Honeybees are pretty extraordinary animals. They have a complex communication system, they make delicious honey, and their pollination is crucial for many common agricultural products. They are also incredible when it comes to their sex. Sex is certainly not a binary, but for these industrious insects, the variation is remarkable.

In a paper, published in the journal Biology Letters, researchers from the University of Sydney have discovered bees with multiple fathers and even one with no mother at all, despite having female organs throughout.

Honeybees are part of the Hymenoptera order of insects. Members of these orders are haploids, meaning their sex determination is determined by the number of chromosomes an individual possesses. Fertilized eggs get two sets of chromosomes (from a mother and father) and mature into females, while unfertilized eggs with a single set of chromosomes (from the mother) develop into a male.

This reproductive strategy has some amazing consequences. It is possible to witness the formation of female clones, male clones, and even bees exhibiting gynandromorphism, also known as sexual mosaics. Often, sexual mosaics show male and female characteristics at the same time, but for the honeybees, things are a bit more complicated.

Queen bees mate with between 10 and 15 drones (male bees) at the same time while in flight, so it is possible that more than one sperm gets into the eggs. This lead to the possibility of bees with multiple fathers.

The researchers studied a hive where they collected 11 newly emerged gynandromorph honeybees. They first assessed the sex of various tissues morphologically and then performed genetic analysis to establish the correct origin, either maternal or paternal. They discovered that 10 of these gynandromorph bees had up to three fathers. The last one was all fathers, with no maternal allele whatsoever. The team believes that this unusual insect was born by the fusion of two sperm nuclei. This is the first case of sperm fusion reported in Hymenoptera insects.

These remarkable observations provide an incredible look at the flexibility that social insects have when it comes to reproduction. That said gynandromorphism is not the norm, and the researchers think that a possible genetic mutation in the queen is responsible for the high occurrence in this particular colony.

[H/T: New Scientist]