New work on royal jelly produces some interesting findings!

In Brief  

Honeybee queen larvae are raised in specific cells which are vertically oriented, opening downwards. Nurse bees deposit protein rich royal jelly at the cell ceiling as larval food. Buttstedt et al. show that two of these proteins are crucial for queen development. They control royal jelly viscosity, preventing the larva to fall out of its cell.  

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MRJP1 is indeed crucial for queen rearing, but not as erroneously claimed in its monomeric form as physiological caste determinator [21], which has been clearly rebutted [10]. The current evidence suggests that quantity, rather than the quality, of the larval food is the trigger for queen determination [22–24]. 

In any case, it is obvious that the correct viscosity of RJ is vital for queen rearing in honeybees; if the larva falls out of the cell, food quality becomes irrelevant. These physical requirements are achieved by oligomeric MRJP1 in complex with apisimin, which is of particular importance in the entire genus Apis, where the workers construct upside- down-oriented queen cells [25]. 

It is highly adaptive that RJ secretion in honeybees is handled by two separate specialized head glands. It is the mixture of the hypopharyngeal and mandibular gland secretions that reduces pH levels such that the oligoMRJP1/apisimin complexes form fibril networks to achieve the required RJ viscosity. 

The nurse bees eventually control the viscosity of RJ when filling a queen cell by simply combining the secretions of two independent glands, an extraordinary adaptation that is even more sophisticated than the two-component adhesives used in human technology since it also serves as excellent food.

Buttstedt et al., How Honeybees Defy Gravity with Royal Jelly to Raise Queens, Current Biology (2018), https://
doi.org/10.1016/j.cub.2018.02.022

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