Weirdest Animals of the Ocean Depths

Many creatures of the deep are not well known, and we feel that all of them deserve a bit more publicity (even if some of them have faces more suitable for radio than the internet). So, we present our top favourite weird sea creatures that you may not have heard of before.

 7. Amphioxus

Considering we filmed a video about Scottish wildlife, it’s only fair that the first animal on this list can be found in Scottish waters. Although, it looks like a fish, it is actually a distant relative. Amphioxus doesn’t have a backbone. I don’t mean it’s a cowardly animal, rather, it’s spinal chord is surrounded by  a rod of cells called a notochord. Scientists believe that this arrangement was also found in our earliest vertebrate ancestors.

Again, no disrepect to the Amphioxus  but they are very simple creatures. They have no respiratory organs like gills (instead they breathe through their skin). They have no heart and no blood cells either. They also have no brain, just a collection of nerve cells in the front part of their body.

With no backbone, no brain and no heart, Amphioxus really needs to pay a visit to the Wizard of Oz.

 

amphioxus

Apologies for my terrible photoshopping

 

6. Squidworm

squidworm

This beautiful creature is not a squid, but it is a worm – an annelid like earthworms and leeches. It lives on the bottom of the ocean floor in the region known as the bentho-pelagic zone (the bottom several hundred metres that is influenced by the seafloor)
They have an odd diet, eating what is known as marine snow – a delightful term disguising an unappetising mix of fecal material, discarded mucus and dead things floating in the water.

It’s cool yellow curvy moustache are really palps – structures that the worm uses for feeling it’s way around the ocean floor. It also use them to look badass.

 

 

5. Sea Spider

As a self-confessed screaming-like-a-little-girl arachnophobe, I thought perhaps I would be safe for my 8-legged nemeses in the water. But, no. They’re in the ocean too. Although sea spiders are not actually archanids, they are relatives having split from the  true spiders 400 million years ago. All that time, they’ve kept their 8 legs though.

seaspider

 

Living in the sea gives them certain advantages over their terrestrial cousins. With water to support their bodies, sea spiders can grow much larger.  Some can have leg spans of over 50 cm – nearly double the size of the largest land spider.

Sea spider legs are much thinner than land spiders (as a result of the ocean water supporting most of the sea spider’s weight). One group – the Pycnogonids – have legs so small that they only have one muscle cell in each leg.

If you’re freaked out right now, move on to number 7 – it’s much cuter.

 

 

4. Nudibranch

As well as having an hilarious name, nudibranchs are the coolest little molluscs under the sea. There’s over 3000 species of nudibranch and their body forms vary quite wildly.

nudibranch

Many are extremely colourful – like Berghia coerulescens with its striking blue and yellow cerata. It’s believed that nudibranchs evolved to be so colourful because they lost a major defence mechanism – their shell.  As a result, they evolved poisons to avoid being eaten. But it’s no use being poisonous if your enemies don’t know. So, many poisonous animals evolve to be colourful in tandem to warn away potential predators. Treefrogs in the Amazon and banded Coral snakes also do this.

 

3. Christmas tree worms

Spirobranchus giganteus

From the ridiculous to the sublime, Christmas tree worms may be the most beautiful creatures in the sea. They’re not plants as their appearance may suggest, and they don’t feed on sunlight. Instead they use their delicate fans to filter and trap plankton from the water. The worms begin their lives as tiny larvae, which hunt for a hard coral surface to make its home. It then builds a tubular suit of armour out of calcium carbonate. The video below shows how quickly the worms can retract their feathery gills into their tube to protect themselves from harm.

2. Giant Isopod

Giant_isopod

Congratulations Mrs Jones – it’s a beautiful four pound, 14 legged bundle of joy.  This monstrous creature is a giant isopod and is closely related to the common woodlouse (which are also cutely called chuggypigs or cheeselogs). There isn’t much cute about the giant isopod though. Feeding on the flesh of dead whales and squid in the pitch darkness on the bottom of the ocean floor, giant isopods gorge themselves on anything they can find. When nothing can be found, the isopods can successfully fast for four whole years.

 

 

 

1. Mantis Shrimp

mantis-shrimp

You should pay attention to their threatening-sounding name rather than their cute appearence – Mantis shrimps are a terrible force of death in the ocean. Just consider how biologists divide up mantis shrimps into groups – Spearers and Smashers. Spearers use their claws to (you guessed it) spear unfortunate nearby animals. Smashers are more brutal – they have claws that bludgeon their puny victims to death.

Their claws (both smashers and speares) are deadly in another way too. Mantis shrimps are incredibly fast. Some species can accellerate at around 102,000 m/s2 and pull 10,000 g in the process. This produces a lot of bubbles. Bubbles generally aren’t that dangerous – unless they’re accelerating 300x the speed of sound. As they smash into the shrimp’s prey they cause a noticeable amount of damage.

Mantis shrimp bubbles are cool in another way, an almost magical way. They produce light as they collapse. This is called Sonoluminescence. Noone really knows yet why this happens, but is probably due to ionised gaess produced when the bubble heats up as it collapses.

 

N.B. The weirdest sea creature ever described by science is this starfish. Check it out.

 

Charlie

Charlie is a science writer from London. He tweets @UnpopSci.

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9 Comments

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  3. bmat

    okay it may be just me, but I feel like the squidworm looks like that thing that Khan put it to everyones ears on the old Star Trek Movies. Creepy!

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