When Madagascar’s fish-scale geckos sense a ᴛʜʀᴇᴀᴛ, they go to great measures to defend themselves, pulling away from their own skin. The geckos’ enormous, overlapping scales ᴘᴇᴇl off so readily that when a scientist attempted catching them with cotton and handled them carefully in the late 1800s, only a few individuals were kept with all scales intact. However, scientists have just made an astonishing discovery: the scales are actually a tough armor akin to crocodile skin. Dr. Bauer stated, ‘Schmidt was a wonderful anatomist, and I’m sure he was confident in what he observed.’
‘Indeed, anatomists of his time were fairly successful at getting animal anatomy right, while dealing with considerably less technically advanced equipment than we have now.’ The researchers believe that osteoderms originated separately in Geckolepis, Tarentola, and Gekko gecko since they are not related, and CT scans revealed that osteoderm shape and density differed among the three. G. gecko and Tarentola mauritanica contain plate-like and granular osteoderms, whereas G. maculata has deposits that resemble little irregular mosaic pieces.
Paluh believes that further research is needed to know how bone deposits form in Geckolepis and if they can be rebuilt when scales are pulled away. ‘There are still a lot of intriguing things to be answered,’ Paluh remarked. ‘Clearly, our understanding of gecko anatomy isn’t comprehensive,’ says the researcher. They have osteoderms, which are the same substance that makes up crocodilian scales. Fish-scale geckos (Geckolepis maculata) are cream in color with black stripes and have enormous scales.
The species is extensively dispersed in Madagascar, according to the IUCN, and is considered to occur from northern to southern Madagascar, including the offshore island of Nosy Be. The osteoderms of fish-scale gecko scales are the same substance that makes up the robust scales and plates of crocodilians and aramadillos, according to a new study published in the African Journal of Herpetology. This prompted the researchers to ask, “If these geckos have armor, why do they shed it?”
‘The fundamental question is why there are these competing defense tactics,’ said lead scientist Daniel Paluh, a doctorate student at the Florida Museum of Natural History. ‘This gecko can drop its skin as a protective mechanism, but it also has these mineralizations – commonly considered of as body armor – that it’s just leaving behind.’ However, according to Paluh, the osteoderms may not always act as a protective screen; they may give calcium for egg formation in female geckos or even assist control body temperature.
Paluh examined hundreds of geckos using X-ray computed tomography (CT) technology, which employs thousands of X-rays to produce high-resolution, multilayered 3-D pictures of specimens. Paluh’s CT scan of the gecko revealed thick, bone material inside the skin, something he hadn’t seen in most other geckos. ‘I thought to myself, “Wow, this is pretty unusual,” Paluh remarked. ‘We began delving further to confirm that what we were seeing in the CT scan was indeed these mineralized materials.’
While osteoderms are seen in certain lizards, they are uncommon among geckos, a group of over 1,600 species. Prior to Paluh’s research, only wall geckos (Tarentola) and tokay geckos (Gecko gecko) were known to have this type of protective exterior armor. Most geckos have thin skin covered in small, granular scales and rely on camouflage and the cover of darkness to protect themselves from predators. However, other groups, such as Geckolepis, which includes the fish-scale gecko, have evolved fragile skin as a kind of defense. Dr. Aaron Bauer, a Villanova University researcher, and study co-author, remarked
When they are ᴀᴛᴛᴀᴄᴋed by a predator, the geckos may pull out of their skin to flee, ‘like the tear-away football jerseys of the 1970s,’ he added. The paradox of’sheddable armor’, on the other hand, contributed to widespread skepticism of a 1911 research by biologist W.J. Schmidt, who reported his discoveries of osteoderms in the scales of Geckolepis polyepis. Researchers were doubtful about Schmidt’s results until Paluh’s CT scan revealed that he was correct. Paluh employed procedures similar to Schmidt’s to confirm that the fish-scale geckos had osteoderms.
He cleaned and dyed removed areas of skin with many scales to see if the tissue was mineralized, and this showed small, interlocking osteoderms – much like the ones Schmidt described and illustrated over a century ago. Dr. Bauer stated, ‘Schmidt was a wonderful anatomist, and I’m sure he was confident in what he observed.’ ‘Indeed, anatomists of his time were fairly successful at getting animal ᴀɴᴀᴛᴏᴍʏ right, while dealing with considerably less technically advanced equipment than we have now.’
The researchers believe that osteoderms originated separately in Geckolepis, Tarentola, and Gekko gecko since they are not related, and CT scans revealed that osteoderm shape and density differed among the three. G. gecko and Tarentola mauritanica contain plate-like and granular osteoderms, whereas G. maculata has deposits that resemble little irregular mosaic pieces. Paluh believes that further research is needed to know how bone deposits form in Geckolepis and if they can be rebuilt when scales are pulled away.
‘There are still a lot of intriguing things to be answered,’ Paluh remarked. ‘Clearly, our understanding of gecko anatomy isn’t comprehensive,’ says the researcher.
