Circadian Variations In The Digestive Enzyme Activities Of Gut Homogenates Of Adult American Cockroach, Periplaneta Americana

Cockroaches are important pests with public health implications. Little is known about their daily activities and there have been controversies about the peak time of their activities. At four equal intervals (00:00, 06:00, 12:00 and 18:00), adult male and female Periplaneta americana (L.) (Blattodea: Blattidae), were captured and their guts removed and divided into three major regions: foregut, midgut, and hindgut. From each gut section, the presence and quantity of five enzymes (amylase, lipase, proteinase, glucosidase and cellulase) were analysed using standard methods. Result showed that all enzymatic activities (except cellulase) were at the highest level at 00:00, followed by 06:00, whereas at 18:00 the enzyme activities were the lowest. Amylase activities were 55.6, 50.7, 38.5 and 35.9 absorbance/min at 00:00, 06:00, 12:00 and 18:00 sample periods, respectively. Amylase had the highest level of enzyme activity. The hindgut had the highest enzyme activities (except for cellulase) and the foregut had the least. Comparison of means showed that adult females of P. americana had a higher level of enzyme activity than males for all the enzymes except amylase. This study suggests that cockroaches are endowed with enzymes necessary for the digestion of the various diets, also there are variations in the daily activities of these enzymes, with the highest enzyme activities at night. This suggests that nocturnal insects not only restrict their activities at night, but also their internal physiological activities.