Halloween is often associated with spooky and scary stories filled with ghosts and monsters👻. Do you believe that scary looking creatures actually exist deep in the ocean? Let us introduce the Chimaeras, not the mythological fire-breathing creature with a lion head and a snake tail, but a group of cartilaginous fishes living in the darkness of the ocean. Interestingly, chimaeras’ closest relatives are sharks🦈and rays from which they diverged about 400 million years ago, and for which the morphology of chimaeras has not changed much since. Like sharks and rays, their bodies are supported by cartilage instead of bones. If most sharks have five gill openings, chimaeras on the other end only have one which is protected by an operculum (gill cover), just like those found in bony fishes (about 90% of all fish species🐟 that are supported by a skeletal body).
Most chimaeras live in the deep sea between 200 to 2600 meters under the surface, with just a few exceptions for species found in shallower waters. Now, we have to talk about their truly remarkable appearance. Chimaeras have a spectral (ghost-like) look with their skin resembling one of Dr. Frankenstein's creatures, with what may seem like stitches all over their body. If you look closely though, you can actually see lines of dots around the snout (nose), they are actually electroreceptor pores which helps chimaeras for sensing the surroundings🧏. Their dorsal fin is terminated by an acute venomous spine which serves a defensive function. In addition, they generally glide slowly through the ocean using their wingy pectoral fin, which has led to their name of ‘ghost shark’.
Interestingly, adult male chimaeras have not just one, but two unique structures to hold on to females during copulation😯. During the ritual, males will use the frontal tenaculum (stalked structure on top of the head) and pre-pelvic tenaculum (hooked structure before the pelvic fin) to anchor into the pectoral (lateral) fin of females and get stabilized. Chimaeras really live up to their name as “haunting” their partners like a ghost👻.
At the HKBM, come and observe our two specimens of chimaera, available during Halloween or at any other time of the year!
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