Welcome back to the FINdex! As it’s Christmas I thought it would be a good idea to make this report a bit more festive. Not only that, as you’ve had to wait a while since the last edition of the FINdex, let’s have a look at a few different critters this time! Rather than our usual way of looking at a creature, we will take a short look at each one, in turn, to see what’s interesting about them!

All of the critters that we are going to look at today are linked in some way to Christmas or the festive period. Some are things that you will see on every dive; others are a bit more elusive. Let me know how many of them you have seen!

The first thing you might think of when you think about the festive period is a tree, so what better critter to represent that than the Christmas Tree Worm!

Christmas Tree Worms – Spirobranchus giganteus

Christmas tree worms are polychaete worms that are found on many reefs around the world. You have probably seen them sticking out of a coral head, usually Porites or brain coral, where they are protected from predation.

Polychaete worms, also known as Bristle worms, are part of the Polychaeta class with over 10,000 species described within it. They are segmented worms, with each segment possessing a pair of fleshy protrusions called parapodia, each covered with many bristles. They use these bristles to move around and to sense the environment around them.

Christmas tree worms are a bit different from other polychaetes as once they have burrowed into the coral head they secrete a calcareous (made of calcium carbonate) tube around themselves for an extra layer of protection. They then spend the rest of their lives in this tube with just their crowns stuck out in the water column.

The name Spirobranchus means ‘spiral gills’ and this refers to the best known part of the critter, the brightly coloured spirals that stick out of the coral.

Rather than being gills, these are structures called radioles and they work as a combined gill and mouthpart for the worm. They are covered in very fine cilia, tiny hair-like fibres, which catch microscopic algae and zooplankton that drifts past, as well as providing a huge surface interval for gas exchange. The radioles are then retracted into the tube so the worm can feed. They are also able to retract the sensitive radioles very quickly if they sense any movement in the water around them which could signal a predator. Any photographers out there are probably aware of this quick retraction as they swim up to take a photo of them!

Radioles come in all sorts of colours from vivid yellows and blues to mottled purples and reds. If you are lucky enough you can see groups of them in all different colours, which makes for a stunning picture.

Christmas tree worm

The next part of our festive collection would be some decorations, so why not look at the Tinselfish!

Tinselfish- Grammicolepis brachiusculus

Tinselfish are a very strange looking deep sea fish. You probably won’t see one on your average dive, as they are found between 300m to 1000m. Related to the dories, or Zeidae, a family of fish that contains six species including one British divers should be familiar with – the John Dorie.

Very little is known about the Tinselfish, as they are not regularly found by scientists on dives. What I can tell you is that the scientific name, Grammicolepis, means geometric scales. This can be seen on the body of the body of the fish.

The fish is a silvery colour, with a laterally compressed body. This means that they are flattened on their sides, a strategy allowing the fish to move quickly though the water as it swims. Another useful element to being laterally compressed is that from the front or back the fishes profile is very small, whereas from the side it is very large. This can confuse a predator so as not to know which part of the fish to attack.

This is all well and good but I’m sure you are wondering where the fish gets the name Tinselfish. Under the fish, there grows a long extended fin ray with thorny, bramble like growths along it. It is unknown what the purpose of this structure is. It could be used as a lure to attract food or could be used as a sacrificial body part in case of attack, in much the same way as a lizard losing its tail.

At full size, it grows to around 65cm in length.

While I can’t recommend a place to see the Tinselfish, as I don’t know anywhere that does 1000m bathysphere rides, you can see the similar looking John Dory in the Mediterranean so look out for them around Malta and Cyprus.

Christmas roundup

Another thing that I love about Christmas is seeing reindeer, so let’s have a look at the Reindeer wrasse.

Reindeer Wrasse – Novaculichthys taeniourus

Better known as the Rockmover wrasse, these guys get the name Reindeer wrasse from their juvenile stages. As juveniles, they are a beautiful mottled brown and white colour, or green and white around Hawaii. It’s not the colour that gives them their name though. On their heads are a pair of large fin-like structures that look like reindeer antlers! They make a stunning photo subject so please if you have any shots feel free to send them my way!

Adult Reindeer wrasse measures up to 30cm long and gets the name Rockmover by knocking around and flipping coral rubble and small rocks to find prey living underneath.

They can be found all around the Indo-Pacific but I found them in the Philippines, where they live on coral reefs with plenty of rubble patches up to around 30m.

Like other wrasses, they reproduce via broadcast spawning and can change their sex as their environment requires. Have a look at my article on the Humphead Wrasse, Cheilinus undulates, for more information.

One last thing about Christmas… food!

Turkeyfish – Pterois volitans

One last jokey entry, in some parts of the United States the Red Lionfish, is called a Zebra Turkeyfish! This is due to the pectoral fins kind of looking like a Thanksgiving turkey’s plumage. This is a great example as to why scientific names are important, as scientific names are standardised and common names are not!

Christmas roundup

So there we have it, a few Christmas critters to tide you over until the next proper edition of the FINdex. If you would like any more information about any of these, feel free to drop me a line and I’d be more than happy to chat about them.

In the meantime, have a great Christmas and a very happy New Year! I’ll be in the office pretty much all throughout the festive period so if you have any questions about sea creatures or if you would like to book a trip feel free to drop me a line.

Eat, drink, be merry and I’ll see you in the water!