To examine the impact of regional and seasonal variations on the incidence and severity of sheath rot, a major seed-borne disease of rice caused by Sarocladium oryzae, data on incidence and severity were collected from 27 selected fields in the Gazipur, Rangpur, Bogra, Chittagong, Comilla, Gopalgonj, Jessore, Manikgonj, and Bhola districts of Bangladesh in rain-fed and irrigated conditions. Cultural variability of 29 pathogen isolates obtained from 8 different locations was studied on potato dextrose agar (PDA) and genetic variability was determined by DNA fingerprinting using variable number tandem repeat-polymerase chain reaction markers. Overall, disease incidence and severity were higher in irrigated rice. Disease incidence and severity were highest in the Bhola district in rain-fed rice and lowest in irrigated rice. Mycelial growth of 29 representative isolates was found to vary on PDA and the isolates were divided into 6 groups. The range of the overall size of conidia of the selected isolates was 2.40-7.20 x 1.20-2.40 μm. Analysis of the DNA fingerprint types of the 29 isolates of S. oryzae, obtained from the amplification reactions, revealed 10 fingerprinting types (FPTs) that were 80% similar. FPT-1 was the largest group and included 13 isolates (44.8%), while FPT-2 was the third largest group and included 3 isolates. Each of FPT-3, 4, 5, and 6 included only 1 isolate. We observed no relationship between cultural and genetic groupings.
BACKGROUND: Allopatric populations present challenges for biologists working with vectors. We suggest that conspecificity can be concluded in these cases when data from four character sets-chromosomal, ecological, molecular, and morphological-express variation no greater between the allopatric populations than between corresponding sympatric populations. We use this approach to test the conspecificity of Simulium nodosum Puri on the mainland of Southeast Asia and Simulium shirakii Kono & Takahasi in Taiwan. The validity of these two putative species has long been disputed given that they are morphologically indistinguishable.
FINDINGS: The mitochondria-encoded cytochrome c oxidase subunit I (COI), 12S rRNA, and 16S rRNA genes and the nuclear-encoded 28S rRNA gene support the conspecific status of S. nodosum from Myanmar, Thailand, and Vietnam and S. shirakii from Taiwan; 0 to 0.19 % genetic differences between the two taxa suggest intraspecific polymorphism. The banding patterns of the polytene chromosomes of the insular Taiwanese population of S. shirakii and mainland populations of S. nodosum are congruent. The overlapping ranges of habitat characteristics and hosts of S. nodosum and S. shirakii corroborate the chromosomal, molecular, and morphological data.
CONCLUSIONS: Four independent sources of evidence (chromosomes, DNA, ecology, and morphology) support the conspecificity of S. nodosum and S. shirakii. We, therefore, synonymize S. shirakii with S. nodosum. This study provides a guide for applying the procedure of testing conspecificity to other sets of allopatric vectors.
Samples of mangrove snails Nerita lineata and surface sediments were collected from nine geographical sampling sites in Peninsular Malaysia to determine the concentrations of eight metals. For the soft tissues, the ranges of metal concentrations (μg g(-1) dry weight (dw)) were 3.49-9.02 for As, 0.69-6.25 for Cd, 6.33-25.82 for Cu, 0.71-6.53 for Cr, 221-1285 for Fe, 1.03-50.47 for Pb, and 102.7-130.7 for Zn while Hg as 4.00-64.0 μg kg(-1) dw(-1). For sediments, the ranges were 21.81-59.49 for As, 1.11-2.00 for Cd, 5.59-28.71 for Cu, 18.93-62.91 for Cr, 12973-48916 for Fe, 25.36-172.57 for Pb, and 29.35-130.34 for Zn while for Hg as 2.66-312 μg kg(-1) dw(-1). To determine the ecological risks on the surface habitat sediments, sediment quality guidelines (SQGs), the geochemical indices, and potential ecological risk index (PERI) were used. Based on the SQGs, all the metals investigated were most unlikely to cause any adverse effects. Based on geoaccumulation index and enrichment factor, the sediments were also not polluted by the studied metals. The PERI values based on As, Cd, Cu, Cr, Hg, Pb and Zn in this study were found as 'low ecological risk'. In order to assess the potential health risks, the estimated daily intakes (EDI) of snails were found to be all lower than the RfD guidelines for all metals, except for Pb in some sites investigated. Furthermore, the calculated target hazard quotients (THQ) were found to be less than 1. However, the calculated total target hazard quotients (TTHQ) from all sites were found to be more than 1 for high level consumers except KPPuteh. Therefore, moderate amount of intake is advisable to avoid human health risks to the consumers.
In Peninsular Malaysia child mortality rates (5q0) vary from 13 to 63 per thousand at district level. The spatial pattern is closely associated with the regional distribution of socio-economic factors. But due to multicollinearity it is difficult to isolate the influence of socio-economic variables from other variables by employing aggregated data. However, individual data collected in a case-control-study that was conducted in Perlis and Kuala Terengganu confirm the important role of socio-economic factors. So it should be possible to achieve a further reduction of child mortality by raising the income and educational level of the under-privileged groups. Apart from that, as the case of Perlis shows, the provision of family planning and preventive medical services may also contribute to lower child mortality independent from socio-economic changes. But, as the comparison with Kuala Terengganu shows, the utilization of family planning and preventive medical services is not only influenced by the accessibility to, but also by the socio-culturally determined acceptability of such services.
Studies on age groups within activity cycles, age composition and survivorship in natural populations of Mansonia in Kampung Pantai, Bengkoka Peninsula of Sabah state have been described. Early activity of 3-5 parous Ma. bonneae during the first hour after sunset was noted. Age composition of Ma. bonneae at forest shade, indoor and outdoor of house, comparative buffalo vs human bait outdoor in Kampung Pantai showed all round high parous rates ranging from 66.7 to 75.4%. Population 3-parous and older ranged from 18.8 to 26.7%. Nine of the 14 infective Ma. bonneae were 3-parous and this segment of the population was engaged in active transmission. High parous rates were observed in Ma. dives and Ma. uniformis taken in small numbers. Parous rates of Ma. bonneae taken in Kampung Delima and Kampung Taradas were also high. Estimates of daily survivorship of Ma. bonneae and Ma. dives determined by two methods were very high.
Tetrahymena of the T. pyriformis complex collected from varied habitats in Malaysia, Thailand, and The People's Republic of China include strains of the micronucleate species T. americanis and T. canadensis and the amicronucleate T. pyriformis and T. elliotti. Two new breeding species are described-T. malaccensis from Malaysia and T. asiatica from China and Thailand. Two wild selfers from China and some of the amicronucleate strains from all three countries fall into isozymic groups similar to named micronucleate and amicronucleate species. The T. patula complex is represented by two groups of clones from Malaysia that fit the morphological description of T. vorax. They, however, have radically different isozymic electrophoretic patterns and both groups differ from those of previously described T. vorax. As their molecules indicate relationships to other "T. vorax" strains as distant as that between T. vorax and T. leucophrys, they are considered to be new species, T. caudata and T. silvana. A third new breeding species, T. nanneyi, was identified among strains previously collected in North America. Viable immature progeny were obtained from the new strains of the five breeding species. Maximum temperature tolerances were determined for the new strains of four of the breeding species.
In this study, concentrations of heavy metals, rare earth elements (REEs), Uranium (U) and Thorium (Th) of the actinide group were determined from Linggi estuary sediment samples by neutron activation analysis (NAA) and inductive coupled plasma - mass spectrometry techniques. The geo-accumulation (Igeo) and ecological risk index (Ri) values were calculated to identify the quality status of Linggi estuary sediments. Results indicated Linggi estuary was polluted by arsenic (As), lead (Pb) and antimony (Sb). REEs, U and Th showed significant increase of concentration in Linggi estuary sediments. Ri of Linggi estuary was categorised as low to considerable ecological risk, which indicates no significant to moderate effect on the majority of the sediment-dwelling organisms. Correlation matrix and principal component analysis assessed pollution sources to be both natural and anthropogenic.
Clostridium bifermentans serovar malaysia (C.b.m.) is highly toxic to mosquito larvae. In this study, the following aquatic nontarget invertebrates were treated with high C.b.m. concentrations (up to 1,600-fold the toxic concentration for Anopheles stephensi) to study their susceptibility towards the bacterial toxin: Planorbis planorbis (Pulmonata); Asellus aquaticus (Isopoda); Daphnia pulex (Cladocera); Cloeon dipterum (Ephemeroptera); Plea leachi (Heteroptera); and Eristalis sp., Chaoborus crystallinus, Chironomus thummi, and Psychoda alternata (Diptera). In addition, bioassays were performed with mosquito larvae (Aedes aegypti, Anopheles stephensi, and Culex pipiens). Psychoda alternata larvae were very susceptible, with LC50/LC90 values comparable to those of mosquito larvae (about 10(3)-10(5) spores/ml). The tests with Chaoborus crystallinus larvae showed significant mortality rates at high concentrations, but generally not before 4 or 5 days after treatment. The remaining nontarget organisms did not show any susceptibility. The investigation confirms the specificity of C.b.m. to nematocerous Diptera.
The authors review common themes in the ecology of emerging viruses that cause neurological disease. Three issues emerge. First, 49% of emerging viruses are characterized by encephalitis or serious neurological clinical symptoms. Second, all of these viruses are driven to emerge by ecological, environmental, or human demographic changes, some of which are poorly understood. Finally, the control of these viruses would be enhanced by collaborative multidisciplinary research into these drivers of emergence. The authors highlight this review with a case study of Nipah virus, which emerged in Malaysia due largely to shifts in livestock production and alterations to reservoir host habitat. Collaboration between virologists, ecologists, disease modelers and wildlife biologists has been instrumental in retracing the factors involved in this virus's emergence.
This study aimed to evaluate the spatial and temporal distribution of heavy metals (Cd, Cr, Cu, Co, Fe, Pb, Ni, V, and Zn) in the sediments of Bayan Lepas Free Industrial Zone of Penang, Malaysia. Ten sampling stations were selected and sediment samples were collected during low tide (2012-2013). Metals were analyzed and the spatial distribution of metals were evaluated based on GIS mapping. According to interim sediment quality guidelines (ISQG), metal contents ranged from below low level to above high level at different stations. Based on the geoaccumulation index (Igeo) of sediment, sampling stations were categorized from unpolluted to strongly polluted. The enrichment factor (EF) of metals in the sediment varied between no enrichment to extremely high enrichment. The potential ecological risk index (RI) indicated Bayan Lepas FIZ was at low risk.
The geographic distribution and habitat association of most mammalian polymorphic phenotypes are still poorly known, hampering assessments of their adaptive significance. Even in the case of the black panther, an iconic melanistic variant of the leopard (Panthera pardus), no map exists describing its distribution. We constructed a large database of verified records sampled across the species' range, and used it to map the geographic occurrence of melanism. We then estimated the potential distribution of melanistic and non-melanistic leopards using niche-modeling algorithms. The overall frequency of melanism was ca. 11%, with a significantly non-random spatial distribution. Distinct habitat types presented significantly different frequencies of melanism, which increased in Asian moist forests and approached zero across most open/dry biomes. Niche modeling indicated that the potential distributions of the two phenotypes were distinct, with significant differences in habitat suitability and rejection of niche equivalency between them. We conclude that melanism in leopards is strongly affected by natural selection, likely driven by efficacy of camouflage and/or thermoregulation in different habitats, along with an effect of moisture that goes beyond its influence on vegetation type. Our results support classical hypotheses of adaptive coloration in animals (e.g. Gloger's rule), and open up new avenues for in-depth evolutionary analyses of melanism in mammals.
1. Of the scarce Calyptra minuticornis, C. orthograpta and C. labilis, 51, 24, and 7 adults, respectively, were observed during some 600 night inspections at over 100 sites in 1965--1967 and 1971--1977. 2. Hitherto biologically completely unknown, and not recorded before in S.E. Asia, the latter two species flew in or near tropical monsoon forests in hilly regions (300--600 m) of N. Thailand (C. orthograpta also N. Laos). C. minuticornis was found in these and in tropical evergreen and semi-evergreen rain forests of S. Thailand and N.W. Malaysia. 3. In N. Thailand the three species were more common at the end of the cool season/start of the hot season and at the start of the rainy season. They were active mainly during the first half of the night 4. Flight and piercing behaviour, alighting, resting, enemies, and the lack of females, were similar to virtually identical with the "classical" skin-piercing blood-sucking C. eustrigata. 5. C. labilis was seen attacking elephant, C. orthograpta also water buffalo and sambar, C. minuticornis also zebu and tapir but not sambar. C. minuticornis settled on man also but did not pierce. 6. Through no piercing of hosts' skin has actually been seen in nature, indirect evidence suggests that the 3 moths are likely to be occasional blood-suckers. They pierced and sucked blood from the author's skin in experiments. 7. Reasons for lack of direct evidence may be: less developed hematophagy, less favoured hosts, lack of easy-to-pierce injured skin (which also trigger the piercing response), different climatic and phytoecological environment, fewer specimens than in the case of C. eustrigata. 8. Field observations and experiments indicate that the closely related, fruit-piercing Oraesia emarginata is not skin-piercing blood-sucking--a habit likely to be exhibited mainly in humid equatorial regions by a few Calyptra only.
The fluorescent antibody (FA) technique was used to detect the presence of malarial antibody in populations living in 3 different ecological areas of Malaysia. Serum samples were tested using Plasmodium falciparum, P. vivax, P. malariae and P. fieldi antigens. An area of hyperendemic malaria had a good correlation between the antibody responses and active parasitaemias. The percentage and intensity of responses increased with the age of the individuals. In an area of hypoendemic malaria, each of 17 sites had ecological conditions which would favour or discourage the transmission of malaria. The reasons for high FA responses in some villages and low responses in others were readily apparent. The effect of even limited control programmes on the malarial ecology could be measured by an examination of the antibody responses. An aboriginal population receiving suppressive drugs had FA responses indicating both past experience and the effect of the drug programme.
The world’s biodiversity is not distributed uniformly throughout the globe. Some areas such as the tropical rainforests, seas and coral reefs teem with the varieties of life whereas others such as some deserts and polar regions are almost devoid of them (Gaston, 2000). Malaysia, with her tropical jungles and seas, is rich with biodiversity. She is fortunate to have had eminent pioneers such as Ridley (1967), Corner (1972), Soepadmo (1972) and Whitmore (1983) to study her flora and Medway (1968) and Lim (1991) to study her fauna taxonomy. Other pioneers in Malaysian biology included Berry, Dhaliwal and Mohsin. These pioneers are then ably followed by workers such as Latiff, Kiew, Go, Khoo, Davidson, Saberi, Omar, Jambari, Idris, Zekri, Teo, Marziah, Tan, Mukherjee, Shapor, Yusoff, Azmi and many others studying the various subdisciplines of biology. In addition to the more obvious large plants and animals, microorganisms and aquatic organisms had not been neglected either. Workers such as Nawawi, Verghese, Ho and Faridah are known
for their work on fungi while Fatimah, Phang, Japar and Anton had studied algae, seaweeds, diatoms and seagrasses. However, some of these workers have now either retired or are soon going to attain retirement age and the worrying part is that there are not many younger
workers keen to pursue research in taxonomy and biosystematics, a prerequisite to further studies in ecology, genetics, biotechnology which in turn are prerequisites for rational conservation, management and sustainable utilization of our rich biological resources. With each passing day species are becoming extinct sometimes without us even knowing that they had ever existed. Even in a developed country such as the USA, one third of her plant and animal species are at risk of extinction (McCann, 2000). Hence, taxonomic and biosystematic studies of our plants, animals and microbes whether terrestrial or aquatic, freshwater and marine, should be priority areas. So should studies on their reproductive biology, life cycles, physiology, feeding habits, migration patterns, predators and their sensitivities to environmental changes.
The overall comparisons of habitats are given in (Table III). The habitats are arranged in order of extent of alterations by man, with the least disturbed at the top. The highest average blood isolation rates came from the least disturbed areas. The highest monthly maximal rickettsial isolation rates from blood and maximal prevalence rates of antibody per month were also obtained at Bukit Lanjan, the habitat least altered by activities of man. The lowest average blood isolation rate (6%) and the lowest monthly maximal rickettsial isolation and antibody prevalence rates were obtained at Bukit Mandol, the habitat most extensively and intensively altered by man. The intermediate habitats had intermediate rates. We caution anyone interpreting these observations, however, in terms of human disease, which seem to be associated with hyperendemic foci. Here we are not dealing with hyperendemicity from the standpoint of human disease, but present evidence of widespread endemicity from which hyperendemic foci may derive. Also, we have not yet identified the prevalent strains and do not know their infectivity to man.