Ovitrap Modification in Improving the Ability of Aedes Sp. Egg Trapping in Banjarbaru City

Introduction: Dengue Hemorrhagic Fever (DHF) is a vector-borne disease that spreads through the bite of Aedes aegypti and Aedes albopictus. Until recently, vector control still becomes an essential step in breaking the dengue transmission chain. Besides of imago or larvicide method, the ovitrap way is also often used to trap the eggs of Aedes sp. This study aims to determine the trapping ability of modified ovitrap with various container colors and shrimp-paste attractant concentration levels. Method: This study was an experimental study using a post-test only design. This Research’s object was Aedes sp eggs trapped in modified ovitrap at 20 research locations in Banjarbaru City. The data obtained were analyzed statistically using the Kruskal Wallis test. The Research used The Mann-Whitney test to perform a post-hoc analysis. Result and Discussion: Results have shown that differences in attractant concentration and color of ovitrap have a significant effect in attracting Aedes sp to lay eggs. Zero percent concentration (without attractants) has a substantial difference in trapping Aedes sp with 10, 20, and 30% concentrations. Colorless ovitrap is also significantly different from black and green ones in trapping Aedes sp eggs. Conclusion: The use of attractants with a 10% shrimp-paste concentration solution and a black ovitrap can be an alternative to control DHF vectors affordable and safer for the environment and humans.

Peculiarities of Bacterial Chemotaxis in a Cylindrical Pore

The process of bacterial redistribution in a cylindrical pore filled with an attractant has been considered. The attractant concentration decreases linearly along the pore, and the redistribution of bacteria occurs due to their diffusion (the motion of bacteria along the gradient of their concentration) and chemotaxis (the motion of bacteria along the gradient of attractant concentration). The influence of a spatial confinement on the bacterial distribution in the pore is analyzed. It is shown that if the pore wall is “repelling” for bacteria, the spatial confinement can change the bacterial distribution. In particular, as the pore radius decreases, the chemotaxic effect becomes weaker. The non-uniformity of a bacterial distribution in the system is estimated. The chemotaxis sensitivity function (the deviation of the ratio between the local average bacterial concentration and the average bacterial concentration over the whole system from unity) is calculated, and its dependence on the attractant concentration at the system ends and on the pore size is determined.

Chemotactic reorientation of granulocytes stimulated with micropipettes containing fMet-Leu-Phe

Human granulocytes were stimulated by means of a micropipette, with an orifice of about 0.2 micrometer in diameter, which contained fMet-Leu-Phe at a concentration of 10(−5) M. The cells were reorientated by extending lamellipodia towards the source of the attractant, often within less than 10 s. Any part of the granulocyte, from the front to the tip of the tail, could be stimulated to produce new lamellipodia. Usually, but not always, this response occurred at the side of the cell nearest to the micropipette. Cells stimulated from behind responded in one of the following ways: (1) Cells that maintained their polarity extended new lamellipodia at one side of the leading front and reorientated by moving in a U-turn towards the micropipette. Occasionally, the leading front was split because one part of the front tried to make a left-hand and the other a right-hand turn. (2) Formation of lamellipodia at the leading front was arrested and new lamellipodia were formed at the tail instead, indicating reversal of polarity. The result was an immediate change in the direction of locomotion by about 180 degrees. (3) A combination of the first 2 forms of behaviour was observed occasionally. Transiently, lamellipodia were extended from cell surface areas both close to and distant from the micropipette. These observations show that parts of a cell can respond independently to chemotactic gradients by extending lamellipodia towards the source of the attractant. The phenomenon can easily be explained by assuming that a temporal change of attractant concentration is recognized.

The Range of Attractant Concentrations for Bacterial Chemotaxis and the Threshold and Size of Response over This Range

Attractant was added to a suspension of bacteria (the background concentration of attractant) and then these bacteria were exposed to a yet higher concentration of attractant in a capillary. Chemotaxis was measured by determining how many bacteria accumulated in the capillary. The response range for chemotaxis lies between the threshold concentration and the saturating concentration. The breadth of this range is different for attractants detected by different chemoreceptors. Attractants detected by the same chemoreceptor can have their response ranges in widely different places. Over the center of the response range (on a logarithmic scale), bacteria give similar sized responses to similar fractional increases of concentration, i.e. they respond to ratios of attractant concentration, but the response peaks at the center of the range. The size of the response is different for attractants detected by different chemoreceptors. For a detectable response, a smaller increase in attractant concentration is needed for attractants detected by some chemoreceptors than for attractants detected by others. Although the data are inadequate, it appears that the Weber law may be observed over a wide range of concentrations for some attractants but not for others. In the Appendix we aim to explain some of these results in terms of the interaction of an attractant with its chemoreceptor according to the law of mass action.

Some Quantitative Aspects of Insect Attraction

The measurement of insect attraction by the number of specimens collected in a certain time, or by the duration of the attractive effect, does not distinguish between the roles of intrinsic attraction and the attractant concentration. It is shown that the number of D. melanogaster responding to a food odor is proportional to the logarithm of the attractant concentration, in conformity with the Weber–Fechner Law. The implications of this result are discussed.