Juli’s Take on 3 Christmas Critters
Written by Juli Cole, November 2024.
Some critters can be quite cute. But you probably don’t want to find these Christmas critters under your tree.
Sea Angel
Angels are often Christmas tree toppers or depicted flying through the night sky on Christmas cards. Like the heavenly counterparts, Sea angels seemingly fly through the ocean waters. They move by fluttering their “wings” or parapodia – appendages that arise from the equivalent of the “foot” you see in a land snail. They have fascinated sailors for hundreds of years who would observe them in the nighttime surface of the water. They are actually a type of sea slug, a shell-less pteropod, cousins to nudibranchs. They are found up and down the ocean column and throughout the world, even in arctic waters. Only 5 cm at the largest, they are best seen during a blackwater dive.
A few interesting facts of why I chose them and thought they were interesting. They are actually born with shells but lose them when they become adults, where they transform into nimble little hunters. Their favourite food is Sea Butterflies, another type of pteropod only with a shell. They grab onto them lightning fast with tentacles that pop out of their head and grab their prey, in complete contrast to their cute heavenly flutterings of just a second before. Check out this short video on sea angels: https://www.youtube.com/watch?v=7KzUmOwJhg0
Another interesting thing about them is some species produce a toxic slime to deter predators. These are useful to some amphipods (shrimp like creature that floats around in the plankton) who will grab onto them and hug them tight, similar to the defense used by a Pom Pom crab with sea anemones – relying on angels for protection.
Cookie Cutter Shark
The gingerbread that bites back! While you are cutting out those cute cookie shapes, you might think about Cookie Cutter sharks. Though you probably don’t want to enlist their help. And you probably don’t want to find these annoying pests under your tree, or in the water next to you either. These pesky sharks are small, slightly more than half a meter in length, and hang out in the deep waters of the ocean during the day, as much as 2-3 km depth. They rise up at dusk to suspend vertically in the upper limits of the ocean column and take bi
tes out of whatever passes by. They are called “cookie cutter” because as they bite, they twist leaving circular cookie shaped bites out of their prey. They are sometimes in schools, so they can do a lot of damage that results in lifetime scars for larger animals.
They are a real annoyance as they chew on EVERYTHING including underwater cables, sonar equipment on submarines, and other underwater equipment, more than likely attracted to the electromagnetic fields. They are found throughout the world in warmer waters, usually near islands where there are deeper channels. Human long distance swimmers in Hawaii for instance reported problems with them when traversing the Ka’iwi channel near Molokai. Likewise long distance swimmers in Australia have also reported being bitten. Their bites are not life threatening but because of the round shape, they take a long time to heal and leave obvious scars.
Outside of being annoyances however, there are some interesting facts about them. As I mentioned earlier, they are mostly night predators and hang vertical in the water. Their eyes are large and glow green and the dark collar around their necks is thought to be decoy to mimic the shadow of a fish and lure prey to them. Their bellies have green photophores that also glow at night, possibly another trap to lure prey in as their bellies would be exposed outwardly as they maintain a vertical position. They do shed their teeth like other sharks and grow replacements. However, unlike other sharks, they shed their row of teeth in one go and swallow the discarded dentures whole. It is thought to help them reabsorb the calcium.
Pinecone Fish
Okay, you might want to find one of these little cuties on your tree. Cuter than their conifer counterparts, though probably just as prickly, these little fellows grow only to about 12 cm. They are nocturnal so during the day they are squeezed into caves and under ledges. At night they come out and float around, sometimes in schools. They are in their own family Monocentridae comprised of four species. Monocentris reedi, Reed’s Pineconefish, is only found off the coast of Chile. Monocnetris neozelanicus or Maori pinecone fish, is endemic to New Zealand. Monocnetris chyrsadmas has been identified in Taiwan and supposedly Monocentris japonica is everywhere else. I say supposedly as when trying to pin down the distribution of this fish, the descriptions have varied widely and supposedly the pinecone fish is here in our regional waters, yet no one has seen it. It is used in aquariums; one discussion reported a source from a diver who scooped up anything he could find on his dives to sell on the hobby market – diving from an undisclosed city in China. I only mention the aquarium as pinecone fish are difficult to keep, having a specific cooler temperature range than other tropical fish. This makes me suspect that they will not be found in that nice 28- 30 degree water and so probably are found further north or south of the equatorial zone. This coincides with where divers have reported seeing them such as Japan, Hong Kong, and Taiwan.
What makes them so unique is their armored bodies. They do not have scales like other fish but have scutes – more akin to the thick cutaneous coverings on turtles. They are built like mini armored trucks of the ocean. And as you can see from the photos, their fins are not large, so they are weak swimmers relying on their thick scutes to protect them. Some of the species are also referred to as “pineapple fish” because of the scutes thick and pointed appearance. On either side of their jaw are photophores, locations of symbiotic bacteria. The bacteria produce a spot of color – orange by day and blue green by night which attracts zooplankton on which the fish feed.
I don’t think we would be able to spot these on our dive trips around South East Asia, but you never know. Nonetheless, you can still enjoy your dives with us, so check out our dive trips for next year!
Photo Credits
Sea Angels: Wikipedia; Smithsonian Institution
Cookie Cutter Sharks: Fishes of Australia; University of Hawaii; Whiskey Riff
Pinecone Fish: Wikipedia; instagram.com/nationalaquarium/p/Cw5Q0V-MOiX/