This is a) a worm (really, it is) b) which looks like a bum, which is absolutely relevant to my interests. It is a segmented worm whose middle segments are greatly enlarged, which resulted in it being given a Latin name that roughly translates as 'resembling a pig's rear'.
C. pugaporcinus has no apparent reproductive organs, which implies it's actually a larva. We don't yet know what its adult form looks like, as this species was only described as recently as 2007!
09. European medicinal leech (Hirudo medicinalis)
Yes, leeches are worms! They are members of the phylum annelida, like every other worm in this list. Historically, medicinal leeches were used for blood-letting. They were later used to help stimulate blood flow after surgery and skin grafts. This means that the 1930s (when Manchester Royal Infirmary got rid of its leech aquarium) to the 1970s (the resurgence of hirudotherapy) represented a weird blip in European history in which we stopped using leeches.
Leeches are often depicted as plain black. Many of them are, but Hirudo is green and brown with red and yellow stripes. It's like a disco leech!
08. Christmas tree worm (Spirobranchus giganteus)
This worm is best known for its colourful gill/mouthpart structures. The worm itself is sessile and stays within its tube, waiting for prey. It uses its 'Christmas trees' to grab prey and pass it towards its actual mouth.
This is a deep-sea worm discovered only in 2004! I think it's absolutely beautiful. Look at those lovely fibre-optic-like bristles and those elegant tendrils!
How lovely to live in a world where there are still beautiful worms waiting to be discovered.
06. Bone-eating worm (Osedax sp.)
These deep-sea worms are extremely unusual, in that they don't have mouthparts or a stomach! Instead, they secrete acid to dissolve bone and free the proteins - which are then digested by symbiotic bacteria living in the worm's digestive tract. It's still unknown how the bacteria transfer nutrients to their host, or whether the worm simply digests them. The first Osedax species to be named was Osedax mucofloris, which translates as 'bone-devouring mucus flower', referring to the fluffy-looking 'crown' of gills. The three tentacle-like appendages are the worm's 'roots', with which it anchors itself to bone.
The Osedax in this picture is female. In fact, any Osedax you can see is female - males are microscopic and live in the females' bodies. This is an extremely weird animal. I love it.
05. Methane ice worm (Hesiocaeca methanicola)
I mainly just love these because they're cute! They're also pretty fascinating because they were discovered in 1997 living on methane ice mounds on the sea floor. It was hypothesised that bacteria might live in these mounds, so it was a surprise to find a multicellular animal there!
Picture credit: public domain, donated by U.S. National Oceanic and Atmospheric Administration | Source
04. Hydrothermal tube worm (Riftia pachyptila)
These worms are just brilliant! They're 2 metres long and can survive in the extremely harsh environments around undersea volcano events. The worm's 'plume' is red from the haemoglobins with which it gathers nutrients from its environment. I think it's just a remarkable creature!
Picture credit: public domain, donated by NOAA Okeanos Explorer Program | Source
Not to be confused with the name 'tube worms' sometimes ascribed to the shipworm - which is in fact not a worm, but a mollusc.
03. Antarctic scale worm (Eulagisca gigantea)
This is actually a picture of a different scale worm, Lepidonotus squamatus. I'm leading with it because it better shows the cuteness of scale worms, which are often called 'sea mice' because of their fluffy bristly appearance!
Eulagisca is still very cute, but it's hard to find a picture that isn't a dead specimen, like this one:
Picture credit: Smithsonian Institution National Museum of Natural History | Source
Its jaws are actually normally retracted - this specimen is shown with its jaws fully extended. What this photo does do a good job of showing is the worm's iridescent bristles. So pretty! I love the combination of the ethereal bristles and the dangerous bite.
You might be surprised that the common earthworm is my second favourite, after all the unusual marine worms that occupy the rest of my list. But I just love earthworms! They're such jolly and agreeable little things - and they're of vital ecological importance. For all our achievements, we humans owe our entire existence to a few inches of topsoil and the fact that it rains. Worms play an important role in improving soil quality.
It's among the largest of the polychaete worms, and has fearsome clacking jaws that sometimes shear its prey clean in half. It also has absolutely stunning rainbow iridescence! How pretty! What a worm!
Honorable mention: Velvet worm
I consider only the phylum Annelida to be true worms, and this little thing is from the phylum Onychophora. But I have to give it a shout-out because it is so cute! Look at its little feelers and its stubby little legs! Also, it catches prey by shooting slime at it.
