Influence of diet, age and colony condition upon intestinal proteolytic activity and size of the hypopharyngeal glands in the honeybee ( Apis mellifera L.)

Abstract

Intestinal proteolytic activity, size of hypopharyngeal glands and dry weight of bees were investigated. Bees were either kept in cages (isolated or in groups) in an incubator, hived in small hives (200–300 individuals in three small combs) or in observation hives (about 2500 individuals in two combs). Artificial diets such as sucrose solution, sucrose with casein, sucrose with amino acids, honey, and honey with beebread were fed to the caged bees. Colony conditions such as the presence of brood and/or queen varied in the small hives. After emergence all bees, even those fed with sucrose solution, showed an increase in all parameters investigated. In all caged bees, except in those fed only sucrose, proteolytic activity increased at least till the 3rd day of life; the size of hypopharyngeal glands then decreased till the 8th day except in bees fed honey and beebread. In all bees that lived in small hives both these parameters increased at least till the 8th day and then were much lower and smaller in older bees that were already foragers respectively. The presence of a queen and unsealed brood neither influenced the intestinal proteolytic activity nor the size of the hypopharyngeal glands. In bees that lived in small hives these parameters developed in a similar manner to those of bees kept in observation hives. Bees fed for the first 3 days with merely a sucrose solution had low levels of proteolytic activities and small hypopharyngeal glands. If they were then put into a queenright observation hive till their 8th day, they could make up almost the entire deficiency.