#not like doctor who

[bethanythebogwitch]

Last week on Wet Beast Wednesday I covered some of the biggest animals ever so this week I'm going to do a complete 180 and talk about the smallest animals in this series so far. Not so small as to be micro-animals (I'm sure I'll get to tardigrades eventually) but pretty small. Meet the hydra, a genus of freshwater cnidarians that can be found in temperate and tropical water worldwide. There's a lot of neat stuff about these tiny critters. Such as the fact that they're immortal, but we'll get to that in good time.

(image id: several hydras attached to a rock. Each hydra is a long, anrrow tube that branches at the top into 4 or more thin tentacles. They are milky-white in color. Source: Jan Hamrsky)

Hydras are visually similar to tiny anemones, but they're more closely related to siphonophores and jellyfish. Their bodies are pretty simple, consisting of a tubular body. On one end of the body is the basal disc, a simple foot that adheres to substrate. On the other end of the tube is the mouth, which leads into the gut. Ringing the mouth are tentacles that are covered in stinging cells. The gut is pretty simple and like other cnidarians, it doesn't go all the way through. That's right, when a hydra poops it comes out the same way it went in. A typical hydra consists of 50,000 to 100,000 cells and I hope for their sake that none of them are used for taste. Hydras are diploblastic, consisting of two layers of cells. For comparison, all vertebrates are triploblasts, with three cell layers. The hydra's layers are the epidermis on the outside and the gastrodermis making up the gut. Separating the layers is a gelatinous matrix called the mesoglea that functions as a hydrostatic skeleton. Hydras can contract their bodies and will do so if disturbed. When fully extended, they reach no longer than 10 mm (0.4 in). Hydras are in the cnidarian subphylum medusozoa. Other animals in this subphylum go through two stages of their lifecycle, a polyp that attaches to some substrate and a free-swimming medusa. In most, the polyp is a larval stage that will metamorphose into a medusa during maturation. Hydras instead stay as polyps their entire life. This could be a form of neoteny, the retention of juvenile traits into adulthood. Like other cnidarians, hydras are radially symmetrical. What is most impressive about hydras are their regenerative abilities.

(image id: a drawn diagram of a cross-section of a hydra with labeled anatomical features. source)

Hydras are masters of regeneration. It is this trait that earned them their name, a reference to the hydra of Greek mythology, who would grow two new heads whenever one was severed. Chop a hydra in half and each will grow into a new hydra. Chop a hydra into many pieces and you will get many hydras. Their regeneration is so impressive that if you chop one up into many cells and put them next to each other, the cells will reassemble themselves back into the original hydra. Similarly, hydras primarily reproduce asexually through budding, where one hydra will grow a new hydra out of its body. The daughter hydra will eventually split off from the parent and go on to live independently (unlike certain people I knew in high school). The daughter hydra is a genetic clone of the parent. A hydra living in good conditions can make a new clone every few days. In some species, sexual reproduction is also possible and usually only done when conditions are poor. Depending on the species, individuals can be either hermaphrodites or dioecious (either male or female). Gametes are released into the water to fertilize. Imagine if you wanted to make a baby and to do so you took a handfull of sperm or eggs and threw them all over the place, hoping that someone else also did the same thing in the right time and place. Broadcast spawning is weird.

(image ID: photos of a hydra in the process of regeneration. The hydra is green. It is cut in half, creating a head and foot end. Additional photos taken over time show each end growing into a new hydra. source)

(image id: a pale white hydra growing a bud. the bud emerges from below the head and appears as a small tube. The head of the tube is branched into 5 small nubs that will grow into tentacles. )

Hydras are predators that feed on insect larvae, tiny invertebrates, and small enough fish larvae. They use their basal discs to attach to a hard surface like a rock or branch and extend their tentacles into the water. When something brushes against the tentacle, it triggers the stinging cells. These stinging cells are called nematocysts. Each nematocyst can release what is essentially a tiny harpoon that injects neurotoxin into the target. Nematocysts fire so fast that the harpoon can experience up to 40,000 Gs of pressure. Because nematocysts are tiny, an animal that touches a tentacle will be injected with venom from many of them, getting poisoned even more as they thrash about and get tangled up. The tentacle will then transfer the prey to the mouth. Hydras can swallow pretty large prey, expanding and contracting to fit the prey animal into them. It's kind of like a snake swallowing an egg bigger than its head. While typically sessile, hydras can move around. They can slither around on their basal discs, but when they need to move fast, they summersault. When summersaulting, a hydra will reach down and grab the ground with its tentacles. It then detaches the disc and moves it to a new position. This repeats until the hydra finds itself in a good spot. A speedy hydra can move a food few inches in a day. Hydras can also secrete gas bubbles from their basal discs to float around, upside-down, in the water. A hydra will usually only move from its spot in response to pressure such as predation, competition, or lack of food.

(video: a video of a hydra capturing and eating a mosquito larva. It starts with the mosquito touching a tentacle, which adheres to and stings it. Once the larva is dead, the hydra pulls it in and gradually engulfs it. Despite the larva being larger than the hydra, the hydra can stretch its body to fully swallow the mosquito)

So about that immortality thing. Yeah, it's not just that hydras can regenerate from just about anything, they also don't age. They're kind of like Tolkien's elves in that while they won't die on their own, they can be killed. No undying lands for hydras though. As far as we know. It has been found that hydra stem cells can infinitely renew the body, preventing the effects of aging. This means that a hydra living in a place with no threats could theoretically just keep going forever. They can still die due to predation, disease, starvation, poor environment, and all the other usual suspects. We actually know the gene sequence responsible for this. I tried to read up on it, but genetics is way over my head and it literally game me a headache trying to read. Along with their longevity, hydras also have an incredible ability to repair damage to their DNA. This is important as damage or mutations in DNA accumulate with age. This is why cancer is primarily a disease of old age. As damage accumulates past the body's ability to repair it, eventually a mutation that causes cancer will come along. The longer you live, the more time this mutation has to occur. The hydra's ability to repair its DNA keeps them from all inevitably getting cancer. Naturally, scientists are hugely interested in hydra regeneration, DNA repair, and immunity to aging. If we could figure out how these things work and apply them to humans it would be huge. Expanded, perhaps even indefinite life spans with reduced effects of aging are obvious, but there are other applications. Better DNA repair could vastly reduce the chances of getting cancer or other genetic conditions while regeneration could potentially allow people to regrow limbs or organs. This is obviously still in the realm of speculation, but it's exciting to think about. In conclusion, all hail our immortal overlords, the hydras.

(image id: a hydra growing on the shell of a dead snail. The hydra is a pale yellow color and contracted, causing its midsection to bulge out. A bud is growing from one side of it. Source: Jan Hamrsky)

#wet beast wednesday #hydra #hydra animal #hydrozoan #cnidarians #biology #zoology #ecology #freshwater ecology #freshwater biology #aquatic biology #biological immortality #immortality #regeneration #not like doctor who #Youtube

[yesokayiknow]

i hope that sometimes fifteen's psychic paper shorts out and shows what fourteen's thinking back on earth. he tries to sneak in somewhere and the guard's like this just says 'need to pick up cat food'? and fifteen's like 🥺 they got a cat

#doctor who #the doctor #fifteen #he shows up at the noble house next day with a bunch of cat toys and 14 explains that he was just picking up food for next door #and 15's like ah. well. the thing is. i thought if you only had one cat they'd be lonely so. and pulls out a kitten #rose after 15 leaves: is this an alien cat #14: 100% yeah. don't tell donna that bit

[expelliarmus]

#mine #doctor who #dwedit #david tennant #catherine tate #yasmin finney #karl collins #jacqueline king #bonnie langford #dw spoilers #i would like to just live in this scene forever :')))) #so this means we can MOST DEFINITELY have big finish stories with fourteen and donna now yes????? #i love that mel is part of this too #and please let donna work for unit on camera PLEASE!!!!! #10k

[nat-20s]

Ten and Donna end up on a fucked up deadly space newlyweds show despite uh. Not being newlyweds but they get almost all the questions right. They start to sweat when the final question is "what's one secret desire you have involving the other?" And Donna writes "sometimes I wish I could occasionally shrink down the doctor real small so I could carry him around in my pocket and make sure he doesn't get lost' while Ten writes "sometimes I wish I was small enough that Donna could carry me around in like a cat backpack or maybe a shirt pocket" and they look at each other like AYYYYYY because not only are they deeply drift compatible they're also fuckin weird about it 💖

#doctor who #donna noble #tenth doctor #tennant doctor #you know i usually have the doctor say weird shit about her (positive) like idk #'u know i think me and donna wouldve crushed being conjoined twins' #but i think donna also says weird shit about him. i think shell say out loud something like #'you know i look at you and wonder of i could use you as a paintbrush: #nobody knows what the FUCK those two are talking about

[alternativeulster]

dont let anyone ever tell you the doctor who tv movie (1996) sucks. this is literally the best scene in all 60 years of doctor who

#eight is a creature who just does literally the first thing that crosses his mind in any scenario and you HAVE to like him #he dresses like oscar wilde he's a lesbian he has 97 mental illnesses he's banned from most public spaces #doctor who #dw #doctor who 1996 #paul mcgann #eighth doctor #8th doctor #all timer

[colbrot]

its 2053. 90 year old russell t davies is made showrunner of doctor who just in time for the show’s upcoming 90th anniversary. 82 year old david tennant feels a chill in the air

#and i WILL be watching #he’s gonna drag his ass out of retirement for one last spin #not like he’s gonna say no!! #doctor who #dw spoilers #doctor who spoilers #the giggle

[robiniswriting]

david tennant, matt smith, and jodie whittaker: if doctor who calls me and im available I am so there

me: omg yes slay I love that for you

christopher eccleston and peter capaldi: there’s nothing on god’s green earth that makes me want to reprise the role of the doctor on television

me: omg yes slay I love that for you

#a bit tragic for me as nine and twelve are consistently my top 2 docs #but I respect them so much for that #theyre so real #but also I would absolutely be a david matt jodie #like I get to play the doctor u bet ur ass im gonna do it as much as possible!! #doctor who #the doctor #thirteenth doctor #tenth doctor #eleventh doctor #twelfth doctor #fourteenth doctor #ninth doctor #christopher eccleston #david tennant #matt smith #peter capaldi #jodie whittaker #new who #nuwho

[twilight-zoned-out]

Learning about the Doctor Who specials' expanded budget: oh no, what if they overuse CGI to look more 'professional' and high-budget?

The first scene of the Doctor Who Special:

#:D #[ID: The Fourteenth Doctor looking tired in front of a green screen of space \End ID] #it's still just as cheesy and silly as it was during 10's run #doctor who #fourteenth doctor #the image looks like something a fan would make tbh #the only very jarring part of the budget was how nice quality the camera was throughout the episode #I kind of wish it was a little less crisp because it made everything look a bit off in a way #but I also haven't watched 13's run so maybe it's not as stark of a jump as it felt for me #10 especially always felt very fuzzy and warm in terms of camera quality #tenth doctor #the star beast #twilight-zoned-out #doctor who spoilers #dw #dw spoilers

[softestaries]

Ncuti rly just rocked up trouserless, played a high-stakes game of catch, told his younger self to get some fucking therapy, cloned the Tardis (HELLO?), and left to go clubbing. Iconic behaviour. No notes.

#doctor who #dw #HE'S SO UNBOTHERED IT'S SO FUNNY #I LOVE HIM #fr 14 was about to crumple to the ground over the Tardis and 15 was like ok nw i'll just make another one. i wanted a jukebox anyway #david tennant #ncuti gatwa #fifteenth doctor #doctor who spoilers #fourteenth doctor #dw spoilers

[causalityparadoxes]

Cannot emphasise how OBSESSED i am with the Doctor being able to hear the show's backing music. Does he have favourites? Does he ever miss the funky classic who tunes?

Its giving Day of the Doctor novelisation, where the Doctor's vision changed when the show's colour grading did.

I love whenever they make allusions to the 4th wall or skirt near it. 1st Doctor talking to the people at home. 4th Doctor's laugh at the camera. 12th Doctor's monologues and playing of the Theme tune. Its all so wonderful.

But to put it in the forefront. To literally have him say " I Thought that was non-diegetic " (music not actually present in the world and only for the audience) to have him WINK at us.

Obsessed is too weak a word for what I'm feeling right now. I love them

[image description first image: The Fifteenth Doctor with an expression of surprise saying, "I thought that was non-diegetic." second image: The Fifteenth Doctor looking directly into the camera, about to wink. end description]

(Thank you @thevalleyisjolly for the image description text!)

#not even getting into how it implies he is a godlike being like the maestro!!! did that in my other post #doctor who #dw spoilers #15th doctor #series 14 #season 14 #dw #the devil's chord

[olympain]

In 2017, Peter Capaldi wrote a comforting letter to a 9-year-old Doctor Who fan who was dreading to see his favourite Time Lord leave the show. At the 10th anniversary Letters Live show, Jodie Whittaker read the letter.

#jodiewhittakeredit #petercapaldiedit #dwedit #letters live #jodie whittaker #peter capaldi #doctor who #twelfth doctor #thirteenth doctor #original #*gifs #i jumped when i saw the notification for this video earlier like god that letter was everything #peter's letters are one of the best parts of experiencing dw

[heyitsspaceace]

“doctor who is too silly now!”

oh you mean the doctor who that has flattened human skin as a character? the doctor who that has the episode love and monsters? the doctor who that says that the english royal family is werewolves? the doctor who that has james corden in it? the doctor who that in the same episode that james corden is in not only does the doctor speak baby, but the baby wants to be named Stormageddon, Dark Lord of All, AND the doctor can also play soccer very well.

doctor who has always been silly

#feel free to add more in the tags #this show has ALWAYS been so so goofy i don’t know what yall are talking about #like guys #it’s doctor who #irs gonna be campy as hell #doctor who #dr who #dw #the doctor #9th doctor #ninth doctor #tenth doctor #10th doctor #11th doctor #12th doctor #13th doctor #eleventh doctor #twelfth doctor #thirteenth doctor #15th doctor #fifteenth doctor

[taardisblue]

can someone explain to me why david tennant Standing There like🧍‍♂️over a space background monologuing with the spikiest hair ever achieved on a human being was THE funniest thing I’ve seen this year

#doctor who #doctor who spoilers #I GUESS #dw #dw spoilers #like. what an opening I was CRYING

[thefiresofpompeii]

on tumblr you can say words such as ‘doctor who is like mythology to me. it’s like an ongoing cosmogonic folktale’ and you will recieve 5 notes from people that are willing to indulge your insanity. in real life you say things like how are the kids and was your holiday fun and the weather’s lovely this morning. and i think that’s beautiful. autism.com/careers

#capaldi’s right when he calls the doctor a folk hero. actually he says that the folk hero isn’t ‘the doctor’ the folk hero is the #time traveller named doctor who. he’s also right when he says that this show is about death. well of course it is. death and time and #change and memory. he gets it like no one else. well let’s hope russell gets it too #actually in way this is um #blog thesis #jamie.txt #dw #doctor who

[nipuni]

Tinkering! 🥰

#doctor who #tenth doctor #eleventh doctor #thirteenth doctor #david tennant #matt smith #jodie whittaker #my art #will it blow up? very likely #I've been doing so many sketches like these lately they are so fun #I think I found a comfortable style to sketch in at last

[the-worms-in-your-bones]

The thing about doctor who is that it’s so fucking stupid and unserious at times but after a while you get used to it and don’t even bat an eye when some guy introduces himself with the stupidest name you’ve ever heard because it’s doctor who

#doctor who #fucking love this show #especially the time lords this is about tiem lord names #there’s like four normal ones