Aggressive reproductive competition among hopelessly queenless honeybee workers triggered by pheromone signaling.

In the honeybee, Apis mellifera, the queen monopolizes reproduction, while the sterile workers cooperate harmoniously in nest maintenance. However, under queenless (QL) conditions, cooperation collapses and reproductive competition among workers ensues. This is mediated through aggression and worker oviposition, as well as shifts in pheromones, from worker to queen-like composition. Many studies suggest a dichotomy between conflict resolution through aggression or through pheromonal signaling. In this paper, we demonstrate that both phenomena comprise essential components of reproductive competition and that pheromone signaling actually triggers the onset of aggression. We kept workers as QL groups until first aggression was observed and subsequently determined the contestants' reproductive status and content of the mandibular (MG) and Dufour's glands (DG). In groups in which aggression occurred early, the attacked bee had consistently more queen-like pheromone in both the MG and DG, although both contestants had undeveloped ovaries. In groups with late aggression, the attacked bee had consistently larger oocytes and more queen-like pheromone in the DG, but not the MG. We suggest that at early stages of competition, the MG secretion is utilized to establish dominance and that the DG provides an honest fertility signal. We further argue that it is the higher amount of DG pheromone that triggers aggression.

Task-related chemical analysis of labial gland volatile secretion in worker honeybees (Apis mellifera ligustica).

Chemical analyses revealed that the labial gland complex of worker honeybees possesses a series of hydrocarbons dominated by odd-numbered carbon chain alkanes along with minor amounts of alkenes and branched alkanes. Foragers contained significantly more secretion than nurse bees. Experiments with bees from colonies induced to have a division of labor independent of age revealed that the differences in the amount of secretion were task, but not age dependent.

Plasticity in caste-related exocrine secretion biosynthesis in the honey bee (Apis mellifera).

Plasticity of Dufour's gland secretion in the honey bee is correlated with the individual's plasticity. Queens and queenless (QL) egg-laying workers possess a bouquet of esters and hydrocarbons, whereas queenright (QR) workers produce exclusively hydrocarbons. The effects of social environment (QR vs. QL conditions) and possible physiological constraints on the gland were studied by following the biosynthesis of these classes of compounds in vivo and in vitro. Biosynthesis in vivo followed the prediction based on glandular chemistry. Queens and QL egg-laying workers, but not QR workers or QL foragers, showed incorporation of sodium acetate into both hydrocarbons and esters. In contrast, the in vitro studies revealed that, in addition to queens and QL egg-laying workers, QR nurses retained their ability to produce the queen characteristic esters. Although there was some ester production in foragers, it occurred to a lesser extent. It is possible that the glands in the older foragers undergo irreversible changes. The in vitro incubation also revealed a temporal activation of ester biosynthesis in QR workers. In these glands alcohols, corresponding to the alcohol moiety of the esters, predominated in short-term incubations but decreased as the amount of newly synthesized esters increased. In contrast, queens and QL egg-laying workers showed predominant incorporation into esters from the onset of incubation. Thus, expression within the workers' Dufour's gland is regulated. In the presence of a queen, ester production is inhibited. Once the queen is removed the physiologically unconstrained gland starts to biosynthesize the queen-specific esters after a certain lag needed for the build-up of precursors and the enzymatic machinery.

Effect of monoclonal antibodies in preventing carboxypeptidase A aggregation.

With an increase in temperature, carboxypeptidase A shows a decrease in solubility that is accompanied by loss of enzymic activity and conformational changes leading to its aggregation. In the present study we investigated the suppression of enzyme aggregation via its interaction with two monoclonal antibodies raised against the native protein. The protein aggregation process was monitored by ELISA measurements and determination of residual enzymic activity. As previously found, selected monoclonal antibodies which do not inhibit the biological activity of the antigen and bind with a similar affinity constant to their epitopes on the molecule exhibit a chaperone-like activity in the refolding of their antigen. These antibodies have an inhibitory effect on the aggregation of the enzyme which seems to be related to the location of the antigenic site recognized by each antibody. Identifying the aggregating epitopes' as sequences that are related to the sites where protein aggregation is initiated and preparing monoclonal antibodies against these regions may facilitate the understanding and prevention of protein-aggregation processes.