  
Tree Biomass ◽  
Carbohydrate Reserves ◽  
Effect Of Water ◽  
Significant Difference ◽  
Almond Trees ◽  
The Difference ◽  
Whole Tree

The effect of water stress during the harvest period on carbohydrate reserves at the end of the growing season was studied for mature, field-grown almond trees. The following irrigation treatments were imposed during 1995, 1996, and 1997: a) full irrigation (FI) (irrigation every 3–7 days), b) moderate stress (MS) (18 days of irrigation cut-off), and c) severe stress (SS) (35, 47, and 53 days of irrigation cut-off for 1995, 1996, and 1997, respectively). Midday stem (Yms) and predawn leaf (Ypd) water potentials were monitored during each season's stress. Three trees of contrasting treatments (FI vs. SS) were excavated on 10 Dec. 1997 and divided into tree components for dry weight and TNC concentration determination. Although there was no significant difference in whole-tree biomass between the excavated FI and SS trees, total new stem growth of SS trees was half of FI trees. TNC concentrations in the organs of SS trees were significantly reduced compared to FI trees. Total calculated whole tree TNC content for SS trees was 26.1% less than FI trees. The difference in TNC content between FI and SS trees was larger for roots (34.9%) than for the aerial parts (21.1%) indicating the higher sensitivity of roots for reflecting reserve status. Although roots constituted just 13.4% of the whole tree biomass, they stored 36.4% of TNC. Only roots exhibited a clear association between the minimum values of Yms and Ypd during the season and TNC concentration of 12 non-excavated additional trees that were subsampled at the end of the growing season.

Interior spruce seedlings compared with emblings produced from somatic embryogenesis. I. Nursery development, fall acclimation, and over-winter storage

1994 ◽  
Vol 24 (7) ◽  
pp. 1376-1384 ◽  
Author(s):  
S.C. Grossnickle ◽  
J.E. Major ◽  
R.S. Folk
Keyword(s):  
Somatic Embryogenesis ◽  
Root Growth ◽  
Freezing Tolerance ◽  
Growth Rates ◽  
Frozen Storage ◽  
Dry Weight ◽  
Growing Season ◽  
First Year ◽  
Terminal Bud ◽  
Interior Spruce

Interior spruce (Piceaglauca (Moench) Voss × Piceaengelmannii Parry) seedlings and emblings (plants produced via somatic embryogenesis tissue culture) were grown as container 1 + 0 plants. Seedling and embling morphological development was monitored during the growing season. Needle freezing tolerance, days to terminal bud break (DBB1), root growth capacity (RGC), and shoot dry weight fraction (DWF) were monitored during the fall and in frozen storage. Emblings had slower height, diameter, and root growth rates during the initial 2.5 months in the nursery. Thereafter, seedlings and emblings had equal height growth rate, while emblings had greater diameter and root growth rates. At the end of the growing season, seedlings and emblings, respectively, had 23.8 and 14.2 cm shoot height, 4.0 and 3.4 mm diameter, and 0.81 and 0.80 g root dry weight. During the fall, DBB1 of both seedlings and emblings decreased, with emblings having a more rapid decrease. Both seedlings and emblings showed a similar increase in freezing tolerance. Emblings had a greater increase in DWF. During the fall, RGC decreased then increased, with seedlings displaying a greater increase than emblings. While in frozen storage, seedlings and emblings maintained a low DBB1, and a high RGC and DWF. Freezing tolerance decreased while in frozen storage, with the loss more pronounced among seedlings. A degree growth stage model describes the first year cycle of development for seedlings and emblings. Results indicate that seedlings and emblings have slightly different patterns of first year growth and fall acclimation. However, both seedlings and emblings were at the end of rest when lifted for frozen storage.

Comparative Study of Size, Total Protein, Fibrinogen and 5-HT Content of Human and Canine Platelet Density Subpopulations

1986 ◽  
Vol 56 (03) ◽  
pp. 288-292 ◽  
Author(s):  
Diego Mezzano ◽  
Eduardo Aranda ◽  
Arnaldo Foradori
Keyword(s):  
Comparative Study ◽  
Protein Content ◽  
Cell Density ◽  
Total Protein ◽  
Unit Volume ◽  
Low Density ◽  
Dense Bodies ◽  
Artifactual Changes ◽  
Platelet Release ◽  
The Difference

SummaryThe size, total protein, fibrinogen and 5-HT content were evaluated in density subpopulations of human and canine platelets fractionated in linear arabinogalactan gradients. The methodology was assessed to ascertain that platelet separation was by density and to discard artifactual changes and platelet release during the procedure. EDTA or PGEi increased the size of human PRP-platelets, but not of dog platelets. In humans, high density (HD) platelets were 1.26 times larger and contained 1.88 times more fibrinogen, 2.23 times more 5-HT and 1.37 times more protein than low density (LD) platelets; in dogs, these density cohorts did not differ in protein content, but LD platelets were 1.29 times larger and had 1.33 times more fibrinogen and 5-HT than HD platelets. These findings suggest that cell density is mostly dependent on the protein content per unit volume of platelets (and not on dense bodies). The differences in fibrinogen and 5-HT content between HD and LD cohorts in humans and dogs may be related to platelet age. The difference in volume between HD and LD platelets in dogs is of uncertain interpretation.

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