Mysids are one of the most abundant and important fauna in estuarine hyperbenthic communities. They form important links in estuarine food chains and play a critical role in the cycling of energy within estuarine systems. Therefore, it is important to recognize the distribution of estuarine mysids in Sri Lanka. The present study was undertaken in Bolgoda estuarine system and Lunawa lagoon, in order to find out the distribution of mysids in these brackish water systems. Reconnaissance surveys were conducted, in Bolgoda North Lake, Panadura estuary of the Bolgoda estuarine system and the Lunawa lagoon from April 2012 to February 2013. The samples were collected using a hand held dip net, during day time at low tide along an eighty meter transect at the boundary of the estuarine waters. Mesopodopsis zeylanica was the only mysid species observed from the low water areas of the lagoon along the boundary of the stream. In each collection, it was recorded, higher percentages of females than the males. Mysids were recoded only from unpolluted areas and they were absent, where Eichhornia crassipes (water hyacinth) was widespread. The findings of this analysis could be used to establish the fact that boundary condition and polluted condition are having a great effect on presence of mysids. It may be due to their specific niche requirements and specialized habitats. Accordingly, mysids serve as pollution indicator species in estuarine ecosystems. An immediate management strategy is required in protecting the Bolgoda estuarine systems from dumping household pollutants as well as other pollutants and complete elimination of the invader plants like E. crassipes, in order to protect estuarine biodiversity.
Mysids are minute crustaceans that occur in large numbers in estuarine waters. Their significant role as a main food source for fish populations is becoming apparent. There is currently, limited information on mysids in Sri Lankan estuarine waters. The present study investigated the distribution of mysids in the Negombo Lagoon from June 2012 to May 2013 at 18 randomly selected-sites along the lagoon. Surveys were conducted along the boundary of the lagoon, during day time, using a dip net (opening of 25 × 20 cm 2) with 500 µm mesh size. The spatial distribution survey recorded 11 mysid habitats. Mesopodopsis zeylanica, and a potentially new Siriella sp. were identified, M. zeylanica being the most abundant species. Survey of temporal variation in mysid abundance was also carried out at two sites for a sixmonth period. Mysid species did not show any temporal variation and the distribution and abundance was not affected by any single environmental factor. The spatial distribution of mysids along the lagoon boundary was found to depend mainly on the estuarine boundary conditions. Mangrove vegetation along the estuarine boundary was found to be favorable for mysids while concrete boundaries and accumulation of garbage along boundaries were found to be unsuitable.
Since the publication of Preston's Fauna of British India-Freshwater Gastropoda and Pelcypoda in 1915, a vast amount of knowledge has accumulated on the fresh water molluscs. Starmühlner (1974) published a monograph on the fresh water gastropods, in which he listed 31 species of freshwater snails from Sri Lanka. Until the early 20th century, malacologists used mainly conchological characters to describe species. However, the shells of freshwater gastropods are highly variable, show ecological plasticity, and are known to suffer from convergence and homoplasy, and therefore do not always reliably reflect systematic boundaries. It is already known that other groups of freshwater organisms in Sri Lanka including fish and crabs show high levels of endemism within individual river basins. It remains to be discovered whether molluscs too, show such basin-level endemism. These studies also found that there was significant altitudinal stratification and basin-level endemism of species, a factor that remains to be assessed for aquatic molluscs. In order to address these questions, and assess the diversity of this fauna, we surveyed the freshwater mollusc fauna (focusing mainly on the genus Paludomus) in the Mahaweli, Kelani, Kalu, Gin and Maha-Oya River basins of Sri Lanka. A total of 10 morphospecies were recorded, based on examination of 20 specimens of each species from 20 locations in the altitude range 100-2000 m above mean sea level. Species-level identification is in progress, and further surveys are needed to assess the full diversity of this important fauna.
Natural products of plant and animal origin are preferred over synthetic insecticides due to their eco-friendly nature. The use of natural products and their derivatives are being advocated for the control of insect vectors of human diseases. The crude extracts of the fruits of Sapindus emarginatus (a medicinal plant) and the skin of Holothuria atra (a nonedible sea cucumber) were tested under laboratory conditions against Aedes aegypti, a vector of dengue and chikungunya, for their larvicidal properties. Bioassay experiments carried out with crude extracts of S. emarginatus and H. atra revealed LC 50 values of 92.9 and 68.82 ppm respectively. Both crude extracts showed positive result for the presence of saponin. This preliminary study suggests that not only plant but also animal sources can be effectively used to produce less expensive and safe compounds to control mosquito vectors in Sri Lanka.
Glycoside fractions from ten holothurians were isolated and subjected to a comparative examination. All ten species contained holothurin A. Except .Vglorhurio edulis and Havelockia versicolor all other species were found to contain holothurin B. The acid hydrolysis of glycoside fractions of all species examined yielded mainly two genins (22,25epoxy-7. 9 (1 1) holostadien-3-17-diol and its d e o x~a n a l o~u e) and four sugars namely glucose, xylose. 3-0-methyl glucose agd quinovoce.
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