Some Aspects Of Chemoreception In The Adult House Fly Musca Domestica

Abstract

In the present work, the sensitivity of adult housefly, Musca domestica, chemoreceptors on the tarsi to substances related to its food or breeding sites were investigated, a matter that enhance our knowledge about this fly and contribute to a better control methods, environmental, mechanical or otherwise, to combat it. The mean threshold concentration (RD50) of each test substance was done with live laboratory bred preconditioned (starved and well watered) adults of M. domestica. The substances used to test the chemo-sensitivity of adults were aqueous solutions of glucose, lactose, ammonia; sheep slaughter offal, cow faeces, and mango juice. The right fore leg tarsus of a fly mounted on a fly holder was stimulated by a droplet of the test solution. Proboscis extension was taken as a positive response to the stimulant. The flies were tested in groups of 25 and for each test substance the tarsi were stimulated with logarithmically spaced doses. The RD50 and knockdown effects of each test substance were determined mathematically. Lactose was the most effective in eliciting proboscis response (0.0044 m/l) followed by Glucose (0.0024 m/l) and the least effective was ammonia (0.0102 m/l). In addition, Sheep offal (7.1%) was the most effective, followed by mango extract (8.5%) and the least effective was cow dung (10.0%). Lactose showed a more “knockdown effect” than either glucose or ammonia. There was no significant difference in the “knockdown effect” between mango, cow dung and sheep offal extracts. II The olfactory/gustatory reactions of well-watered sound adult flies to the test solutions were investigated by finding the mathematical relationship between time lapse and the number of flies attracted to each of the test substances. The test was done in a large cage, the bottom of which was 3oC above the air temperature and containing the test substances. Both glucose and lactose showed strong positive correlation with time lapse, the values were + 0.9781 and + 0.9784 respectively. The flies showed an insignificant tendency to prefer glucose over lactose. On the other hand, Ammonia showed a strong negative correlation, - 0.9781. In all the three cases, the regression line is very steep indicating rapid change in number of flies attracted to or repelled by the chemical stimulus. However, the regression lines describing the relationship between time and mango, cow dung and sheep offal were very gentle compared to the very steep lines described for glucose, lactose and ammonia – i.e., the number of flies attracted by one test material or the other change or fluctuate very slowly. The behavioural mechanisms involved in the orientation of the adults to chemical stimulation was done using starved well- watered de-winged adults of M. domestica in a choice chamber apparatus with two alternative choices: water and sheep offal. The reactions of the flies in either half of the arena and at the boundaries indicated that the mechanisms involved included: chemotelotaxis for quick reach (positive) to the source of stimulation or quick retreat (negative) of the stimulus, and chemoklinotaxis, low chemotropokinasis and some time chemo- and/or thigmo- akinasis to stay longer at the source of stimulation.