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PubMedDate not supplied

Differential expression of peroxidase isogenes during the early stages of infection of the tropical forage legume Stylosanthes humilis by Colletotrichum gloeosporioides.

Infection of Stylosanthes humilis by the fungal phytopathogen Colletotrichum gloeosporioides is associated with an increase in peroxidase enzyme activity within 24 h postinoculation. Peroxidase gene expression was investigated as a first step towards understanding the regulation and functional importance of this host response to fungal attack. Four distinct cDNAs Shpx 2, 5, 6, and 12, isolated from a cDNA library of S. humilis contained deduced amino acid (aa) sequence motifs characteristic of peroxidases. Three of these (Shpx 2, 5, and 6) were full-length and their deduced proteins each fell into a different homology group based on comparisons with other plant peroxidases. Each cDNA appeared to hybridize to only one or two genes in S. humilis. mRNAs corresponding to Shpx2, Shpx6, and Shpx12 were expressed relatively abundantly in young leaves, with lesser expression of Shpx2 and Shpx6 and no expression of Shpx12 detected in roots. No expression of these genes was detected in stems or old leaves. The mRNA of Shpx5 was relatively abundant in stems and to a lesser extent in young leaves. However, infection of young leaves with C. gloeosporioides greatly increased expression of the mRNAs of Shpx2 and Shpx6 but not Shpx5 nor Shpx12 compared to mock-inoculated controls. The mRNA of Shpx6 was strongly induced by the pathogen 4 h postinoculation, a time which precedes fungal penetration, while Shpx2 was induced to higher levels than controls at 24 h after inoculation. The mRNAs of both Shpx2 and Shpx6 but not Shpx5 and Shpx12 were also induced by wounding.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Transfer kinetics and coefficients of 90Sr, 134Cs, and 137Cs from forage contaminated by Chernobyl fallout to milk of cows.

A experiment was conducted to study kinetics, transfer coefficients, and biological half-lives of 90Sr, 134Cs, and 137Cs from feed to milk. A cow was fed a diet containing alfalfa hay contaminated by Chernobyl fallout for 14.5 wk. The time-dependent activity in milk was approximated by a two-compartment model with fast biological half-lives of 2, 0.9, and 1 d and slow biological half-lives of 36.9, 8.7, and 12.4 d for 90Sr, 134Cs, and 137Cs, respectively. The transfer coefficients determined in the experiment were 0.0008 d L-1 for 90Sr, 0.0029 d L-1 for 134Cs, and 0.0031 d L-1 for 137Cs. The biological elimination phases of 134Cs and 137Cs were described by a two-compartment model while a one-compartment model was proposed for 90Sr.

Accidents↗
PubMed2000

Daily foraging routines and feeding effort of a small bird feeding on a predictable resource.

According to theory, a small diurnal bird living in a predictable environment should have the highest feeding effort as late as possible in the day in order to minimize the time it carries large and costly reserves. The feeding effort should also decline with increasing food availability. We tested both these ideas with the lesser spotted woodpecker (Dendrocopos minor). For most of the year, this bird feeds on wood-living insects in dead tree branches. This food supply is likely to be highly predictable on a daily scale. Our results corroborated the theory. We found that the proportion of time spent actively feeding was lower in the mornings (before noon) than in the afternoons. We also found that woodpeckers spent less time feeding the higher their food availability However, for a given food availability they spent more time feeding in the afternoons. This supports the idea that feeding is less and other activities are more valuable in the mornings given a predictable food resource. This is the first demonstration of daily routines in small birds concordant with a predictable environment. In spring, males but not females reduced their feeding time. This difference between the sexes may be related to their sex-specific reproductive effort.

Animals↗
PubMed2001

Separating the effects of predation risk and interrupted foraging upon mass changes in the blue tit Parus caeruleus.

The optimal amount of reserves that a small bird should carry depends upon a number of factors, including the availability of food and environmental predation risk levels. Theory predicts that, if predation risk increases, then a bird should maintain a lower level of reserves. Previous experiments have given mixed results: some have shown reduced reserves and some, increased reserves. However, the birds in these studies may have been interpreting a staged predation event as a period when they were unable to feed rather than a change in predation risk: theory predicts that, if the food supply within the environment is variable, then reserves should be increased. In the present study, we presented blue tits (Parus caeruleus) with a potential predator and compared this response (which could have been potentially confounded by perceived interruption effects) with a response to an actual interruption in the environment during both long and short daytime lengths. During long (but not short) days, the birds responded in line with theoretical predictions by increasing their reserves in response to interruption and reducing them in response to predation. These results are examined in the light of other experimental manipulations and we discuss how well experimental tests have tested the predictions made by theoretical models.

Animals↗
PubMed2004

Risk allocation and competition in foraging groups: reversed effects of competition if group size varies under risk of predation.

Animals often feed more quickly when in larger groups. This group-size effect is often explained by safety advantages for groups but an alternative explanation is that animals feed faster in larger groups because of greater scramble competition for limited food. We show that predation risk enhances the group-size effect if groups vary in size. By contrast, competition leads to the group-size effect only when individuals feed in groups of constant size. When individuals feed in groups that vary in size, the best strategy for dealing with competition is to feed intensely when in smaller groups and feed little when in larger (more competitive) groups. In all situations, the effects of competition interact with the effects of predation risk in a simple multiplicative way. Our results suggest that scramble competition is not a general explanation for the group-size effect on vigilance in situations where group size changes relatively rapidly.

Animals↗
PubMed1991

Hominid carnivory and foraging strategies, and the socio-economic function of early archaeological sites.

New evidence for the tissue types exploited by early hominids from carcasses possibly acquired through scavenging is derived from the larger mammal bone assemblages from FLK I, level 22 (Zinjanthropus floor), and FLKN levels 1 and 2 from Bed I, Olduvai Gorge, Tanzania. Published skeletal part profiles from the two archaeological sites are evaluated using (i) modern observations on the sequence by which carnivores consume carcass parts in order to assess the timing of hominid access to carcasses, and (ii) measurements of flesh and marrow yields to assess the tissue types sought and acquired. These results suggest that the maximization of marrow (fat) yields, not flesh (protein) yields, was the criterion shaping decisions about carcass processing. Because of evidence for density-dependent destruction of some flesh-bearing parts by scavengers of the hominid-butchered assemblages, however, it is uncertain whether carcass parts were transported and acquired by hominids in a largely defleshed condition. The results on tissue types acquired are combined with a discussion of predation risk, feeding competition and the equipment needs of carcass processing in an attempt to identify archaeological test implications of competing hypotheses for the socio-economic function of the earliest archaeological sites.

Animals↗
PubMed2004

Stability analysis of social foraging swarms.

In this article we specify an M-member "individual-based" continuous time swarm model with individuals that move in an n-dimensional space according to an attractant/repellent or a nutrient profile. The motion of each individual is determined by three factors: i) attraction to the other individuals on long distances; ii) repulsion from the other individuals on short distances; and iii) attraction to the more favorable regions (or repulsion from the unfavorable regions) of the attractant/repellent profile. The emergent behavior of the swarm motion is the result of a balance between inter-individual interactions and the simultaneous interactions of the swarm members with their environment. We study the stability properties of the collective behavior of the swarm for different profiles and provide conditions for collective convergence to more favorable regions of the profile.

Animal Migration↗