Queenright Workers Research Articles

Queen and colony odour in the multiple nest ant species, Cataglyphis iberica (Hymenoptera, Formicidae)

We investigated the queen's effect on the cuticular hydrocarbon profile of workers in the monogynous and polydomous species Cataglyphis iberica. Within each of the three colonies tested, workers were separated for three months in queenright and queenless groups. After regrouping, nestmate recognition remained unchanged but the duration of antennal interactions between workers previously separated increased relative to controls. Separated groups presented slightly divergent cuticular hydrocarbon profiles which may induce the longer antennations. A quantitative analysis of major cuticular hydrocarbons showed that the total amount per unit of cuticular surface area remains similar between the two castes; but queens had higher quantities of n-alkanes than workers. The lack of a queen did not affect the workers' cuticular hydrocarbon profile in queenless groups. Indeed, the profile of queenless workers remained significantly different from the queen profile as did that of queenright workers. These results show that queens are not at the origin of the hydrocarbons' colonial profile. Two recognition processes seem to coexist within C.iberica colonies: nestmate discrimination based on the colonial odour which includes all nestmate workers, and a queen caste-specific odour. In a polydomous species such as C.iberica, the queen does not seem to contribute more than any other nestmate to the colonial odour, which probably derives from worker cues, confirming the existence of a "Gestalt" colonial odour.

Effects of social conditions on Juvenile Hormone mediated reproductive development in Bombus terrestris workers

Abstract. During the annual life cycle of the bumble bee Bombus terrestris (L.) colony, there is a stage characterized by worker reproduction in the presence of the queen. It has been proposed that this is a result of a decrease in queen inhibition. This hypothesis was examined by studying the effects of queens taken from colonies at different stages of development on several aspects of worker physiology and behaviour: rates of Juvenile Hormone (JH) release in vitro, ovary development, and behaviour associated with reproduction. After optimizing and validating the radiochemical assay for JH release for bumble bee workers, we found that queenless workers had significantly more developed ovaries and higher rates of release of JH than did queenright workers, confirming and extending previous findings that suggest that bumblebee ovarian development is under JH control. Mated queens, separated from their colony and brood, can have the same inhibitory effect on the reproductive development of callow workers. In contrast, workers confined with virgin queens or in queenless groups demonstrated a significantly higher rate of release of JH, overt aggression and threatening behaviours. However, there were no differences in rates of release of JH between workers confined in groups in the laboratory with queens taken from colonies either before or after the onset of worker reproduction. Furthermore, overt aggression and threatening behaviours were similar and low in both types of groups. These results gave no support to the hypothesis that a decrease in queen inhibition is associated with the onset of worker reproduction. We also show that young workers reared in colonies either before or after worker reproduction occurs, or in queenless colonies, all demonstrated similar, low rates of release of JH. These results suggest that older workers may inhibit the corpora allata of younger workers in queenless colonies.

Role of juvenile hormone biosynthesis in dominance status and reproduction of the bumblebee, Bombus terrestris

In Bombus terrestris females, dominant status is correlated with high levels of juvenile hormone (JH) biosynthesis and rapid oocyte maturation. Queenright workers, which are inhibited by the dominant queen, complete the cycle of oocyte maturation while exhibiting a continuous low rate of JH production, but their egglaying is inhibited. Measurements in foundress queens suggest that the low JH titer during oogenesis is probably not responsible for the inhibition of egg-laying. Queenless workers, kept individually, are not activated either for JH production or oocyte maturation. In groups of three queenless workers, a dominance order becomes established and high rates of JH synthesis are observed in the dominant egg-laying workers, with low rates in subordinated workers. In groups of founder queens, also, a dominance order becomes established and results in a reduced rate of JH production in subordinated females.

Mandibular gland components and ovarian development as measures of caste differentiation in the honey bee ( Apis mellifera L.)

Changes in mandibular gland pheromone production and ovarian development were investigated in queenless North American honey bees ( Apis mellifera L.). An intercaste, false queens, laying workers, queenless foragers and queenright workers were analyzed for the amounts of five mandibular gland pheromone components and for ovarian development. Pheromone composition was not related to ovarian development, in contrast to some previous studies with the African race, Apis mellifera capensis. These results suggest that queen/worker caste differentiation may be more strongly fixed during development in some honey bee races than in others.

Primer effect of queen pheromone on juvenile hormone biosynthesis in adult worker honey bees

Juvenile hormone synthesis in adult worker honey bees was measured by an in vitro corpora allata bioassay. Adult queenless workers exhibit higher rates of juvenile hormone biosynthesis than queenright workers. Hormone synthesis is not correlated with the volume of the glands. Extract of queen mandibular glands, applied to a dummy, reduces juvenile hormone biosynthesis in caged queenless workers to the level of queenright workers. The same result was obtained with synthetic (E)-9-oxo-2-decenoic acid, the principal component of the queen mandibular gland secretion. This pheromonal primer effect may function as a key regulating element in maintaining eusocial colony homeostasis. The presence of brood does not affect the hormone production of the corpora allata.

Identification of vitellogenin in the ant, camponotus festinatus: Changes in hemolymph proteins and fat body development in workers

Vitellogenin has been identified in the ant Camponotus festinatus, both in queens and workers. In the workers, it is already present before adult eclosion in low concentrations (less than 1 microgram/microliter hemolymph). Vitellogenin and vitellin are immunologically identical and are composed of a single type of apoprotein with an apparent Mr = 185,000. The molecular weight of the native molecules was estimated as approximately 460,000 by pore limiting gradient electrophoresis. Vitellogenin was detected as a major protein in the hemolymph of young workers, both under queenright and queenless conditions. Thus, in spite of their sterility in the presence of the queen, C. festinatus workers are able to synthetize vitellogenin which is identical both in size and immunologically to the queen vitellogenin. About 6-7 weeks after adult eclosion, however, vitellogenin was usually undetectable in the hemolymph of queenright workers, particularly the minor workers, while it constituted about 30% of total protein in queenless workers. Protein concentration in the hemolymph of queenless insects increased up to 20-fold as compared to 1-day-old insects. Queenless workers also developed large amounts of perivisceral fat body, while queenright workers, particularly the minor workers, showed a dramatic fat body regression about 6 weeks after emergence.

Effect of the queen, brood and worker caste on haemolymph vitellogenin titre in Camponotus festinatus workers

Haemolymph concentration of vitellogenin and ovary development have been examined in Camponotus festinatus workers under inhibited (queenright) and uninhibited (queenless) conditions, in order to determine which social factors may affect worker oögenesis. While most queeright workers had very low vitellogenin titres, queenless workers maintained either in the presence or absence of pupae showed increasing vitellogenin titres. Mean vitellogenin concentration in 7-week-old queenless soldiers and 10-week-old queenless minor workers were 15-fold higher than those found in queenright workers of the same age. Larvae had an inhibitory effect on the haemolymph vitellogenin titres of workers, particularly of minor workers. Soldiers in the presence of minor workers showed significantly higher vitellogenin titres during early adult life. In spite of the accumulation of vitellogenin in the haemolymph of queenless workers, even far above the levels detected in some queens, oöcyte development did not occur in the majority of these animals.

Seasonal changes in ovarian state in a eusocial halictine bee, Lasioglossum duplex , based on stages of the oldest oocytes in each ovariole (Hymenoptera: Halictidae)

The changes in ovarian activity in the life cycle of the eusocial halictine bee Lasioglossum (Evylaeus) duplex (Dalla Torre) was studied in both queens and workers by examining the stages of the terminal follicle in each of the six ovarioles. By this method, ovarian activities of both queens and workers were more quantitatively determined than by observation of gross ovarian features as usually conducted. Queen ovaries clearly exhibited two active periods, corresponding to the spring solitary phase and the summer eusocial phase, with distinctly greater activity in the latter. In ovaries of overwintering queens oosorption of young follicle was observed. Worker ovaries were found more active in orphan than in queenright colonies. The order of ovarian activity obtained from pooled data, summer queens>spring queens>orphan workers>queenright workers, was also recognized by comparison of individual females.

Studies on the regulation of the juvenile hormone titre in bumblebee workers, Bombus terrestris

The synthesis of juvenile hormone (JH) by corpora allata (CA) in vitro was studied in queenright and queenless workers during the first 5 days after emergence. In queenless workers the activity of the CA is strikingly higher than in queenright workers, the first differences were observed on the very first day of adult life. The synthetic activities of the CA correspond fairly well with the JH titre obtained by Galleria bioassay. Since the excretory rate was not found to be lower in queenless workers, it is postulated that the increased JH titre is caused mainly by higher activities of CA. The activity of the CA for its part depends upon the presence or absence of a queen. It is shown by HPLC determination as well as by Galleria bioassay that only JH III is produced in vitro.

Juvenile hormone control of oögenesis in bumblebee workers, Bombus terrestris

In queenright workers of Bombus terrestris oögenesis is inhibited by the queen, the activity of the corpora allata is suppressed, and the resulting JH titer in the haemolymph remains low. In contrast, in queenless workers the JH production is stimulated on the first day of adult emergence, the JH titer increases, and eggs are rapidly formed. After injection of JH I in newly emerged workers oögenesis can also be induced in the presence of a queen in the same way as in queenless workers. The induced oögenesis is JH dosage dependent, dosages of less than 8 μg stimulate the production of vitellogenins, whereas a complete oögenesis can be induced by high dosages of about 50 μg. From studies on the rate of JH excretion it can be concluded that such high dosages must be injected to obtain the required JH titer during the whole egg maturation of 5 days. It is evident, therefore, that the initiation and the maintenance of oögenesis depends on JH. The injected JH ester is completely degraded to JH acid and JH diol mainly in the hindgut. The excretion starts quickly after the injection, but only traces of unchanged JH are excreted. From these results it can be suggested that a queen inhibits egg maturation in workers by suppressing the JH production in the corpora allata and thus lowering the JH titer. This influence also enables a queen to block oögenesis once stimulated, for instance in queenless workers. Breakdown of JH and excretion are not under the control of the queen and therefore neither of them play any rôle in regulating egg maturation in the worker caste.

Ovary development of worker honeybees when separated from worker brood by various methods

Ovary development of workers increased progressively with the following treatments: (a) with queen, with brood or without queen, with brood; (b) with queen (confined or free), without brood; (c) without queen, without brood.Ovary development of queenless, broodless workers separated from worker larvae (or pupae) by single or double screens was similar, but was significantly higher than that of queenright workers with brood (controls) and significantly lower than that of queenless, broodless workers; possibly a volatile brood (or brood-related) scent was acting to inhibit ovary development in these workers.