Major viral diseases of the black tiger prawn (Penaeus monodon) in Thailand

There are five different viruses which are currently being studied for their impact on commercial farming of the black tiger prawn (Penaeus monodon) in Thailand. Some of these viruses cause disease in other penaeid shrimp species and even other crustacean species. Some occur not only in cultivated shrimp in other Asian countries, but also in those from Australia and the western hemisphere. In descending order from greatest to least economic impact on the Thai shrimp industry, the five viruses are: white-spot baculovirus, yellow-head virus, hepatopancreatic parvo-like virus, infectious hypodermal and hematopoeitic necrosis virus and monodon baculovirus. The purpose of this review is to summarize recent work on these viruses and to suggest future directions of research that may be useful in the effort to develop a sustainable shrimp industry.     

Seasonal variation of phytoplankton community in Thale Sap Songkhla, a lagoonal lake in southern Thailand

The phytoplankton in Thale Sap Songkhla was investigated at 2–3 month intervals from August 1991 to October 1993. The abundance of phytoplankton ranged from 1.4×10⁶ to 1.3×10⁹ cells m^–3. A total of 6 divisions with 103 genera were identified as Bacillariophyta: 49 genera, Chlorophyta: 21 genera, Pyrrhophyta: 15 genera, Cyanophyta: 12 genera, Chrysophyta: 3 genera and Euglenophyta: 3 genera. Although phytoplankton abundance was distinctly greater in the first year of study (August 1991–June 1992) than in the second year (August 1992–October 1993), their patterns are similar: 2 peaks yearly. The peaks of phytoplankton occurred in the heavy rainy season (northeast monsoon) and the light rainy season (southwest monsoon). The main bloom was found during December–January, with a predominance of blue-green algae (e.g. Aphanizomenon andPhormidium) and green algae (e.g. Eudorina). Their species composition also increased, an effect of the large amount of rainfall resulting in low salinity during the northeast monsoon. The minor bloom was produced by diatoms during June–July when water salinity was moderate to seawater. Both phytoplankton numbers and species composition were high. However, unpredictably heavy rainfall during the southwest monsoon period may reduce diatom production due to rapid immediate replacement by blue-green species. Besides salinity concentration, a low total nitrogen: total phosphorus (TN: TP) ratio tended to support the growth of blue-green algae. The diversity of phytoplankton was lowest in the heavy rainy period.     

Serotypes of Cryptococcus neoformans isolated from patients prior to and during the AIDS era in Thailand

One hundred and eighty-seven strains of Cryptococcus neoformans isolated from patients in Thailand were charcterized by biochemical varieties relating to serogroups. Canavanine-glycine-bromothymol blue (CGB) agar was used for differentiating the varieties of C. neoformans. Slide agglutination tests were performed with Crypto Check (Iatron, Inc., Tokyo) to determine their serotypes. Fifty-five percent (10 out of 18) of the pre-AIDS isolates were serotype B, 28% were serotype A, 5% were serotype D, and an unexpected 11% (2 out of 18) were serotype C. These are the first to be recorded in Asia. In contrast, among the 169 clinical isolates obtained between January 1993 and March 1995 (AIDS epidemic), serotype A was outstandingly predominant-93% (157 out of 169), serotype B was relatively low (3.6%) and both serotypes D and AD were 1.8%. The pattern of serotypes of the 59 isolates from known HIV-positive patients was closely similar to the total isolates during the AIDS epidemic. In determining the varieties of C. neoformans by CGB, only 1 of the 187 isolates gave a false reaction. On the basis of our findings, we believe that in the pre-AIDS era either C. neoformans var. gattii serorype B or serotype C were the common causative agents of cryptococcosis in Thailand. The advent of AIDS changed the pattern of serotypes with serotype A becoming predominant as has been reported world wide.     

Additions to the rotifer fauna of south-east Asia: new and rare species from north-east Thailand

Ninety-three freshwater habitats in the north-eastern part of Thailand were surveyed for rotifers during March–October 1993. Two hundred species were identified, 120 of which are new to Thailand. Brachionus africanuss Segers, B. lyratus Shephard and Trichocerca hollaerti De Smet are new to Asia. Brachionus niwati n.sp. is described and figured. Brachionus donneri Brehm, Keratella edmondsoni (Ahlstrom) and Lecane blachei Berzi, endemic to south and southeast Asia, were found also.Comments are presented on some insufficiently known taxa. Of special zoogeographic interest is the record of several species previously considered endemic to Australia. An attempt is made to characterise the Thai rotifer fauna in the light of recent developments in rotifer zoogeography.     

Microrestes de Vertébrés du Siluro-Dévonien d'Algérie,de Turquie et de Thaïlande

Acanthodian («Shark-like spiny fishes) scaleshave been collected in three Uppermost Silurian-Lowermost Devonian localities from Algeria, southeastern Turkey and Thailand, in association with agnathan remains (heterostracans in Algeria, thelodonts in Thailand). These vertebrate microremains are the oldest ones for those three countries. They were associated with marine invertebrate faunas and are supposed to have lived in littoral environments. Their world-wide biogeographical distribution by the Silurian-Devonian boundary leads to analyse the palaeogeographical relations of north-Atlantis and Siberia on one hand, with southern Europe, southeastern Asia and Gondwanaland on the other hand.     

Weaver Ants Increase Premature Loss of Leaves Used for Nest Construction in Rhizophora Trees1

Oecophylla ants utilize living leaves when they construct their nests. We investigated how Oecophylla smaragdina nests in southern Thailand affected leaf performance on the mangrove tree Rhizophora mucronata. Leaves used in nests and neighboring leaves showed a higher rate of premature leaf loss compared to control leaves farther from the nests. However, a tree's total cost due to the higher premature leaf loss was estimated to be approximately between 3‐ and 20‐fold lower than the benefit derived from ant protection, detected in a previous study ( Offenberg et al. 2004 ).     

High interannual variation in the diet of a tropical forest frugivore (Hylobates lar)

Frugivores must deal with seasonal changes in fruit availability and changes from year to year, as most species of tropical forest fruiting trees have considerable interannual variation in phenology and many are mast fruiters. We quantified seasonal and interannual changes in the fruit diet in a frugivore and important seed disperser, the white‐handed gibbon, Hylobates lar, in Thailand. We used 40‐d following data during April and May replicated in six consecutive years to study interannual variability in the diet and compared it with seasonal changes measured in monthly samples of the same size collected in three successive years. The 40‐d periods of following also allowed us to measure the decline in dietary similarity with time over a finer scale. We measured fruit diet similarity between replicated 5‐d periods using the percentage overlap (Renkonen's) index and Jaccard's similarity index. Seasonally, average dietary overlap between adjacent months was low, and similarity approached zero after four months. Average rate of decline in similarity exceeded 20 percent per 5‐d period. Variation in fruit species in the diet between years was high and was correlated with interannual variation in fruiting phenology. The strongest correlation occurred in the case of Nephelium melliferum, a highly preferred species that dominated the diet in good fruiting years. It is difficult to separate changes in food species preference from changes in availability from year to year. We devised a relative measure of preference that depends on the degree to which the gibbons rely on prior knowledge to find sources.     

Typhonium muaklekense sp. nov. (Araceae) from Thailand

Typhonium muaklekense D. Sookchaloem & S. Maneeanakekul is described and illustrated. This new species resembles T. roxburghii Schott and T. varians Hett. & Sookch. in the spathe. Drawings, photographs and a table comparing diagnostic features of T. muaklekense, T. roxburghii and T. varians are provided.     

Biting patterns and host preference of Anopheles epiroticus in Chang Island,Trat Province,eastern Thailand

A study of species diversity of Anopheles mosquitoes, biting patterns, and seasonal abundance of important mosquito vectors was conducted in two villages of Chang Island, Trat Province, in eastern Thailand, one located along the coast and the other in the low hills of the central interior of the island. Of 5,399 captured female anophelines, 70.25% belong to the subgenus Cellia and remaining specimens to the subgenus Anopheles. Five important putative malaria vectors were molecularly identified, including Anopheles epiroticus, Anopheles dirus, Anopheles sawadwongporni, Anopheles maculatus, and Anopheles minimus. Anopheles epiroticus was the most commonly collected species in the coastal site, whereas An. dirus was found to be most abundant in the forest‐hill site. From both locations, a greater number of mosquitoes was collected during the dry season compared to the wet. Anopheles epiroticus showed greater exophagic and zoophilic behavior with the highest blood feeding densities occurring between 18:00 and 19:00. In contrast, An. dirus demonstrated an activity peak between midnight and 01:00. We conclude that An. epiroticus and An. dirus, in coastal and inland areas, respectively, appear to be the most epidemiologically important malaria vectors on Chang Island. As no studies of vector competency specific to Chang Island have been conducted, our conclusions that these two species play a primary role in malaria transmission are based on evidence from other localities in Thailand and mainland Southeast Asia. This information serves as a basis for designing improved vector control programs that target specific species, and if integrated with other interventions could result in the elimination of malaria transmission on the island.