A #CuteOff Challenge: An Entire Kingdom of Cute

I have spent more hours than I want to admit scrolling through #CuteOff on Twitter. The hashtag (following on the heels of the much more R-rated #JunkOff) is a competition of sorts between tweeps to see who can post the cutest animal photo. But as I was sitting on the couch the other day, showing pic after pic to fellow biologist and science writer (and my boyfriend) Jake Buehler, we started to notice that vertebrates — animals, like us, with backbones — were highly overrepresented. Invertebrate species make up more than 95% of the diversity of animal life on this planet, including all of the major groups of animals (called phyla), yet there were choice few to be found in #CuteOff. The discussion went a little something like this...

J: It's just not fair! C: Well, I don't know... most inverts are pretty... gross-looking. J: You're gross looking — to a ribbon worm! C: <glare> J: Just kidding. But being serious: there are lots of adorable inverts out there that deserve a little love. C: Hm... You think so? Care to make a wager? J: I'm listening. C: How about we take the major phyla of animals, split them down the middle, and see who can assemble the cutest arsenal of inverts? J: What does the winner get? C: Bragging rights. J: You're on. So we looked up a quick phylogeny of animals and decided to take turns starting with what is traditionally considered the most basal multicellular group: phylum Porifera. I drew the short straw, which meant I had to go first. 

A possible phylogeny for all major animal phyla — and the road map for our #CuteOff challenge!

C: You ready for this?

J: I was born ready.

C: Let's kick this bad boy off right. There are some 5,000 sponge species on Earth, almost all found in marine habitats. They're basically masses of channels and tubes that filter yummies out of the water. J: No way you're going to find a cute sponge — they lack symmetry. As humans, our perception of attractiveness is defined by symmetry. They're just ugly, misshapen mounds of filter-feeding boringness. C: Oh yeah?

AHHH I'M SO CUTE IT HURTS!!! (Photo by J. Holdorf) J: I guess you'd think "The Scream"

by Edvard Munch is just adorable. Please. Also, no fair, you are exploiting a coincidental overlap of random sponge growth and human face recognition capabilities. Doesn't count. C: All's fair in love and #CuteOff, baby.

J: Ok, here we go, it's my turn - this time with the phylum Cnidaria. Cnidarians number some 9,000 species strong, and include things like corals, sea anemones, and jellies. All are armed with venomous stinging cells, but don't let that fool you. This little tube-anemone larva, in all his radially symmetrical glory, is pretty adorable. C: You're not allowed to just put a little jelly because you know I like jellies and anything little enough will make me squeal. OTHER people have to possibly find it cute. J: I thought all was fair? Ok, fine. I'll play by your double-standards... He is small, but he has other talents too - like looking like one of those shy ghosts

in a Mario Bros game. Either way, he's cackling because he knows I win this round.

Hear him? Listen. "Tee hee hee, Jake is so smart and good at this tee hee hee..." (Photo by Cheryl Clarke, Hopcroft/UAF/CMarZ/MBL) C: It's more of a creepy smile than a cute one. I don't trust it.

C: Hm... a cute ctenophore... that might be tough, considering they look a lot like jellies, except for their distinctive bands of swimming hair-like projections called cilia. Some of them undulate with beautiful colors, but cute?... J: Yeah, hairy blobs of jelly don't sound cute to me. C: Ok, baby: pucker up!

MUAH! xoxo! (Photo by Steven Haddock)

J: Looks like something out of a fever dream I had once. But, admittedly a weird kind of cute. Weird-cute.

J: I'm pretty sure the flatworms - phylum Platyhelminthes - have my back. These are the soft, squishy pancakes of the animal world, and include forms ranging from plain, microscopic parasites to large, brightly-colored species that live on coral reefs. They lack an internal body cavity, along with a specialized circulatory or respiratory system. Even so, this planarian and its beady eyespots is cute enough to take your breath away.

Thems some pond water puppy dog peepers (Photo by Eduard Solà)

C: Sure, he's cute. But anything that shares a phylum with trematodes and tapeworms automatically gets points against it in the cuddle department.

J: We're not judging them against their relatives!

C: <sticks out tongue>

C: This phylum has also been called "Nemertini", which might be because it would take a few cocktails to find most of these ribbon (or proboscis) worms cute

. Fun fact: larger species (which can grow in excess of 50 ft long!) can break into pieces and have each chunk survive and grow into a new individual. Anyway, not all of them are slimy suckers:

C: It's an adorable ribbon worm, that's what it is. Genus Geonemertes. J: Adorable? We're talking about a nemertean worm here. Ever see one of these things try to eat

? It's horrifying.

J: Let's try a different phylum of so-called "worms"...Nematoda. Nematodes are ubiquitous on this planet, and their 25,000 species or so have invaded and thrived in just about every available ecosystem. And by "thrived" I mean that in regards to sheer population numbers, four out of five animals on Earth are some variety of nematode. This lovely species, Acrobeles complexus, is cuter than most of its kind, looking like a miniature, Ecdysozoan take on a Vegas showgirl.

You know you can-can find this adorable! (Photo by Mundo, Bozhilov & Baldwin) C: That's a fancy headdress! And look at the little puckered mouth.... or, whatever it is. J: ...yeah, about those "feathers"...those are probolae, elaborate extensions of the lips. The mouth is somewhere down in the middle of all that....uh...grabby stuff. Let's get on to the next phylum because this one is getting less cute by the second.

C: Rotifers! Oh I so got this. Even microscopic, plankton-y little creatures can be absolutely adorable.

Bdelloid, more like bella! (Photo by Steve Gschmeissner) J: He's smiling at me! *sigh* Ok, good job. Wait....is that its butt or its face? C: Sssshhhhh.

J: I don't even have to try with tardigrades. I mean, just look at 'em; pudgy, microscopic hacky sacks with legs. That is an immortal level of cute - literally, considering they can survive extreme environmental conditions, like boiling water or the vacuum of space.

Waterbear, Moss piglet, Tardigrade. Even the names are #cuteoff! #TeamTactopoda Img:ScienceSourceImages @AnneWHilbornpic.twitter.com/2FhbbgX54s

— Marj (@CurlyHairDevil) September 1, 2015

C: WATERBEAR!!! <unintelligible baby noises>

C: Ok, up next are the velvet worms, one of my favorite smaller phyla. There are only about 180 species of these 'worms with legs', which use an adhesive mucus to capture their prey (eeeeeewwwwww). But their pudgy little faces are adorable close-up!

This one obviously wants a hug. (Photo by Melvyn Yeo) J: That is one cute snot rocket

!

J: Hmm, arthropods will be tough. I mean, there are millions of species. Literally millions of beetles, barnacles, and butterflies, among countless other creepy-crawlies, blanket every corner of our planet. No pressure, I only have to select a single representative from a group that makes up the overwhelming majority of the diversity of all animal life. Good thing the correct choice is obvious: jumping spiders (family Salticidae). They are basically tiny, inquisitive balls of fuzz punctuated with lots of huge, loving eyes. The males of some species even like to boogie

. These guys are so cute they make me angry.

I'm partial to Ömer Alp Evirgen's shot of this tiny jumping spider. #cuteoffhttp://t.co/5Msgwp05Xapic.twitter.com/NciHC3FTym — Andrés Almeida (@andresdavid) September 1, 2015

C: THE HAT! That little drop of water just kills me!

J: Are you ready to accept your inevitable defeat?

C: Not a chance.

C: With more than 17,000 species, there certainly are plenty to choose from! These "segmented worms" aren't usually considered too adorable, though. Earthworms, for example, have such a slimy reputation, but they're awesome for your garden! I won't go with an earthworm, though, not when there's this little face:

Pink is definitely this guy's color. And he can sport a handlebar mustache better than most! (Photo from Shape of Life) J: I'm totally going to grow a mustache like that. C: No you're not. J: It's ok, you can mull it over. Take your time.

J: Mollusks! This is arguably the shining star invertebrate phylum. Mollusks are hyper-diverse in form and ecological function, ranging from lethargic vegetarians like garden slugs, to burrowing clams, to gargantuan, carnivorous giant squid. This tentacled tyke is Helicocranchia pfeifferi, the banded piglet squid, and he prefers to swim upside down and look like a real-life Pokemon.

So adorable that you'll squeal with delight...see what I did there? (Photo by serpent project 2006)

C: I said no little ones! But, look at those big eyes... Who's a good wittle sqwuid? OK, fine. He counts.

C: Yikes! This is a tough one. "Echinoderm" literally translates to "spiny skin" — which tells you a little something about their looks. Urchins, sea stars, sea cucumbers, and their relatives aren't exactly the most adorable species. Luckily, Julia Notar found a cute one for me:

Ok, #CuteOff : I raise you a picture of the tiniest urchin. #teaminvert#teamechinoderm#mammalssuckpic.twitter.com/QFZvY8QRvJ

— Julia Notar (@indy_sea) September 2, 2015

J: Seriously?! An urchin? Have you never seen a sea pig?! Just take a look at this majestic abyssal beast.

Deep-sea bacon (Photo by Stefano Schiaparelli) C: More like sea blob! No. Not cute. Not cute at all! J: We'll just have to agree to disagree. C: And what is it with you and porcine marine fauna? J: Do not question my methods.

J: Ok, Hemichordata. This is another small phylum with only about one hundred species (including acorn worms and pterobranchs), all from marine environments. Hemichordates, along with the echinoderms, are deuterostomes, and are the closest living relations to our own phylum (Chordata). But you might not guess that looking at this translucent little baby version.

Today, a tornaria larva of an acorn worm - what design - more larval forms in http://t.co/55ucEJz983pic.twitter.com/nL88gZ2nSA — Richard Kirby (@PlanktonPundit) June 10, 2014

C: Also not cute. FAIL. J: Well, have you seen the adults?! I don't have a lot to work with here, Christie!

Pictured: Something irredeemably not cute (Photo by Wikipedia user Necrophorus) C: ...I'm not going to say what that looks like to me. J: Exactly. Well I guess that's it.... C: No way! I got one more for you. J: Verts don't count, remember? So unless you're going to try for a urochordate...

C: MAYBE I AM. Not every species in our phylum has a backbone, after all! There are a few groups of chordates that are still inverts, including the lancets and the tunicates, the latter of which includes one of my favorite groups of animals: the sea squirts. Though on first glance, sea squirts look more like sponges than us, when they're larvae, they look like tadpoles, with a notochord and everything! That's how scientists were able to recognize that these blobby animals were in our phylum. Oh, and they're downright adorable:

ホヤの赤ちゃんは世界で一番かわいい珍味です pic.twitter.com/JNEReA3LmJ — ほそいあや「ゆる猫生活」発売中 (@hosoi) April 14, 2015

J: You know what the cutest chordate of all is? C: What? J: You! C: Aw, you're sweet!...That doesn't mean you win. J: I'm pretty sure it does. Who do you think won? Let us know in the comments!