The Marine Critters of Christmas

Chris -  Now it is our Christmas Special, so let's take a seasonal dip into the underwater world.  Helen Scales has been busy choosing the 12 marine critters of Christmas and here are just three of them to get you in a festive mood.

Helen -   As a marine biologist, I think there's no better place to get in the festive mood than among the weird and wonderful creatures of the ocean.  So, instead of partridges in pear trees, I've been diving beneath the waves to track down the 12 marine critters of Christmas, and here are three of my favourites.  First up is a denizen of the deep that comes complete with its own set of fairy lights...

James -   I've seen many, many weird and wonderful fish, but one of my favourites is a thing call the stoplight loosejaw which is a deep sea fish and it has some very unusual abilities.  Like many of the fish that live at that depth it is capable of producing light.  It has two different lights on its head, one behind its eye, and one a bit further down its jaw. One of these is blue which is not unusual.  A lot of the fish and other organisms at that depth use blue light because it travels quite far through the water.  But the really unusual thing about the stoplight loosejaw is that it also has a red light and it's one of only three kinds of fish that can do this.  Hardly anything else can see it, everything's eyes are tuned to blue light.  So the red light that's produced by the stoplight loosejaw is pretty much invisible.  So it has its own private wavelength of light.  We're still not totally sure what it uses it for.  It could use it as a torch, to shine ahead of it as it's swimming around looking for prey, or it could even use it to communicate with other stoplight loosejaws and of course everything else would be oblivious.

Helen -   James Maclaine there from the Natural History Museum in London with a fish that glows just as brightly as Rudolf's nose.  For my second critter of Christmas, let's swim out into the big blue to catch up with an ocean drifter that's just about perfect for this time of year.

Rob -   So, sea angels are a group of snails.  They're not too distant relatives of garden snails that you would find on land in your backyard.  They are very beautiful animals and you know, they have these transparent bodies and these giant wings, they look a lot like angels.  But one of the really interesting things is that in Antarctic waters, Clione antarctica has developed this evolutionary tactic to sort of make up for the fact that it doesn't have a shell.  These sea angels have lost that protective ability, but instead they've evolved, or at least Clione antarctica has evolved, bad tasting compounds that it synthesises.  So fish and other predators learn very quickly when they take a bite of Clione that it's not something that they want for a meal.  This has led to actually a very curious interaction between sea angels and a totally unrelated group of animals, hyperiid amphipods, they're sort of distant cousins of shrimp and of krill.  And these amphipods have learned that if they grab onto a Clione and essentially hold it hostage and swim around carrying this giant sea angel on its back, fish and other predators won't eat the amphipod because it's got this bad-tasting Clione carried along with it.

Helen -   How crafty is that?  Rob Jennings there from the University of Massachusetts, introducing us to the beautiful sea angels.  Now, let's meet an organism for which one set of sex organs just isn't enough.

Matt -   The Chimaeras are probably what I would describe as the forgotten cousin of the shark and ray.  Chimaera in Greek mythology actually means a creature that's created from other bits of animals, which when you look at a chimaera you can actually sort of believe that.  While chimaera is a sort of a group term for these fish, within that there's individual species that are known as rabbit fish, rat fish, elephant fish.  So there's a range of different names for different chimaera species.  When you get to the head end, that's where it kind of gets really interesting because sharks, rays, and chimaeras, all use electrosense to detect their prey.  And the chimaeras have some very unusual modifications of their snout.  I still sort of have trouble imagining the mechanics of this but the males actually have a retractable sex organ on their head. They have traditional sex organs as well, but they seem to have this other one as well.  And to my knowledge I don't know if anyone's actually seen it in use, but it is something that sort of slightly boggles my mind.

Helen -   A classic example of sex on the brain.  That was Matt Gollock from the Zoological Society of London.

Chris -   Helen Scales there with three festive Marine critters. If you want to find out a bit more about the rest of Helen's picks as the 12 marine critters of Christmas, you can  find them on the special edition of Naked Scientists which is called the Naked Oceans podcasts, and you can find that at
nakedscientists.com/oceans.