It’s rare in the animal world to find an organism that is a combination of both male and female, and even divided right down the middle. Generally speaking, animals are sexually ‘dimorphic’ which means males and females of the same species look different, either in shape, color, size or structure due to sexual patterns in their genetics.  

Once in a while, there is a bolt from the blue, and an organism appears that has a combination of both sexes equally portioned down the middle. The term for this condition is gynandromorphism.

The first gynandromorphic individual in its species—a nocturnal bee that lives in Central and South America—has just been discovered by scientists. It is the Megalopta amoenae.

This bee is physiologically male on its left side from tip to toe, with a long antenna, a small dainty mandible and a thin, delicate hind leg with fewer bristles. On the bee’s right side are the female characteristics, which is a shorter antenna, a thick hairy hind leg and a strong toothed mandible.

This is not the first gynandromorphic bee to be found—there have been finds in at least 140 bee species, as well as some birds, butterflies and crustaceans. This is not a new phenomenon. Normally with bees we only see this condition after they die and are in a museum. The condition is virtually unknown in mammals.

Entomologist Erin Krichilsky of Cornell University led a team of researchers in conducting a study on circadian rhythms in M. amoenae at the Smithsonian Tropical Research Institute on Barro Colorado Island in Panama.

The researchers were working with live bees from the forest there to study circadian rhythms. The study of living gynandromorphic bees can teach us a lot about bees with this rare condition and may offer insight into the evolution of specific morphological traits, like about novel methods of reproduction or male-like morphology of female brood-parasite bee lineages, and the modified morphology of social insect castes, as reported by the researchers in their paper.

A separate 2018 study shed light on how gynandromorphism happens in honeybees (Hymenoptera). In the honeybee hive, a fertilized egg creates a female and an unfertilized egg produces a male. However, in the 2018 study it was found that if sperm from a second or third individual enters an already fertilized egg—a female embryo—it can divide and create male tissue, which would result in a gynandromorph. Sex determination in insects like butterflies, ants and bees is quite peculiar.

Coming back to the new study in Panama, since the team was already studying circadian rhythms—which synchronize a species’ interactions and behaviors with their external environment—they decided to perform the same research on their gynandromorphic individual bee, to see if and how circadian rhythms differed in it. A few other studies have focused on other behavioral areas of live gynandromorphic bees, like courtship and nesting behaviors.

Their study revealed, after tracking their bee for over 4 days, that it woke up a little earlier than either male or female bees, but its periods of highest intensity activity most closely mirrored female behavior.

Does this mean the bee is just acting on an individual preference, or does it indicate that the brains of gynandromorphic bees are boggled by mixed sex-specific signals and they are unable to integrate both?

The most that can be read into this observation is that it is a starting point, a first data point in the event other live gynandromorphic bees are found and are available for study.

The researchers wrote in their paper that we should note they worked only on a single sample bee, and that more studies should be done to learn more about if there is a difference in circadian rhythm based on sex in that particular species, as well as to research where the deviant activity pattern of the gynandromorph results from.

The full report of this research was published in the Journal of Hymenoptera Research  where you can see all the close up images of the bee as well. Research Authors: Erin Krichilsky, Álvaro Vega-Hidalgo, Kate Hunter, Callum Kingwell, Chelsey Ritner, William Wcislo, Adam Smith