RICE AS A TRAP CROP FOR THE RICE FIELD RAT IN MALAYSIA

The potential of rice as a trap crop for the rice field rat, Rattus argentiventer. was clearly illustrated by the studies conducted in 60.7 ha of newly rehabilitated rice land in Pcrmatang Pauh and in the MARDI Research Centre\u27s rice fields in Bumbong Lima. The rice crop was very attractive to the rats, especially at the reproductive phase. The combina¬tion of a physical barrier and traps was very effective in exploiting rice as a trap crop for rice field rats. The trapping patterns indicated a massive influx of rats from the surroundings for a period of three weeks in Permatang Pauh and of a lesser degree in Bumbong Lima. In Permatang Pauh, adult male rats caught ranged in weights of 116-293 g and females 85-230 g. Very few subadults were caught, only 2.3% or 35/1550 measured, whereas in rice fields cultivated continuously, young and adult rats were caught (84 adults to 116 young, or 58% of the rats caught were subadults and juveniles) as in the case of the population in Bumbong Lima. The sex ratio in the Permatang Pauh population showed a preponderance of males in the first two weeks but eventually more females appeared in the 4th and 5th week. The overall sex ratio was 1236 males to 1107 females (a ratio of 1.12:1), which did not depart from the expected ratio of 1:1. The total number of rats caught was 2343 in the first season but in the second season only 24 rats, 22 R. argentiventer (16 males and 6 females; sex ratio of 2.7:1) and a pair of Rattus rattus diardii were caught in Permatang Pauh. In the Bumbong Lima population, the sex ratio for adults was 37 males to 47 females (0.7:1) and in the young 75 males to 41 females (1.8:1). Rats were attracted to the crop only when the adjacent areas were harvested and, as the crop in the surrounding areas matured, the number of rats caught declined and reached zero at the booting phase. Rice at the early reproductive phase is an effective lure for the rice field rats and thus could be used as an efficient trap crop for its control

RICE AS A TRAP CROP FOR THE RICE FIELD RAT IN MALAYSIA

The potential of rice as a trap crop for the rice field rat, Rattus argentiventer. was clearly illustrated by the studies conducted in 60.7 ha of newly rehabilitated rice land in Pcrmatang Pauh and in the MARDI Research Centre\u27s rice fields in Bumbong Lima. The rice crop was very attractive to the rats, especially at the reproductive phase. The combina¬tion of a physical barrier and traps was very effective in exploiting rice as a trap crop for rice field rats. The trapping patterns indicated a massive influx of rats from the surroundings for a period of three weeks in Permatang Pauh and of a lesser degree in Bumbong Lima. In Permatang Pauh, adult male rats caught ranged in weights of 116-293 g and females 85-230 g. Very few subadults were caught, only 2.3% or 35/1550 measured, whereas in rice fields cultivated continuously, young and adult rats were caught (84 adults to 116 young, or 58% of the rats caught were subadults and juveniles) as in the case of the population in Bumbong Lima. The sex ratio in the Permatang Pauh population showed a preponderance of males in the first two weeks but eventually more females appeared in the 4th and 5th week. The overall sex ratio was 1236 males to 1107 females (a ratio of 1.12:1), which did not depart from the expected ratio of 1:1. The total number of rats caught was 2343 in the first season but in the second season only 24 rats, 22 R. argentiventer (16 males and 6 females; sex ratio of 2.7:1) and a pair of Rattus rattus diardii were caught in Permatang Pauh. In the Bumbong Lima population, the sex ratio for adults was 37 males to 47 females (0.7:1) and in the young 75 males to 41 females (1.8:1). Rats were attracted to the crop only when the adjacent areas were harvested and, as the crop in the surrounding areas matured, the number of rats caught declined and reached zero at the booting phase. Rice at the early reproductive phase is an effective lure for the rice field rats and thus could be used as an efficient trap crop for its control

Toxicity and palatability of scilliroside to Rattus argentiventer (Kebisaan dan keenakan scilliroside terhadap Rattus argentiventer)

Abstrak Scilliroside telah diuji di dalam makmal terhadap tikus Rattus argentiventer. Takaran tunggal (oral) LD 50 bagi R. argentiventer ialah 0.64 mg/kg dan LD 99 ialah 2.21 mg/kg. Tikus jantan mati 2.3 (SE 0.3) hari setelah diberi makan racun manakala tikus betina mati selepas 1.8 (SE 0.2) hari. Dalam ujian pemakanan sehari tanpa pilihan, scilliroside tidak dapat membunuh 100% kedua-dua jantina tikus kerana kurang umpan dimakan. Takaran yang paling rendah yang membawa maut pada tikus jantan ialah 0.06 mg/kg dan takaran tertinggi yang dimakan dan tikus terus hidup ialah 1.21 mg/kg. Untuk tikus betina pula, takaran yang paling rendah yang membawa maut ialah 0.10 mg/kg dan takaran tertinggi yang dimakan dan tikus terus hidup ialah 0.46 mg/kg. Bilangan hari purata sebelum mati bagi tikus jantan ialah 2.0 (SE 0.6) hari dan bagi tikus betina pula 2.5 (SE 0.7) hari. Ujian perasa menunjukkan bahawa scilliroside tidak sedap pada R. argentiventer dan ini mengakibatkan bilangan kematian kedua-dua jantina tikus kecil kerana kurang makan umpan racun. Tikus dapat mengesani racun scilliroside pada kepekatan yang paling rendah yang diuji (0.01%) dan ini mengakibatkan umpan racun yang kurang dimakan. Abstract Scilliroside was evaluated against Rattus argentiventer in the laboratory. The median lethal doses (LD 50 ) of scilliroside against R. argentiventer was 0.64 mg/kg and the LD 99 was 2.21 mg/kg. Corrected mean days to death in rats succumbing to a lethal dose by gavage were 2.3 (SE 0.3) days in males and 1.8 (SE 0.2) days in females. Scilliroside at all the concentrations tested did not elicite 100% mortality in both sexes in 1-day no-choice tests as a result of poor bait consumption. The lowest lethal dose was 0.06 mg/kg and the highest dose survived was 1.21 mg/kg in males. In females, the lowest lethal dose was 0.10 mg/kg and the highest dose survived was 0.46 mg/kg. Corrected mean days to death in rats succumbing to a lethal dose in no-choice feeding tests were 2.0 (SE 0.6) days in males and 2.5 (SE 0.7) days in females. Palatability studies (4-day choice feeding tests) indicated that scilliroside at all the concentrations tested showed poor palatability against R. argentiventer, giving low mortality for both sexes as a result of poor consumption of the poison baits. Rats were able to detect scilliroside at the lowest concentration tested (0.01%), resulting in very poor bait consumption

Generalized Background-Field Method

The graphical method discussed previously can be used to create new gauges not reachable by the path-integral formalism. By this means a new gauge is designed for more efficient two-loop QCD calculations. It is related to but simpler than the ordinary background-field gauge, in that even the triple-gluon vertices for internal lines contain only four terms, not the usual six. This reduction simplifies the calculation inspite of the necessity to include other vertices for compensation. Like the ordinary background-field gauge, this generalized background-field gauge also preserves gauge invariance of the external particles. As a check of the result and an illustration for the reduction in labour, an explicit calculation of the two-loop QCD $\beta$-function is carried out in this new gauge. It results in a saving of 45% of computation compared to the ordinary background-field gauge.Comment: 17 pages, Latex, 18 figures in Postscrip

Gauge Consistent Wilson Renormalization Group II: Non-Abelian Case

We give a wilsonian formulation of non-abelian gauge theories explicitly consistent with axial gauge Ward identitities. The issues of unitarity and dependence on the quantization direction are carefully investigated. A wilsonian computation of the one-loop QCD beta function is performed.Comment: 34 pages, 1 eps figure, latex2e. Minor changes, version to appear in Int. J. Mod. Phy

Parallel developmental genetic features underlie stickleback gill raker evolution.

BackgroundConvergent evolution, the repeated evolution of similar phenotypes in independent lineages, provides natural replicates to study mechanisms of evolution. Cases of convergent evolution might have the same underlying developmental and genetic bases, implying that some evolutionary trajectories might be predictable. In a classic example of convergent evolution, most freshwater populations of threespine stickleback fish have independently evolved a reduction of gill raker number to adapt to novel diets. Gill rakers are a segmentally reiterated set of dermal bones important for fish feeding. A previous large quantitative trait locus (QTL) mapping study using a marine × freshwater F2 cross identified QTL on chromosomes 4 and 20 with large effects on evolved gill raker reduction.ResultsBy examining skeletal morphology in adult and developing sticklebacks, we find heritable marine/freshwater differences in gill raker number and spacing that are specified early in development. Using the expression of the Ectodysplasin receptor (Edar) gene as a marker of raker primordia, we find that the differences are present before the budding of gill rakers occurs, suggesting an early change to a lateral inhibition process controlling raker primordia spacing. Through linkage mapping in F2 fish from crosses with three independently derived freshwater populations, we find in all three crosses QTL overlapping both previously identified QTL on chromosomes 4 and 20 that control raker number. These two QTL affect the early spacing of gill raker buds.ConclusionsCollectively, these data demonstrate that parallel developmental genetic features underlie the convergent evolution of gill raker reduction in freshwater sticklebacks, suggesting that even highly polygenic adaptive traits can have a predictable developmental genetic basis