Northwestern Peninsular Malaysia Research Articles

Evaluation of mentum deformities of Chironomus spp. (Chironomidae: Diptera) larvae using modified toxic score index (MTSI) to assess the environmental stress in Juru River Basin, Penang, Malaysia

Morphological mentum deformities which represent sublethal effect of exposure to different types of pollutants were evaluated in Chironomus spp. larvae inhabiting three polluted rivers of Juru River Basin in northwestern peninsular Malaysia. Using mentum deformity incidences, the modified toxic score index (MTSI) was developed based on Lenat's toxic score index (TSI). The suggested MTSI was compared with TSI in terms of its effectiveness to identify different pollutants including heavy metals. The MTSI showed stronger relationship to total deformity incidence expressed as percentage. Additionally, the multivariate RDA model showed higher capability of MTSI to explain the variations in heavy metal contents of the river sediments. The MTSI was recommended in bioassessment of water and sediment quality using the mentum deformities of Chironomus spp. larvae from aquatic ecosystems receiving anthropogenic, agricultural, or industrial discharges.

Prevalence and seasonality of Zoothamnium duplicatum (Protozoa: Ciliophora) epibiont on an estuarine mysid (Crustacea: Mysida) in tropical mangrove brackish water

The estuarine mysid Mesopodopsis tenuipes (Crustacea: Mysida) was often found carrying the peritrich ciliate Zootham- nium duplicatum (Protozoa: Ciliophora) on its body. The prevalence and seasonality of this association were studied on the basis of a year-round survey conducted in the Merbok mangrove brackish water in north-western Peninsular Malaysia from March 2005 to Feb- ruary 2006. The frequency of mysids hosting ciliates varied from 0 to 57.3%, with an annual mean of 17.0%. Juveniles showed a sig- nificantly lower prevalence of ciliates than adult mysids. There was no difference in infestation prevalence between the sexes. An epibi- otic renewal process could be assessed through observations in breeding females. The infestation prevalence and loads were apprecia- bly lower in the females carrying earlier stages of embryos than in those with developed ones, indicating that zoothamnid ciliates may require two or more days to reach a saturation phase in terms of prevalence when ciliate reproduction is high. This, in turn, suggests that the high moulting frequency of the tropical mysid may inhibit high colonisation pressure by the epibiont. A periodic seasonal trend was not determined, although mysids in lower salinity conditions were more likely to carry epibionts than those at higher salini- ties.

Seasonality and biological characteristics of the shallow-water mysid Mesopodopsis orientalis (Crustacea: Mysida) on a tropical sandy beach, Malaysia

The seasonality in abundance, population structure, and other biological aspects of the tropical shallow-water mysid Mesopodopsis orientalis were studied at an open sandy beach with fine sand on the southern coast of Penang Island, north-western Peninsular Malaysia, from December 2004 to August 2006. The monthly collections ranged from 0.7–534 indiv.m−2, with an overall mean of 49 indiv.m−2. The density, however, could reach as high as 8,656 indiv.m−2. There were no correlations between the abundance of mysids and the temperature, salinity, or tidal cycle, and the wide range in the variations of catches was considered to be mainly due to their heterogeneous distribution. Moreover, no distinct pattern was found in abundance between day and night and again between shady and sunny areas. Males accounted for 33.3–56.5% (mean; 47.3%) of the monthly samples; females predominated over males in the entire shore population. Reproduction of M. orientalis in Penang waters is continuous throughout the year and seasonality in reproductive traits is non-existent or, if present, considerably reduced. The number of eggs/embryos carried by females exhibited a positive correlation with female size, and the maximum brood size was 24. The egg diameter ranged from 0.30–0.42 mm, with a mean of 0.37 mm, and was independent of female size. Thus, the clutch size of the Penang population of M. orientalis was more fecund than that observed in the estuarine counterpart, Mesopodopsis tenuipes, but the former was smaller in size than the latter during all stages in its life cycle.

Biostratigraphy and paleobiogeography of Middle and Late Ordovician conodonts from the Langkawi Islands, northwestern peninsular Malaysia

The Middle and Upper Ordovician sequence of the Langkawi Islands, northwestern peninsular Malaysia, contains 20 species of conodonts belonging to 15 genera and four unidentified species, which are described and illustrated. The following four biostratigraphic zones are established for the study area: the Scolopodus striatus assemblage zone, the Periodon sp. A range zone, the Baltoniodus alobatus range zone, and the Hamarodus europaeus range zone, in ascending order. The Middle Ordovician fauna belongs to the low-latitude, warm-water Australian Province. Conodonts of the H. europaeus zone represent the HDS (Hamarodus europaeus-Dapsilodus mutatus-Scabbardella altipes) biofacies, which has been reported from the cool-water North Atlantic Faunal Region. The middle Arenigian limestones in the study area were deposited on a shallow-water shelf, whereas the late Arenigian to middle Darriwilian limestones formed in hemipelagic deeper-water conditions on an outer shelf or slope.

Reproductive biology and seasonality of the Indo-Australasian mysid Mesopodopsis orientalis (Crustacea: Mysida) in a tropical mangrove estuary, Malaysia

A year-round survey of the tropical shallow-water mysid Mesopodopsis orientalis (Tattersall, 1908) (Crustacea, Mysidacea) was conducted in the Merbok mangrove estuary, northwestern Peninsular Malaysia. The mysid formed dense aggregations at the river's edge close to the mangrove forest during the daytime, but very few were captured elsewhere in the estuary system. The sampled population was found in a wide range of salinities from 16 to 32, demonstrating broad euryhalinity, and the number of the catch at the littoral zone ranged from 11.8 to 2273 ind m −2. The overall annual mean was 709.2 ind m −2. Females predominated over males in the entire population, and brooding females were present at every monthly sample, indicating that reproduction is continuous year round. The clutch size positively correlated with female body length. The diameter of eggs (Stage I embryos) was unaffected by the seasonality and independent of the maternal size within an observed size range. The life history pattern of the estuarine population of M. orientalis showed close similarity to that of the coastal counterpart. However, the former was found to produce fewer but larger eggs, and the specimens in this population were larger than those in the coastal population at the embryo, juvenile, and adult stages. This evidence indicates that the life history features of the estuarine population would differ to some degree from those of the coastal counterpart.

A new Permian species of Mooreoceras (Cephalopoda: Orthocerida) from northwestern Peninsular Malaysia

A new orthocerid cephalopod species, Mooreoceras sibumasuense sp. nov., is described from the lowest part of the Chuping Formation in Bukit Tungku Lembu of the Perlis State, northwestern Peninsular Malaysia. The holotype of the species occurs in argillaceous limestone that is most likely late Kungurian (late Early Permian) in age and was deposited under cool-temperate water conditions on the Sibumasu Terrane of the eastern Cimmerian Continent. Most Permian species of Mooreoceras appear to be palaeobiogeographically confined to cool to cool-temperate palaeoclimate zones of the Australian Gondwana to Sibumasu region. Mooreoceras sibumasuense sp. nov. belongs to a group that probably survived due to isolation from high predatory stress in tropical to temperate seas. (Communicated by Tatsuro MATSUMOTO, M.J.A.)

Meiofaunal Communities in a Malaysian Mangrove Forest

The free-living benthic copepods and nematodes in samples of decaying leaves and sediment, from aRhizophora apiculata-dominated mangrove forest bordering the Sungai Merbok Estuary in north-western peninsular Malaysia, were identified to putative species. Analyses of community structure of these taxa revealed that both are concentrated within the surface layers of the sediment; communities associated with decomposing leaves are distinct from those associated with the sediment surface; and variation between physically similar sites within the forest is relatively small. It is suggested that the meiofaunal communities in tropical soft sediment mangrove estuaries respond primarily to salinity and exposure gradients as in temperate non-vegetated estuaries. Copepod communities of the Merbok mangrove system appear to be much more diverse than those in estuarine and saltmarsh habitats in other climatic regions, and detailed faunal analysis suggests that there is a high degree of species endemism, particularly in genera which are only found on decaying plant material.

Nesting Biology, Seasonality, and Mating System of Malaysian Fantail Warblers

The breeding biology of Fantail Warblers (Cisticola juncidis) in a rice field in northwestern peninsular Malaysia was studied. Data were collected on 38 nests found in rice plants on the 15-ha study area. Clutch size was three or four, incubation lasted 10-14 days, and fledging occurred 14-15 days after hatching. Two breeding seasons occurred annually, January-March and June-September, coinciding with the availability of suitable rice field nesting cover. The presence of several closely spaced, simultaneously active nests on plots occupied by single male birds indicated a polygynous mating system. This was based on the ability of some males to monopolize the limited available nesting habitat early in the rice-growing cycle. These findings differ from those of previous studies, presumably because of differences in the habitat types and mating systems examined. The Fantail Warbler (Cisticola juncidis) is a small sylviid widely distributed in tropical and temperate parts of Europe, Africa, Asia, and Australia. It chiefly inhabits wet grassy areas and rice fields and is rather secretive except during the breeding season when males perform conspicuous aerial displays (Lynes 1930, Givens and Hitchcock 1953). Recent studies in Japan (Motai 1973), France (Robert and Bellard 1975), and Australia (Ey 1977) indicate that the species may be regularly polygynous throughout a substantial part of its range. In this paper, I present results of a study of the nesting biology and mating system of the Fantail Warbler in a Malaysian rice field environment. This research was part of an investigation of the influence of rice cultivation on the breeding seasonality of certain common rice field birds (Avery 1980), and it is the first detailed account of Fantail Warbler breeding biology from the Malayan region since Gibson-Hill's (1950) study, which was conducted on Singapore during the mid-1940's. STUDY AREA AND METHODS The study area consisted of 15 ha of experimental rice fields at the Rice Research Center of the Malaysian Agricultural Research and Development Institute at Bumbong Lima, Northern Province Wellesley (5033'N, 100028'E). The fields were irrigated, and two crops of rice were harvested annually in March-April and September-October. The study period was June 1975-March 1977. Most nests were found by observing the movements of adult birds carrying nest material or food. Other nests were pointed out to me by field workers. I visit6d each nest site every second or third day and recorded the number of eggs or young and the presence or absence of adults. Several nests were observed using a spotting scope in order to monitor the foraging activity of female birds. Boundaries between breeding territories were estimated by observing encounters between males during aerial displays. I distinguished sexes of adult birds by plumage differences (Chasen 1939) and behavioral traits (during the breeding season, males make extended song flights whereas females make brief, low, usually silent flights). Recently fledged birds were easily distinguished from adults by the yellow wash on the pale feathers of the breast and abdomen. Throughout the study, I mist-netted and banded birds, but did ot uniquely mark them for sight identification. Thus, individual recognition in the field was not possible. Field counts of birds on the study area were made an average of three times weekly to obtain an indication of population levels.

Diet and Breeding Seasonality among a Population of Sharp-Tailed Munias, Lonchura striata, in Malaysia

Abstract From April 1975 through March 1977, the food habits and breeding seasonality of a population of Sharp-tailed Munias (Lonchura striata) were studied in northwestern peninsular Malaysia. The abundance of munias on the study area varied in accordance with the 6-month rice-growing cycle there. The population peaked in March and September when juvenile birds were most numerous and when rice was most plentiful. Field observations and stomach analyses showed that the munias ate rice and the green filamentous alga, Spirogyra, almost exclusively. The primary periods of algae eating occurred in January and June-August, coinciding with the munias' two peak periods of reproductive activity, as determined by gonadal examination. Apparently munias on the study area ate Spirogyra as a source of protein to enable them to become physiologically ready for breeding, much as othe tropical bird species eat insects. Thus, unlike other species, Sharp-tailed Munias' breeding seasonality is determined by manmade cycles of rice cultivation rather than by natural cycles of rain and insect abundance.