Dengue is a fatal arthropod-borne disease that affects humans worldwide. The mosquito Aedes albopictus (Skuse) is the secondary vector of dengue in Sri Lanka, however, studies on oviposition preferences of Ae. albopictus is scarce. The objective of the current study was to investigate the oviposition attraction of Aedes albopictus to selected household containers; black colour basins, metal cans, rain gutter parts, curd pots, coconut shells and yoghurt cups. For this, water containers for oviposition were placed in three outdoor shady sites and at three different heights. The mosquito larvae were collected after 5 days. The larvae were reared to adult stage and then they were identified and enumerated. Wing lengths of adult female mosquitoes that developed in different containers were measured. In the meantime, temperature, pH, dissolved oxygen (DO) and total dissolved solids (TDS) were measured in each container. The Ae. albopictus larval density was higher in coconut shells. The maximum mean number of mosquito larvae was observed in the containers at ground level. The oviposition attraction of Ae. albopictus was increased with the aging of coconut shells and old coconut shells were preferred than new coconut shells. Highest TDS level and neutral pH were observed in coconut shells which support the mosquito oviposition. The highest wing lengths were observed in female Ae. albopictus that developed in curd pots, representing higher fecundity. In conclusion, discarded coconut shells and curd pots should be carefully managed as means of eliminating dengue vector mosquito breeding sites.
In this study, the variation of aquatic molluscan diversity concerning seasonal water level fluctuations (WLF) and sediment texture was investigated in some perennial irrigation reservoirs and the associated head headwater streams in the Kala Oya river basin in Sri Lanka. Altogether 11,752 molluscan specimens belonging to 10 gastropod taxa (96.6%) and 2 bivalve taxa (3.4%) were identified. Of these, 11,282 specimens (96.0%) were from reservoir sampling sites and the remainder 470 (4.0%) was from the associated headwater streams. Of the gastropods, the individuals of the genus Melanoides showed the highest distribution index (DI) of 0.75 followed by Bellamya (DI = 0.63) and Thiara (DI = 0.60). The DI of the gastropod molluscs showed a significant positive relationship with their shell size (p < 0.05). Although molluscan diversity and taxa richness were comparatively lower in headwater streams than in reservoir sampling sites, Viviparidae (Bellamya; 0.06±0.03), Bithyniidae (Bithynia; 0.21±0.07) and Thiaridae (Thiara; 4.8±1.9 and Melanoides; 1.1±0.8) showed higher relative abundance (expressed as individuals per dm 3 ) in the headwater streams. The reservoir water level fluctuation showed a significant negative relationship with molluscan taxa richness (p < 0.05), but not with the Shannon-Weaver diversity index (p = 0.073). The distribution of molluscs was also found to be related to the sediment texture where the most abundant gastropod genera Bellamia, Bithynia, and Thiara were widely distributed in sandy substrates in reservoirs and associated streams in the Kala Oya river basin.
Reservoir construction is a worldwide enterprise, resulting in continuous changes in the landscapes of the tropical belt (Fernando & Holčik, 1991;Marmulla, 2001). Because reservoirs are productive biological systems, they are often utilized for fisheries development (Welcomme, 2001). They also are constructed for other diverse purposes such as irrigation, municipal water supply, hydropower generation and flood control. Reservoirs also substantially alter freshwater fluxes on the land surface and impact surface water storage through water management activities. On a global scale, water from reservoirs supplies an estimated 30%-40% of irrigated areas (World Commission on Dams, 2000). Seasonal water-level fluctuations, attributable mainly to water releases for their primary intended purposes (e.g. irrigation; hydroelectricity generation) are the characteristic feature of these lentic ecosystems. The seasonal pulses of water levels carry nutrients from associated rivers and surrounding terrestrial environments, enhancing the trophic status especially of shallow reservoirs (Geraldes & Boavida, 2005;
Seasonal water‐level fluctuations (WLFs) in reservoirs influence ecological processes, in turn affecting their benthic macroinvertebrate communities. The present study was carried out in 10 irrigation reservoirs of Sri Lanka to investigate the effects of seasonal WLFs on the benthic macroinvertebrate fauna. The study period was divided into two distinct phases: the drained period and the inundated period. Benthic macroinvertebrates were sampled during both periods and enumerated. Air temperature and soil quality parameters were also measured simultaneously, and hydrological data related to the Kala Oya River basin were obtained from irrigation authorities. Data analysis using non‐metric multi‐dimensional scaling revealed two distinct reservoir groups, namely, Hydrological Stress Group 1 (HSG1) and Hydrological Stress Group 2 (HSG2). A low hydrological residence time and low relative reservoir level fluctuations (RRLF) characterized HSG1, with the opposite describing HSG2. Temporal variations of macrobenthos indicated a high taxa richness and diversity in HSG1 reservoirs during the drained period, with scrapers and collector‐gatherers being the dominant functional feeding groups. Reservoirs in the lower river basin (HSG1) exhibited a high taxa richness and diversity. During the inundated periods, insect taxa colonized, particularly, chironomids and ephemeropterans. Molluscan taxa were prominent during the drained periods. These observations highlight the influence of seasonal fluctuations of reservoir water levels on benthic macroinvertebrates. Benthic macroinvertebrate communities in reservoirs were significantly influenced by the RRLF, manifesting the importance of hydrological regimes in reservoirs to develop macroinvertebrate metrics for water‐quality monitoring.
Solid pseudopapillary tumour (SPT) is a rare exocrine tumour of the pancreas predominately seen in females; has a 15% chance of metastasis; and represents 1-3% of all pancreatic tumours. We present two case reports of the disease: first a 13 year old female with abdominal pain and vomiting, and second a 36 year old asymptomatic female with an incidental SPT. Both patients had normal biochemical findings with well-defined masses in the pancreas in the contrast enhanced computed tomography. Treatment involved complete resection of the tumour and the latter also had a splenectomy as the tumour was adherent to the splenic vessels. Both remained asymptomatic following surgery and were followed up for a year after resection. We highlight the importance of having a high index of suspicion of the disease entity due to its varied presentation as surgical treatment provides a good prognosis.
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