Differences In Rate Of Development Research Articles

SEASONAL SELECTION IN THE LEOPARD FROG, RANA PIPIENS.

The leopard frog, Rana pipiens, exists as a polymorphic species in an area of about 100,000 square miles in Minnesota, western Wisconsin, northern Iowa, and northeastern South Dakota (Merrell, 1965). In addition to the usual spotted wild type, the populations frequently contain about 1 to 10% of the unspotted burnsi type, shown by Moore (1942) to be due to a single dominant gene. The wide distribution and fairly high frequency of the burnsi gene seem to rule out the possibility that it is being maintained by recurrent mutation. Furthermore, heterozygote advantage, the mechanism most commonly invoked to explain balanced polymorphism, does not seem an adequate explanation in this case. First, the frequency of the heterozygotes in natural populations is lower than would reasonably be expected if heterosis were involved. Also, the results from crosses in the laboratory between wild-type and burnsi individuals showed no evidence of heterozygote advantage (Merrell-unpublished). Crosses between heterozygous burnsi (B/+) and pipiens (+/+) yielded the expected one-to-one burnsi to pipiens ratio, even under crowded conditions. Crosses between heterozygous burnsi frogs gave the expected 3: 1 ratios with no indication that the homozygous burnsi type (B/B) was less vigorous than the B/+ or +/+ genotypes. Finally, crosses between burnsi and kandiyohi heterozygotes gave the four genotypes, burnsi, kandiyohi, double mutant burnsi-kandiyohi, and wild type pipiens, in the expected equal numbers. (Kandiyohi is another dominant polymorphic gene in R. pipiens not linked to burnsi-Volpe 1955, 1956, 1960; Anderson and Volpe, 1958). Not only were the expected ratios obtained, but there were no significant differences in rate of development or size at metamorphosis among the different types of progeny. Therefore, the available evidence gives no support to heterozygote advantage as an explanation for the burnsi polymorphism. For this reason, other mechanisms for maintaining the burnsi polymorphism must be considered. One possibility is a seasonal shift in selection pressure (Merrell, 1965). The data presented below suggest that the burnsi frogs are somewhat better able to survive the winter than the pipiens type.

BIOLOGY OF STEREMNIUS CARINATUS (COLEOPTERA: CURCULIONIDAE), A REFORESTATION PEST IN COASTAL BRITISH COLUMBIA

AbstractSteremnius carinatus (Boheman), once considered a scavenger, has become recognized as a pest of coniferous seedlings. The weevils breed in roots of fresh stumps and in buried slash on logged areas, and adults emerge by the end of the second summer after logging. Adults girdle young seedlings from near the root collar to 1 in. above ground level, but seldom attack the second year after planting. Adult weevils are long-lived, and can survive three or more winters, establishing broods each spring. They eat a wide variety of vegetation and fruits and other materials containing sugars and starches. Greenhouse trials demonstrated selective feeding on seedlings and field tests showed that the weevils breed in most coastal coniferous species in British Columbia. Rates of brood development ranged from 2 months at 80°F to 24 months in unheated outdoor conditions. Differences in rates of development, apparently related to temperature, were found between localities. Phloem may be suitable for oviposition 2 years after logging, but often is depleted by the feeding of other bark-mining beetles. Although some weevil damage is caused by emergents from stumps on rights-of-way, damage from larger populations emerging later from newly-cut sites may be reduced by planting immediately after cutting.

The difference in development rate of rye in relation to the number of spikelets per ear.

Leaf development in winter rye cv. Petkuser and Zelder [see F.C.A. 17: 1341] was further studied in 1962-3, after sowing on 25 Sep. Average stalk length increased with final number of leaves (11-14). Plants attained the same final leaf number either by a rapid rate of leaf emergence before winter and a slow rate after winter, or the reverse; the former growth pattern produced earlier emergence and greater areas of the 2 uppermost leaves, longer upper leaf sheaths, longer upper (and shorter lower) internodes, and slightly more spikelets/ear.-W.M.S.R. (Abstract retrieved from CAB Abstracts by CABI’s permission)

The development of the lamb with particular reference to the alimentary tract

1. Thirty Suffolk × Half bred lambs were slaughtered at the following ages: two twin lambs at birth and two singles and two twins at 1, 2, 3, 4, 6, 8 and 16 weeks of age.2. The following weights were recorded: live-weight immediately before slaughter; and carcass, head, skin, feet, alimentary tract, heart, liver, kidneys, lungs and trachea, and blood immediately afterwards.3. The alimentary tract was emptied and weighed in four separate parts; reticulo-rumen, omasum-abomasum, small intestine, large intestine.4. The volumes of the reticulo-rumen and the omasum-abomasum were measured by immersing in water and filling the organs with water to 2 cm. pressure.5. The in vitro digestive efficiency of rumen liquor from lambs of 1, 2, 3 and 4 weeks of age was assessed.6. Empty body weight was considered to be valuable in comparing animals of different ages or from different feeding regimes or at different times of the year because variations in gut ‘fill’ were eliminated.7. There were no differences between singles and twins in the relationship of the fresh weights of the parts of the body to empty body weight, except that development of the liver and the blood was rather slower for singles.8. Little evidence was found of a difference in rate of development of the alimentary tract between singles an d twins, although the log an d square root transformation suggested a possible difference in reticulo-rumen size in favour of twins, significant at the 5% level.

Effect of Clipping Wings and Tails in Chicks

Abstract MANY studies have shown that tissues and organs develop at different rates in domestic animals from birth to maturity. This difference in rate of development has been associated with changes in proportions of the various tissues as the animal or bird matures. Palsson (1955) has reported results of many investigators which show that the development of organs and tissues is affected by nutrition. Also, Hammond (1944a) has explained the relationship between nutrition and the development of organs and tissues by his theory of “Partition of nutrients according to metabolic rate.” In this connection, Palsson (1955) observed that Child (1920) was the first to show that tissues and organs with the highest metabolic rates had priority over those with lower metabolic rates for the supply of incoming nutrients No information is available, however, to illustrate the partition of incoming nutrients when parts of an organ or tissue are prevented from growth…

Causes of Variations in Effectiveness of Bracon cephi (Gahan) (Hymenoptera: Braconidae) as a Parasite of the Wheat Stem Sawfly

AbstractAdults of B. cephi emerged at the same time as the adults of their host, the wheat stem sawfly, and started to oviposit about mid-July. The second generation started to emerge between August 5 and 15. This generation, which was complete in some years, was apparently only partial in years in which adults of the first generation continued to oviposit late in the season. In most cases the larvae of Bracon that were present at harvest time were from eggs laid after August 1.Most of the overwintering B. cephi were located in the lower internodes of the sawfly-infested wheat stems. Although B. cephi attacked some sawfly larvae in their stubs most sawflies escaped parasitism once they had cut their host stems.High host densities per stem in hollow-stemmed wheats were detrimental to Bracon during the early part of the season as the unparasitized sawfly larvae in stems containing B. cephi destroyed the parasite larvae.The sawfly-susceptible wheats were more suitable than the resistant for parasitism. Generally, differences in parasitism between wheats and between barleys were caused by differences in length of survival of the sawfly larvae in the different host plants; longer survival led to higher parasitism.The fluctuations in amounts of parasitism mainly depended on the synchronization of development between B. cephi and the sawfly. Parasitism increased when the sawfly larvae cut their host stems sufficiently late to allow establishment by the second generation of B. cephi and decreased when the sawfly cut too early for parasitism by the second generation. The date of ripening of the host plant governs the date of cutting by the sawfly; hence, the amount of parasitism is influenced by the levels of soil moisture and temperature during the growing season, by differences in rate of development of various plant hosts, and by the date of seeding. Low levels of parasitism resulted from early ripening of the sawfly host plants in two consecutive years, whereas a moderately high level occurred even though the weather of the current year was conducive to early ripening, provided that the wheat in the preceding year had ripened late. It appears that moderate to high levels of parasitism required that the crop ripen late in at least one year out of two.

Reminiscence, Drive and Personality—Revision and Extension of a Theory

Some twenty studies have been examined which have purported to test the hypothesis that reminiscence effects are stronger in extraverts than in introverts, or related hypotheses involving the postulation of greater inhibition effects in certain criterion groups. It has been demonstrated that the results on the whole lend support to the original hypothesis. Little support is forthcoming for the additional hypothesis that neuroticism or emotionality, having drive properties, should also correlate positively with reminiscence.The original theory linking reminiscence with extraversion was based on three hypotheses, according to which extraverts (1) generate reactive inhibition more quickly, (2) dissipate it more slowly, and (3) develop greater amounts of reactive inhibition. The third hypothesis has been found to run foul of work done on the relation of drive to reminiscence, according to which the amount of reminiscence developed is a direct function of drive. A reformulation of the theory is therefore offered, using only differences in rates of development and dissipation of IR to account for the observed differences between extraverts and introverts in reminiscence.

THE INFLUENCE OF THE HOST ON OVIPOSITION BY THE WHEAT STEM SAWFLY, CEPHUS CINCTUS NORT. (HYMENOPTERA: CEPHIDAE)

Differences in host development largely determined the relative times, amounts, and locations of oviposition by the wheat stem sawfly in various hosts studied under field conditions. The difference in rates of development of varieties was the main cause of differences in infestations of the varieties. Resistance to oviposition was not a factor in the sawfly resistance of any of the test varieties.

Comparative Studies of Developmental Rates, Hibernation, and Food Plants in North American Colias (Lepidoptera, Pieridae)

Many studies have been done on Colias life histories. However, little work has been reported on the results of rearing in constant conditions and the writer was unable to, find any reports of successful attempts to get a secon'd generation of Colias among the species which, in nature, have one generation a year. Developmental rates are usuially species-specific. At the same time, they are affected extensively by various environmental factors. Therefore, it is essential in obtaining data on interspecific differences in developmental rates to carry out the rearing under constant conditions. Developmental rates for the fastest growing larvae of 6 North American species of Colias, reared under constant conditions, were recorded (Ae, 1956). The writer succeeded also in obtaining second generation butterflies in the 4 species which are univoltine in nature. At the same time, characteristics of hibernation, important for survival of the species, were studied. The reduction of egg fertility was observdd for wild females of Colias that had been kept in a cold room. Some new information on food plants was also obtained. The writer's field collections, at and near Gothic, Colorado, provided data on seasonal isolation of Colias species in nature.

On the glucokinase activity of extracts from normal and atrophic muscles

The glucokinase activity of extracts of muscles of various species (man, rabbit, guinea-pig, rat and chicken) has been determined. The activity of an extract prepared from a rabbit muscle, which had atrophied in the course of three to four weeks as a consequence of severance of the nerve, was always much higher than the activity of the extract prepared from the homologous normal muscle. On the other hand the average activity of extracts from atrophied human muscles was about half the average activity of extracts prepared from normal human skeletal muscles. This difference between atrophy caused by severence of the nerve and atrophy caused by disease might be explained by the difference in rate of development and in time during which the atrophy has existed.

The Relationship between Temperature, Rate of Development and Expression of the Pufdi Gene in Drosophila melanogaster

Pufdi flies reared at temperatures of 16⚬, 19⚬, 22⚬, 25⚬, 28⚬ and 31⚬ C. exhibited minimum divergence of wings at 19⚬, and responded to increases in temperature by progressive increases in wing spread. The wing spread of wild flies was not significantly modified by temperature changes. In both Pufdi and wild populations, males had greater wing spread than females, with the doubtful exception of wild flies reared at 28⚬. The temperature-effective period for Pfd/+ flies started at 19⚬ and transferred to 31⚬ begins in males between 6 and 8 hours before emergence of the imago, and in females between 4 and 6 hours before emergence. In both sexes, the period ended with emergence. In the 31⚬ to 19⚬ transfers, the effective period in both males and females begins between 8 and 10 hours before emergence and ends between 2 and 4 hours prior to that event. Of the Pufdi-and-mutant combinations Pfd/L2, Pfd L2/++, Pfd/+, M(3)w/+, gt2/O, Pfd/+, and gt2/gt2, Pfd/+, the wing spread of the garnet-Pufdi stocks (male and female) and the Pfd L2/++ females exceeded that of Pfd/+, and that of Pfd/L2 males was smaller. The other combinations did not differ significantly from Pfd/+. The Pufdi-Lobe2 arrangement Pfd L2/++ had greater wing spread in both males and females than the arrangement Pfd/L2. In both the Pfd/L2 and Pfd L2/++ arrangements, the L2 gene cancelled the sexual dimorphism which was otherwise characteristic of wing spread. At all temperatures, the duration of development of wild-type flies is greater than that of Pfd/+. The differences were not less at low temperatures where the two stocks were phenotypically most alike nor greater at high temperatures where they were most unlike. The length of the developmental period (at 25⚬ C.) of the Pufdi-and-mutant combinations bore no relationship to the differences in wing spread between these combinations. Male Pfd/+ have longer developmental periods and greater wing spreads than females. It was suggested that the lack of association between rate of development and the expression of the Pufdi gene might be due to the fact that the wings develop during the larval period, whereas the Pufdi gene operates during the final hours of the pupal period. Thus differences in developmental rate during the effective period of the gene would presumably not affect the already concluded wing-forming processes.

The physiology of microbial spoilage in foods

1. In microbial spoilage of foods only a very limited selection of the actual infection (the association of the substrate) plays a role. The genesis of the association is influenced by intrinsic, extrinsic and implicit factors. 2. Intrinsic parameters include chemical composition and processing of the substrate. The most important extrinsic parameters are activity of water, temperature, oxygen pressure and irradiation prevailing in the system during spoilage. 3. Among the microorganisms, whose development is made possible by the other parameters, further selection is effected by what were nominated implicit factors, i.e. differences in rate of development and synergism, resp. antagonism. 4. The complexity of the genesis of the association makes it imperative that researches on microbial spoilage are carried out in the substrate under investigation and under external conditions which do not differ essentially from the situation in practice.

A New Toxicant Occurring Naturally in Certain Samples of Plant Foodstuffs : V. Low Hatchability Due to Deformities in Chicks

FOR many years, residents of certain localities in South Dakota have complained that: (1) It was impossible to obtain satisfactory hatching results in chicks either by natural or artificial incubation. (2) The down on those chicks which did hatch appeared greasy, and never became fluffy. (3) Where higher hatchability was obtained, a high mortality occurred.REVIEWStockard (1920-21) in his studies on the structural and developmental rate states: “For the past ten years I have claimed that all types of monsters not of hereditary origin are to be interpreted simply as developmental arrests.” He also states: “The lengths of time between fertilization and the first cleavage and the rates at which the early cleavage follow one another may differ decidedly among the eggs of even closely related forms. These differences in developmental rate are probably fundamentally connected with differences in chemical structure of the egg substances, and in particular with .