Flying and walking of small insects (Musca domestica) recorded differentially with a standing-wave radar actograph

ABSTRACT. An actograph is described for recording the behaviour of small insects, by using a standing-wave radar system in an enclosed metal cabinet. Experiments show that the system produces an output frequency dependent only on the speed of movement of the subject. By filtering the signal electrically into components below and above 5 Hz, walking and flying of adult Musca domestica could be separately recorded. Each filter is followed by a level-comparator with hysteresis. Activity causing signal to cross the hysteresis-band is recorded as an event on a digital counter, and also integrated or summed to be displayed as a stepped-integral or bar-chart of total distance covered by the subject in each counting period. The energy-density of the radar can be kept very low, so that possible influence on the subject is minimal. The detector is remote from the box containing the subject, giving great flexibility in container design, so that the apparatus is ideally suited to the study of environmental factors.     

Sources of the lipids in the bottom sediments of an English oligo-mesotrophic lake

SUMMARY. 1. The organic geochemistry of Coniston Water, a low productivity lake, has been investigated.
2. The relative inputs of the various known sources to different compound classes suggest terrestrial higher plants as the major source of sedimentary organic matter.
3. Early lipid diagenesis, proceeding in the bottom sediments as a result of microbial activity, produces relatively rapid changes, with shorter chain and unsaturated compounds being preferentially degraded.
4. Free and bound (acid liberated) lipids exhibit significant differences in composition, related to their respective sources and stability towards degradation.
5. The lipid composition of an aquatic higher plant, growing in the margins of the lake, has been determined; comparison with the sedimentary lipids reveal it not to be a significant source.     

ELISA absorbance cut-off method affects malaria sporozoite rate determination in wild Afrotropical Anopheles

ABSTRACT. Malaria sporozoite infection rates in a mixed species group of 244 Anopheles gambiae Giles sensu lato and 115 An. funestus Giles wild female mosquitoes were compared using three methods to determine cutoff absorbance values for positivity of a Plasmodium falciparum Welch enzyme-linked immunosorbent assay (ELISA). Positive controls were based on P. falciparum circumsporozoite protein. As negative controls, four wild male Anopheles were included on each microtitre plate; tests were repeated on four consecutive days for each plate.
Infection rates were estimated at 13.1–22.8% using the mean absorbance value of negative controls plus three standard deviations, 11.7–12.8% using double the mean and 12.5–13.6% using the fixed cut-off value of 0.20 (allowing for 20% variation in negative control absorbance values).
Observed agreement for positivity or negativity among samples tested four times was 98.6% for the 2× mean method, 97.2% for the fixed cut-off 0.20 value, but only 82.7% for the mean +3 SD method. It was concluded that the 2× mean cut-off method is most reliable for field studies. P. falciparum sporozoite rates of 12.2% in An. funestus and 11.9% in An. gambiae s. l . were thus determined on the basis of the 2× mean cut-off method.
This comparative evaluation demonstrates that vector infectivity rates can be seriously over-estimated from sporozoite ELISA tests, by as much as 87% in one case considered here, depending on the absorbance cut-off method applied for negative controls.