Differential Expression of Mitochondrial Genes between Queens and Workers during Caste Determination in the Honeybee Apis Mellifera Miguel Corona , Enrique Estrada

was the first to establish that the development of honeybee larvae to queen or worker is not due to genetic differences, but is regulated by the differential nourishment that the female larvae receive from the nurse bees. Queen larvae are nourished with royal jelly, a mixture of hypopharyngeal and mandibular gland secretions. In contrast, worker larvae are nourished with worker jelly formed at first as a hypopharyngeal gland secretion by the nurse bees and later, this diluted with honey and pollen (Jung-Hoffman, 1966). Worker and royal jelly thus differ in chemical composition (Rembold, 1965). One of the most important differences between these types of food is the sugar concentration: royal jelly contains approximately 12 % sugar (wet mass) while worker jelly contains only 4 % sugar (Shuel and Dixon, 1959). In addition, nourishment quantity is also drastically different between queens and workers, since nurse bees visit a queen larva 1600 times compared with 150 times for worker larvae (Lindaver, 1952). Therefore, the nutrition that the queen and worker larvae receive is quantitatively and qualitatively different. In general, three major consequences result from the differential nutrition between worker and queen larvae. First, at the early fifth instar (approximately 96 h of larval development), the worker larva is larger than the queen larva (Asencot and Lensky, 1976); however, by the end of the fifth day (approximately 120 h of larval development), the queen larva is approximately 60 % heavier (Wang, 1965). Second, the queen larva has a higher metabolic rate, reflected in a higher rate of oxygen uptake starting at mid third instar (approximately 50 h of larval development) and reaching a maximum in the mid fourth instar (72 h) (Shuel and Dixon, 1968). Third, there are important differences in the levels of juvenile hormone between the two castes. It is known that juvenile hormone secretions of the corpora allata depend on the quality and quantity of the food ingested by the larvae (Bettsma, 1979; Wirtz and Bettsma, 1972). Juvenile hormone levels increase in queen larvae during the third to fifth instars, reaching a peak at early stages of the fifth instar, when they are 15 times higher than in worker larvae (Lensky et al., 1978; Rembold, 1987; Rachinsky et al., 1990). Several physiological and biochemical approaches have been documented in the study of caste determination in the honeybee. However, no molecular strategies have been used in analyses 929 The nourishment received …