Onset Of Summer Research Articles

The Effect of the Timing of Post-Diapause Egg Development on Survival, Growth, and Body Size in Gryllus pennsylvanicus

A trade-off between early mortality and reproduction may influence the evolution of the timing of post-diapause development in insects that exploit seasonal environments. To test this prediction, we manipulated hatching date experimentally in three successive years within a population of Gryllus pennsylvanicus, a univoltine cricket that overwinters in the egg stage. Each year, cohorts of nymphs derived from eggs maintained under identical conditions in the laboratory were simultaneously raised in the laboratory and in the field from where the population was collected. In the field, nymphal mortality was high early in the season, but was independent of hatching date in the laboratory under favorable rearing conditions. This suggests that the low temperatures encountered by the nymphs early in the season had a detrimental effect on survival. Growth rate and adult body size decreased with a delay in hatching date in the laboratory, which suggests that delayed hatching had a direct effect on the timing and rate of subsequent life history processes. The nymphs in the laboratory developed under a long and constant photophase indicating the onset of summer, whereas nymphs in the field experienced a declining photophase. Such a difference in photoperiod apparently induced a plastic response in growth rate, with nymphs growing faster under the declining than the constant photophase. It also appears that the declining photophase reduced the degree-days required for metamorphosis in the cohorts, and induced a decline in adult size with development time within each cohort. In either case, such an accelerating effect on metamorphosis implies a decrease in fecundity with a delay in hatching date. Therefore, these findings provide evidence for the hypothesis that a trade-off between early mortality and reproduction influences the evolution of the timing of post-diapause development at this locality.

Bacteriological study of Upper Lake of Bhopal, India

In order to assess the water quallty of the upper lake of Bhopal (India) after the leakage of methyl isocyanate (MIC) gas from the Union Carbide factory, Bhopal, bacteriological study of the lake water was carried out. Water samples were collected from eight different sampling stations from the eastern, western, northern and southern sides of the lake. The study has revealed that the coliform bacteria are increased (24000/mL) at the onset of summer and are dropped to a minimum (120/mL) during monsoon season against the permissible limit of 100/mL recommended by the World Health Organisation (WHO) for water to be used for drinking purposes. The data collected show that the water quality of the Upper lake is deteriorated and is gradually becoming unfit for drinking.

Changes in levels of GnRH in the brain and pituitary and GTH in the pituitary in male masu salmon, Oncorhynchus masou, from hatching to maturation

Levels of two types of gonadotropin-releasing hormone (salmon GnRH and chicken GnRH-II) in the brain and pituitary, and content of gonadotropin (GTHIβ and IIβ) in the pituitary were measured in male masu salmon from hatching to gonadal maturation for three years in order to clarify the involvement of GnRHs in precocious maturation.Underyearling precocious males were distinguishable in summer of year 1 and were marked by an increased GSI. Spermiation was observed among these individuals thereafter every autumn. Pituitary GTHIβ content in both precocious and immature males, and GTHIIβ content in precocious males showed seasonal fluctuations - high in autumn and low in winter. Pituitary GTHIIβ content was low in immature males.Pituitary sGnRH content in precocious males increased from spring to autumn during the three-year period. sGnRH concentrations in discrete brain areas showed seasonal changes - high during autumn to winter and low in summer. Concentrations in the olfactory bulbs and hypothalamus increased significantly in association with testicular maturation during year 3. sGnRH concentrations in the hypothalamus were significantly higher in precocious males than in immature males; this was possibly due to positive feedback of steroid hormones. cGnRH-II was undetectable in the pituitary and no distinct changes were observed in its concentration in the brain in relation to maturation.The phenomenon of underyearling precocious maturation is considered to be triggered before the onset of early summer. It is suggested that males which mature precociously are larger in size and contain much sGnRH in the pituitary before the outward signs of precocity appear; sGnRH may stimulate GTH II synthesis and induce precocious maturation.

Seasonal variation in algal species richness and abundance in the presence of molluscan herbivores on a tropical rocky shore

Seasonal variation in species and percentage cover of macroalgae was investigated over a 15-month period on a semi-exposed tropical rocky shore. Cages were used to manipulate herbivore access in mid and low shore areas. Algal species richness and abundance showed a marked seasonal pattern, peaking during the winter months and decreasing in the summer. At both mid and low shore the number of species and abundance of algae was greatest in herbivore exclusion treatments and the effect was more pronounced in the low shore where there was a consistent difference between treatments throughout the year. In the mid shore there was a difference in the cover of algae between treatments in the winter months only; for the remaining period there was little difference. Algal abundance and species numbers declined dramatically in all treatments as the temperature increased with the onset of summer, although the decline was less pronounced in the lower shore treatments. The results indicate that at higher tidal levels physical factors influence algal abundance to a greater extent than lower on the shore where herbivory is important, although lower on the shore the physical extremes of a tropical summer are also strong limiting factors.

The significance of the dormant stage in the growth cycle of deciduous plants for biogeochemical uranium prospecting, India

Abstract Three plant species, Shorea robusta, Emblica officinalis and Lagerstroemia parviflora , have higher uranium uptake capacities and more uniform distribution than other species growing over and near the Jajawal Uranium Deposit, India. The twigs of these species were sampled at the onset of summer to assess their relative efficiencies in delineating U anomalies. The trees of L. parviflora were in their dormant stage, bearing no leaves or flowers at the time of sampling. At that time S. robusta had growing leaves and flowers and E. officinalis had only young leaves, therefore both species were in the active stage of their growth cycle. The average concentration of U (0.87 ppm) in twigs of L. parviflora was higher than the average of 0.33 and 0.32 ppm U in twigs of S. robusta and E. officinalis , respectively. The biogeochemical contrast for U shown by L. parviflora in the dormant stage was higher than the other two species during their active growth. The magnitude of the anomalies varied, with L. parviflora giving the most pronounced anomalies.

Outdoors and Active.

In brief Summer's onset means physicians will see many skin conditions they don't usually see at other times of the year. Heat, humidity, and exposure to outdoor elements combine to make skin vulnerable to sunburn, parasite contact, infection, insect bites, and allergic reactions to noxious plants. Most conditions are easy to diagnose and treat, but others are less common and require greater effort to determine the etiology. Rapid recognition along with prevention tips can help keep patients active.

Seasonal changes in plasma testosterone concentrations in response to administration of hCG in a desert rodent, the sand rat (Psammomys obesus)

In adult male sand rats inhabiting the Béni-Abbès area (Algeria), testicular endocrine activity increased in early summer (June-July), was highest in autumn-winter and decreased throughout spring. Testosterone secretion by the testis of the sand rat was stimulated (by 10-60-fold) throughout the year by exogenously administered hCG (25 i.u.). However, the response exhibited annual changes mainly characterized by a marked increase in early summer (June-July); the response to hCG was depressed in autumn and became minimal in winter and in early spring. The results strongly suggest that the summer onset of testicular endocrine activity is, at least in part, due to an increase in the testis sensitivity to LH.

Mortality of Cape Proteaceae Seedlings During their First Summer

SYNOPSIS Summer (December-March) drought mortality of Cape Proteaceae seedlings during an average summer is low (about 7%) on the inland mountain ranges of the Southern Cape. Mortality depends on moisture conditions (soil depth, aspect) and the age of the seedlings by the onset of summer. Micro-site conditions, such as microweir formation, appear Important for successful establishment. No density dependent mortality was observed. The implications of these results for fynbos dynamics are discussed.

Cascading trophic interactions: Uncoupling at the zooplanktonphytoplankton link

Four limnocorrals (8 m dia. by 15 m deep) located at Lake St. George, Ontario, Canada; were used to examine the interactions between planktivorous fish, crustacean zooplankton (notably Daphnia galeata mendotae), and phytoplankton. During the spring, in all of the limnocorrals, high Daphnia biomasses were correlated with increased water transparency and a spring ‘clear-water’ phase. However, as the summer progressed, the relationship between Daphnia biomass and phytoplankton abundance became more complex and less predictable. Investigation of these interactions suggested four conclusions. (1) During late July and throughout August and September, water transparency decreased and algal cell counts increased. In 3 of 4 limnocorrals, deterioration in water quality occurred 3–5 weeks before zooplankton (and Daphnia populations) declined. In all cases decreased transparency was associated with increased concentrations of algal cells (Gloeococcus) that were poor food sources for Daphnia. These results suggested that decreased water transparency was not ‘caused by’ decreases in Daphnia biomass. (2) Taken together, data from all of the limnocorrals showed no correlation between the magnitude of July Daphnia biomasses and the percentage of ‘poor food source’ algae that were observed in August. This suggested that grazer effects were not necessary for the onset of summer ‘poor food source’ algal blooms. (3) In two limnocorrals, there was a positive correlation between increased Daphnia mortality and the onset of ‘poor food source’ blooms. In the other two limnocorrals there was no correlation. In all limnocorrals there was no correlation between decreased Daphnia reproductive capacity and ‘poor food source’ blooms. These data suggested that blooms of ‘poor food source’ algae were not necessary for the collapse of Daphnia populations. (4) In all 4 limnocorrals there was a strong correlation between the time that 0+ yellow perch planktivores reached biomasses of 30–50 kg ha−1 and the collapse of Daphnia populations Species and size selection was also observed. These results suggested that for this set of limnocorral experiments, fish biomasses in the 30–50 kg ha−1 were responsible for the collapse of Daphnia populations in the summer.

Seasonal meromixis in three hypersaline lakes on Rottnest Island, Western Australia

Three of the six permanent hypersaline lakes on Rottnest Island become meromictic 'hot lakes' during winter and spring. An important factor contributing to this transient stratification is a surface input of fresh water from seepages around the lakes, which overlays the existing hypersaline layer. Heat penetrates to the monimolimnion of these clear-water lakes and is trapped by the insulating effect of the overlying less-saline water. The disappearance of the stratification at the onset of summer is thought to be due to reduced freshwater input and evaporation of the less-saline mixolimnion.

Sea ice effective microwave emissivities from satellite passive microwave and infrared observations

Microwave sea ice emissivities are investigated on a global scale by using near‐simultaneous images from the temperature‐humidity infrared radiometer (THIR) and the dual‐polarization scanning multichannel microwave radiometer (SMMR), both onboard the Nimbus 7 satellite. The emissivities in several study areas in the Arctic region are observed to be approximately constant during a 9‐month period within the fall, winter, and spring months for both first‐year and multiyear ice, with a standard deviation of about 3%. During the onset of summer, when the snow cover starts to melt, emissivity increases of about 30% are observed at 37 GHz for multiyear ice, with the effect decreasing to less than 5% at the 6.6‐GHz channels. Multichannel cluster analysis over very large study areas during winter shows considerable variability in emissivities of well‐defined clusters of consolidated ice at 37 GHz and about one third as much at 18 GHz. Some nonlinearities in the functional relationship of the emissivities in the consolidated ice regions between first‐year and multiyear ice are also evident, especially when data from one frequency is plotted against that of another. However, the cluster analysis technique separates the various emissivity data points into distinct clusters corresponding to radiometrically different ice types. If the variability within each cluster is quantified and taken into account by using multispectral analysis, in addition to improving the capability of classifying ice by age, information about ice thickness and surface characteristics might also be obtainable.

Chronic Lyme Arthritis

Ten patients with Lyme arthritis have developed chronic involvement of one or both knees. Lyme arthritis was diagnosed by onset with erythema chronicum migrans (six patients); residence in Lyme, Connecticut (eight); seasonal onset in summer and early fall (nine); early periods of short recurrent attacks (nine); absence of rheumatoid factor (nine); and absence of symmetrical polyarthritis, morning stiffness, subcutaneous nodules, or antinuclear antibodies (in all). Five patients had synovectomies; pannus formation and underlying cartilage erosion were present in all. Seven of the 10 patients had the same B-cell alloantigen, DRw2 (frequency in normal control subjects, 22% [P less than 0.005]), but did not have an increased frequency of the alloantigens associated with rheumatoid arthritis. Chronic Lyme arthritis, the result of an apparent tick-transmitted infection, resembles rheumatoid arthritis pathologically but generally differs from it in both prearticular and immunogenetic characteristics.

WATER POLLUTION AS AFFECTED BY STREET SALTING1

ABSTRACTThe use of salt to melt ice and snow on streets and roads has become prevalent throughout the Northeast. Several states apply as much as 20 tons per lane‐mile.Salt runoff may be sorted in various locations within the hydrologic system. Eventually the salt reaches streams and lakes. In Meadowbrook, it was observed that the chloride content reached a high of 11,000 ppm in December 1969. The runoff from the watershed was emitted in several surges. Chloride concentrations declined with the onset of summer, but still remained high, suggesting that some of the salt applied during the past winter appeared in the summer stream flow.Salt runoff entering a small lake, flowed directly to the lake bottom. The buildup of high density saline water in the lower portion of the lake prevented complete mixing in the spring. Incomplete mixing led to anoxic conditions in the lower lake strata. The population of bent hic fauna of the lake was changed by the flow of salt water into the lake. From a total of 10 species of dipteran larva and oligochaetes, only 4 species of the latter remained.

Eco-physiological studies on desert plants : VII. Water relations ofLeptadenia pyrotechnica (Forsk.) Decne. growing in the Egyptian Desert.

1. Leptadenia pyrotechnica (Forsk.) Decne. grows in valleys of the Eastern Desert in Egypt where the climatic and edaphic drought is very severe. 2. The transpiration rate is low in winter months and rises by the onset of summer. The rise in transpiration rate is not comparable with that of the evaporation. 3. The maximum transpiration rate is generally attained earlier than the maximum of the evaporating factors, specially in summer. The transpiration curves show a rapid decrease after this maximum despite the continuous rise of the evaporating power of the atmosphere. This points to an effective stomatal regulation. 4. The osmotic pressure ofLeptadenia is relatively low. The osmotic pressure values show narrow daily and seasonal fluctuations. 5. Leptadenia pyrotechnica is one of the most drought resistant plants. Its xeromorphic leafless habit implies reduction in the transpiring surface, while its deep extensive roots and low transpiration rate ensure a favourable water balance. The mechanisms of drought resistance in this plant were discussed.

The effect of thermal acclimation on the heat tolerance of the intertidal Prosobranchs littorina littorea (L.) and Monodonta lineata (da Costa).

ABSTRACT The effect of exposure time and acclimation temperature on the survival of the winkle Littorina littorea and the topshell Monodonta lineata is described. It was found that acclimation to temperatures between 5 and 16°C enhanced survival whereas acclimation to temperatures above 21°C resulted in little further elevation of the heat-lethal temperature. The process of thermal acclimation is accomplished by raising the heat tolerance of the less-resistant individuals more than that of other members of the population. The increase in sea temperatures which occurs with the onset of summer is sufficient to extend the thermal tolerance so that unusually high temperatures can be tolerated when the animals are uncovered by the tide.

The Activity of a Pair of Common Dormice Muscardinus avellanarius in Conditions of Captivity

The diel activity of a pair of captive dormice Muscardinus avellanarius (L.) was studied from 11 July 1969 to 31 October 1969. In summer (July-September) onset of activity generally occurred at sunset and the activity period on an average came to an end 70 min before sunrise. During August and September the nocturnal activity reached a preliminary peak between 2000 and 2200 hours but the main activity peak occurred between 0100 and 0300 hours. The activity period came to an end before 0600 hours. In October the activity level was lower and the dormice were found to leave the nest at any hour. From July to September the activity period embraced about 6 hr and in October about 2 hr 19 min. During three days in October no activity was registered. The longest period of inactivity was 43 hr 29 min (17-19 October). During the summer months the minimum duration of exercise per night was 3 hr 55 min, 1 hr 50 min, and 50 min, in July, August and September, respectively. Hibernation started 25 November.

Efficacy of Natural Enemies of the California Red Scale on Citrus in Israel1

The interrelations between Aonidiella aurantii (Maskell) and its most important local natural enemies, the aphelinids Aphytis spp. and the coccinellid Chilocorus bipustulatus (L..), were investigated in an orange grove the southern Coastal Plain of Israel. The insecticidal check method was used in this study. It was found that natural enemies play a decisive role in retarding the buildup of California red scale populations on citrus, especially at the onset of summer. Thus, decimation of natural enemy populations at that period causes a marked increase in the percentage of live scales, which is followed by a massive outbreak of the scale’s populations. However, local natural enemies alone were not sufficient to hold the California red scale population below the threshold of economic injury in the test plot.

Limitations to animal production imposed by seasonal fluctuations in pasture and by management procedures

An experiment with Merino wethers on a Phalaris tuberosa-subterraneum clover-volunteer grass pasture has compared throughout an annual cycle the effects of: (a) Seasonal fluctuations in quantity and quality of pasture on liveweight gains and wool production in sheep. (b) Different grazing systems at equal stocking rates both on pasture growth and on liveweight and wool production in sheep. (a) Availability of dry pasture did not affect animal production so long as green pasture was present. Small increases in green pasture in the period of slow growth (winter) gave large increases in liveweight and wool production. Large increases in green pasture in the period of rapid growth (spring) had no effect on the animal. On dry pasture (summer) heavy sheep lost more weight than light sheep. Increasing the amount of dry pasture reduced liveweight loss only slightly but resulted in a greater rate of breakdown of plant material. An asymptotic relationship between availability of green pasture aid animal gain is presented, the asymptote in this instance occurring at a,pproxirnatnly 1400 lb dry matter per acre. The implications of the results are discussed with reference to methods of investigation of species, fertilizers, end management procedures aimed at 01-ercoming pasture limitations to animal production. The validity of investigations which do not take into account the relative constancy of grazing pressure throughout the year, and the continuing effects of plant on animal and animal on plant, is questioned. (b) Regardless of the degree to which pastures had been checked by grazing in spring, all dried out simultaneously on the onset of summer, and all sheep on all treatments reached their peak liveweight turning point on approximately the same date. Less than one-third of the liveweight gain potential of the pasture was attained on any one of the three grazing systems. The mean amounts of the individual pasture components, and of the total weight of pasture, were identical at any one time under the three grazing systems. The closer the systems approached towards continuous grazing the greater were the liveweight gains and wool production.

GUNSHOT FRACTURES OF THE SKULL

While I was laboring short-handed in a 1,500 bed hospital during the onset of the Somme push last summer, it was my lot to care for several hundred gunshot fractures of the skull. In spite of the stress of operative and directing work and with no clerical help, I made detailed notes on seventy-five patients, including necropsy records in the fatal ones. To group patients and lighten the work for medical officers and nurses it seemed wise to put patients with head injuries in one ward, using a neighboring ward when an overflow of the thirty-five bed unit occurred. As a routine, spinal puncture, roentgenography and scalp incision were employed to establish diagnosis. We were not supplied with a sphygmomanometer, and so could not make observations on the blood pressure findings. Routine eye examinations were made in every case. To Major Charles A. Maghy, oculist