A reexamination of litter size in some North American microtines

1978 ◽  
Vol 56 (7) ◽  
pp. 1488-1496 ◽  
Author(s):  
Duncan G. L. Innes
Keyword(s):  
Litter Size ◽  
North American ◽  
Clethrionomys Gapperi ◽  
Multiple Correlation ◽  
Independent Variables ◽  
Species Specific

Data from the literature on litter sizes of several species of Microtus and Clethrionomys were examined in relation to latitude and elevation by single and multiple correlation. Litter size in these genera was significantly correlated with latitude, as it was with latitude and elevation together. In Microtus, litter size within species was not significantly correlated with either of the independent variables. Litter size in Clethrionomys gapperi was significantly correlated with latitude and with latitude and elevation together. Multiple range tests revealed that some species which occur at the same latitudes and elevations have significantly different litter sizes from each other. Litter size may be species specific and not primarily determined by latitude and elevation.

scholarly journals Effects of BMP15 and GDF9 on Ovine Oocytes in an In Vitro Maturation System

2021 ◽  
Author(s):  
◽  
Aanchal Singh
Keyword(s):  
Cell Death ◽  
Litter Size ◽  
In Vitro Maturation ◽  
Cumulus Cell ◽  
Oocyte Quality ◽  
Mature Oocyte ◽  
High Ratio ◽  
High Fecundity ◽  
Species Specific

<p>Oocyte developmental competency is the intrinsic measure of oocyte quality and the capacity for a mature oocyte to support the early stages of embryo development and implantation. Oocyte-secreted factors (OSFs), such as growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15), play a pivotal role in regulating the synchrony of various complex maturation events within the cumulus-oocyte complex (COC) through the induction of paracrine and endocrine signalling. These proteins act synergistically to influence the proliferation and differentiation of granulosa cells (GCs), cumulus cell (CC) expansion, promote survival, ovulation, the attainment of developmental competency and fertility. Species-specific ratios suggest that poly-ovulatory mammals have increased fecundity due to high ratios of GDF9:BMP15, which is directly reflected in their large litter size. Interestingly, it has also been found that higher ratios of GDF9:BMP15 also increased blastocyst rate in sheep implying that these embryos develop from oocytes that are more developmentally competent.  In this study, I investigated the hypothesis that supplementing a commercial in vitro maturation (IVM) system with a high ratio of GDF9:BMP15 would increase the developmental competency sheep oocytes; a species with low-moderate litter size. To test this hypothesis, ovine oocytes were matured in a biphasic IVM system containing GDF9 and BMP15 at three divergent ratios (1:6, 1:1, 6:1). The results herein show that the 6:1 ratio resulted in higher levels of reagent transfer to the ovine oocyte through gap junctions (GJs) after 24 hours of incubation. Similarly, it was also observed that at the higher ratio, glutathione (GSH) levels were higher at 7.5 hours of incubation. The high GDF9:BMP15 ratio also facilitated the increased consumption of pyruvate by the COC consistently throughout the culture period. Importantly, the high GDF9:BMP15 ratio showed higher expression of the gene that encodes GJ (CX43) at 24 hours relative to the control. It was also demonstrated through decreased apoptotic factor (BAX:BCL2) ratios, that the addition of OSFs, regardless of ratio, protected against cell death. In summary, this study provides novel results that support the notion that a high GDF9:BMP15 ratio improves oocyte quality by delaying the timing of meiotic resumption. This subsequently improves the transport of key metabolites and antioxidants to protect against oxidative stress and cell death and aid in the completion of maturation, ultimately resulting in the increased developmental competency observed in high fecundity poly-ovulatory species.</p>

scholarly journals Wing Morphology and Flight Behavior of Some North American Hummingbird Species

The Auk ◽  
2005 ◽  
Vol 122 (3) ◽  
pp. 872-886 ◽  
Author(s):  
F. Gary Stiles ◽  
Douglas L. Altshuler ◽  
Robert Dudley
Keyword(s):  
Breeding Season ◽  
North American ◽  
Theoretical Models ◽  
Wing Disc ◽  
Territorial Behavior ◽  
Flight Behavior ◽  
Adult Males ◽  
Wing Morphology ◽  
Reversed Sexual Size Dimorphism ◽  
Species Specific

Abstract We explored the relationship between wing morphology and flight behavior with respect to sex and age in five species of North American hummingbirds. We first measured the length, chord or “width,“ and area of entire hummingbird wing planforms. We then calculated additional parameters of wing shape and size, including aspect and shape ratios, degree of taper or “pointedness,“ wing loading, and wing disc loading (WDL). Wings of adult males are not only shorter but also more narrow and tapered than those of adult or immature females; immature males have larger wings and lower WDL, more like those of females. A proposed relationship between WDL and territorial behavior and dominance is not supported, given that adult and immature males show similar feeding territoriality outside the breeding season but females rarely do. The more extreme and divergent wings of adult males probably reflect sexual selection in connection with aerial displays that include species-specific sound effects given during the breeding season. North American species are unusual among hummingbirds in showing reversed sexual size-dimorphism (males smaller, with relatively shorter wings), a feature shared with some other small hummingbirds, notably the “Pygmornis“ hermits. Attempts to explain hummingbird foraging and territorial behavior on the basis of differences in WDL have failed because many aspects of wing morphology, physiology, and flight behavior were not taken into account. Several wing parameters appear more related to other modes of flight than to strategies of nectar exploitation, and the morphology of any given wing represents a compromise between the often conflicting aerodynamic demands of different flight modes. Understanding hummingbird flight will require broad comparative studies of wing morphology and wingbeat kinematics in relation to flight behavior, and new theoretical models and experimental data will be needed to elucidate physiological and aerodynamic mechanisms underlying forward flight and maneuvering. Morfología Alar y Comportamiento de Vuelo de Unas Especies de Colibríes de Norteamérica

Reproduction in laboratory colonies of Clethrionomys gapperi and Microtus pennsylvanicus: a comparison between species and among populations

1994 ◽  
Vol 72 (6) ◽  
pp. 995-1001
Author(s):  
Duncan G. L. Innes ◽  
John S. Millar
Keyword(s):  
Litter Size ◽  
Reproductive Effort ◽  
Microtus Pennsylvanicus ◽  
Clethrionomys Gapperi ◽  
General Hypothesis ◽  
Litter Mass ◽  
In The Wild ◽  
Eyes Open ◽  
Weaning Age ◽  
Laboratory Colonies

Reproduction in laboratory colonies of Clethrionomys gapperi and Microtus pennsylvanicus was examined by comparing six populations (three per species) to test the general hypothesis that populations subject to the lowest temperatures and the shortest breeding seasons would be at the "fast" end of the "fast–slow" continuum. All colonies were derived from three sites in western Canada from females that were inseminated in the wild. Postpartum mass, mass of adult females during lactation, litter size, litter and neonate masses at birth, litter mass at weaning, age when the eyes opened, and age at weaning as well as two variables describing the energetics of reproduction were examined between species and among populations within species. Three indices of physiological reproductive effort were also compared. Only neonate mass, age when eyes were open, and one index of reproductive effort differed between species. In C. gapperi, litter mass, litter size, age when the eyes opened, age at weaning, and one index of reproductive effort differed among populations. In M. pennsylvanicus, postpartum, litter (at birth and weaning), and neonate mass, age when eyes open, age at weaning, and maintenance costs during lactation were different among populations. In both species, some differences could be attributed to sampling biases, while others were simply a consequence of differences in maternal mass. In both species, the maximum difference in the age at weaning and the age when the eyes opened was less than 2 days. Differences among populations did not appear to be related to meteorological conditions, and populations in either species could not be ranked on a continuum.

Productivity of coyotes (Canis latrans) from southern Québec

1984 ◽  
Vol 62 (11) ◽  
pp. 2240-2243 ◽  
Author(s):  
Yves Jean ◽  
Jean-Marie Bergeron
Keyword(s):  
Litter Size ◽  
Age Structure ◽  
North American ◽  
Turnover Rate ◽  
Canis Latrans ◽  
Corpora Lutea ◽  
High Turnover ◽  
Large Litter ◽  
The Mean ◽  
Eastern Townships

A sample of coyotes harvested in the Eastern Townships of southern Québec indicate that 84% of the sample comprised females under 3 years old. The examination of mature follicles, corpora lutea and corpora albicantia, indicated that the ovulation rates ranged from 6.6 to 8.0, and the mean ovulation frequency was of 57%. The mean litter size was estimated at 7.1 with 46% of the females producing pups. The mean population productivity was of 316 pups per 100 females annually, concurring with rates found in other North American populations. Results suggest that a strong harvesting pressure could be at the origin of the large litter size, of the age structure that favors young animals, as well as the high turnover rate in the population.

scholarly journals The feature of morphological traits and their effects on body weight in the red crab (Charybdis feriata)

2015 ◽  
Author(s):  
Xiong Zou ◽  
Hongyu Ma ◽  
Jianxue Lu ◽  
Yangyang Gong ◽  
Lianjun Xia
Keyword(s):  
Body Weight ◽  
Morphological Traits ◽  
Correlation Coefficients ◽  
Regression Equation ◽  
Multiple Correlation ◽  
Ideal Model ◽  
Correlation Relationship ◽  
Independent Variables ◽  
Path Coefficients ◽  
Best Fit

The red crab (Charybdis feriata) is one of most important fishery resources in China. In the present study, we first measured 17 morphological traits and body weight of C. feriata, characterized these 18 traits, and then estimated the effects of morphological traits on body weight by statistical methods including correlation coefficients, determination coefficients, path coefficients, and regression equation. All correlation coefficients between 17 morphological traits and body weight reached an extremely significant level (P<0.01). Determination and path coefficients analysis revealed the real correlation relationship between the independent variables and the dependent variable. Significant path coefficients were found between three morphological traits (stemum width, X8; meropodite length of pereopod 3, X16; meropodite length of pereopod 4, X17) and body weight that suggested these three traits were the key traits directly influence body weight. Multiple correlation index (R2) between above three morphological traits and body weight was of 0.977, which indicated that the main independent variables influencing body weight has been found. Finally a best-fit linear regression equation was established as Y = 13.078 X8 + 7.048 X16 - 4.902 X17 - 576.635, which provided an ideal model for better understanding the feature of morphological traits and body weight of C. feriata.

The importance of meat, particularly salmon, to body size, population productivity, and conservation of North American brown bears

1999 ◽  
Vol 77 (1) ◽  
pp. 132-138 ◽  
Author(s):  
G V Hilderbrand ◽  
C C Schwartz ◽  
C T Robbins ◽  
M E Jacoby ◽  
T A Hanley ◽  
...  
Keyword(s):  
Body Size ◽  
Population Density ◽  
Body Mass ◽  
Litter Size ◽  
Adult Female ◽  
North American ◽  
Female Body ◽  
Brown Bears ◽  
Hair Samples ◽  
Female Body Mass

We hypothesized that the relative availability of meat, indicated by contribution to the diet, would be positively related to body size and population productivity of North American brown, or grizzly, bears (Ursus arctos). Dietary contributions of plant matter and meat derived from both terrestrial and marine sources were quantified by stable-isotope analysis (δ13C and δ15N) of hair samples from 13 brown bear populations. Estimates of adult female body mass, mean litter size, and population density were obtained from two field studies of ours and from other published reports. The populations ranged from largely vegetarian to largely carnivorous, and food resources ranged from mostly terrestrial to mostly marine (salmon, Oncorhynchus spp.). The proportion of meat in the diet was significantly correlated with mean adult female body mass (r = 0.87, P < 0.01), mean litter size (r = 0.72, P < 0.01), and mean population density (r = 0.91, P < 0.01). Salmon was the most important source of meat for the largest, most carnivorous bears and most productive populations. We conclude that availability of meat, particularly salmon, greatly influences habitat quality for brown bears at both the individual level and the population level.

“Party Effort and Its Impact on the Vote”

1971 ◽  
Vol 65 (2) ◽  
pp. 439-450 ◽  
Author(s):  
William J. Crotty
Keyword(s):  
North Carolina ◽  
Correlation Analysis ◽  
National Level ◽  
Multiple Correlation ◽  
Total Contribution ◽  
Research Attention ◽  
Independent Variables ◽  
Structural Variables ◽  
Multiple Correlation Analysis ◽  
Variance Explained

The effect of party activities on the vote, while a fundamentally important question for any understanding of party operations, has received little research attention. This neglect has come about partly because the analysis is difficult to conceptualize and because the data have to be generated principally by the investigator. In addition, structural variables relevant to the nature of the environment in which the parties compete must be introduced into the analysis, and the canvas must be broad enough to permit comparative assessments within a controlled research design.The present study sets out to deal with precisely these problems. It analyzes the contribution of the competing parties' efforts to the final vote in elections for five levels of office, from local to national, in 100 North Carolina counties.Multiple correlation analysis was used to judge the association between the final vote and three sets of independent variables: demographic, institutional (specifically the extent of competition between the contending parties), and political, with emphasis on those associated with campaigning. The variance explained by each is described, as well as the total contribution of all to understanding the outcome of the election.The variables proved quite successful in explaining the final vote. The strength of the associations increased as one proceeded from the local to the national level, and party output measures proved more impressive contributors to explaining the votes in competitive as against non-competitive areas. Overall, the variables relating to party effort were found to add significantly to the under-standing of the election outcomes.

FATTY ACIDS AND STEROIDS AFFECTING FLAVOR AND AROMA OF MEAT FROM RAM, CRYPTORCHID, AND WETHER LAMBS

1973 ◽  
Vol 53 (4) ◽  
pp. 673-678 ◽  
Author(s):  
J. A. VESELY
Keyword(s):  
Fatty Acids ◽  
Linoleic Acid ◽  
Correlation Coefficient ◽  
Small Variation ◽  
Multiple Correlation Coefficient ◽  
Residual Variance ◽  
Multiple Correlation ◽  
Simple Correlation ◽  
Independent Variables ◽  
Independent Variable

Organoleptic tests of meat and fat samples from 33 ram, 37 cryptorchid, and 31 wether lambs showed no significant differences in flavor or aroma among the three sex types. There was, however, a small variation in flavor and aroma among the animals. Analyses of variance of flavor and aroma scores revealed that there was a larger Variation within animals (between judges) than that between animals and the repeatability estimates for the two traits were 0.10 and 0.03. However, a significant (P < 0.01) multiple regression of flavor on 15 independent variables (six fatty acids and nine steroids) was determined and its multiple correlation coefficient was 0.56. The reduction in residual variance due to stearic acid was significant (P < 0.05) and linoleic acid was the best predictor of flavor as a single independent variable (P < 0.10). Simple correlation coefficient between flavor and aroma was estimated to be negative and nonsignificant, −0.12.

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