S.ᴇ x change in reptiles is rare and the team believes this is the first time it has been observed in this species!
In February, aquarium keepers noticed one of their female Boyd’s forest dragons – a green-grey lizard with a spiny crest that is native to Queensland’s tropical rainforests – change colour, grow a larger crest, and stop laying eggs.
On ultrasound, the team says it has confirmed the lizard has lost its ᴏᴠᴀʀɪᴀɴ tissue and developed mature ᴛᴇsᴛᴇs.
“After these changes we also noticed a significant growth spurt and increase in weight. Given it’s extremely uncommon to come across reptiles transitioning, we decided to bring in an ultrasound machine to discover exactly what was occurring here,” said Tom Fair, Aquarist at SEA LIFE Melbourne.
“We performed an ultrasound examination to determine which ʀᴇᴘʀᴏᴅᴜᴄᴛɪᴠᴇ ᴏʀɢᴀɴs were present. Surprisingly, we discovered that there was no longer any ᴏᴠᴀʀɪᴀɴ tissue present and mature ᴛᴇsᴛᴇs had developed. This confirmed to us that a change in female to male ʀᴇᴘʀᴏᴅᴜᴄᴛɪᴠᴇ ᴏʀɢᴀɴs had indeed occurred against the odds.”
A few lizard species are known to reverse s.ᴇ x in the egg but it is thought to be extremely rare. In fish, some adults can change s.ᴇ x in response to changes in their environment or other fish.
“If it can be verified, this is an astonishing discovery,” the University of Canberra’s Professor Arthur Georges, one of Australia’s leading reptile experts, said in an email. “This is the first time there is any suggestion of s.ᴇ x reversal in an adult reptile.”
Sarah Whiteley, a researcher stuᴅʏɪɴɢ the s.ᴇ xual development of dragons at the University of Canberra, said “such an ᴜɴᴜsᴜᴀʟ occurrence would require very convincing data”.
“Without having seen any of the data myself, I must remain sceptical, though very intrigued,” she said.
The aquarium keepers have had the lizard examined by a vet, who confirmed the presence of male ɢᴇɴɪᴛᴀʟs. They hope to soon publish findings in an academic journal.
The small creature, known as Doris, has been with the aquarium for six years, living quietly in the tropical forest exhiʙɪᴛ alongside two other dragons – a male and a female. Doris spent her time hiding on logs, eating bugs, laying a cache of eggs every month. Several hatched into baby forest dragons.
Late last year, the male forest dragon – known as Old Mᴀᴛᴇ – ᴅɪᴇd, and the keepers moved the two females into a new exhiʙɪᴛ.
The first sign of change was food. Most female dragons won’t eat until it’s time to lay eggs, when they binge. Doris started eating all the time, like a male dragon.
“Not long after, the secondary s.ᴇ x characteristics started changing, like a brighter colour, a thicker crest, and she started getting quite a lot bigger,” Fair said.
At her monthly weigh-in, Doris’s weight had shot up, from 112 grams to 159 – “which is normal for a male”, said Mr Fair. “It’s a massive difference.”
He took the dragon to the aquarium’s vet, who gave it an ultrasound, revealing ᴏᴠᴀʀɪᴇs and undeveloped eggs. A month later, they brought in a team of specialist vets who performed a more thorough ultrasound.
There, unmistakable on the screen, was the evidence: No eggs. No ᴏᴠᴀʀɪᴇs. “They confirmed Doris now has ᴛᴇsᴛɪᴄʟᴇs,” said Mr Fair.
Skinks and central bearded dragons have shown the ability to reverse s.ᴇ x but only in eggs before they hatch.
Among fish, male clownfish living in a school can change gender to female when the alpha female ᴅɪᴇs, a process known as sequential hermaphroditism.
Independent experts were fascinated but skeptical.
“The most simple explanation is an ᴇɴᴅᴏᴄʀɪɴᴇ issue – ᴅɪsᴇᴀsᴇ or an environmental ᴇɴᴅᴏᴄʀɪɴᴇ disruptor, but this would need to be significant,” said Dr Jane Melville, senior curator of terrestrial vertebrates at Museums Victoria.
Or perhaps the aquarium had misidentified Doris’s s.ᴇ x in the first place.
Mr Fair considered that as well. “But really, once we have the confirmation the ᴛᴇsᴛᴇs are there, it is a definite shift over. I personally have observed that individual laying eggs many, many times.”
His theory: Doris – who has not yet been given a new name – is displaying social gender switching, similar to clownfish, making the switch due to the absence of a male.
“But that’s just guesswork. There are more questions than answers,” Mr Fair said.
Boyd’s forest dragons are an Australian reptile found in rainforest areas in Northern Queensland. They are generally brown or grey in colour with some individuals having a green fʟᴜsʜ. They have enlarged cheek scales, a prominent crest and a yellow dewlap under their chin.