Digitisation uncovers rare specimens that highlight the diversity of sex in nature| Digital Collections Programme

Digitisation enables us to understand exactly what we have in the collection. This can provide updated and accurate collection records, improve estimates for digitising future collections and occasionally uncover the unexpected. 

Digitising the entire Birdwing butterfly collection, we now know in more detail what species we hold, and where and when they were collected and can share this with the world through the Museum’s Data Portal and Wikipedia.

As a group, Birdwings show a large degree of sexual dimorphism, meaning that males and females look substantially different from each other, beyond the differences in their sexual organs. This is most notable in the Ornithoptera species and is believed to function in mate recognition via the use of photoreceptors in the eye that respond to light.

 Three examples of Ornithoptera victoriae, top left: female, bottom left: male, right: Gynandromorph

The top two specimens above, of Victoria’s Birdwing, show the kind of dimorphism present in Ornithoptera species. The females are larger than the males and brown, with flecks of white and yellow. The males are smaller with vibrant green radiating into black and yellow tips on each wing. However, the third specimen displays both male and female characteristics through its wing size, pattern and colouration. This is a rare condition known as a gynandromorph. 

Diversity of sex in nature

The Collins Dictionary defines a gynandromorph as “an organism, especially an insect, that has both male and female physical characteristics”. Gynandromorphism has been observed in numerous animal species, for example crustaceans such as lobsters and crabs, and many species of bird, but is particularly notable in butterflies, moths and other insects that usually display a high level of sexual dimorphism.

Sexual dimorphism is not noticeable in humans, so gynandromorph is not used to describe humans. In human biology the term intersex refers to individuals born with any of several variations in sex characteristics. The UN High Commissioner for Human Rights defines intersex as individuals that “do not fit the typical definitions for male or female bodies”

Intersex people were referred to as hermaphrodites in the 19th century, however the word “hermaphrodite” is considered misleading and scientifically specious in reference to humans so is no longer used. A hermaphrodite is now defined as “an animal or plant having both male and female reproductive organs.” The Clownfish is a well-known hermaphrodite, while clownfish are initially born male (but carry both male and female reproductive organs), the largest fish in the group becomes a female. Therefore, in Finding Nemo, when Nemo’s mother gets eaten by a barracuda, his father would have transformed into a female. 

What these gynandromorph specimens do bring to light is that bisecting line between the sexes in the animal kingdom isn’t clear cut. Just as with humans many creatures straddle that line. It is fantastic to find these specimens during a digitisation project at the Museum because this means that we have accurate photography and data about these specimens that we can share with the world as evidence of the diversity of sex in nature.   

Taking a closer look

During the Birdwings digitisation project, a second gynandromorph was also discovered. This belonged to the species known as Rajah Brooke’s Birdwing (Trogonoptera brookiana) 

Clockwise from left: Gynandromorph, female right and male Rajah Brooke’s Birdwing (Trogonoptera brookiana), Upperside view

First impressions from the image in the bottom row is that it is a male specimen.  However taking a look at the underside of the wings reveals something different. On the underside view we can see an area on the left forewing shows the colour and markings of the female specimen. Another exquisite gynandromorph example from within the same collection.

Clockwise from left: Gynandromorph, female and male Rajah Brooke’s Birdwing (Trogonoptera brookiana), Underside view

The conservation of birdwing butterflies is a priority as several species are rare or endangered and the accessibility of data is critical to support this process. Creating access to comprehensive sets of data across time and geography, such as museum collections, will assist the monitoring of species and habitats.  By sharing this resource on the Museum’s Data Portal and wikipedia, a platform used by 13 million per day, we hope we can engage a larger and more diverse audience and raise awareness about the beauty and fragility of this important group of organisms. 

To find out more about the birdwings digitisation project please read our previous blog. To stay in touch with the Digital Collections Programme you can follow us on twitter or instagram or find out more about the programme on the website.