This is a chimera! The chimera is a Greek mythical beast with the body of a lion, a snake for a tail, and a goat’s head on its back… for some reason. In Greek mythology, it’s a sibling of Cerberus and the hydra. The word has come to mean, in modern times, any creature that’s a combination of animals.
These are Chimaeras! They just… have an extra “a” in the name.
Chimaeras are a class of fish that live deep under water. They’re related to rays and sharks, and they’re perfect to learn about for spoopy month because they’re also called SPOOKFISH and GHOST SHARKS!
Like sharks and rays, their skeletons are made completely out of cartilage, and like rays, they have a long, whip-like tail. That snake-like tail might be why they’re called “chimeras” — like the snake tail on the greek chimera.
There are 3 types of ghost sharks, and they’re all distinguished by their snoot! There are long-nosed, plow-nosed, and short-nosed chimaeras (Finucci et al., 2020).
But all of their snoots are used for sensing electric signals in the water! Even with their massive eyes, there’s not much light to see at about 1000 m below the ocean’s surface where they live. To make up for that, they have electroreceptors in their snouts that help with navigation, finding food, and avoiding predators (Bottaro, 2022).
These electroreceptors are called Ampullae of Lorenzini, which… I think I fought that guy in DND once
DM: As you guys turn the corner, you see the back of a man wearing a large cloak. He slowly turns. His skin is pale and he bears his fangs — you recognize him: Ampullae of Lorenzini, level 10 vampire wizard! Roll for initiative!
Players: Aw man! rolling dice
Player 1: Nat 20!
Their Ampullae of Lorenzini help them avoid predators, but most chimaeroids also have a venomous spine in their dorsal fin to protect themselves from predator attacks.
Dr. Didier: “I have probably touched and fondled more ghost sharks than anyone on the planet”
That’s Dr. Dominique Didier. She’s studied ghost sharks for just over 3 decades
She knows to watch for the spines. In fact, she has ahem “personally observed” them (Didier et al., 2012).
In undergrad, she became interested in ghost sharks when she saw that there wasn’t a lot of research on them.
Dr. Didier: “To find current work, I was delving into work that was published in the early 1900s. And I realized ‘wow, there’s nothing known about these fish, no one is studying them!'”
And over the last 28 years, she’s helped discover eleven different species of ghost sharks, which is pretty amazing when you consider it’s actuALLY TWELVE SHE JUST FOUND ANOTHER ONE
Dr. Didier: “We’re coming to the conclusion that what we thought was this one, global species, Harriotta raleighana, is probably not”
Hariotta avia, or the Australia narrow-nosed spookfish, used to be thought of as the same thing as Hariotta raleighana. Then this year, a paper that Dr. Didier worked on (Finucci et al., 2024) discovered that some of the populations near Australia and New Zealand are their own, unique species!
But how do you tell one species from another?
There are 2 main ways these researchers proved that this is a distinct species. The first one is taking detailed measurements known as morphometrics. For each specimen, the researchers took 64 different morphometric measurements (Finucci et al., 2024).
Dr. Didier: “I get just piles of fish. I’ll go to a museum and just measure all day long measuring and measuring and measuring. We use different things like calipers and forceps, tape measures if it’s really big because there’s just no device that can capture that whole size. But yeah, that’s what we do. And then write it down, put it in our spreadsheets and analyze it.”
Genetic analysis also played a role in identifying the new species
Dr. Didier: “Now we have a lot more evidence, partly because we can do molecular studies to say, “this is probably something new””
This figure from the study maps some of the genetic mutations between individual specimens, and you can clearly see that the Harriotta avia specimens are very different from the rest of the Harriotta specimens collected.
Given the morphological and genetic data, the team was able to confidently declare the new species.
When a new species is declared, a few things generally happen. Most importantly, something needs to describe the species, pretty much always a scientific paper. In this case, that’s obviously that Finucci et al. 2024 paper that provides morphometrics and a physical description. That provides documentation of the unique traits of this species.
Next, a holotype and paratypes need to be defined. The holotype is the definitive, “name-bearing representative of a new speices” (AMNH, 2015). In other words, this is what peak Harriotta avia performance looks like.
His name is NMNZ: P.061676. Isn’t that cute??
That’s a specimen identifier for the Museum of New Zealand Te Papa Tongarewa, so other researchers can identify the actual physical thing in the museum’s catalog.
The paratypes are basically alternates or supplemental to the holotype. They help provide a more complete picture of a species definition, and they might end up replacing the holotype if it ever gets lost or damaged.
Me: Before I let you go, I have to ask one more question: what’s your favorite thing about these weird little guys, about ghost sharks?
Dr. Didier: “Oh my gosh, there’s so much to love about them! I just think they’re, like, cool to look at! They’re ancient, so looking at their anatomy can give us clues to the evolution of vertebrates, which some people are doing! They’re weird-looking, they have these strange snouts and sensory systems. We still know very little about their reproduction, where the little guys are. So even now, after working with them for decades, there’s still, like, tons of stuff to be done! So that’s why I like them, I get excited about all this neat stuff”
Me: Is there anything else you want to share for the end of the video?
Dr. Didier: Coming up, on October 30th, is national ghost shark day! So break out your ghost shark juju and have a great day! … And they should be on the lookout for “ghost sharks of the world,” our upcoming book!
Thank you so much to Dr. Didier for helping out, check out the link in the description for references, and follow for more cool science!
AMNH. (2015, February 26). Type Specimens: An Overview | American Museum of Natural History. American Museum of Natural History. https://www.amnh.org/explore/news-blogs/from-the-collections-posts/just-our-types-a-short-guide-to-type-specimens
Bottaro, M. (2022). Sixth sense in the deep-sea: the electrosensory system in ghost shark Chimaera monstrosa. Scientific Reports, 12(1). https://doi.org/10.1038/s41598-022-14076-2
Didier, D., Kemper, J., & Ebert, D. (2012). Phylogeny, Biology and Classification of Extant Holocephalans. Marine Biology/CRC Marine Biology Series, 97–122. https://doi.org/10.1201/b11867-6
Finucci, B., Cheok, J., Ebert, D. A., Herman, K., Kyne, P. M., & Dulvy, N. K. (2020). Ghosts of the deep – Biodiversity, fisheries, and extinction risk of ghost sharks. Fish and Fisheries, 22(2), 391–412. https://doi.org/10.1111/faf.12526
Finucci, B., Didier, D., Ebert, D. A., Green, M. E., & Kemper, J. M. (2024). Harriotta avia sp. nov. – a new rhinochimaerid (Chimaeriformes: Rhinochimaeridae) described from the Southwest Pacific. Environmental Biology of Fishes. https://doi.org/10.1007/s10641-024-01577-4
Halstead, B. W., & Bunker, N. C. (1952). The Venom Apparatus of the Ratfish, Hydrolagus colliei. Copeia, 1952(3), 128–128. https://doi.org/10.2307/1439692
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