Researchers used medical imaging techniques to peer inside a deep-sea octopus, allowing them to describe a new species without destroying the unique specimen.
Showing that an octopus species is novel requires evaluation of its internal features, a process that usually damages the specimen. In a study published April 22 in BMC Biology, researchers used less-invasive techniques to describe a new dumbo octopus, which they dubbed the Emperor dumbo.
Named for their ear-like fins that resemble the eponymous Disney elephant, dumbo octopuses dwell deep in the ocean and are rarely collected by scientists.
So, when a pinkish-red, football-sized dumbo octopus was hauled onboard the scientific vessel that Alexander Ziegler, lead author of the study and an evolutionary biology and ecology lecturer at Universität Bonn, was working on, he "knew this was something special."
To identify and describe species of the intelligent invertebrates, researchers measure external features such as the head, fins, arms and number of suckers as well as internal organs such as the gut, "parrot-like" beak and rasping tongues, Ziegler said.
"Normally, you would take a specimen, put it on a table, dissect it open, take out different organs one by one: the digestive tract, the brain, the gills, different organ systems," he explained. "It's a very invasive approach."
But this type of destructive analysis isn't ideal for rare species or valuable specimens.
"We decided that we wanted to [describe the octopus] non-invasively," Ziegler continued, "because from the initial observation it seemed likely that this could be a new species, and we didn't want to destroy the specimen because it was a single specimen."
The Emperor dumbo was collected during a research cruise from a sample scraped from the seafloor at a depth of about 4,400 meters — equivalent to the length of almost 10 Empire State Buildings.
To minimize damage to the specimen, Ziegler and Christina Sagorny, now a Ph.D. student in Ziegler's lab who did this work as a master's student, only took small tissue samples for DNA analysis, and they used non-invasive imaging techniques to perform virtual dissections, an approach previously applied only to smaller organisms such as flatworms and centipedes.
The team used MRI, a common technique for brain scans, to take images of the octopus's soft organs, and they used micro computed tomography, or CT, to visualize hard structures such as the beak and rasping tongue. Then they compiled layers of images to reconstruct 3D models of the animal's organs.
By comparing these reconstructions and external measurements with descriptions of similar species, the researchers concluded that the octopus was a new species, which they called Grimpoteuthis imperator. The name is inspired by the Hawaiian–Emperor seamount chain, an underwater mountain range in the North Pacific Ocean where the specimen was collected, Ziegler told The Academic Times. It's also a nod to the fictional Galactic Empire because a Star Wars film was released when the researchers were doing their analyses, Ziegler added.
The researchers have made their data publicly available online, which Ziegler hopes encourages additional research.
"I think the main power of this approach is data transparency," Ziegler said. "Here we have a data set that is digital, like a molecular sequence, and the dataset is deposited online for everyone to download and check for themselves to see if our interpretation is correct or maybe we made a mistake."
Another strength of non-destructive analyses is that the specimen could be reanalyzed in the future, Ziegler said.
"Maybe 10 or 100 years down the road, better techniques will be available," he said. "But there's no worry because the specimen is still there and you can look it again with the new technique."
However, according to Ziegler, one disadvantage of the approach is a lack of sensory characteristics.
"When you dissect an animal, you have more information: color, hardness, softness," he said. "Maybe you spot something while dissecting that you cannot see in our data set."
The study, "Holistic description of new deep sea megafauna (Cephalopoda: Cirrata) using a minimally invasive approach," published April 22 in BMC Biology, was authored by Alexander Ziegler and Christina Sagorny, Rheinische Friedrich-Wilhelms-Universität Bonn.