scholarly journals On competition between different species of graminivorous insects

1945 ◽  
Vol 132 (869) ◽  
pp. 362-395 ◽  
Keyword(s):  
Census Data ◽  
Single Species ◽  
The Other ◽  
Ecological Niches ◽  
Initial Population ◽  
General Validity ◽  
Rhizopertha Dominica ◽  
Rate Of Increase ◽  
Limited Food ◽  
Determining Factor

The growth of pure populations of the beetles Rhizopertha dominica and Oryzaephilus surinamensis , and of the moth Sitotroga cerealella , was observed in a standard medium of wheat. This was maintained at a constant level by the periodic removal of ‘conditioned’ frass and the addition of fresh grains. The population of each species rose to a maximum and remained fluctuating about this value indefinitely. A comparison of the rates of oviposition, with the rates at which adults emerged, showed that in the maximum population there was an enormous mortality (always over 90%) in the immature stages. When pairs of species competed Rhizopertha eliminated Sitotroga because their larvae, between which most of the competition occurred, have the same needs and habits. But each of these species was able to survive with Oryzaephilus because this species occupies a different ‘ecological niche’. The Verhulst-Pearl ‘logistic’ equation (1), for the growth of population of a single species in a limited environment, and the Lotka-Volterra simultaneous equations (2), for the growth of population of two species competing for the same limited environment, were fitted to the census data from all the experiments. The biological assumptions on which they are based proved to be true for practical purposes for Rhizopertha and Sitotroga populations. These assumptions are that the value of the potential rate of increase remains statistically constant and that all the factors inhibiting increase are linearly related to population density. Further­ more, a single factor, larval competition, was represented by the single indices standing for interspecific inhibition. It follows that the maximum population (or equilibrium position) should be independent of the initial population, and this proved to be so for all species. Equations (2) did not always fit the observed points very well, but they were always success­ful in predicting the outcome of competition. It does not follow from this that these equa­tions have any general validity. Their basic assumptions are by no means universally true and, unless they are shown to be so for a particular species under known, environmental conditions, no biological deductions can be drawn from them. Where they do apply they describe the course of change of population of two competing organisms with an accuracy which depends on the constancy of the coefficients involved. Two kinds of organism will be able to survive together only if they differ in needs and habits, i. e. occupy different ecological niches. Populations living in a medium of unrenewed wheat rose to a maximum and then declined as the food became exhausted and ‘conditioning’ increased. The eventual extinction of the population was due, not to the cessation of oviposition, but to the failure of the larvae to survive. The longevity of Rhizopertha adults was lower in unrenewed than in renewed medium, and lower still when this species was competing with Sitotroga in unrenewed medium. The longevity of the other species, and the sex ratio of Sitotroga , were apparently unaffected by these conditions. The fecundity of Rhizopertha females decreased with time, and the length of Sitotroga adults of both sexes decreased in succeeding generations. The competitive relation­ship between both Sitotroga and Rhizopertha , and Oryzaephilus shifted slightly in favour of the former species in unrenewed as compared with renewed media. In a renewed medium this relationship probably depends chiefly on the destruction of eggs and pupae by adults and larvae, for which the more predaceous Oryzaephilus is better placed. In an unrenewed medium the ability of the larvae to make the best use of the limited food supply is the determining factor, and here the other two species have the advantage. The competitive relationship between Rhizopertha and Sitotroga remained the same in both media.

Sodium Benzoate Inhibits Growth of or Inactivates Listeria monocytogenes

1988 ◽  
Vol 51 (7) ◽  
pp. 525-530 ◽  
Author(s):  
MOUSTAFA A. EL-SHENAWY ◽  
ELMER H. MARTH
Keyword(s):  
Listeria Monocytogenes ◽  
Incubation Period ◽  
Sodium Benzoate ◽  
The Other ◽  
Complete Inhibition ◽  
Initial Population ◽  
Limited Growth ◽  
Complete Inactivation ◽  
Low Concentrations ◽  
Slight Growth

The ability of Listeria monocytogenes to grow or survive was determined using tryptose broth at pH 5.6 or 5.0, supplemented with 0, 0.05. 0.1, 0.15. 0.2. 0.25 or 0.3% sodium benzoate, and incubated at 4,13,21 or 35°C. The bacterium grew in benzoate-free controls under all conditions except at 4°C and pH 5.0. At pH 5.6 and 4°C, after 60 d, L. monocytogenes (initial population ca. 103/ml) was inactivated by 0.2, 0.25 and 0.3% sodium benzoate. Other concentrations of benzoate permitted slight growth during the first 36 d of incubation followed by a decrease in populations of the pathogen. At pH 5.0 and 4°C, from 0.15 to 0.3% benzoate completely inactivated the pathogen in 24 to 30 d, whereas the other concentrations caused a gradual decrease in the population during the 66-d incubation period. At 13°C and pH 5.6, L. monocytogenes grew (more at lower than higher concentrations of benzoate) in the presence of all concentrations of benzoate except 0.25 or 0.3%, which prohibited growth throughout a 264-h incubation period. Reducing the pH to 5.0 minimized growth at the two low concentrations of benzoate and caused slight decreases in population at the other concentrations of benzoate. At 21 and 35°C and pH 5.6, appreciable growth of L. monocytogenes occurred in the presence of 0.2% or less sodium benzoate, whereas higher concentrations were inhibitory, permitting little if any growth by the pathogen. Reducing the pH to 5.0 allowed limited growth of the pathogen at 21 and 35°C when the medium contained 0.05 or 0.1% sodium benzoate. Higher concentrations caused either complete inhibition or inhibition plus partial or complete inactivation of the pathogen during incubations of 117 h at 21°C or 78 h at 35°C.

Effect of sleep on nocturnal bronchoconstriction and ventilatory patterns in asthmatics

1989 ◽  
Vol 67 (1) ◽  
pp. 243-249 ◽  
Author(s):  
R. D. Ballard ◽  
M. C. Saathoff ◽  
D. K. Patel ◽  
P. L. Kelly ◽  
R. J. Martin
Keyword(s):  
Airway Resistance ◽  
Minute Ventilation ◽  
The Other ◽  
Lower Airway ◽  
Sleep Laboratory ◽  
Sleep State ◽  
Asthmatic Patients ◽  
Ventilatory Responses ◽  
Rate Of Increase ◽  
Normal Controls

To assess the effect of sleep on airflow resistance and patterns of ventilation in asthmatic patients with nocturnal worsening, 10 adult subjects (6 asthmatic patients with nocturnal worsening, 4 normal controls) were monitored overnight in the sleep laboratory on two separate occasions. During 1 night, subjects were allowed to sleep normally, whereas during the other night all sleep was prevented. The six asthmatic patients demonstrated progressive increases in lower airway resistance (Rla) on both nights, but the rate of increase was twofold greater (P less than 0.0001) during the sleep night compared with the sleep prevention night. However, overnight decrements in forced expired volume in 1 s (FEV1) were similar over the 2 nights. The asthmatic patients maintained their minute ventilation as Rla increased during sleep, demonstrating a stable tidal volume with a mild increase in respiratory frequency. We conclude that in asthmatic patients with nocturnal worsening 1) Rla increases and FEV1 falls overnight regardless of sleep state, 2) sleep enhances the observed overnight increases in Rla, and 3) sleep does not abolish compensatory ventilatory responses to spontaneously occurring bronchoconstriction.

scholarly journals Why are mayflies (Ephemeroptera) lost following small increases in salinity? Three conceptual osmophysiological hypotheses

2018 ◽  
Vol 374 (1764) ◽  
pp. 20180021 ◽  
Author(s):  
Ben J. Kefford
Keyword(s):  
Turnover Rate ◽  
Ph Regulation ◽  
Research Effort ◽  
Ion Homeostasis ◽  
Single Species ◽  
Toxicity Tests ◽  
Future Prospects ◽  
Theme Issue ◽  
Vital Functions ◽  
Rate Of Increase

The salinity of many freshwaters is increasing globally as a result of human activities. Associated with this increase in salinity are losses of Ephemeroptera (mayfly) abundance and richness. The salinity concentrations at which Ephemeroptera decline in nature are lower than their internal salinity or haemolymph osmolality. Many species also suffer substantial mortality in single species laboratory toxicity tests at salinities lower than their internal salinity. These findings are problematic as conventional osmoregulation theory suggests that freshwater animals should not experience stress where external osmolality is greater than haemolymph osmolality. Here I explore three hypotheses to explain salt sensitivity in Ephemeroptera. These conceptual hypotheses are based on the observations that as the external sodium ion (Na + ) concentration increases so does the Na + turnover rate (both uptake and elimination rates increase). Sulphate ( ) uptake in mayflies also increases with increasing external although, unlike Na + , its rate of increase decreases with increasing external . The first hypothesis is premised on ion turnover being energetically costly. The first hypothesis proposes that individuals must devote a greater proportion of their energy to ion homeostasis at the expense of other uses including growth and development. Lethal levels of salinity presumably result from individuals not being able to devote enough energy to maintain ion homeostasis without critical loss of other vital functions. The second hypothesis is premised on the uptake of Na + exchanged for (an outgoing) H + , leading to (localized) loss of pH regulation. The third hypothesis is premised on localized Na + toxicity or poisoning with increased Na turnover as salinity increases. None of the proposed hypotheses is without potential problems, yet all are testable, and research effort should be focused at attempting to falsify them. This article is part of the theme issue ‘Salt in freshwaters: causes, ecological consequences and future prospects’.

scholarly journals Spiribacter aquaticus Leon et al. 2017 is a later heterotypic synonym of Spiribacter roseus Leon et al. 2016. Reclassification of Halopeptonella vilamensis Menes et al. 2016 as Spiribacter vilamensis comb. nov.

2020 ◽  
Vol 70 (4) ◽  
pp. 2873-2878 ◽  
Author(s):  
María José León ◽  
Cristina Galisteo ◽  
Antonio Ventosa ◽  
Cristina Sánchez-Porro
Keyword(s):  
Type Species ◽  
Single Species ◽  
Amino Acid Identity ◽  
The Other ◽  
Phylogenomic Analysis ◽  
Content Type ◽  
Link Type ◽  
Average Amino Acid Identity ◽  
Single Genus ◽  
Type Strains

A comparative taxonomic study of Spiribacter and Halopeptonella species was carried out using a phylogenomic approach based on comparison of the core genome, orthologous average nucleotide identity (OrthoANIu), Genome-to-Genome Distance Calculator (GGDC) and average amino acid identity (AAI). Phylogenomic analysis based on 976 core translated gene sequences obtained from their genomes showed that Spiribacter aquaticus SP30T, S. curvatus UAH-SP71T, S. roseus SSL50T, S. salinus M19-40T and Halopeptonella vilamensis DSM 21056T formed a robust cluster, clearly separated from the remaining species of closely related taxa. AAI between H. vilamensis DSM 21056T and the species of the genus Spiribacter was ≥73.1 %, confirming that all these species belong to the same single genus. On the other hand, S. roseus SSL50T and S. aquaticus SP30T showed percentages of OrthoANIu and digital DNA–DNA hybridization of 98.4 % and 85.3 %, respectively, while these values among those strains and the type strains of the other species of Spiribacter and H. vilamensis DSM 21056T were ≤80.8 and 67.8 %, respectively. Overall, these data show that S. roseus SSL50T and S. aquaticus SP30T constitute a single species and thus that S. aquaticus SP30T should be considered as a later, heterotypic synonym of S. roseus SSL50T based on the rules for priority of names. We propose an emended description of S. roseus , including the features of S. aquaticus . We also propose the reclassification of H. vilamensis as Spiribacter vilamensis comb. nov.

Predestination

2018 ◽  
Author(s):  
George I. Mavrodes
Keyword(s):  
Thomas Aquinas ◽  
The Other ◽  
John Calvin ◽  
Eternal Life ◽  
Human Beings ◽  
Equal Condition ◽  
Divine Grace ◽  
The World ◽  
The Will ◽  
Determining Factor

Predestination appears to be a religious or theological version of universal determinism, a version in which the final determining factor is the will or action of God. It is most often associated with the theological tradition of Calvinism, although some theologians outside the Calvinist tradition, or prior to it (for example, Augustine and Thomas Aquinas), profess similar doctrines. The idea of predestination also plays a role in some religions other than Christianity, perhaps most notably in Islam. Sometimes the idea of predestination is formulated in a comparatively restricted way, being applied only to the manner in which the divine grace of salvation is said to be extended to some human beings and not to others. John Calvin, for example, writes: We call predestination God’s eternal decree, by which he compacted with himself what he willed to become of each man. For all are not created in equal condition; rather, eternal life is foreordained for some, eternal damnation for others. Therefore, as any man has been created to one or the other of these ends, we speak of him as predestined to life or to death. (Institutes, bk 3, ch. 21, sec. 5) At other times, however, the idea is applied more generally to the whole course of events in the world; whatever happens in the world is determined by the will of God. Philosophically, the most interesting aspects of the doctrine are not essentially linked with salvation. For instance, if God is the first cause of all that happens, how can people be said to have free will? One answer may be that people are free in so far as they act in accordance with their own motives and desires, even if these are determined by God. Another problem is that the doctrine seems to make God ultimately responsible for sin. A possible response here is to distinguish between actively causing something and passively allowing it to happen, and to say that God merely allows people to sin; it is then human agents who actively choose to sin and God is therefore not responsible.

A new species of Liophloeothrips (Thysanoptera, Phlaeothripidae) from leaf litter from Iran

Zootaxa ◽  
2019 ◽  
Vol 4571 (1) ◽  
pp. 138
Author(s):  
MAHSA HAKIMARA ◽  
KAMBIZ MINAEI ◽  
SABER SADEGHI ◽  
LAURENCE MOUND
Keyword(s):  
New Species ◽  
Leaf Litter ◽  
Type Species ◽  
Single Species ◽  
The Other ◽  
Single Female ◽  
Label Data ◽  
Fungal Hyphae ◽  
Plant Families ◽  
A New Species

Of the 16 species listed in the genus Liophloeothrips (ThripsWiki 2018), 13 are known only from India, and all of these are phytophagous with some inducing galls in various plant families (Tyagi & Kumar 2011). However, the biology of the type species, L. glaber, as well as that of the other two species, L. hungaricus and L. pulchrisetis, remains in doubt. Each of these three species is from Europe, with L. pulchrisetis known from a single female, L. glaber from two specimens, and hungaricus recorded from Hungary, Finland and Iran on a very few individuals (Minaei & Mound 2014). The record of L. hungaricus from Iran was published without any information concerning the locality, date of collection, or number of specimens (Mortazawiha 1995). However, Minaei and Mound (2014) pointed out that the slide label data of L. hungaricus specimens from Europe suggested that this species is associated with the bark of certain Salicaceae. Moreover, they indicated the possibility that the three names might actually represent a single species, although the male of L. glabrus has a sternal pore plate whereas this is apparently absent in hungaricus. Given the few known specimens, it is not possible to know if these thrips live under bark and feed on fungal hyphae, or if the few specimens collected were actually leaf-feeders that were sheltering under bark. In this paper, a new species of the genus is described from southern Iran, based on both sexes. These specimens were extracted from leaf litter using a Berlese funnel, thus again it is not possible to be certain if the species is part of the community of fungus-feeding litter thrips, or if the specimens were merely sheltering. 

Diagnosis of ectopic pregnancy by the rate of increase of choriogonadotropin in serum: diagnostic criteria compared

1990 ◽  
Vol 36 (12) ◽  
pp. 2097-2101 ◽  
Author(s):  
K Emancipator ◽  
J L Bock ◽  
M D Burke
Keyword(s):  
Ectopic Pregnancy ◽  
Diagnostic Criteria ◽  
Lower Limit ◽  
Normal Pregnancy ◽  
Rate Of Change ◽  
The Other ◽  
Human Choriogonadotropin ◽  
Rate Of Increase ◽  
Sampling Intervals ◽  
Lower Limit Of Normal

Abstract We compare three methods for using the rate of change of human choriogonadotropin (hCG) concentration in serum to diagnose ectopic pregnancy. With Method I, the lower limit for the rate of increase of serum hCG in normal pregnancy is 66% per 48 h. With Method II, a different lower limit of normal is specified for each of four discrete sampling intervals of hCG. With Method III, the lower limit of normal is determined by a continuous discriminant function of the initial hCG concentration. If the initial hCG concentration is less than or equal to 2000 int. units/L (Second International Standard), all three methods have acceptable diagnostic efficiencies, and there are no statistically significant differences among conclusions from the methods. None of the three methods performs satisfactorily if the initial hCG concentration is greater than 2000 int. units/L. We recommend Method I because it is simpler than the other two.

Language maintenance in the second generation

1992 ◽  
Vol 15 (1) ◽  
pp. 53-70 ◽  
Author(s):  
E. Jane Bennett
Keyword(s):  
Statistical Analysis ◽  
Positive Attitude ◽  
Second Generation ◽  
Language Maintenance ◽  
Census Data ◽  
The Other ◽  
English Only ◽  
Frequency Of Use ◽  
Computer Aided ◽  
Maintenance Activities

Abstract The article discusses the attitude of the second generation Dutch in Australia to language maintenance. It gives a profile of the group’s language maintenance activities, and examines factors related to language maintenance attitudes and the use of Dutch. The research involved detailed personal interviews with 100 members of the target group. Some of the information collected was evaluated quantitatively using computer-aided statistical analysis; other responses were analysed primarily in qualitative terms. The results revealed a more positive attitude to language maintenance and greater frequency of use of Dutch than might have been expected on the basis of the (limited) previous research on the second generation or the national census data. On the other hand, there was relatively little participation in activities with the potential to influence the use of Dutch: visits to the Netherlands, association with Dutch organizations, and attendance at Dutch classes. Overall the research provided no evidence of a continuing decline in frequency of use of Dutch to the point of a complete shift to English only. It was also clear that many informants valued their current use of Dutch.

EFFECT OF ANTICHOLINESTERASES ON ACETYLCHOLINI LEVELS IN INSECTS

1958 ◽  
Vol 36 (6) ◽  
pp. 575-586 ◽  
Author(s):  
B. N. Smallman ◽  
R. W. Fisher
Keyword(s):  
Normal Level ◽  
Nerve Cord ◽  
Nervous Tissue ◽  
The Body ◽  
The Other ◽  
Steady Increase ◽  
Partial Recovery ◽  
Rate Of Increase ◽  
Sublethal Doses ◽  
Lethal Doses

In accordance with the hypothesis for the lethal action of organophosphate insecticides, the ACh content of the nervous tissue of poisoned insects was shown to increase, and the rate of increase to depend on the degree and duration of ChE inhibition. Lethal doses of parathion, malathion, and TEPP caused increases in the ACh content of housefly heads up to 260% above normal; increased levels of ACh were also found in the thoracic nerve cord of roaches and the brains of mice after treatment with TEPP. Sublethal doses of TEPP resulted in transitory depression of ChE activity coinciding with a limited elevation of ACh levels followed by a return to normal; lethal doses resulted in prolonged inactivation of ChE and a corresponding steady increase of ACh to 90% above the normal level. Subsequent partial recovery of ChE activity, observed with lethal doses of TEPP and malathion, coincided with a fall in ACh values to below normal. At death, a portion of the ACh normally bound to tissue components is released and hydrolyzed by ChE. In contrast to the other compounds, DFP reduced the ACh levels in the heads of treated flies. The loss from the heads was associated with an equivalent gain by the rest of the body of DFP-treated flies. The ACh content of whole flies therefore remained constant (at 20% above normal) after treatment with DFP suggesting that this compound, unlike the others examined, interferes with the synthesis of ACh.

scholarly journals A revision of the Pyura stolonifera species complex (Tunicata, Ascidiacea), with a description of a new species from Australia

Zootaxa ◽  
2011 ◽  
Vol 2754 (1) ◽  
pp. 27 ◽  
Author(s):  
MARC RIUS ◽  
PETER R. TESKE
Keyword(s):  
New Species ◽  
Species Complex ◽  
Taxonomic Status ◽  
Single Species ◽  
Distinct Species ◽  
The Other ◽  
Solitary Ascidian ◽  
Different Populations ◽  
A New Species ◽  
Dorsal Tubercle

Pyura stolonifera is a large solitary ascidian found in Africa, Australasia and South America. The taxonomic status of different populations of this species is disputed, especially since there is evidence for several distinct morphological and genetic units that point towards the existence of multiple cryptic species. While some researchers still recognize P. stolonifera as a single species, others treat the different populations as distinct species. Here, we present a revision of the P. stolonifera species complex based on the examination of samples from all regions where there are reliable reports of this taxon. We recognize four species that are both morphologically and genetically distinct, one of which is new to science and is formally described here. This species is morphologically distinct from the other three members of the species complex in terms of the colour and texture of the tunic, the arrangement of the gonads within the gut and the shape of the dorsal tubercle, among other characters. We name the new species Pyura dalbyi after Dr. J.E. Dalby Jr., whose research on its ecology and distribution provided the incentive for examining this species more closely.

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